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Controlled Solder Dam Structure by Special Evaporation-Gun Design

IP.com Disclosure Number: IPCOM000039060D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Koopman, NG: AUTHOR [+2]

Abstract

A method is described to control terminal design and wettable area of braze/solder for a multilayer ceramic substrate pin braze joint. A schematic cross-section is shown in Fig. 2. Pin 15 is attached to a multilayer terminal pad 13 on the multilayer ceramic substrate 6 by a braze 8. The braze is restricted to the central region of the terminal pad since the periphery of the pad is not wettable by braze. This particular structure is fabricated in an evaporator by positioning the evaporation sources such that the evaporant will automatically create a wetting barrier at the terminal pad edges. Referring to Fig. 1, the solder (or braze) dam can be obtained by placing the Au source at the center line of the evaporation dome and the other sources Ti (or Cr) 2 and Cu 3 off-center.

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Controlled Solder Dam Structure by Special Evaporation-Gun Design

A method is described to control terminal design and wettable area of braze/solder for a multilayer ceramic substrate pin braze joint. A schematic cross-section is shown in Fig. 2. Pin 15 is attached to a multilayer terminal pad 13 on the multilayer ceramic substrate 6 by a braze 8. The braze is restricted to the central region of the terminal pad since the periphery of the pad is not wettable by braze. This particular structure is fabricated in an evaporator by positioning the evaporation sources such that the evaporant will automatically create a wetting barrier at the terminal pad edges. Referring to Fig. 1, the solder (or braze) dam can be obtained by placing the Au source at the center line of the evaporation dome and the other sources Ti (or Cr) 2 and Cu 3 off-center. The evaporants are deposited on the ceramic substrate 6 through the opening 4 of a suitable metal mask 5. Shadowing by the edge of the mask 5 inherently causes the structure shown in Fig. 2 wherein a non-wettable surface 12

(Image Omitted)

at the periphery of the BSM (Basic Storage Module) structure 13 is created. Cu vias 7 are part of the ceramic structure. The complete evaporated multilayer structure, as shown in Fig. 2, comprises the braze or solder joint 8 having an underlying top layer of Au 9 which is wettable; Ti (or Cr) non-wettable layer 10; with Cu layer 11 and the Ti (or Cr) layer 10A completing the structure.

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