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Browse Prior Art Database

Method to Prevent Bowing and Cracking for Semiconductor Packages

IP.com Disclosure Number: IPCOM000106404D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Ikeda, H: AUTHOR [+3]

Abstract

Disclosed is a method to prevent bowing and cracking of semiconductor memory packages applying A-Wire Technology, which has a construction of leads on chip using double sided adhesive tape.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 81% of the total text.

Method to Prevent Bowing and Cracking for Semiconductor Packages

      Disclosed is a method to prevent bowing and cracking of
semiconductor memory packages applying A-Wire Technology, which has a
construction of leads on chip using double sided adhesive tape.

      Semiconductor memory packages have a characteristic of body
bowing (bending) caused by the difference of thermal expansion of its
component as lead/chip/tape/mold.  The repeated stress generated by
this bowing causes package cracking problem.  Especially for TSOP
(Thin Small Outline Package), this phenomenon easily happens because
of its small mold plastic volume as shown in Fig. 1.

      Currently, to minimize this problem, the position of
lead-chip-tape is designed to be in the center of the mold body (T1 =
T2).  But as shown in Fig. 2, (1) bowing and cracking still happens
around the no chip-tape area, because the mold thickness from the
lead (T3) is different.  On the other hand, this lead-chip-tape
position should be changed in case of applying another lead frame
material, which has different thermal expansion ratio.  And,
solder/flux problems exist under the TSOP body which has stand-off
dimension of 0.1 mm, and the inspection for these defects is not
available.

      To avoid these problems, in the proposed scheme, (1) reduce the
bottom half mold thickness at no chip-tape area, and (2) add round
area to the mold body to reduce stress concentration as shown in Fig.
3.  This method...