Semiconductor lead frame

• US 5,939,774 A
• Filed: 06/17/1997
• Issued: 08/17/1999
• Est. Priority Date: 06/14/1994
• Status: Expired due to Term

• Current Assignee: Dai Nippon Printing Company Limited
• Original Assignee: Dai Nippon Printing Company Limited
• Inventors: Yamada, Junichi
• Primary Examiner(s): Brown, Peter Toby
• Assistant Examiner(s): POTTER, ROY KARL
• Application Number:
  US08/877,348
• Time in Patent Office: 791 Days
• Field of Search: 257/666, 257/676, 257/669, 257/672
• US Class Current: 257/666
• CPC Class Codes: H01L 21/4828 Etching etching for cleaning without patterning H01L21/4835
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 23/49548 Cross section geometry H01L23/49562 takes precedence
• CPC Class Codes: H01L 24/45 of an individual wire connector
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/00015 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed as prior art
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01078 Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: Y10T 29/49121 Beam lead frame or beam lead device

Abstract

A method for producing a lead frame having outer leads and inner leads, for use in constructing a resin-sealed semiconductor package comprises etching processes for etching a blank. A first resist pattern having a first opening and a second resist pattern having second openings are formed on the first and the second major surfaces of a blank. The first and the second major surfaces of the blank are etched through the first and the second resist pattern by a first etching process using a first etchant to form a first recess corresponding to the first opening and second recesses corresponding to the second recesses in the first and the second major surfaces, respectively. The first recess is filled up with an etch-resistant layer. The second major surface is etched through the second resist pattern by a second etching process using a second etchant so that portions of the blank corresponding to the second openings of the second resist pattern are etched through to form the tips of the inner leads.

Claims

1. A lead frame for a resin-sealed semiconductor package, having outer leads and inner leads with tips and formed by etching a blank;

wherein

the tips of the inner leads have a thickness smaller than that of other portions of the lead frame;

the tip of each inner lead has an upper surface depressed relative to one of the surfaces of each of other portions of the lead frame, and a lower surface flush with other lower surfaces of each of other portions of the lead frame; and

both of the opposite surfaces of the tip of each inner lead have areas greater than the sectional area of the middle portion with respect to the thickness of the tip of the same inner lead; and

the upper surface of the tip of each inner lead is formed by etching the blank to form an etched recess with a flat bottom so that each inner lead has a tip wherein the upper surface of the tip is in a level plane.

2. The lead frame according to claim 1, wherein the thickness of the tips of the inner leads is 1/5 to 1/2 of the thickness of other portions of the lead frame.

3. The lead frame according to claim 1, wherein

both the major surfaces of each outer lead have areas smaller than the sectional area of the middle portion with respect to the thickness of the same outer lead.