Method of stabilizing lead dimensions on high pin count surface

Details Method of stabilizing lead dimensions on high pin count surface Method of stabilizing lead dimensions on high pin count surface

1990-11-29

1992-03-24

Chaudhuri, Olik

Fishing, trapping, and vermin destroying

437220, 29827, 29840, 29841, 2281801, 439876, H01L 2156

Patent

active

050988638

ABSTRACT:
A method for packaging integrated circuits for surface mount which provides advantages over prior art techniques by providing increased strength to integrated circuit package leads for increased lead dimensional stability to accommodate the finer pitches needed for high density integrated circuits, i.e., with leadcounts of 200 or more leads. The method is for producing a plastic integrated circuit package that allows for transfer molding using a non-conductive, permanent dambar. The invention includes the resulting leadframe. The method produces a package having embedded leads (on both sides and in between) in a double sided film/adhesive combination which increases lead dimensional stability and which does not require removal before device mounting. The double sided film/adhesive combination is non-conductive, is able to withstand all the package assembly process steps and is applied before a die is dedicated to a leadframe. The non-conductive film/adhesive combination on both sides of the leadframe performs the function of a dambar which does not require removal before testing and/or device mounting. The film/adhesive combination also functions as a gasket to eliminate flashing during molding. A laminated copper and film/adhesive combination is used as a test ring that matches the leadframe thermal coefficient of expansion and is applied before a die is dedicated to the leadframe. By having the ring segmented instead of one solid piece, forming the leads before trimming them is possible.

REFERENCES:
patent: 4280132 (1981-07-01), Hayakawa et al.
patent: 4835120 (1989-05-01), Mallik et al.
patent: 4859614 (1989-08-01), Sugahara et al.
patent: 4859632 (1989-08-01), Lumbard
patent: 4908337 (1990-03-01), Treffer

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