Browse Prior Art Database

Stencil Aperture Design for Tombstone and Solder Ball Reduction

IP.com Disclosure Number: IPCOM000123756D
Original Publication Date: 1999-Apr-01
Included in the Prior Art Database: 2005-Apr-05
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Cook, MK: AUTHOR [+2]

Abstract

Disclosed is a solder paste stencil aperture design for reducing both solder balls and chip component tombstoning in electronic card assembly.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 61% of the total text.

Stencil Aperture Design for Tombstone and Solder Ball Reduction

   Disclosed is a solder paste stencil aperture design for
reducing both solder balls and chip component tombstoning in
electronic card assembly.

   Sub-optimal pad design for 0603 chip component packages
has been found to result in "tombstoning" of the components after
solder reflow.  Placement of surface-mount chip components,
particularly when no-clean solder paste is used in assembly, has
been found to result in solder balls after solder reflow.  Both
conditions reduce assembly yield and solder balls have been found to
break free and cause failure of completed and shipped product.

   Previous stencil treatments documented address either
condition, but not both.  Combining an aperture design reported to
reduce tombstoning with a treatment used to reduce solder balls
results in a new aperture design to address both.  This aperture can
be used for components larger than 0603 chip packages.

   The amount of solder paste deposited on component pads is
significantly reduced where it would be directly under the chip
component during placement.  By using a "pinch point" design, where
the solder is deposited only as narrow triangles along the outside
edges of the component soldering surfaces and solder is not deposited
in a triangle located at the inner edges of the pad pair, the
likelihood of tombstoning is decreased because the volume of solder
paste remains relatively comparable for each end of the ch...