Browse Prior Art Database

Tape Structure for Controlled Solder Attachment

IP.com Disclosure Number: IPCOM000119810D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 74K

Publishing Venue

IBM

Related People

Kang, SK: AUTHOR [+2]

Abstract

Disclosed is a new beam structure for tape automated bonding (TAB) and flex used in solder interconnection. To make successful solder joints, control of solder melting and freezing is critical. Insufficient melting of solder leads to poor solder joints of low pull strength, while an extended processing can easily cause solder wicking along the leads. Because solder joint formation mainly deals with the liquid- state reaction, the bonding process is sensitive to each process parameter.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 55% of the total text.

Tape Structure for Controlled Solder Attachment

      Disclosed is a new beam structure for tape automated
bonding (TAB) and flex used in solder interconnection.  To make
successful solder joints, control of solder melting and freezing is
critical.  Insufficient melting of solder leads to poor solder joints
of low pull strength, while an extended processing can easily cause
solder wicking along the leads.  Because solder joint formation
mainly deals with the liquid- state reaction, the bonding process is
sensitive to each process parameter.

      Here, an improved beam structure is proposed, with which an
optimum solder joint can be obtained  with a larger window of
processing parameters.  The basic idea of the proposed structure is
to provide a solder 'dam' in the tape structure by various means.
The figure schematically shows a typical tape design used for
controlled solder attachment, where gold-plated copper beams are
supported by a polyimide layer.  In this diagram, the cantilever
beams are extended about 25 mil from the polyimide window and the
beams are about 4 mil wide.  The hatched area in the figure, a band
of 4 to 5 mil wide, serves as solder dam, which locates approximately
10 mil away from the tip of leads.  The solder dam area can be formed
by heating locally using a focused high-energy beam of electrons,
ions or laser.  The reacted band area possibly consists of
gold-copper alloy, copper oxide or their mixtures.  In case of
solder- or tin-p...