Metal fusion bonding – Process – With shaping
Patent
1990-10-11
1993-08-10
Rosenbaum, Mark
Metal fusion bonding
Process
With shaping
228102, 228170, B23K 2000
Patent
active
052341500
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of manufacturing a clad material to be used for a lead frame of a semiconductor integrated circuit such as a flat package, and in particular it relates to a method of manufacturing a spotwise partial clad material composed of a metal substrate material such as and Fe-Ni alloy or the like and metal foil pieces of a brazing material, Al, Cu or the like, each having a determined size, the metal foil pieces being pressure-welded on the substrate material at determined intervals.
BACKGROUND ART
Recently, it has become increasingly desirable to make devices having semiconductor integrated circuits small in size, and flat packages have become frequently used in such integrated circuits.
As a lead frame for a flat package, for example, a construction as shown in FIG. 2 is known. In particular, the lead frame (3) which is to be provided with terminal parts on all four edges thereof needs to have metal-coated parts for improving the weldability, for example, as coated with a metal of Ag-brazing material, Al, Cu or the like, on the parts to be wire-bonded.
For providing such metal-coated parts, heretofore a lead frame as worked has been subjected to (a) a vapour-deposition method or (b) a plating method. However, a method having a higher producibility is desired because the noted methods have some drawbacks. In particular, in accordance with the vapour-deposition method (a), not only expensive plants are necessary but also the parts which are not to be coated with metals need to be masked. Therefore, the vapour-deposition speed is slow and the producibility is low. On the other hand, in accordance with the plating method (b), metals usable in the method are limited as some metals cannot be plated, and the thickness of the metal layer to be efficiently plated is also limited.
In order to previously provide the metal-coated parts, there is a method of spotwise applying the metal-coated parts (2) onto the lead frame material (1) with high accuracy, as shown in FIG. 1, followed by press-working or etching the spotwise metal-coated material.
For instance, a technique in which an Al or Ag foil is stripewise provided on a lead frame-forming strip material by pressure-welding or rolling and thereafter the unnecessary parts are removed mechanically or chemically so as to form the desired metal foil-coated spots on the strip material has been proposed (Japanese Patent Publication No. 59-1078). However, in accordance with the proposed technique, the yield of the coated metal is poor, the working efficiency is low as the necessary parts to be metal-coated must be masked when removing the unnecessary parts, and provision of the desired metal foil-coated spots, each having the desired size, at a desired pitch with high accuracy is difficult.
Although it is possible to lap metal foil pieces, each having a determined size, over a substrate material having a determined extremely short length at the determined positions to form a spotwise partial clad material having a determined length by pressure-welding or rolling, it is impossible to cut a metal foil to be coated into pieces, each having a determined size and a determined length, with high accuracy so as to attach the thus-cut metal foil pieces to a continuous long substrate material strip as unwound from a coil of the strip, with highly accurately adjusting the positions of the substrate material strip to be coated with the metal foil pieces, thereby to continuously tack the pieces on the strip at a determined pitch. For this reason, it is said that industrial mass-production of a spotwise partial clad material is impossible.
On the other hand, formation of a lead frame by tacking Al foil pieces on a lead frame material by spot-welding followed by cladding the pieces-tacked material has been proposed (Japanese Patent Publication No. 60-227456). However, the method of highly accurately adjusting the positions of the lead frame material to be coated with the metal pieces at a determined pitch for continuously tacking the
REFERENCES:
patent: 4887343 (1989-12-01), Ohishi
Nemoto Shin
Okamoto Jun
Okazaki Susumu
Yamamoto Kazuhiro
Miner James
Rosenbaum Mark
Sumitomo Special Metal Co.
LandOfFree
Method of manufacturing spotwise partial clad material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of manufacturing spotwise partial clad material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of manufacturing spotwise partial clad material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1720231