EP0963605A2

EP0963605A2 - Improved leadframe structure with locked inner leads and process for manufacturing same

Info

Publication number: EP0963605A2
Application number: EP97953573A
Authority: EP
Inventors: Guiseppe D. Bucci; Paul H. Voisin
Original assignee: GCB Technologies LLC
Current assignee: GCB Technologies LLC
Priority date: 1996-12-19
Filing date: 1997-12-19
Publication date: 1999-12-15
Also published as: WO1998029899A2; WO1998029899A3; JP2001506422A; EP0963605A4

Abstract

An improved leadframe structure and process of manufacturing the same are provided. The leadframe includes a plurality of leads (10) with inner portions (32) extending toward an IC bonding pad (25) within an IC encapsulation area. A polymer structure (80) having a preselected configuration is provided to interlock the inner portions of the leads to prevent lateral, torsional and vertical displacement thereof during the IC packaging process, thus improving yield and reducing packaging cost.

Description

IMPROVED LEADFRAME STRUCTURE WITH LOCKED INNER LEADS AND PROCESS FOR MANUFACTURING SAME

This application is related to Application No. 08/744,520, filed November 5, 1996, for IMPROVED LEADFRAME STRUCTURE AND PROCESS FOR PACKAGING INTEGRATED CIRCUITS, naming as inventors G. D. Bucci and

Paul Voisin, the inventors of the subject matter of the present application, and assigned to the assignee of the present application, GCB Technologies, LLC. The disclosure of that application is incorporated herein by reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the packaging of semiconductor integrated circuits and more particularly to "leadframes" that provide electrical connection between a packaged integrated circuit and the external environment.

2.Background and Related Art

Current leadframe designs used in the packaging of integrated circuits ("ICs") have a number of shortcomings that result in increased costs and reduced yields. A number of such shortcomings are identified and described in related application No.

08/744,520, which is further identified above and incorporated herein by reference. An additional shortcoming of many current leadframe designs is that the inner portion of the leads within the IC encapsulation area and adjacent to the IC mounting pad are free and unsuppoπed. During the packaging process, the unsupported leads are susceptible to displacement or damage. This susceptibility to displacement or damage slows the packaging process, increases the cost and results in reduced yields. The problem is particularly severe in high lead count and fine lead pitch designs, where the leads tend to be very fine and fragile. For example, during the wire bonding process, it is desirable to bond the ends of the connecting wires between the IC and the inner leads as close as possible to the center of the bonding pads on the IC and to the center of the inner leads. Bonding the ends of the connecting wires at the center of the inner leads minimizes the chance of shorting leads, particularly in very fine lead pitch designs. It also maximizes the strength of the bond and minimizes the possibility of lead "roll" in certain very fine lead pitch designs where the leads are formed by differential etching. Such etching results in the top surface of the lead being wider than the bottom surface, which facilitates denser lead packing, but which renders the leads susceptible to torsional displacement, or "rolling" from off- center bonds. Lateral displacement of the leads prior to or during the wire bonding process is a primary cause of off-center bonds.

Because the inner leads are known to be susceptible to such displacement, extensive and expensive measures have been taken to both detect and prevent such displacement. An optical recognition system or Video Lead Locator (VLL) is often used to locate the leads prior to bonding. However, using a VLL to locate the leads typically contributes as much as 30% to the overall process time. Moreover, the VLL system tends to be more successful with stamped leadframes, which tend to have straight leads, than with etched leadframes, which tend to have leads with more rounded features. In some instances, the VLL equipment can become confused by rounded lead features and give false readings, resulting in off-center bonds. Accordingly, the VLL system tends to work less successfully with high lead count, fine lead pitch designs, which are typically etched, than with lower lead count designs, which are typically stamped. Moreover, the VLL equipment tends to be quite expensive.

One known approach to preventing lead displacement during the packaging process has been to apply sections of tape to the inner leads within the encapsulation area. Commonly used tapes include Kapton, made by DuPont, and Upilex, made by Ube Industries. The tape is typically applied on one surface of the leads, usually the top side, under heat and pressure. Unfortunately, however, while the tape is somewhat successful in lessening lateral displacement of the leads, it is largely ineffective in preventing torsional, or vertical displacement. This type of lead shift, resulting in loss of co-planarity, is a very common cause of yield loss at the leadframe level and during handling prior to wire bonding. Another drawback of the tape approach is that if the leads have already been displaced prior to applying the tape, the tape tends to retain the leads in the displaced position. Moreover, even if the tape is properly applied and the leads are not already displaced, the tape is not always effective to prevent displacement during the packaging process.

Yet another drawback of the tape approach is that different leadframe designs, user specifications, and packaging processes will have different requirements insofar as the configuration of the tape is concerned. Each configuration requires relatively expensive machinery and tooling to cut the tape and to place it in the desired location on the leadframe. Still further, the tape itself tends to be quite expensive, often costing more than twice the leadframe metal itself. There is thus a significant need for an improved inner lead support structure to provide more effective protection against lead displacement during the IC packaging process. It would be desirable for the support structure to be easy and inexpensive to apply. It would also be desirable for the structure to be more effective than the currently used tape in preventing not only lateral lead displacement, but also torsional and vertical or non-planar displacement.

It is an object of the present invention to provide a lead support structure which overcomes the shortcomings of known tape structures.

It is a another object of the present invention to provide such a structure which is effective in preventing not only lateral lead displacement, but also torsional and non-planar displacement, thus reducing or eliminating the need for expensive and time consuming VLL equipment and processes.

It is another object of the present invention to provide such a structure that is easy and inexpensive to apply and that is cost effective.

It is yet another object of the present invention to provide such a structure that is compatible with other steps of the overall packaging process and that does not add removal or other extraneous steps to the process.

SUMMARY OF THE INVENTION One aspect of the present invention is an improved leadframe structure and method for manufacturing the same. The improved leadframe structure has a frame, a pad adapted to mount an integrated circuit chip, and a plurality of leads, with inner portions extending toward the pad and outer portions extending toward the frame. The inner portions have surfaces for making electrical connections with the integrated circuit chip. A polymer strucmre interconnects the inner portions of at least some of the leads to help prevent displacement or damage thereof during the packaging process.

Another aspect of the invention is an improved IC package and packaging process using the improved leadframe structure. The improved IC package includes a leadframe having a pad and a plurality of leads. The leads have inner portions extending toward the pad and provide surfaces for making electrical connections with an IC chip. A polymer strucmre interconnects the inner portions of at least some of the leads to prevent displacement or damage during the packaging process. An IC chip is mounted to the pad and a plurality of electrical conductors connect the IC and the leadframe. An epoxy strucmre encapsulates the IC chip, the pad, the electrical conductors and the inner portions of the leads. The outer portions of the leads extend outside the epoxy strucmre. For preventing flashing of the epoxy material during the encapsulation process, the leadframe may include either a traditional dambar strucmre, which must be removed subsequent to the encapsulation process, or a second polymer strucmre, which is incorporated as part of the finished package.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a typical 168 pin leadframe in a quad flat pack configuration with tape applied to the inner leads; FIG. 2 is a graphical illustration in plan of a portion of adjacent inner leads showing a preferred bonding area;

FIG. 3 is a graphical illustration in perspective of a portion of adjacent inner leads showing the application of a tape strucmre thereto;

FIG. 4 is a plan view of a 208 pin leadframe in a quad flat pack configuration with a preferred polymer strucmre according to the present invention interlocking the inner leads;

FIG. 5 is a graphical illustration in cross section of adjacent, relatively square inner leads interlocked with a preferred polymer strucmre according to the present invention; and FIGs. 6a and 6b are graphical illustrations in cross section of adjacent, differentially etched inner leads interlocked with a preferred polymer strucmre according to the present invention, the polymer applied from the top and bottom of the leads respectively. DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT A presently preferred embodiment of an unproved leadframe strucmre according to the invention may be manufactured using known stamping or etching methods or any other suitable method The invention is not limited with respect to the manner m which the leadframe is formed Any suitable material may be used for the leadframe, including such known materials as various copper or nickel alloys Applicability of the invention is not limited by the specific material used for the leadframe

In addition, the leadframe may be formed in essentially any configuration, including presently known quad flat pack (QFP), molded carrier ring (MCR), small outline (SO), chip carrier (CC) or dual in line package (DIP) configurations Applicability of the invention is not limited by the configuration, lead count or lead pitch of the leadframe

An example of a typical leadframe for which the present invention is suitable is shown in FIG 1 The leadframe 10, which is shown in a QFP configuration, includes an outer frame 15 Many hundreds or thousands of such leadframes may be formed from a common strip of material according to known methods, and the outer frame 15 will be common to all leadframes in the same strip, until the individual leadframes are separated The outer frame 15 typically includes one or more placement and location openings 20 All of the functional elements of the leadframe are precisely located relative to these openings 20 to facilitate the precise positioning of the elements during formation of the leadframe and during the IC packaging process The leadframe also includes a pad or paddle 25, on which an IC chip will be mounted, and a plurality of leads 30, in this case 168 of them Each lead 30 has an inner portion 32 adjacent to the pad 25 and an outer portion 34 The inner ends of the leads 30 are unconnected to the frame 15, l e , are free, while the outer ends are connected to and supported by the frame 15 The inner portions 32 near the ends provide points for electrical connection to the IC, once it is mounted on the pad The inner portions 32 and the free ends are typically encapsulated with the IC during the IC encapsulation or molding step The outer portions 34 typically extend outside the IC package to provide a point of electrical connection with external electrical components and circuits A "dambar" strucmre 40 may be provided to interconnect the leads at a point intermediate their inner and outer ends. As described in co-pending related application No. 08/744,520, the primary purpose of the dambar 40 is to serve as a barrier during the molding or encapsulation process to prevent epoxy from escaping the mold and "flashing" onto the outer leads. Secondarily, the dambar provides additional support for the leads to assist in maintaining the relative positions of the leads during the IC assembly process. It is preferred, however, that the leadframe 10 be formed without a dambar and that a polymer strucmre as shown and described in application No. 08/744,520 be provided instead. As described therein, the polymer strucmre provides not only an improved barrier against "flashing" during the IC encapsulation process, but also provides improved support for the leads. Moreover, unlike the dambar strucmre which must be removed following encapsulation, the preferred polymer strucmre is incorporated in the finished package. It should be noted, however, that the present invention is suitable for use with leadframe designs using a dambar strucmre, a polymer structure, a combination of both, or neither.

Referring to FIG. 2, a graphical representation of parts of the inner portions 32 of two adjacent leads 30, including the free ends thereof, are shown in plan. Typically, the width dimension 45 of the leads will be on the order of about 0.006 inches and the inter-lead spacing 50 will be on the order of about 0.0035 inches, at least in many current high lead count designs. A desired wire bonding target area 55 is defined by dimensions 60 and 65 or 70. Dimension 60 extends back from the end of the inner lead 32 adjacent the pad 25 (shown in FIG. 1) along the length of the lead 30 by approximately 0.007 inches or so. Dimension 65 comprises about 50% or so of the width of the lead, symmetrical about the longitudinal center of the lead, and defines the most preferred bonding target area. However, depending on the thickness of the lead and the method used to form it, a somewhat wider dimension 70, comprising up to about 80% of the width of the lead symmetrical about the longitudinal center, may be acceptable. As previously noted, off-center bonds resulting from displacement of the leads 30 prior to the wire bonding step are very undesirable for a variety of reasons, including the potential for "rolling" of the leads, short circuiting of adjacent leads, and poor bonding to the intended lead.

Referring to FIGs. 1 and 3, prior to the present invention, one or more sections of tape 75 might be applied to one surface of the inner portions 32 of the leads 30 in an effort to prevent displacement thereof during the IC packaging process. Typically, a layer of tape 75 having an underlying adhesive layer 80 would be applied directly to a surface of the leads 30. As shown in FIG. 1 , the tape 75 would typically be applied on the inner portions of the leads 30 in the area to be encapsulated with the IC. Where a dambar strucmre 40, as shown in FIG. 1 , was provided, the tape would be applied intermediate the inner free ends of the leads 30 and the dambar strucmre. The tape 75 could be applied as multiple interconnected strips as shown in FIG. 1, or as a single, contiguous piece, depending on the needs and requirements of the particular leadframe configuration and packaging process. As best shown in FIG. 3, however, the tape 75 would cover only one surface of the leads 30. The leads 30 could therefore be displaced either torsionally, by a twisting force, such as an off-center bond, or vertically, resulting in a loss of co- planarity. In addition, although the leads 30 shown in FIG. 3 are in proper position relative to each other, if one or more of the leads 30 were displaced prior to application of the tape 75, the tape 75 would tend to hold the leads in their already displaced positions resulting in problems during the bonding step.

FIGs. 4-6 show a presently preferred embodiment of the present invention which overcomes the various aforementioned shortcomings and problems. According to the present invention, the leadframe 10 is preferably provided with a polymer strucmre 80 which preferably interconnects substantially all of the leads 30. The polymer strucmre 80 may be contiguous, as shown in FIG. 4, or may be one or more discrete sections. The polymer strucmre 80 may be either closed, as shown in FIG. 4, or open on one or more sides or corners. Depending on the design of the leadframe and the needs and requirements of the particular packaging process, the polymer strucmre may be square, as shown, or some other geometry.

The polymer strucmre 80 is preferably formed generally in the area of the inner portion 32 of the leads 30 which will be encapsulated with the IC. This will generally be between the free ends of the inner portions 32 of the leads and the dambar 40, if one is provided as shown, or in a more preferred embodiment, the polymer strucmre that replaces the dambar, as shown and described in the co-pending related application No. 08/744,520.

The polymer strucmre 80 will preferably be encapsulated with the inner portions 32 of the leads 30 and the IC, and will remain a permanent part of the finished IC package. Accordingly, it is preferred for the polymer material used to be electrically and chemically compatible with the epoxy material used to encapsulate the IC. Depending upon the epoxy material to be used, any of the polymer materials identified in the co-pending related application No. 08/744,520 are suitable. In addition to the polymer strucmre 80, the free ends of the inner portions

32 of the leads 30 may be interconnected by one or more interconnection bars 95, if desired, to provide additional support and protection against displacement. These bars will preferably be formed at the time the leadframe is stamped or etched, and may be removed at the same time as the standard pad 25 downset operation, prior to wire bonding. Both the formation and removal of the interconnection structures are well within the skill of those having ordinary skill in the art and further description is unnecessary to a complete understanding of the present invention.

As best shown in FIGs. 5 and 6, the polymer structure 80 preferably interconnects adjacent leads in three dimensions to substantially inhibit displacement laterally, vertically or torsionally. Preferably, the polymer strucmre will be applied to the leadframe after stamping or etching and prior to mounting an IC on pad 25.

A presently preferred process for applying the polymer material to the leads 30 is described in our co-pending related application No. 08/744,520. The leadframe may be placed against a backing plate or other strucmre for support. Pins may be provided to engage the leadframe 's normal locating holes 20 to hold the leadframe in a known, fixed position. The polymer material may then be applied in the desired locations. Unlike the process described in our co-pending related application No. 08/744,520, however, it is generally not necessary to apply the polymer material to both the upper and lower surfaces of the leads in order to substantially achieve the purposes and objectives of the present information. Application of a sufficient volume of polymer material to flow between the leads 90 and on one of the surfaces 85 will generally be sufficient. Complete encapsulation of the leads as shown and described in our co-pending related application No. 08/744,520, can be performed if desired, however. The polymer material may be applied either from the top or bottom of the leadframe. As shown particularly in FIGs. 6a and 6b, when the polymer is applied from the top, polymer material will preferably interconnect the leads on the top surface thereof (FIG. 6a), and when applied from the bottom will preferably interconnect the leads on the bottom surface (FIG. 6b). Another difference from the process described in our co-pending related application No. 08/744,520 is that since the polymer strucmre 80 will not be involved in forming a seal to prevent "flashing" during the IC encapsulation process, the polymer may be completely cured, preferably by ultraviolet light, after application to the leads and prior to encapsulation. However, if it is desired to only partially cure the polymer material prior to encapsulation, the encapsulation process itself may complete the cure. In either event, the curing process and parameters described in co-pending related application No. 08/744,520 are suitable for curing the polymer strucmre 80.

The viscosity of the polymer material may be controlled in the manner described in our co-pending related application No. 08/744,520. The desired width dimension of the strucmre and the depth thereof on the planar surfaces of the leads will depend on the thickness of the leads, the lead pitch and the amount of support desired. Generally, however, it is preferred to provide a sufficient thickness and depth to substantially encapsulate the leads in the strucmre on at least three sides and to inhibit displacement of the leads in at least three directions.

Similarly, whether the polymer is applied from the bottom or the top will depend on the particular leadframe and the packaging process. For example, leadframes formed by stamping tend to have leads 30 with relatively square features, such as shown in FIG. 5. In such cases, it may make little difference whether the polymer material is applied from the top or bottom. However, in the case of leadframes having leads 30 formed by differential etching, as shown in FIGs. 6a and 6b, the leads may be substantially wider at the top surface than at the bottom. In such cases, it can be advantageous to apply the polymer material from the bottom, as particularly shown in FIG. 6b, in order to eliminate the potential for rolling the leads during application of the material. Of course, if additional support is desired, the polymer material may be applied between the leads and to both surfaces thereof, as shown and described in our co- pending related application No. 08/744,520.

Preferably an IC chip is mounted to the pad 25 after the polymer strucmre 80 is applied to the inner portion of the leads 30. Electrically conductive bonding wires are then interconnected between the surfaces 55 of the inner portions of the leads 30 and the IC chip. Many suitable methods and materials are known to those skilled in the art for mounting the IC chip to the bonding pad and for interconnecting the IC chip and the leads. A detailed description thereof is unnecessary to a complete understanding of the present invention.

Following mounting of the IC chip to the pad and interconnection of the IC chip and the leads, the IC and inner portions of the leads are preferably encapsulated in an epoxy package, typically via an epoxy molding process. Many suitable epoxy materials and molding processes are known to those skilled in the art for this purpose and a detailed description thereof is unnecessary for a complete understanding of the present invention. However, in the case of a dambarless leadframe design having a second polymer strucmre in place of the dambar, a preferred molding process is shown and described in our co-pendng related application No. 08/744,520.

The foregoing description of a presently preferred embodiment of the invention is by way of example only and is not intended to be limiting of the scope of the invention. It will be apparent to persons skilled in the art that various changes in materials, designs, dimensions and the like, may be made without departing from the spirit of the invention, the scope of which is intended to be defined solely by the appended claims.

Claims

WHAT IS CLAIMED IS: 1. An improved leadframe strucmre for use in packaging an integrated circuit chip, comprising: a pad for mounting an integrated circuit chip; a frame generally circumscribing said pad; a plurality of leads having inner portions and outer portions, said inner portions extending toward said pad and providing surfaces for making electrical connection with said integrated circuit chip, and said outer portions extending toward said frame; and a polymer strucmre interconnecting the inner portions of at least some of said leads.

2. The leadframe strucmre of claim 1 wherein the outer portions of said leads have outer ends connected to said frame strucmre and the inner portions of said leads have inner free ends adjacent said pad.

3. The leadframe strucmre of claim 1 wherein the inner portions of said leads have inner ends adjacent said pad and at least some of said inner ends are interconnected.

4. The leadframe strucmre of claim 1 wherein said polymer strucmre is a closed strucmre.

5. The leadframe strucmre of claim 1 wherein said leads have a top surface and a bottom surface and wherein said polymer strucmre includes polymer material between adjacent leads and on at least one said surface thereof.

6. The leadframe strucmre of claim 1 wherein said polymer strucmre is annular and interconnects the inner portions of substantially all of the leads.

7. The leadframe strucmre of claim 1 wherein said polymer strucmre comprises a material selected from a group comprising polyamic acids, polyamic esters, poly (amides-imides) acrylates, methacrylates, cyamate esters and epoxies.

8. The leadframe strucmre of claim 7 wherein said material is curable with radiation.

9. The leadframe strucmre of claim 8 wherein said radiation is ultraviolet light.

10. The leadframe strucmre of claim 1 including a dambar interconnecting at least some of said leads intermediate said inner and outer portions thereof.

11. The leadframe strucmre of claim 1 including a second polymer strucmre interconnecting at least some of said leads intermediate said inner and outer portions thereof.

12. Method of manufacturing an improved leadframe strucmre for use in packaging an integrated circuit chip, comprising: forming a leadframe strucmre including: a pad for mounting an integrated circuit chip; a frame generally circumscribing said pad; a plurality of leads having inner portions and outer portions, said inner portions extending toward said pad and providing surfaces for making electrical connection with said integrated circuit chip, and said outer portions extending toward said frame; and providing a polymer strucmre interconnecting the inner portions of at least some of said leads.

13. The method of claim 12 wherein the outer portions of said leads have outer ends connected to said frame strucmre and the inner portions of said leads have inner free ends adjacent said pad.

14. The method of claim 12 wherein the inner portions of said leads have inner ends adjacent said pad and at least some of said inner ends are interconnected.

15. The method of claim 12 wherein said polymer strucmre is a closed strucmre.

16. The method of claim 12 wherein said leads have a top surface and a bottom surface and wherein providing said polymer strucmre includes providing polymer material between adjacent leads and on at least one said surface thereof.

17. The method of claim 12 wherein said polymer strucmre is annular and interconnects substantially all of the leads.

18. The method of claim 12 wherein said polymer strucmre comprises a material selected from a group comprising polyamic acids, polyamic esters, poly (amides-imides), acrylates, methacrylates and epoxies.

19. The method of claim 18 wherein said material is curable with radiation.

20. The method of claim 19 wherein said radiation is ultraviolet light.

21. The method of claim 12 wherein said leadframe strucmre includes a dambar interconnecting at least some of said leads intermediate said inner and outer portions thereof.

22. The method of claim 12 wherein said leadframe structure includes a second polymer strucmre interconnecting at least some of said leads intermediate said inner and outer portions thereof.

23. An improved integrated circuit package, comprising: a leadframe including: a pad for mounting an integrated circuit chip; a plurality of leads having inner portions and outer portions, said inner portions extending toward said pad and providing surfaces for making electrical connection with said integrated circuit chip; and a polymer strucmre interconnecting the inner portions of at least some of said leads; an integrated circuit chip mounted to said pad; a plurality of electrical conductors connected between said integrated circuit chip and said leadframe; and an epoxy strucmre encapsulating said integrated circuit chip, said pad, said electrical conductors and said inner portions of said leads, said outer portions of said leads extending outside said epoxy strucmre.

24. The integrated circuit package of claim 23 wherein said polymer strucmre is a closed strucmre.

25. The integrated circuit package of claim 23 wherein said leads have a top surface and a bottom surface and wherein said polymer strucmre includes polymer material between adjacent leads and on at least one said surface thereof.

26. The integrated circuit package of claim 23 wherein said polymer strucmre is annular and interconnects the inner portions of substantially all of the leads.

27. The integrated circuit package of claim 23 wherein said polymer strucmre comprises a material selected from a group comprising polyamic acids, polyamic esters, poly (amides-imides), acrylates, methacrylates and epoxies.

28. The integrated circuit package of claim 27 wherein said material is curable with radiation.

29. The integrated circuit package of claim 28 wherein said radiation is ultraviolet light.

30. The integrated circuit package of claim 23 including a second polymer strucmre interconnecting at least some of said leads intermediate said inner and outer portions thereof.

31. An improved method for packaging an integrated circuit, comprising: forming a leadframe including: a pad for mounting an integrated circuit chip; a plurality of leads having inner portions and outer portions, said inner portions extending toward said pad and providing surfaces for making electrical connection with said integrated circuit chip; and a polymer strucmre interconnecting the inner portions of at least some of said leads; mounting an integrated circuit chip to said pad; connecting said integrated circuit chip and said leadframe with a plurality of electrical conductors; and encapsulating said integrated circuit chip, said pad, said electrical conductors and said inner portions of said leads within an epoxy strucmre, with said outer portions of said leads extending outside said epoxy strucmre.

32. The method of claim 31 wherein said outer portions of said leads have outer ends, and wherein said leadframe includes a frame strucmre with said outer ends of said leads being connected thereto; and including the step of excising that frame strucmre subsequent to encapsulating said integrated circuit chip.

33. The method of claim 31 wherein said inner portions of said leads have inner ends adjacent said pad, and wherein said leadframe includes a bar interconnecting said inner ends of at least some of said leads; and including the step of excising the interconnection bar prior to connecting said integrated circuit and said leadframe.

34. The method of claim 31 wherein said polymer strucmre is a closed strucmre.

35. The method of claim 31 wherein said leads have a top surface and a bottom surface and wherein said polymer strucmre includes polymer material between adjacent leads and on at least one said surface thereof.

36. The method of claim 31 wherein said polymer strucmre is annular and interconnects the inner portions of substantially all of the leads.

37. The method of claim 31 wherein said polymer strucmre comprises a material selected from a group comprising polyamic acids, polyamic esters, poly (amides-imides), acrylates, methacrylates and epoxies.

38. The method of claim 37 wherein said material is curable with radiation.

39. The method of claim 38 wherein said radiation is ultraviolet light.

40. The method of claim 31 including forming a second polymer strucmre interconnecting at least some of said leads intermediate said inner and outer portions thereof.

41. The method of claim 31 wherein encapsulating the integrated circuit within an epoxy strucmre includes the steps of: providing a mold having a cavity with a predetermined package shape and volume, said mold having an outside edge defining a clamping area; encasing said integrated circuit chip mounted on said leadframe in said mold with said inner portions of said leads within the mold cavity and said outer portions of said leads extending out of the mold cavity; introducing an epoxy material into said mold; and curing said epoxy material.