Browse Prior Art Database

Technique to Prevent Solder Bridging in Dense Array Land Patterns

IP.com Disclosure Number: IPCOM000120455D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 85K

Publishing Venue

IBM

Related People

Potsko, DS: AUTHOR [+2]

Abstract

During wave soldering of square, dense, array land patterns such as a chip C4 land patterns with 5.5 mil metal lands on 10-mil centers, bridging is encountered at the trailing edge of the array (last row to leave the wave). This bridging takes the form of a "blob" of solder in the array area. The bridging cannot be tolerated and must be prevented to allow wave solder processing to deposit solder for surface soldering applications.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Technique to Prevent Solder Bridging in Dense Array Land Patterns

      During wave soldering of square, dense, array land patterns
such as a chip C4 land patterns with 5.5 mil metal lands on 10-mil
centers, bridging is encountered at the trailing edge of the array
(last row to leave the wave).  This bridging takes the form of a
"blob" of solder in the array area.  The bridging cannot be tolerated
and must be prevented to allow wave solder processing to deposit
solder for surface soldering applications.

      As the last row of chip site lands tries to emerge from the
solder wave, the surface tension of the solder tries to restrain the
substrate containing the land pattern from its forward motion.  This
"stretches" the solder as it clings to the C4 lands in the last row
of the chip site (this row of lands is generally parallel to the
solder wave).  As the solder "stretches", a point will be reached
where the strength of the surface tension force is overcome and the
molten solder "curtain" breaks.  When the solder breaks, more solder
than can be normally held by the geometry of the land is pulled back
to the chip site (due to the stretching action).  This results in
solder bridging between lands, and the resultant surface tension
force is overcome and the molten solder "curtain" breaks.  When the
solder breaks, more solder than can be normally held by the geometry
of the land is pulled back to the chip site (due to the stretching
action).  This results in solder bridging between lands, and the
resultant surface tension of this bridged solder now causes the
solder to try to take a spherical shape, and a "blob" or "blobs" of
solder are formed in the chip site. The amount of solder in the
bridging is dependant on how far the substrate has traveled before
the solder curtain breaks. This is a common problem in wave soldering
...