Browse Prior Art Database

Structure and Method to Increase Softness of Joint and Uniformity of Solder Metallurgy for Testing and Assembly

IP.com Disclosure Number: IPCOM000247706D
Publication Date: 2016-Sep-28
Document File: 2 page(s) / 22K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to utilize a modified single peak reflow process to convert solder from an as-received undercooled microstructure or only a partially grain- like structure to a full grain-like structure in order to modify the solder properties. These modified properties enhance its deformation properties during test and its melting properties during subsequent chip or substrate join.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 51% of the total text.

Page 01 of 2

Structure and Method to Increase Softness of Joint and Uniformity of Solder Metallurgy for Testing and Assembly

Hardness of solder to be tested and the variation of lead free solder metallurgy require modification of testing systems and dictate a greater margin in terms of temperature and dwells at assembly.

For testing of die and substrates, the deformation properties of the solder are important. The properties enable the tested solder to compensate for any co-planarity issues across the probe and solder arrays as well as the parallelism between the two. This impacts the type of probe, quantity of probes, force applied, and/or utilizing only partial coverage of the probes to prevent damaging of the probe substrate or the tested product. In other words, by reducing the yield strength of the solder, it will help extend the allowable probe counts or deduce required probe loads.

For the laminates, especially the chip scale packaging (CSP), the testing characteristics of probe count and force impact the flexing applied to the substrate itself. Either this can limit the pressure applied or how the testing is conducted as outlined above.

For assembly, the variation of the metallurgy of the solder, impacts how and where each individual joint melts. This can lead to partial wetting and variation of assembly forces on some joint locations, while others are still in full solidification state. It is better to have each solder contact to melt uniformly within and have each adjacent solder connection have a uniform melting temperature and time. A lower melting point ultimately leads to a lower initial join temperature and lower overall peak temperature and dwell.

The novel contribution is a method to utilize a modified single peak reflow process to convert solder from an as-received undercooled microstructure or only a partially grain- like structure to a full grain-like structure in order to modify the solder properties. These modified properties enhance its deformation proper...