Browse Prior Art Database

Improving Tensile Strength of Multiple Reflowed Solder Joints

IP.com Disclosure Number: IPCOM000088903D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Shah, AS: AUTHOR [+2]

Abstract

It has been found that a module which goes through multiple reflows, for example, because of chip replacements on the modules, the tensile strength drops to very low values. This causes the chips to fall off the substrate when subjected to any indirect or direct impact loading. It has also been found that these multiple reflows cause an increase in electrical resistance of the solder ball interconnections.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 1

Improving Tensile Strength of Multiple Reflowed Solder Joints

It has been found that a module which goes through multiple reflows, for example, because of chip replacements on the modules, the tensile strength drops to very low values. This causes the chips to fall off the substrate when subjected to any indirect or direct impact loading. It has also been found that these multiple reflows cause an increase in electrical resistance of the solder ball interconnections.

It has been found that the following process overcomes the above problems:
(1) Preclean with a normal cleaning process any module which has gone through chip replacement and has degraded pull strength due to multiple reflows. (2) Flux every chip on the substrate. This can be accomplished by using a dropper or any other mechanism which allows control of quantities of flux. The drop of flux which is diluted is placed on the side of the chip and, by capillary action, the flux is drawn under the chip and completely envelops the solder pads. (3) Reflow the module through the chip joining furnace. (4) Clean the module with normal flux cleaning process.

The above process is effective for increasing the tensile strength of the solder joints and decreasing the electrical resistance thereof over solder connections on multiple reflowed modules.

1