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Browse Prior Art Database

Solder Decal with Improved Yield and Utility

IP.com Disclosure Number: IPCOM000112387D
Original Publication Date: 1994-May-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Imken, RL: AUTHOR

Abstract

Disclosed is a design for a solder decal which provides more ruggedness in handling, higher yield, and less susceptibility to bump consolidation at reflow. Also described is a process for producing such a decal.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 62% of the total text.

Solder Decal with Improved Yield and Utility

      Disclosed is a design for a solder decal which provides more
ruggedness in handling, higher yield, and less susceptibility to bump
consolidation at reflow.  Also described is a process for producing
such a decal.

      Solder decals are an effective means of transferring a
controlled amount of solder to a printed circuit carrier [1-3]  Two
difficulties encountered in the production and application of solder
decals are retention of solder bumps on the decal surface during
manufacture and transfer to a carrier, and inadvertent consolidation
of adjacent solder bumps during reflow.

      As shown in Fig. 1, a photoimageable solder mask is applied to
the metal substrate which will serve as the carrier for solder bumps.
The solder mask is photoimaged to produce cavities which represent
the mirror image of the circuit carrier sites to which the solder
will be applied.  A photoresist is then applied to the part and
imaged with the same pattern as shown in Fig. 2.  Next, solder is
electroplated in the cavities formed by the solder mask and
photoresist (Fig. 3).  The photoresist is then stripped from the part
yielding a solder decal which has protruding bumps surrounded by a
permanent solder mask at their base (Fig. 4).  The advantages of this
approach are:

1.  Solder bumps, reinforced at their base, are much less likely to
    be dislodged from the metal substrate during processing.

2.  The solder mask inhib...