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Improved Plating and Tooling Technique for the Contactless Electro-Plating of a Probe in a High Density Matrix

IP.com Disclosure Number: IPCOM000039966D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Lorber, HW: AUTHOR [+2]

Abstract

A "cobra" probe (so named because of its shape) is employed to contact individual solder balls used to electrically and mechanically attach a semiconductor device to a substrate. The tip of the probe is coated with chromium to reduce its adherence to the lead-tin solder balls, thereby increasing the service life of the probe. This article concerns improvements in the means used to obtain a uniform plating thickness on the cobra probe tip [*]. By use of the funnel-shaped tool shown in Fig. 1, auxiliary cathode thievingis employed to control the distribution of chromium deposition while achieving a desired uniform plating thickness. The thumbscrew mechanism 1 allows close control of the probe 2 downward travel in this tool.

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Improved Plating and Tooling Technique for the Contactless Electro- Plating of a Probe in a High Density Matrix

A "cobra" probe (so named because of its shape) is employed to contact individual solder balls used to electrically and mechanically attach a semiconductor device to a substrate. The tip of the probe is coated with chromium to reduce its adherence to the lead-tin solder balls, thereby increasing the service life of the probe. This article concerns improvements in the means used to obtain a uniform plating thickness on the cobra probe tip [*]. By use of the funnel-shaped tool shown in Fig. 1, auxiliary cathode thievingis employed to control the distribution of chromium deposition while achieving a desired uniform plating thickness. The thumbscrew mechanism 1 allows close control of the probe 2 downward travel in this tool. As many as 120 cobra probe contacts may be suspended, by the use of this tool, in the chromium plating bath shown in Fig. 2.

(Image Omitted)

The "throwing power" of the chromium anode 3, a measure of the distribution of the electro-deposit on a cathode surface, may be optimized by using the highest current density possible and, to this end, only the very tips 4 of the probes 2 are submerged in the electrolyte 5 of the plating bath. In Fig. 2, it will also be noted that no direct connection exists between the probes and the power supply employed in plating,
i.e., a direct charge does not exist on the probe tips themselves during the pla...