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Microencapsulated Activator for Solder Paste

IP.com Disclosure Number: IPCOM000122308D
Original Publication Date: 1991-Nov-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 49K

Publishing Venue

IBM

Related People

Antonie, CH: AUTHOR [+3]

Abstract

Disclosed is a method for enhancing solder paste activator function. By microencapsulating the activator (flux), solder paste constituents can be kept separated until contact is required in the reflow process. The solder paste shelf life is increased significantly, and a wider range of chemical activity levels can be accommodated.

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Microencapsulated Activator for Solder Paste

      Disclosed is a method for enhancing solder paste activator
function.  By microencapsulating the activator (flux), solder paste
constituents can be kept separated until contact is required in the
reflow process.  The solder paste shelf life is increased
significantly, and a wider range of chemical activity levels can be
accommodated.

      Solder paste primarily consists of solder particles, a liquid
carrier to evenly disperse them, and an activator which chemically
reacts with, and transports, the oxide phases at reflow temperatures.
These chemical reactions are temperature sensitive, and at prolonged
room temperature exposure, the solder paste system can lose overall
activity and develop unwanted substances in the formulation.  Most
solder pastes are transported and stored at low temperatures, and
have a limited working life after thawing.

      Through a polymerization/emulsification process, the activator
can be microencapsulated in globules.  This eliminates contact with
the solder paste metallurgy which prevents the chemical reactions.
At reflow temperatures the globules melt and release the activator
which initiates the desired fluxing action.

      One embodiment of this method includes dissolving the activator
(an acid) with a monomer (an acid chloride) in a solvent.  A second
monomer (a diamine) is dissolved in a different solvent which is
immiscible with the first solvent.  The two solutio...