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Novel Method and Apparatus for Minimizing Plating Stub Impact in Wire Bond Packages with High Resistance Coating

IP.com Disclosure Number: IPCOM000175662D
Original Publication Date: 2008-Oct-17
Included in the Prior Art Database: 2008-Oct-17
Document File: 3 page(s) / 267K

Publishing Venue

IBM

Abstract

In this invention, proposed is a novel method and apparatus for minimizing the plating stubs impact with high resistance conductor coating to mitigate the quarter-wave length resonance which is detrimental to high-speed data transmissions.

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Novel Method and Apparatus for Minimizing Plating Stub Impact in Wire Bond Packages with High Resistance Coating

Signal conductors in wirebond packages are formed through electroplating traces extended to the edge of the substrates leaving unwanted open conductor stub in the middle of signal transmission path after manufacturing. As frequency increases, signal performance is greatly impacted by reflections from those open stubs. A quater-wave length resonance is particularly detrimental in high speed data transmissions.

Current Art:

In current industry practice, those trace stubs are removed through additional etching process, which causes a substantial cost increase for wirebond packaging and not to mention decrease in product yield depending on the depth of the etching and package characteristics.

Plating stubs are added to signal interconnects and extended to the edge of the package to form conductor traces in wirebond packages during manufacturing. Figure 1 shows the screen shots of board files showing the plating stub.

Figure 1: Screen capture of a wire bond package conductor layer design

Plating stubs are left open at the end of the package after manufacturing. Open stubs cause unwanted high speed signal transmission nulls near ΒΌ wavelength frequencies. In Figure 2 the black curve shows the insertion loss on a link having a plating stub. The resonance due to the plating stub is clearly visible in the 2.5GHz region. This particular link ran 5cm in length on a organic package and 13cm in length on a standard FR-4 card. The stub length was 1.5cm.The insertion loss is pl...