Browse Prior Art Database

Standoff Tab Design

IP.com Disclosure Number: IPCOM000041282D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Agarwala, BN: AUTHOR [+3]

Abstract

A problem of braze splashing has been observed during joining of Au plated KOVAR* tabs on ceramic modules. A high degree of yield loss is associated with this problem. In this approach a process of tab joining is proposed to overcome the splashing problem. The braze splashing is believed to be caused by the pressure exerted on the liquid braze due to a lack of appropriate dimensional control of the substrate-to-tab gap with respect to the available liquid volume. Fig. 1 shows a typically used tab-joining fixture design. As shown in the diagram, the standoff pins maintain a gap between the substrate and the top of the pin nest. The Au-Sn preform of nominal height is used for joining.

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Standoff Tab Design

A problem of braze splashing has been observed during joining of Au plated KOVAR* tabs on ceramic modules. A high degree of yield loss is associated with this problem. In this approach a process of tab joining is proposed to overcome the splashing problem. The braze splashing is believed to be caused by the pressure exerted on the liquid braze due to a lack of appropriate dimensional control of the substrate-to-tab gap with respect to the available liquid volume. Fig. 1 shows a typically used tab-joining fixture design. As shown in the diagram, the standoff pins maintain a gap between the substrate and the top of the pin nest. The Au-Sn preform of nominal height is used for joining. Thus, the dimensional tolerance of the tab and of the substrate camber should be such that a 6-mil gap between the tab surface and the substrate is maintained during the joining. The liquid splashing is believed to be caused by a lack of tab dimensional tolerance and an inherent substrate camber, resulting in the squeezing of the liquid during joining. Another view of the tab design is shown in Fig. 2. In this technique it is proposed to use tabs with both ends extended and bent by a fabrication process allowing a substrate-to-tab gap of 6Å 0.5 mil. The proposed tab design is shown in Fig. 3; the ends of the tab rest freely on the substrate surface away from the metallized surface. The proposed tab design ensures a minimum gap between the substrate and the tab surf...