Thermosensitive etch resist for forming a mask
OwnerDavid A. Morganinventor
Life of this patent
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Abstract
A thermosensitive resist used in the manufacturing of printed circuit boards comprising a mixture of polyacrylic acid, a salt of a long chain fatty acid such as silver behenate, an infra-red absorber and modifiers such as additional polymers. In the unheated form the resist can be easily washed away with water-based mild solutions or pure water. When selectively heated by an IR laser a non-soluble, etch resistant composition is formed protecting the copper clad printed circuit board from the etchants used in the process.
Claims22
An etch resist used to form a protective mask during a selective etching process of printed circuit boards and similar articles,
- said etch resist comprising a thermosensitive composition having a first and a second state;
- said thermosensitive composition in said first state comprising a water washable composition stable at room temperature;
- said thermosensitive composition in said second state further comprising a water resistant composition attained when said thermosensitive composition is selectively exposed to temperature greater than room temperature;
- said water resistant state being resistant to copper etchants comprising FeCl.sub.3 ;
- said thermosensitive composition further comprises a water soluble polymer and a metallic salt of a fatty acid having a chain of between 10 to 30 carbon atoms.
An etch resist forming a protective coating on a surface subjected to selective exposure to heat comprising:
- a thermosensitive material capable of switching from a soluble state to an etch resistant protective mask when heated briefly, said etch resistant protective mask being resistant to copper etchants comprising FeCl.sub.3, and without requiring a prior or subsequent exposure to energy, the etch resist comprises;
- (i) a metallic salt of a fatty acid having a chain of between 10 to 30 carbon atoms;
- (ii) a water soluble polymer;
- and (iii) a laser absorber capable of absorbing the radiation from a laser.
Dependencies are inferred from the claim text.