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Browse Prior Art Database

Improved Composition for a Dry Film Soldermask

IP.com Disclosure Number: IPCOM000102604D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 87K

Publishing Venue

IBM

Related People

Day, RA: AUTHOR [+4]

Abstract

The disclosed formulations can be coated in dry film form and vacuum laminated to give conformal soldermasks capable of tenting plated through holes. The coating is photoimagable and survives soldering processes when fully cured.

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

Improved Composition for a Dry Film Soldermask

       The disclosed formulations can be coated in dry film form
and vacuum laminated to give conformal soldermasks capable of tenting
plated through holes.  The coating is photoimagable and survives
soldering processes when fully cured.

      Materials formulated for use as soldermasks must meet a variety
of criteria.  These requirements include final material properties,
such as insulation resistance, resistance to cleaning solvents and
fluxes, and withstanding soldering and rework temperatures.  In
addition, there are material properties critical to the processing of
the soldermask that need to be met.

      In the case of a dry film photoimagable soldermask, properties
such as a good coating quality with few defects, flexibility, good
adhesion to the poly(ethylene teraphthalate) base, and coating as a
tack-free film for contact expose are important.  Process
requirements, such as suitable flow under heat and pressure to give a
good conformal coverage without the final coating being too thin over
the conductor traces, and good image definition for the photoprocess,
are equally important.

      Recently a formulation for a liquid apply cationically curable
epoxy based resist material was disclosed [*].  This material was
subjected to extensive testing and demonstrated excellent final
material properties rendering it useful for a variety of soldering,
assembly, and rework processes. Although the disclosed formulation
had properties suitable for processing it as a liquid apply coating,
preliminary investigation into its usefulness as a dry film showed
that the dried films were too brittle and could not be rolled when
coated on the poly(ethylene teraphthalate) base.

      Several materials were investigated for their ability to
plasticize films of the liquid soldermask [*] without affecting the
other properties.  Two compounds, a cycloaliphatic epoxide
(ERL-4221*) and a polyol (LHT-240*), were found useful in this
application.

      Example 1:  An epoxy resin mixture was prepared as a 40% solids
mixture in 1-methoxy-2-propanol acetate containing about 30 parts
phenoxy resin PKHC*, 45 parts Epi-Rez 5183**, 25 parts Epi-Rez
SU-8**, and 6 parts E...