Thermally stable photoimaging composition
AssigneeInternational Business Machines Corporation
InventorsVoya Rista Markovich, Ashit Arvind Mehta, Eugene Roman Skarvinko, David Wei Wang
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Abstract
A thermally stable photoimaging composition and a method of using the same, especially on circuit boards as a solder mask is provided. The composition includes a polymerizable resin or resin system, a cationic photoinitiator, a solvent, and an optically transparent ceramic filler. Preferably, the composition has a coefficient of thermal expansion of about 28-40 ppm/.degree. C., which closely matches the coefficient of thermal expansion of the solder used on the circuit board components.
Claims16
A process for photopatterning a solder mask on an organic dielectric circuit board, such solder mask being thermally stable at 360.degree. C. and having a coefficient of thermal expansion of 28-40 ppm/.degree. C., comprising the steps of:
- (a) providing a photosensitive solder mask, consisting essentially of:
- 30-70% by a combined resin-filler weight of a cationic polymerizable bisphenol A formaldehyde novolak epoxy resin,
- 0.5% to approximately 10% per resin weight of a photosensitive, cationic photoinitiator,
- a solvent and
- 30-70% by a combined resin-filler weight of an optically transparent silicon dioxide filler transparent to wavelength of 310 to 400 nanometers, wherein said solder mask is both an encapsulant and a dielectric;
- (b) then disposing said solder mask upon the organic dielectric circuit board;
- (c) then exposing the solder mask through a pattern to light;
- (d) then removing the unexposed areas of the solder mask by placing in a developer;
- (e) then applying solder to the patterned circuit board;
- and
- (f) then reflowing the solder in a furnace;
- wherein the solder mask is characterized by adhering to the circuit board during step (f).
Dependencies are inferred from the claim text.