WO1997016742A1

WO1997016742A1 - Conditionally generating test instructions depending on device defect data

Info

Publication number: WO1997016742A1
Application number: PCT/US1996/017423
Authority: WO
Inventors: Steven M. Blumenau; William S. Schymik; Richard Pye; Paul L. Keating
Original assignee: Genrad, Inc.
Priority date: 1995-11-02
Filing date: 1996-10-30
Publication date: 1997-05-09

Abstract

A system for generating test programs while inhibiting unnecessary testing of devices. The system includes a database of defect statistics (2105) organized by package type. The system generates a test program (5100) by following, for each part on the circuit board, a rule for each type of test instruction (3120). Each rule may have an expression dictating whether the corresponding type of instruction should be generated for a certain circuit board part. Each expression may have a variable called DPM, which is a defect statistic corresponding to the package type of the part. Thus the system conditionally generates a test instruction for a part depending on whether the package type of the part has a defect statistic above a certain threshold.

Description

CONDΓΠONALLY GENERATING TEST INSTRUCTIONS DEPENDING ON DEVICE DEFECT DATA

BACKGROUND OF THE INVENTION Field ofthe Invention

This invention relates generally to a system and method for programming a testing system, and, more particularly, to a system and method for system and method of conditionally generating test instructions depending on defect data for a device to be tested. Description of Related Art

Electronic products such as televisions typically contain one or more circuit boards manufactured by an assembly line. One method of testing a circuit board, after manufacture, is to insert the board in its product. If the product then operates, the board is deemed to be good. If the product does not operate, the board is deemed to be defective. One option in dealing with a defective board is to discard it. This option is often undesirable, however, because a board can be expensive to manufacture. Another option is to have a technician manually locate the defect on the board by probing with an oscilloscope, for example. A problem with this second option is substantial labor cost for the technicians time.

Another method of testing a circuit board, after manufacture, is to employ automatic test equipment that can detect a defective board and, sometimes, automatically diagnose a board defect. Test programs for the automatic test equipment have been complex. Complex test programs can be expensive to debug, as substantial engineering time must be expended in the debugging process. Complex test programs can be expensive to support, as complex programs tend to require more complex test hardware and fixturing. Finally, and often most important, complex test programs can be expensive to execute, as more complex programs take longer to execute and, therefore, can be a bottleneck in the in the circuit board production process.

Test programs have been unnecessarily complex because test program writers, or generators, often generate every available test for each part on a circuit board, even when generation of a particular test for a particular part is not cost effective. As a practical matter it has been difficult to limit this unnecessary complexity of test programs. Although systems exist that record certain aspects of test program performance in a production environment, these systems are employed for quality reports to managers ofthe manufacturing process.

SUMMARY OF THE INVENTION

It is an object ofthe present invention to provide an efficient system for generating test programs while limiting test program complexity, by inhibiting certain unnecessary testing of devices.

To achieve this and other objects ofthe present invention, in a system including an electronic memory, a first plurality of circuit boards and a second plurality of circuit boards, a method comprises the step of testing the first plurality of circuit boards, to generate defect data; writing the defect data into the electronic memory; generating a test program by reading the defect data from the electronic memory; and testing the second plurality of circuit boards by executing the test program.

According to another aspect ofthe present invention, a system comprises an electronic memory; means for testing a first plurality of circuit boards, to generate defect data; means for writing the defect data into the electronic memory; means for generating a test program by reading the defect data from the electronic memory; and means for testing a second plurality of circuit boards by executing the test program.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is diagram of a manufacturing process incoφorating the programming method of the preferred embodiment ofthe invention.

Figs. 2A is a plan view of a circuit board produced by the process shown in Fig. 1

Fig. 2B is a side view ofthe circuit board shown in Fig. 2A.

Fig. 3 is an illustration showing an aspect of the testing section shown in Fig. 1

Fig. 4 is a diagram showing another aspect ofthe testing section.

Fig. 5 is a diagram of a data flow in the testing section.

Fig. 6 is a diagram emphasizing a portion of Fig. 5.

Fig. 7 is another diagram emphasizing another portion of Fig. 5.

Fig. 8 is a diagram showing another data flow in the testing section.

Fig. 9 is a procedural flow chart showing a processing performed by the preferred embodiment ofthe invention. Figs. IOA, 10B, and IOC show a flow of defect data in the preferred embodiment ofthe invention.

Fig. 1 1 shows tables for translating faults into site defects.

The accompanying drawings which are incoφorated in and which constitute a part of this specification, illustrate embodiments ofthe invention and, together with the description, explain the principles ofthe invention, and additional advantages thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment is a system for generating a test program, including a plurality of test instructions, while inhibiting unnecessary testing of devices. The system includes a database of defect statistics organized by package type. The system generates a test program by following, for each part on a circuit board, a rule for each type of test instruction. Each rule may have an expression dictating whether the corresponding type of instruction should be generated for a certain circuit board part. Each expression may have a variable called DPM, which is a defect statistic corresponding to the package type ofthe part, as described in more detail below. Thus the system conditionally generates a test instruction for a part depending on whether the package type ofthe part has a defect statistic above a certain threshold.

Fig. 1 shows a circuit board manufacturing facility according to a preferred embodiment ofthe present invention. Paste section 1010 receives bare circuit boards 1005 and applies paste to selected portions ofthe top of a board. Component placement section 1015 then receives the board and places electrical components 1020 on board locations having paste. Components 1020, 1022, and 1024 include integrated circuit (IC) packages and discrete resistors, capacitors, diodes, and transistors.

Reflow section 1025 then applies heat to melt the paste. Flip section 1030 then turns the board over to expose the other side ofthe board. Glue section 1045 applies glue to selected portions ofthe bottom ofthe board and shoot section 1050 applies additional components 1024 to board locations containing glue. Flip section 1052 then turns the board over to expose the other side ofthe board. Insertion section 1020 places additional components 1022 on top ofthe board by inserting components 1022 in through holes in the board. Wave solder section 1055 applies molten solder, an alloy having a low melting point, to the bottom ofthe board to secure components onto the board and establish electrical contact between the components and electrical paths on the board

Fig. 2A is a plan view of a television circuit board 100 after leaving wave solder section 1055, and Fig. 2B is a view ofthe board 100 taken along the line A— A shown in Fig 2 A Circuit board 100 includes a top surface 105 and a bottom surface 115 These surfaces include parts 2015, 2020, 2010, 2025, 2030, 2035, 2037, 2040, 2043, 2057, 2045, 2050, 2055, 2067, and 2069 Printed on board 100 are "designators" IC 2015, IC 2020, IC 2010, C 2025, C_2030, R_2035, IC_2037, R_2040, IC_2043, IC_2057, IC_2045, IC_2050, SW_2055, R_2067, and C_2069, each corresponding to one of parts 2015, 2020, 2010, 2025, 2030, 2035, 2037, 2040, 2043, 2057, 2045, 2050, 2055, 2067, and 2069 respectively

Testing section 1100, shown in Fig 1, performs tests to verify that each circuit board 100 is assembled properly.

Fig. 3 shows testing section 1100 in more detail Conveyor 1 105 moves circuit boards 100 through various testing stations in the direction of arrow 1 106 Electrical station 2130 applies electrical signals to one ofthe circuit boards 100 and receives electrical signals from the circuit board 100 through pins 2132 Electrical station 2130 may be any one of a variety of automatic testers now available

Subsequently, optical station 2200 illuminates the board with lamps 2232, allowing optical recognizer 2236 to electronically photograph the board and analyze the photograph with a processor. Optical analyzer 2236 may be any one of several programmable optical inspectors now available, including one ofthe Theta Vision Systems available from Theta Group, Inc., 3077 A Leeman Ferry, Rd., Huntsville, AL 35801

Subsequently, x-ray station 2300 irradiates the board with an x-ray source 2332 and detects x-rays passing through the board with detector 2334 X-ray station 2300 may be any one of several programmable x-ray analyzers now available, including one of he systems available from Nicolet Imaging Systems, 8221 Arjons Drive, San Diego, CA 92126, or from FEINFOCUS USA, Inc 5142 N Clareton Drive, Suite 160, Agoura Hills, CA 91301

If a board 100 passes all tests at stations 2100, 2200, and 2300, a board then goes to manual inspection station 2400 At manual inspection station 2400, an inspector 245 manually inspects board 100 in an attempt to detect latent defects Inspector 245 consults a list of defects not covered by any of stations 2130, 2200, or 2300 These types of uncovered defects, called "escapes," are compiled by programming station 2100, as discussed in more detail below. Inspector 245 consults a list 2410 of escapes for board 100 List 2410 was printed by printer 2425, connected to networks 21 15 (described in connection with Fig 4) Alternatively, inspector 245 can view the escapes for board 100 on computer terminal 2415, also connected to network 2115

Subsequently, if board 100 passes manual inspection at manual inspection 2400 a technician 220 inserts the board 100 in its respective location in television 105 If television 105 fails to operate properly after insertion of board 100, board 100 is taken to manual diagnostic station 2430, where technician 225 attempts to diagnosis the defect in the board, by manually inspecting the board and by probing with an oscilloscope, a volt meter, or a logic analyzer. After diagnosis, technician 225 enters diagnostic infoπnation into computer terminal 2435, connected to network 21 15, for transmission to data collection program 10035, described in connection with Fig 10A et seq.

Fig. 4 shows another aspect of testing section 1 100 Programming station 2100 includes an IBM compatible PC having processor 2010, random access memory 2150, disk memory 2105 for storing programs and data, and network interface 2110 Programming station 2100 also includes a user interface having a CRT display 120 and a mouse input device 4125.

Processor 2010 executes programs 2015 stored in memory 2150, to generate test programs for electrical station 2130, vision station 2200, and x-ray station 2300 Processor 2010 sends the generated test programs to stations 2130, 2200, and 2300 through network interface 2110. Processor 2010 also generates an uncovered defect ("escape") list, allowing inspector 245 at manual inspection station 2400 to focus on possible defects not adequately covered by any of stations 2130, 2200, and 2300

Processor 2010 receives defect reports from manual diagnostic/repair station 2430

In the data structures shown throughout the drawings, dotted lines represent a reference, such as a pointer, between one element and another These references are not necessarily direct memory address pointers Instead, more generally, each reference is a data entity, stored in association with one (referencing) element, that enables a processor to find a related (referenced) element. To physically address the referenced element, the processor may subject the reference to various translations or mappings

Fig 5 shows data structures in testing system 1 100, with solid lines representing a data flow between elements. "Panel" database 31 10 includes a list of "designators" for board 100 and the electrical interconnection between designators. A "panel" includes one or more circuit boards manufactured on a common substrate. Panel database 31 10 may include X-Y location information for electrical or optical access to a particular component, and may include X-Y location information for the component itself.

Technique generation rules 3120 control whether a particular technique will be inserted into a program. A "technique" is a type of instruction executable by a station. Table 1 below illustrates the organization of rules 3120.

In this application, a "designator" corresponds to the term "reference designator," a term commonly used to refer to a specific part on a specific printed circuit board type. As will be apparent from the description below, however, a technique performed for a particular designator name tests circuit board structure in addition to the part associated with the designator name, as interconnection to the part are also tested.

ELECTRICAL Shorts [condition set 1 ]

ELECTRICAL Resistance [condition set 2]

ELECTRICAL_OpensXpress [condition set 3]

ELECTRICAL Capacitance [condition set 4]

ELECTRICAL Inductance [condition set 5]

ELECTRICAL_Transistor [condition set 6]

ELECTRICAL Diode [condition set 7]

OPTICAL_Wrong [condition set 8]

OPTICAL Damaged [condition set 9]

OPTIC AL_Missing [condition set 10]

OPTICAL Orientation [condition set 11]

OPTIC AL Skew [condition set 12]

OPTICAL SolderJoint [condition set 13]

OPTIC AL Theta [condition set 14]

XRAY S older Joint [condition set 15]

ELECTRICAL OpensXpress [condition set 16]

OPTICAL Wrong [condition set 17]

ELECTRICAL_Orientation [condition set 18]

TABLE 1

Each row in Table 1 is a rule that controls whether a particular technique will be generated for a particular designator. In general, multiple rules may correspond to a single technique; a single technique may have a set of rules. The left column designates a particular technique to be performed on a particular station. Electrical station 2130 executes the electrical techniques ELECTRIC AL Resistance, ELECTRICAL_OpensXpress, ELECTRICAL Capacitance, ELECTRICAL Inductance, ELECTRICAL_Transistor, and ELECTRICAL Diode Each of these electrical techniques includes an identification of a first pin on station 2130, through which station 2130 measures a current from the board 100 being tested. Each of these electrical techniques also includes identification of a second pin on station 2130, through which station 2130 supplies an electrical measurement signal Thus, station 2130 measures an electrical characteristic associated with a particular designator This characteristic may be the characteristic of a part associated with the designator.

ELECTRIC AL Shorts is a technique that takes an identifier for a group of nets on the circuit board. In the prefeπed system, panel database 31 10 comes with a default identifier called WHOLE_BOARD, which identifies all nets on the board The ELECTRICAL_Shorts technique performs an impedance test between nets to ensure that nets are not shorted together.

The ELECTRICAL_Resistance, ELECTRICAL_Caρacitance, and ELECTRICAL Inductance techniques measure impedances using an AC signal source

The ELECTRICAL Diode technique is a discrete diode test to detect the presence and proper orientation of a reversed biased PN junction

The ELECTRICAL Transitor technique performs the processing of two ELECTRICAL Diode techniques to test the PN junctions between the base and collector and between the base and emitter. Alternatively, ELECTRICAL Transitor test may be a veta test

The ELECTRICAL_OpensXpress technique uses capacitive coupling to measure the capacitor formed by the lead frame of a device package and a test probe placed on top ofthe package. The package material acts as an insulator between the probe and the lead frame (Opens Xpress is a mark used by GenRad Inc to describe the type of test referred to here)

The ELECTRIC AL Orientation technique employs a probe placed on top ofthe package, sends a signal through the probe, and detects the respective signals at each lead ofthe device under test. The device lead connected to the package exterior should have the larger signal, thereby indicating the orientation ofthe device

Optical station 2200 executes the optical techniques. OPTICAL Wrong, OPTICAL_Damaged, OPTICAL Missing, OPTICAL Drientation, OPTICAL Skew, OPTICAL_Solder Joint, and OPTICAL Theta Each of these optical techniques includes x-y coordinates specifying a portion ofthe optical image, of board 100, to be processed by station 2200. Each optical technique also includes image data for an image to be recognized in the specified portion, and a code specifying the type of processing to be performed For example, the OPTICAL_Theta technique attempts to recognize the image of a certain structure, such as a resistor package, within the specified image portion, and measures the orientation ofthe package relative to a nominal axis. In other words, each optical technique contains coordinates specifying a portion ofthe image of board 100 (a portion of the received radiation reflected from board 100), and contains image data corresponding to an image to be recognized

The OPTICAL Wrong technique performs an optical character recognition (OR) on the label printed on the device package.

The OPTICAL_Damaged, OPTICAL Missing, OPTICAL_Orientation, OPTICAL Skew, and OPTIC AL_Theta techniques each attempt to recognize the image of a package and detect the orientation and position ofthe package relative some nominal position

In other words, optical station 2200 operates by applying a wave from a wave source (lamps 2232), through a space between lamps 2232 and board 100, to board 100, optical station 2200 operates by applying electromagnetic radiation, in the form of ambient light and light from lamps 2232 to board 100. Optical recognizer 2236 receives some ofthe radiation (visible light) reflected from board 100. Optical station 2200 executes an optical technique by correlating image data, in the technique, with the technique-specified portion ofthe received radiation reflected from board 100.

X-ray station 2300 executes an x-ray technique X-RAY_Solder Joint This x-ray technique includes x-y coordinates specifying a portion of an x-ray image, of board 100, to be processed by station 2300. This x-ray technique also includes image data for an image to be recognized in the specified portion, and a code specifying the type of processing to be performed. This x-ray technique attempts to recognize a specified structure, such as a pattern of solder corresponding to a well-formed solder connection for a certain type of package. In other words, the X-RAY_SolderJoint technique contains coordinates specifying a portion of the image of board 100 (a portion ofthe received radiation passed through board 100), and contains image data corresponding to an image to be recognized

In other words, station 2300 operates by applying radiation, using x-ray source 2332, to board 100. Station 2300 receives some ofthe applied radiation (x-rays) that passes through board 100, using detector 2334. Station 2300 executes the X-RAY_Solder Joint technique by coπelating image data, in the technique, with the technique-specified portion of the received radiation passed through board 100

The right column of Table 1 specifies the conditions under which the corresponding technique is inserted into a test program. Each condition set in the right column is essentially an expression for evaluation by program generator 5100. Some variables that may appear in a condition set are summarized below:

DPM (Defects Per Million) is equal to a sum of selected defect statistics associated with the designator being processed. The defect statistics associated with the designator include statistics having the same package type and board side as the designator, as described in connection with Fig. IOA et seq. below. The selected defect statistics will be for those defects covered by the technique associated with the rule(see Table 5 below)

PACKAGE_TYPE is equal to the type of package ofthe part corresponding to the designator presently being processed. Possible values of PACKAGE TYPE include FLAT PACK, GRID-ARRAY, CYLINDER, VERTICAL SURFACE-MOUNT, LONG-FORM HORIZONTAL, IN-LINE, DIP 18, DIP 10, DIP 16, CCI 56, DRLY-12, SOT23F, and LED2

PINS is equal to the number of interface contacts on the package of the part corresponding to the presently processed designator. Depending on the type of package, an interface contact may be a pin, a lead, a pad, or a ball.

PITCH is equal to the pitch between pins on the package ofthe part coπesponding to the presently processed designator.

BOARD SIDE is equal to TOP if the part resides on the top ofthe board or BOTTOM if the package resides on the bottom ofthe board.

DATASHEET_TYPE is equal to a certain field of an entry, in the datasheet library, corresponding to the presently processed designator, as shown in Table 7, below Some possible values of DATASHEET TYPE include C, R, L, IC.

For example, Table 2 shows [condition set 3] for the ELECTRIC AL OpensXpress technique:

(PIN _ COUNT > = 24) AND (BOARD _SIDE = TOP)

TABLE 2 In Table 2, PIN_ COUNT is equal to the number of pins in a package associated with a particular "designator," and BOARD SIDE is equal to TOP if the package resides on the top ofthe board or BOTTOM if the package resides on the bottom ofthe board. A "designator" identifies a structure on a circuit board, as described in more detail below

Table 3 below shows [condition set 14] for the OPTIC AL THETA technique (PACKAGE_TYPE= LONG FORM, AXIAL, 2) AND (BOARD SIDE = TOP)

TABLE 3 In Table 3, PACKAGE TYPE is the name of an entry in package type library 61 10. Thus, generator 5100 will generate the techniques OPTICAL Theta (C_2025), OPTICAL Theta (C_2030), OPTICAL_Theta (R_2035), and OPTICAL Theta (R_2040), because the designators C 2025, C 2030, R 2035, and R 2040 each have an associated part that satisfies the conditions of Table 3

Table 4 below shows [condition set 4] for the ELECTRICAL_Capacitance technique (DATASHEET_TYPE = C) AND (DPM>750)

TABLE 4

In Table 4 , DPM (defects per million) represents defects statistics for the package type ofthe part associated with a particular designator. To process this rule, program generator 5100 inserts the ELECTRICAL Capacitance technique into test program 21 10 for any designator having both an entry in datasheet library 6015 for which the type field is C, and a package type and board side for which the sum of defects detectable by the ELECTRICAL_Capacitance technique occurs at a rate greater than 750 per million. Evaluation ofthe DPM variable will be described below in more detail in connection with Table 8.

Processor 2010, and one ofthe programs 2015, act as program generator 5100 Program generator 5100 reads database 31 10 and rules 3120, and generates program 21 10 for optical station 2230, generates program 2115 for electrical station 2130, and generates program 2120 for x-ray station 2300. Program generator 5100 conditionally generates a certain technique depending the corresponding condition set in rules 3120, and on the board description in database 31 10. Defect-technique table 3115 associates a technique with a set of defects, as shown in

Table 5:

TECHNIQUE FAULT GENERIC DEFECT CERTAINTY

ELECTRICAL Shorts Short Etch Short 100%

Solder Short 100%

Mod Wire Misconnected 100%

ELECTRICAL Resistance Short Etch Short 100% Solder Short 100%

Value Wrong Component 100%

Tolerance Bad Component 100%

Open Missing Component 100% Open Track 100% Insufficient Solder 100% Solder Hole/Crack/Void 100%

ELECTRICAL_Capacitance Short Etch Short 100% Solder Short 100%

Value Wrong Component 90%

Tolerance Bad Component 95%

Open Missing Component Open Track 100% Insufficient Solder 100% Solder Hole/Crack/Void 100%

ELECTRICAL_Orientation Polarity Misoriented Component 80%

ELECTRICAL Inductance Short Etch Short 100% Solder Short 100%

Value Wrong Component 100%

Tolerance Bad Component 100%

ELECTRICAL Diode Value Wrong Component 100% Missing Component 100%

Tolerance Bad Component 100%

ELECTRICAL Transistor Value Wrong Component 100% Missing Component 100%

Tolerance Bad Component 100%

ELECTRICAL OpenXpress OpenPin Insufficient Solder 100% Lifted Lead 100% Bent Pin 100% Open Track 100%

Open Missing Component 100%

Orientation Misoriented Component 100%

OPTICAL_Wrong Wrong Component Wrong Component 100%

OPTIC AL Damaged Damaged Board Damaged 100%

OPTICAL Missing Missing Missing Component 100%

OPTICAL_Orientation Orientation Misoriented Component 50%

OPTICAL Skew Offset Misoriented Component 100%

OPTICAL SolderJoint Bad Solder Bad Solder 100%

OPTICAL Theta Rotated Misoriented Component 100%

XRAY SolderJoint Bad Solder Bad Solder 100%

TABLE 5 In Table 5, the left column designates a technique, the second column designates possible results, called "faults," the technique can generate, and the third column designates a set of generic defects associated with a particular fault. Thus, defect-technique table 31 15 relates a defect to a technique by way of a fault. In Table 5, the fourth column designates a certainty that the technique will detect a particular defect This certainty may be displayed with a report of defect coverage for a particular designator It is presently preferred that Table 5 be initialized with a certainty of 100% for all defects Subsequently, analysis of process history, including defect data and the techniques that detected the defect, can cause a particular certainty to be revised downward

Program generator 5100 generates defect tables 51 10 for a plurality of designators in panel database 3110 The possible defects for a designator include problems with a particular part associated with the designator and problems with the connection ofthe part

Program generator 5100, in response to the contents of table 31 15, updates defect tables 5110 to record how a technique, generated for a particular designator, relates to one or more defects

Fig 6 shows panel database 31 10 in more detail Panel database 31 10 includes information for each designator including whether the part corresponding to the designator is on the top or bottom ofthe circuit board In database 3110, each designator also has a list of possible defects, described in more detail below in connection with Fig 7 In database 31 10, each designator also includes references for associating the designator with a part More specifically, each entry in panel database 31 10 includes a reference into package type library

6010, thereby identifying the package type ofthe part associated with the designator Each entry in package type library 6010 may also include pin pitch information or coordinate information for the package leads, as show for the package name DIP 18 in Table 6 below

Package Name DIP 18

Description

Origin Units Height Pitch

Center mils 0 2 100

Nun nber of Leads 18

Leai i name Lead XLead Y

1 075 0

2 175 0

3 275 0

4 375 0

5 475 0

6 575 0

7 675 0

8 775 0 9 875 0

10 875 3 1 1 775 3 12 675 3 13 575 3 14 475 3 15 375 3 16 275 3 17 175 3 18 075 3

TABLE 6

Each entry in panel database 31 10 also includes a reference into datasheet library 6015, thereby identifying the circuit associated with the part Table 7 below shows the library entry for the SO datasheet

Datasheet Name SO

Description

Guard Type U Datasheet Types IC

Number of Signals 14

Signal Name Enable

END] (pin 1)

Edge Flags Digital-Input-Chip Select

DATA[l] (pin 2)

Edge Flags Digital-Input

Q[l] (pin 3)

Edge Flags Digital-Output-Tπstate

EN[2] (pin 4)

Edge Flags Digital-Input-Chip Select

DATA[2] (pin 5)

Edge Flags Digital-Input

Q[2] (pin 6)

Edge Flags Digital-Output-Tπstate

GND (pin 7)

Edge Flags Power - Power Low

Q[3] (pin 8)

Edge Flags Digital-Output-Tristate DATA[3] (pin 9)

Edge Flags: Digital-Input

EN[3] (pin 10)

Edge Flags: Digital-Input-Chip Select

Q[4] (pin l l)

Edge Flags: Digital-Output-Tristate

DATA[4] (pin 12) Edge Flags: Digital-Input

EN[4] (pin 13)

Edge Flags: Digital-Input-Chip Select

VCC (pin 14) Edge Flags: Power

TABLE 7

Thus, in the preferred system, a designator identifies a structure on board 100 The structure may include a part having a certain package type and circuit. The structure may also include an electrical interconnection between the part and the board 100 For example, when station 2100 executes the technique ELECTRIC AL Resistance (R 2040), station 2100 measures the resistance between the two fixture pins connected to board 100: the resistance of a path including both resistor 2040 and circuit board wires between these fixture pins and resistor 2040.

In Fig. 6, and in other figures and tables of this application, many data items and references have been omitted for clarity of explanation.

Fig. 7 shows an aspect of program generator 5100 and tables 51 10 in more detail Each dotted line in Fig. 7 represents a double (bidirectional) reference. Program generator 5100 writes double reference 7010 for relating the bad component defect for C 2030 to the ELECTRICAL_Capacitance C 2030 technique in program 21 15. In other words, dotted line 7010 represents both a reference from the ELECTRICAL Capacitance C 2030 technique to the bad component defect for C 2030, and a reference from the bad component defect for C_2030 to the ELECTRICAL Capacitance C_2030 technique

Program generator 5100 also writes double reference 7015 for relating the wrong component defect for C_2030 to the ELECTRIC AL Capacitance C 2030 technique, thereby writing a relationship between a two defects and one ofthe techniques Program generator 5100 also writes double reference 7020 for relating the MISORIENTED COMPONENT defect for C_2030 to the OPTICAL Orientation C_2030 technique in program 21 10, and writes double reference 7025 for relating the misoriented component defect for C 2030 to the ELECTRICAL_Orientation (C_2030) technique in program 21 15, thereby writing a relationship between one defect and two techniques Similarly, generator 5100 writes relationships between other designators (not shown in Fig 7) and possible defects

To generate Tables 51 10, generator 5100 generates respective defect tables for each component, using the respective "possible defects" data from panel database 31 10 Subsequently, as generator 5100 generates techniques, generator 5100 reads Table 5 to determine when to write a reference in a certain defect table to a certain generated technique Along with the reference to a technique, generator 5100 also writes the corresponding certainty, read from Table 5, into table 51 10

Thus, tables 51 10 store a relationship between a two defects and one ofthe techniques, and stores a relationship between one defect and two techniques Similarly, table 51 10 writes relationships between other designators (not shown in Fig 7) and possible defects

In other words, the defects in Table 5 are essentially a first signal and the "possible defects" in panel database 3110 are essentially a second signal Table 5 stores, for each technique type, the first signal representing a defect type detectable by execution ofthe technique. Panel database 31 10 stores the second signal representing possible defects board 100. Generator 5100 generates a plurality of instructions for testing of board 100, and generates, responsive to the first and second signals, a reference (a third signal) representing a possible defect detectable by execution of one the plurality of instructions The possible defects data in panel database 31 10 is a function of the part corresponding to the designator (a function ofthe package type and data sheet corresponding to the designator) The possible defect data is oriented by part because, although defect statistics are organized by package type, as described in more detail below, the possible defects for a part are a function of both package type and the circuit within the part For example, although both a resistor and a capacitor may have the package type LONG FORM AXIAL, 2, an electrolytic capacitor can be mounted on a board backwards, thereby having the misoriented component defect A resistor with this package type, however, cannot have the misoriented component defect.

Fig 8 shows another data flow within testing section 1 100 Processor 2010, and another one ofthe programs 2015, act as program manager 61 15 After completion of program generation, program manager 61 15 reads defect table 2105 and compiles a report of a defect coverage for designator C 2030 This report allows the user to modify the technique generation rules 3120, using technique editor 5200, to ensure appropriate defect coverage for each designator.

Generator 5100 sends a list of "escapes," defects that remain uncovered, to manual inspection station 2400

Fig 9 shows a processing, performed by program generator 5100, to generate programs 21 10, 21 15, and 2120 Program generator 5100 selects a first rule from technique rules 3120 (step 9010) Program generator 5100 then selects a first designator from panel database 3110. (step 9020) Generator 5100 then determines whether the conditions for the presently selected rule are satisfied for the presently selected designator (step 9030) If the conditions are satisfied, generator 5100 inserts a technique for the designator into one of programs 21 10, 21 15, or 2120 (step 9032) If there are designators remaining to be processed for the present rule (step 9035), generator 5100 selects the next designator (step 9040) and processing proceeds to step 9030. If there are no designators remaining to be processed for the present rule (step 9035), generator 5100 determines whether there are rules remaining to be processed (step 9050). If there are rules remaining to be processed, generator 5100 selects the next rule (step 9080) and processing proceeds to step 9020.

In other words, disk memory 2105 and random access memory 2150 are each electronic memories that store rules 3120 and other data processed by programming station 2100. Each rule 3120 corresponds to a respective technique type, and each rule 3120 may contain a variable (such as DPM, for example) Memories 2105 and 2150 also store panel database 3110, datasheet library 6015, package type library 6010, and DPM data 10040 (discussed in more detail below). Package type library 6010 may have common pin count data for first and second parts, the first part having a first circuit configuration and the second part having a circuit configuration different from the first circuit configuration For example, designator C 2025 and C 2030 correspond to different parts, as they have different entries in datasheet library 6015, but have a common entry in package type library 6010 The entry in package type library 6010 has pin count information for the package.

Processor 2010 and one of the programs 2015 together act as program generator 5100 Program generator 5100 receives Panel database 3110, which contains a description of a circuit assembly. Program generator 5100 then generates, based on the database 31 10, test program 2110 for testing the circuit assembly by performing steps 9030 and 9032, a plurality of times for each rule.

Steps 9030 and 9032 act to conditionally generate an instruction for test program 21 10, depending on a value of a variable in one ofthe OPTICAL technique rules.

Similarly, steps 9030 and 9032 act to conditionally generate an instruction for test program 21 15, depending on a value of a variable in one ofthe ELECTRICAL technique rules For example, steps 9030 and 9032 conditionally generate ELECTRICAL OpenXpress (a type of instruction) for a particular designator depending on whether the package associated with the designator has a pin count of greater than 24 (depending on a package configuration ofthe part associated with the designator). To determine the pin count, generator 5100 accesses a record, in package type library 6010, associated with the designator being processed Figs. IOA, 10B, and IOC show another aspect of testing system 1 100 Over a period of time, program executor 10020, in electrical station 2130, tests a plurality of circuit boards 110. Circuit board 1 10 has a different collection of parts than circuit board 100, and has a different interconnection between parts than circuit board 100. Circuit board 1 10, however, has some package types in common with circuit board 100.

Executor 10020 tests a circuit board by executing techniques in test program 2110. When execution of a particular technique results in a fault, executor 10020 reads fault-defect map 10010 to translate the fault into list of site defects. A site defect is text describing a problem with the circuit board. Executor 10020 then sends a defect report to data collection program 10035. The defect report includes the designator ofthe technique that produced the fault and one or more site defects corresponding to the fault. For example, if, while testing board 78912345, execution of ELECTRIC AL_CAPACIT ANCE (C 2030) results in the fault OPEN, executor 10020 sends the ASCII text: "BOARD 78912345, C_2030, MISSING COMPONENT or OPEN TRACK or INSUFFICIENT SOLDER or SOLDER

HOLE/CRACK/VOΓD "

After program executor 10020 sends a defect report for a particular board, the board is sent to manual diagnostic/ repair station 2430, where an operator diagnoses the actual defect on the board. Manual diagnostic/ repair station 2430 then sends a defect confirmation report, for the board, to data collection program 10035. For example, station 2430 may send BOARD 78912345, C_2030, OPEN TRACK. Data collection program 10035 processes the report from station 2430 by translating the designator in the report into a package type, by accessing a data object for the designator in panel database 3110, to obtain a reference into package type library 6010. By receiving such reports over time, data collection program 10035 compiles DPM (defects per million) data 10040, which records defect rates for respective package types. Table 8 below shows an organization of DPM data 10040:

DIP 18-TOP-B AD COMPONENT 3 15

DIP 18-TOP-INSUFFICIENT SOLDER 1 1 1

DIP 18-TOP-LIFTED LEAD 518

DIP 18-TOP-MISSING COMPONENT 650 DIP 18-TOP-OPEN TRACK 897 DLP18-BOTTOM-BAD COMPONENT 31 1 DIP18-BOTTOM-LNSUFFICIENT SOLDER 514 DIP18-BOTTOM-LIFTED LEAD 312 DIP18-BOTTOM-MISSING COMPONENT 897 DIP18-BOTTOM-OPEN TRACK 457 INLINE,DUAL, 16-TOP-BAD COMPONENT 213

ΓNLΓNE,DUAL .,, 16-TOP-LNSUFFICIENT SOLDER 517 ΓNLΓNE,DUAL -,, 16-TOP-LIFTED LEAD 31 1 ΓNLΓNE,DUAL .,, 16-TOP-MISSING COMPONENT 957 INLINE.DUAL .,, 16-TOP-OPEN TRACK 1012 ΓNLINE,DUAL .,,16-BOTTOM-BAD COMPONENT 37 ΓNLΓNE,DUAL -,,16-BOTTOM-LNSUFFICIENT SOLDER 556 ΓNLΓNE,DUAL -,,16-BOTTOM-LIFTED LEAD 427 ΓNLINE,DUAL -,,16-BOTTOM-MISSING COMPONENT 312 ΓNLΓNE,DUAL .,, 16-BOTTOM-OPEN TRACK 898 ΓNLΓNE,DUAL .,, 14-TOP-BAD COMPONENT 717 ΓNLΓNE,DUAL .,, 14-TOP-INSUFFICIENT SOLDER 657 ΓNLΓNE,DUAL .,, 14-TOP-LIFTED LEAD 1 12 INLΓNE,DUAL -,,14-TOP-MISSING COMPONENT 131 ΓNLΓNE,DUAL .,, 14-TOP-OPEN TRACK 574 ΓNLΓNE,DUAL .,, 14-BOTTOM-BAD COMPONENT 415 ΓNLΓNE,DUAL .,,14-BOTTOM-LNSUFFICIENT SOLDER 851 ΓNLΓNE.DUAL .,, 14-BOTTOM-LIFTED LEAD 73 ΓNLΓNE,DUAL .,, 14-BOTTOM-MISSING COMPONENT 574 ΓNLLNRDUAL _.,, 14-BOTTOM-OPEN TRACK 131 LONG FORM,AXIAL,2-TOP-BAD COMPONENT 815 LONG FORM,AXIAL,2-TOP-INSUFFICIENT SOLDER 213 LONG FORM,AXIAL,2-TOP-MISSING COMPONENT 75 LONG FORM,AXIAL,2-TOP-OPEN TRACK 75 LONG FORM,AXIAL,2-TOP-BAD SOLDER 51 1 LONG FORM,AXIAL,2-BOTTOM-BAD COMPONENT 205 LONG FORM,AXIAL,2-BOTTOM-INSUFFICIENT SOLDER 37 LONG FORM,AXIAL,2-BOTTOM-MlSSING COMPONENT 307 LONG FORM,AXIAL,2-BOTTOM-OPEN TRACK 15 LONG FORM,AXIAL,2-BOTTOM-BAD SOLDER 51 1

etc

Table DPM Following is an example ofthe calculation ofthe DPM variable for a rule for the ELECTRICAL Capacitance technique and the designator C_2069 Because designator C_2069 has a package type of LONG FORM,AXIAL,2 located on the bottom ofthe board, the last five statistics in Table 8 (205, 37, 307, 15, and 51 1) correspond to designator C_2069 Of these five statistics, only four are detectable by the ELECTRICAL Capacitance technique (205,37,307, and 15), since the defect BAD SOLDER is not detectable by the ELECTRICAL Capacitance technique Thus, the value of DPM for an ELECTRICAL Capacitance rule processing the designator C_2069 is 564 (the sum of 205, 37, 307, and 15)

Because DPM data 10040 affects the triggering of technique generation rules that contain the variable DPM, as described above, program generator 5100 can generate a program to test board 100 using defect data generated by testing board 1 10

Data collection program 10035 can be any program that receives test results and compiles defect data in an appropriate format. Similarly, although it is presently preferred that panel database 31 10 be an object orientated data structure, other structures, such as electrical CAD (computer aided design) data, may be employed

Fig. 10B shows defect data processing performed by optical station 2200 Program executor 10120 executes techniques in program 21 15 to receive and process a light image reflected from circuit board 110. When a technique generates a fault, program executor 10120 reads fault-defect map 101 10 to generate a defect report and send the defect report to data collection program 10035.

Fig. 10C shows defect data processing performed by x-ray station 2300 Program generator 10220 executes test program 2120 to receive x-rays passed through circuit board 110 and processed the received x rays. When execution of a technique in program 2120 generates a fault, program executor 10220 reads fault - defect map 10210 to generate a defect report and send the defect report to data collection program 10035

In other words, the preferred system tests boards 1 10 (a plurality of first circuit assemblies), to generate DPM data 10040. Subsequently program generator 5100 receives panel database 31 10 containing a description of board 100 (a second circuit assembly) Generator 5100 generates, based on database 31 10, program 21 15 (a first test program for testing the second circuit assembly), by performing the following steps a plurality of times for one ofthe electrical technique rules: writing a value in the DPM rule variable, using DPM data 10040; and conditionally generating a technique for program 21 15, depending on the value of DPM. Generator 5100 also generates, based on database 31 10, program 21 10 (a second test program for testing the second circuit assembly), by preforming the following steps a plurality of times for one ofthe optical technique rules: writing a value in the DPM rule variable, using DPM data 10040; and conditionally generating a technique for program 21 10, depending on the value of DPM.

As described above, DPM data 10040 includes a plurality of statistics, each ofthe boards 100 (second plurality of circuit assemblies) includes a plurality designators (structures). The step of generating, in the previous paragraph, includes step 9040 (selecting one ofthe designators); and selecting, from DPM data 10040, at least one statistic corresponding to the package type ofthe selected designator. The writing step, in the previous paragraph, includes the step of: writing a value into the DPM variable based on the selected statistic.

Thus, the preferred system coordinates test program generation, for multiple stations, to promote the most cost effective techniques for each defect on a circuit assembly. The preferred system thus optimizes defect coverage while minimizing programming costs.

Fig. 11 shows an organization of fault - defect map 10010 in electrical station 2130. When technique execution generates a fault, program executor 10020 locates an entry for the fault in list 1 1100. The entry for the fault contains a reference into generic defect list 1 1200. Generic defect list 1 1200 contains references into site defect list 1 1300

Fault-defect map 10010 is the product of processing performed on programming station 2100. More specifically, editor 5200 has a screen interface that allows the user to create the data in site defect list 1 1300. Editor 5200 also allows the user to adjust the references in generic defect list 1 1200, to complete the mapping of faults to site defects.

The combination of lists 1 1 100, 1 1200, and 1 1300 is essentially a two layer mapping of faults to site defects. This two layer mapping allows the user to customize the site defect report to a particular site (factory) without having to define the relatively complicated mapping of faults to defect types. In other words, the mapping of generic defects to site defects will tend to be 1-to-l. The more complicated mapping of faults to generic defects can be provided by the manufacturer of programming station 2100.

Other data organizations shown in this application are also the result of processing performed on station 2100. In general, the station provides the user with screen interfaces that allow the user to create data structures and to conveniently make associations between data structures. For example, station 2100 provides a screen allowing the user to enter new designator names into the panel database. Subsequently, the station presents a screen displaying a list of designators, a list of package types, and a series of buttons allowing the user to associate a designator with a package type

In summary, electrical station 2130 executes, at a first location, test program 21 15 by applying an electrical current to one ofthe circuit boards 100 and receiving an electrical cuπent from the circuit board 100. Optical station 2200 executes, at a second location different from the first location, test program 21 10 by applying light to board 100 and receiving some ofthe applied light reflected from board 100, and x-ray station 2300 executes, at a third location different from the first and second locations, test program 2120 by applying x-rays to circuit board 100 and receiving some ofthe x-rays that have passed through circuit board 100

Thus, the preferred system limits unnecessary test program complexity, by inhibiting the generation of certain types of test instructions for certain parts. To determine whether to generate an instruction for a particular part, the system evaluates an expression having a value dependent on selected defect statistics collected for a variety of parts. The selected statistics are for those parts sharing certain attributes for the particular part under consideration. These shared attributes include package type and package location (board side).

Additional advantages and modifications will readily occur to those skilled in the art The invention in its broader aspects is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or the scope of Applicants' general inventive concept.

Claims

1. In a system including an electronic memory, a first plurality of circuit boards and a second plurality of circuit boards, a method comprising the step of testing the first plurality of circuit boards, to generate defect data, writing the defect data into the electronic memory, generating a test program by reading the defect data from the electronic memory, and testing the second plurality of circuit boards by executing the test program

2. The method of claim 1 wherein the defect data includes a plurality of statistics and the system further includes a plurality of instruction types, and a plurality of rules each corresponding to one ofthe instruction types, each rule having an expression having a value dependent upon one ofthe statistics, and the step of generating includes the steps of selecting one ofthe rules; evaluating the expression corresponding to the selected rule, and conditionally generating the instruction corresponding to the selected rule, depending on a result ofthe evaluating step.

3. The method of claim 2 wherein each ofthe second plurality of circuit boards includes a plurality of structures, and the generating step further includes the steps of selecting one of the structures, selecting, from the plurality of statistics, a statistic corresponding to the selected structure, and the evaluating step includes the step of evaluating the expression using the selected statistic

4. The method of claim 3 wherein the step of selecting a statistic includes the step of selecting a statistic corresponding to a package type corresponding to the selected structure.

5. The method of claim 3 wherein the step of selecting a statistic includes the step of selecting a statistic corresponding to a location on the circuit board ofthe selected structure

6. The method of claim 3 wherein the step of selecting a statistic includes the step of selecting a statistic coπesponding to a board side on the circuit board ofthe selected structure.

7. A system comprising: an electronic memory; means for testing a first plurality of circuit boards, to generate defect data, means for writing the defect data into the electronic memory; means for generating a test program by reading the defect data from the electronic memory; and means for testing a second plurality of circuit boards by executing the test program.

8. The system of claim 7 wherein the means for testing a first plurality of circuit boards includes means for generating defect data including a plurality of statistics, and the generating means includes a plurality of rules each corresponding to an instruction type, each rule having an expression having a value dependent upon one ofthe statistics, means for selecting one ofthe rules; means for evaluating the expression corresponding to the selected rule to produce an evaluation result; and means for conditionally generating an instruction ofthe type corresponding to the selected rule, depending on the evaluation result.

9. The system of claim 8 wherein each ofthe second plurality of circuit boards includes a plurality of structures, and the generating means further includes means for selecting one ofthe structures, means for selecting, from the plurality of statistics, a statistic corresponding to the selected structure, and the evaluating means includes means for evaluating the expression using the selected statistic.

10. The system of claim 9 wherein the means for selecting a statistic includes means for selecting a statistic corresponding to a package type corresponding to the selected structure.

11. The system of claim 9 wherein the means for selecting a statistic includes means for selecting a statistic corresponding to a location on the circuit board ofthe selected structure.

12. The system of claim 9 wherein the means for selecting a statistic includes means for selecting a statistic corresponding to a board side on the circuit board ofthe selected structure