Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified material other than unalloyed aluminum
Patent
1995-06-07
2000-08-29
Hardy, David
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
257772, 257780, 257781, 257737, 257738, H01L 2348, H01L 2352, H01L 2940
Patent
active
061113212
ABSTRACT:
A two-step masking process is disclosed for forming a ball limiting metallurgy (BLM) pad structure for a solder joint interconnection used between a support substrate and a semiconductor chip. A solder non-wettable layer and a solder wettable layer are deposited on the surface of a support substrate or semiconductor chip which are to be connected. A phased transition layer is deposited between the wettable and non-wettable layers. A thin photo-resist mask defines an area of the solder wettable and phased layers which are etched to form a raised, wettable frustum cone portion. A second mask is deposited on the surface of the support substrate or semiconductor chip, and has an opening concentrically positioned about the frustum cone. Solder is deposited in the opening and covers the frustum cone and the area about its periphery. When solidified, the solder, acting as a mask, is used to sub-etch the underlying solder non-wettable layer thereby defining the BLM pad. When reflowed, the solder beads away from the surface of the solder non-wettable layer to form a ball which securely adheres about the frustum cone.
REFERENCES:
patent: Re27934 (1974-03-01), Merrin et al.
patent: 3392442 (1968-07-01), Napier et al.
patent: 4268849 (1981-05-01), Gray et al.
patent: 5048744 (1991-09-01), Chang et al.
Electronic Packaging & Interconnection Handbook Charles A. Harper, pp. 6.71-6.73.
Clark Jhihan B
Hardy David
International Business Machines - Corporation
Soucar, Esq. Steven J.
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