The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 27, 1996
Filed:
Oct. 23, 1995
Nobuhiko Tada, Ushiku, JP;
Naoki Miyanagi, Ibaraki-ken, JP;
Yoshiaki Shimomura, Ibaraki-ken, JP;
Shigeyuki Sakurai, Ibaraki-ken, JP;
Shinya Okumura, Ibaraki-ken, JP;
Yoshinari Nagano, Ibaraki-ken, JP;
Hitachi Construction Machinery Co., Ltd., Tokyo, JP;
Abstract
In a method for forming a lead frame (1) from a metallic plate, a metallic plate (11) is first etched to form outer leads (4) and outer portions (3b) of inner leads of the lead frame (1). Inner portions (3a) of the inner leads (3) are then laser-cut under the condition that a joint portion (7) is left so as to interconnect the inner leads (3) at their distal ends. Mechanical surface treatment and chemical surface treatment are then carried out to remove dross (10), spatters (9) and oxide films deposited during the laser cutting. Inner areas of the inner leads (3) connected to respective terminals of a semiconductor chip are then plated with gold to form plated terminal portions (3A). Subsequently, the region of the lead frame other than the outer leads (4) is coated with a protective film for solder plating and the outer leads (4) are plated with solder. The joint portion (7) left at the distal ends of the inner leads (3) is then cut off by laser cutting so that the inner leads (3) are separated from one another, thereby forming a final lead frame pattern. The protective film for solder plating is then removed, followed by washing and drying. The inner leads (3) are prevented from being curved due to thermal deformations with the laser cutting, resulting in highly accurate processing.