LEAD FRAME SYSTEM

Abstract

A lead frame strip with corrugated saw street metal where the corrugated saw street metal is comprised of a partial thickness of the lead frame strip metal. A lead frame strip with corrugated saw street metal where the corrugated saw street metal is comprised of a half thickness of the lead frame strip metal.

Claims

1. A lead frame strip with corrugated saw streets comprised of corrugated metal where a portion of the corrugated saw streets are attached to a lead frame strip support tape.

2. The lead frame strip of claim 1, further comprising a plurality of lead frames coupled to the corrugated saw streets by tie bars wherein a thickness of the lead frames are a full lead frame strip metal thickness and wherein a thickness of the corrugated metal and the tie bars are a partial lead frame strip metal thickness.

3. The lead frame strip of claim 1, further comprising a plurality of lead frames coupled to the saw streets by tie bars wherein a thickness of the lead frames are a full lead frame strip metal thickness and wherein a thickness of the corrugated metal and the tie bars are a half lead frame strip metal thickness.

4. The lead frame strip of claim 1, further comprising a plurality of lead frames coupled together with the corrugated saw streets.

5. The lead frame strip of claim 4, wherein the lead frames contain one IC chip pad and contain a plurality of wirebond pads.

6. The lead frame strip of claim 4, wherein the lead frames contain a plurality of wirebond pads and do not contain an IC chip pad.

7. The lead frame strip of claim 5, wherein the IC chip pad and the plurality of wirebond pads are formed of full lead frame strip metal thickness and are attached to the lead frame strip support tape.

8. The lead frame strip of claim 1, wherein the lead frame strip is composed of copper or a copper alloy.

9. A lead frame strip, comprising: lead frame strip support tape; a plurality of corrugated saw streets comprised of corrugated metal with a partial thickness of the lead frame strip metal and where a first portion of the corrugated saw street is separated from the lead frame strip support tape by a void and where a second portion of the corrugated saw street is attached to the lead frame strip support tape. a plurality of lead frames coupled on all sides to corrugated saw streets; and a plurality of wirebond pads within each lead frame comprised of a full thickness of lead frame strip metal and attached to the lead frame strip support tape and coupled to the corrugated saw streets.

10. The lead frame strip of claim 9, wherein the partial thickness of the Corrugated saw streets is 30% to 60% the thickness of the lead frame strip metal thickness.

11. The lead frame strip of claim 9, wherein the partial thickness of the Corrugated saw streets is about half the thickness of the lead frame strip metal thickness.

12. The lead frame strip of claim 9, further comprising an IC chip pad comprised of a full lead frame strip metal thickness and coupled to the corrugated saw streets and electrically isolated from the wirebond pads.

13. The lead frame strip of claim 12, wherein the IC chip pad is coupled to the corrugated saw streets with tie bars where the tie bars are comprised of a partial thickness of lead frame strip metal.

14. The lead frame strip of claim 9, further comprising tie bars with a partial thickness of the lead frame strip metal and wherein the tie bars couple the wirebond pads to the corrugated saw streets.

15. The lead frame strip of claim 9, wherein the lead frame strip is comprised of copper or a copper alloy.

Description

DESCRIPTION OF THE VIEWS OF THE DRAWINGS

[0022] FIG. 1 (Prior art) is a plan view of a lead frame strip.

[0023] FIGS. 2A and 2B (Prior art) are a plan view of a lead frame and an IC chip pad with 4 package leads mounted on the lead frame.

[0024] FIG. 2C (prior art) is a cross section along the cut line in the plan view in FIG. 2B.

[0025] FIGS. 3A and 3B (Prior art) are a plan view of chip on lead IC package with 6 package leads.

[0026] FIG. 3C (prior art) is a cross section along the cut line in the plan view in FIG. 3B.

[0027] FIG. 4A (Prior art) is a plan view of a lead frame strip with 4 lead frames.

[0028] FIGS. 4B, 4C, 4D and 4E (Prior Art) are cross sections along cut lines in the plan view in FIG. 4A.

[0029] FIG. 5A (Prior art) is a plan view of a lead frame strip with 4 lead frames.

[0030] FIG. 5B (Prior art) is a plan view of two lead frames that are separated by sawing along the saw streets of FIG. 5A.

[0031] FIGS. 5C, 5D, 5E, and 5F (Prior Art) are cross sections along cut lines in the plan view in FIG. 5B.

[0032] FIG. 6 is a plan view of a lead frame strip with 9 lead frames and with embodiment corrugated saw streets.

[0033] FIGS. 7A, 7B, and 7C are cross sections along cut lines through embodiment saw streets in the plan view in FIG. 6.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0034] Embodiments of the disclosure are described with reference to the attached figures. The figures are not drawn to scale and they are provided merely to illustrate the disclosure. Several aspects of the embodiments are described below with reference to example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide an understanding of the disclosure. One skilled in the relevant art, however, will readily recognize that the disclosure can be practiced without one or more of the specific details or with other methods. In other instances, well-known structures or operations are not shown in detail to avoid obscuring the disclosure. The embodiments are not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with the present disclosure.

[0035] An example improved lead frame strip 600 is illustrated in FIGS. 6 and 7. The portion of a lead frame strip 600 shown in FIG. 6A consists of 9 lead frames 606 (FIG. 6B) connected together by half thickness metal vertical saw streets 602 and half thickness metal horizontal saw streets 604

[0036] As shown in the cross section FIG. 7B taken along cut line 622 through a horizontal corrugated saw street 604 in FIG. 6A and FIG. 7C taken along cut line 620 through a vertical corrugated saw street 602, the half thickness metal in the corrugated saw streets, 602 and 604, have corrugations so that a portion of the half thickness metal in the corrugated scribe streets, 602 and 604, is attached to lead frame support tape 112. First portions 610 of the embodiment half thickness metal corrugated saw streets, 602 and 604, are separated from the first lead frame support tape 112 by voids 114 and second portions 612 of the embodiment half thickness metal corrugated saw streets, 602 and 604 are attached to the surface of the first lead frame support tape 112. Corrugation of the half thickness metal saw streets, 602 and 604, substantially improves the mechanical stability of the lead frame during wire bonding and during molding compound injection. The added strength of the lead frame improves yield by reducing the number of ball bonds that delaminate from the bond pads on the chip or that delaminate from the package leads due to stress caused when the lead frame flexes.

[0037] The corrugation of the half thickness metal in the saw streets, 602 and 604, adds significant strength and rigidity to the corrugated saw streets, 602 and 604, with little increase in the amount of metal used to manufacture the lead frame strip 600 and with little increase in the amount of metal that is sawed through when separating the packaged die. This keeps the cost of the lead frame manufacture and also avoids excessive wear and replacement of saw blades.

[0038] The embodiments are illustrated using lead frames with four wirebond pads. The idea is generic and may be used to improve lead frame strips with lead frames with any number of wire bond pads.

[0039] While various embodiments of the present disclosure have been described above, it should be understood that they have been presented by way of example only and not limitation. Numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the disclosure. Thus, the breadth and scope of the present disclosure should not be limited by any of the above described embodiments. Rather, the scope of the disclosure should be defined in accordance with the following claims and their equivalents.