Metal working – Method of mechanical manufacture – Assembling or joining
Patent
1980-07-07
1981-08-18
Walton, Donald L.
Metal working
Method of mechanical manufacture
Assembling or joining
29576S, 29591, H01L 2150
Patent
active
042838398
ABSTRACT:
A carrier tape (20) is provided for assembling components to make semiconductor devices. The tape (20) is made from soft, copper foil (21) and eliminates a plastic substrate (12) of the prior art. Patterns (27) containing clusters (24) of inner leads (28) and (30) are accurately formed into tape (20) for bonding to chips (52). Patterns (27) also contain precisely located sprocket holes (22) for indexing the tape (20) for chip and lead bonding.
Tape (20) is indexed for bonding the free ends (36) of inner leads (28) and (30) to pads (54) of chip (52). Then tape (20) is indexed for bonding fixed ends (34) of leads (28) and (30) to stiff outer leads (86).
Leads (28) and (30) in cluster (24) are deformed into a precise bell-like shape called a "bug" with chip (52) riding horizontally on top of the bell. Bugging develops flexural and tensile stresses and bonding causes thermal stresses in leads (28) and (30). Such stresses can shift or twist bug (51); warp the structural margin (26) and holes (22) of tape (20), and they can distort adjacent lead clusters (24) on tape (20).
One or more stress relief sites (39) are provided in leads (28) and (30) to uniformly control such stresses. Sites (39) advantageously prevent stresses from being transmitted outside cluster (24). Also sites (39) aid in deformation of leads (28) and (30) to form bug (51).
Tape (20) contains a high density of lead clusters (24) per linear foot of web (21). Costly plastic substrates (12) are eliminated. More precise registration of leads occurs at bonding. And good bonding improves thermal cycling performance of assembled devices. Also proper bugging assures good posture of chip (52) on top of bug (51). And good bugging reduces likelihood of short circuiting in the assembled devices.
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Lyman, Special Report: Film Carriers Star in High-Volume IC Production, Electronics, Dec. 25, 1975.
Houseweart G. W.
Walton Donald L.
Western Electric Co. Inc.
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