Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame
Reexamination Certificate
2002-06-12
2004-04-20
Williams, Alexander O. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
C257S775000, C257S696000, C257S698000, C257S690000, C257S669000, C257S672000
Reexamination Certificate
active
06724070
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to lead frames, and more particularly to a lead frame having finely pitched leads, and the method of making.
BACKGROUND OF THE INVENTION
Conventional fine-pitched lead frame designs rely upon lead separation in the X-Y plane to prevent electrical shorting between adjacent leads. In some designs, an insulating tape is placed across the leads to stabilize them and to hold them in place. However, as lead pitch (distance between the center lines of the leads) gets finer, and the number of leads increase, other means must be used to prevent shorting of lead.
Fine pitched leads have been formed with the lead end adjacent to the semiconductor die reduce in thickness and tapered to provide narrower leads as the leads converge toward the semiconductor die. A similar lead is disclosed in U.S. Pat. No. 5,454,905.
SUMMARY OF THE INVENTION
The invention is a lead frame that has leads formed in two levels during the etching process in which the lead frame is formed. A lead frame form, or continuous strip of lead frame material, is coated on two sides with a photo resist material. Each photo resist coated side is patterned to define leads on the lead frame. The lead patterns on the two sides are offset from each other so that patterns on one side of the lead frame material alternate with the patterns on the other side of the lead frame material. Both sides of the photo resist patterned lead frame material are etched to a depth exceeding one-half the thickness of a lead. The photo resist material is then removed. The resulting lead frame has leads that are in two levels, each level having leads offset by a lead width from the other level, but with an effective zero distance between leads horizontally.
REFERENCES:
patent: 4308339 (1981-12-01), Lindberg
patent: 4329642 (1982-05-01), Luthi et al.
patent: 4411719 (1983-10-01), Lindberg
patent: 5221428 (1993-06-01), Ohsawa et al.
patent: 5230144 (1993-07-01), Ootsuki
patent: 5403466 (1995-04-01), West et al.
patent: 5420758 (1995-05-01), Liang
patent: 5424577 (1995-06-01), Szuki et al.
patent: 5466966 (1995-11-01), Ito
patent: 5530281 (1996-06-01), Groover et al.
patent: 5683943 (1997-11-01), Yamada
patent: 5864173 (1999-01-01), Fogelson
patent: 5945259 (1999-08-01), Kim
patent: 6008542 (1999-12-01), Takamori
patent: 59-88855 (1984-05-01), None
patent: 63-299369 (1988-12-01), None
patent: 404094564 (1992-03-01), None
patent: 6-45497 (1994-02-01), None
patent: 11-330132 (1999-11-01), None
Abbott Donald C.
Fritzsche Robert M.
Brady III Wade James
Tung Yingsheng
Williams Alexander O.
LandOfFree
Fine pitch lead frame does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fine pitch lead frame, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fine pitch lead frame will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3272009