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I/O Lead Isolation to Prevent Solder Joint Fatigue

IP.com Disclosure Number: IPCOM000050082D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Darrow, RE: AUTHOR [+2]

Abstract

MC substrates are input/output (I/O) pin limited. To increase the size of the MC substrate to overcome this problem, it has been proposed to use I/O pin spring clips which attach to the substrate edges and are soldered to small solder pads. Due to the difference in thermal expansion between the substrate and the spring clip molding, cyclic shear stresses are applied to the solder joint which reduce the reliability of the solder joint. To isolate the spring clip from being affected by these cyclic shear stresses, a new arrangement is proposed.

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I/O Lead Isolation to Prevent Solder Joint Fatigue

MC substrates are input/output (I/O) pin limited. To increase the size of the MC substrate to overcome this problem, it has been proposed to use I/O pin spring clips which attach to the substrate edges and are soldered to small solder pads. Due to the difference in thermal expansion between the substrate and the spring clip molding, cyclic shear stresses are applied to the solder joint which reduce the reliability of the solder joint. To isolate the spring clip from being affected by these cyclic shear stresses, a new arrangement is proposed.

As shown in Fig. 1, the ceramic substrate 1 is provided with slots 2 around its periphery which are located opposite the solder pads 3. Fig. 2 shows the spring clip lead 4 located within the slot 2 and soldered to the solder pad 3. To complete the isolation, adhesive 5 has been applied to the slot to fill in any clearances between the spring clip and the edges of the slot. The purpose of this adhesive is to capture the lead to the ceramic. The resulting effect is to force the lead to physically move at the rate of expansion of the ceramic and not be affected by the expansion rate of any molding material or any other organic strip that may be used to hold the leads on location to each other. The final result is that the solder joint between the lead and the solder pad does not experience any shear stresses.

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