Flame Retardant Photoimagable Coverlay Compositions and Methods Relating thereto

Abstract

The present invention is directed to phosphorus containing (or “halogen free”) flame retardant photoimagable compositions useful as a coverlay material in a flexible electronic circuitry package. These compositions are generally photosensitive and comprise phosphorus containing acrylates and phosphorus-containing photo-initiators mixed with a polymer binder. The compositions of the present invention typically comprise elemental phosphorus in an amount between, and including, any two of the following numbers 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8 and 6.0 weight percent.

1 . A photosensitive circuit coverlay composition comprising a phosphorus containing monomer, a phosphorus containing photo-initiator, and a polymer binder, wherein the total composition has a phosphorus content in an amount between, and including, any two of the following numbers 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8 and 6.0 weight percent. 
   
   
       2 . A composition in accordance with  claim 1  wherein the polymer binder is an acrylic, epoxy, or epoxy modified acrylic polymer. 
   
   
       3 . A composition in accordance with  claim 1  wherein the phosphorus containing monomer is an acrylate that, under radical polymerization, forms a three-dimensional polymer network. 
   
   
       4 . A composition in accordance with  claim 1  wherein the polymer binder contains an unsaturated bond, carboxylic acid group, acid group or hydroxyl group and wherein the polymer binder is capable of chemically reacting with the phosphorus containing monomer and phosphorus-containing photo-initiator. 
   
   
       5 . A composition in accordance with  claim 1  wherein the phosphorus containing monomer, prior to being chemically reacted with the composition, is an oligomer. 
   
   
       6 . A composition in accordance with  claim 1  wherein the phosphorus containing monomer is a mono-functional or multi-functional methacrylate or acrylate derivative. 
   
   
       7 . A composition in accordance with  claim 1  wherein the phosphorus containing monomer contains an unsaturated bond and is capable of chemical crosslinking. 
   
   
       8 . A composition in accordance with  claim 1  wherein the phosphorus containing monomer is present in an amount between and including any two of the following numbers 20, 25, 30, 35, 40, 45, 50, 55, 60, 65 and 70 weight percent of the total composition. 
   
   
       9 . A composition in accordance with  claim 1  wherein the phosphorus containing monomer is present in an amount between and including any two of the following numbers 30, 35, 40, 45, 50, 55 and 60 weight percent of the total composition. 
   
   
       10 . A composition in accordance with  claim 1  wherein the phosphorus containing photo-initiator is a phosphine oxide or acrylphosphine oxide derivative. 
   
   
       11 . A composition in accordance with  claim 1  wherein the phosphorus containing photo-initiator has the chemical structure, 
     
       
         
         
             
             
         
       
     
   
   
       12 . A composition in accordance with  claim 1  wherein the phosphorus containing photo-initiator has the chemical structure, 
     
       
         
         
             
             
         
       
     
   
   
       13 . A composition in accordance with  claim 1  wherein the phosphorus containing photo-initiator is present in an amount between and including any two of the following numbers 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 12.0, 14.0, 16.0 and 18.0 weight percent of the total composition. 
   
   
       14 . A composition in accordance with  claim 1  wherein the phosphorus containing photo-initiator is present in an amount between and including any two of the following numbers 4.0, 5.0, 6.0, 7.0 and 8.0 weight percent of the total composition. 
   
   
       15 . A composition in accordance with  claim 1  further comprising a thermal crosslinking agent. 
   
   
       16 . A composition in accordance with  claim 1  further comprising a thermal crosslinking agent wherein the thermal crosslinking agent is a blocked isocyanate or blocked polyisocyanate. 
   
   
       17 . A composition in accordance with  claim 1  further comprising a thermal crosslinking agent wherein the thermal crosslinking agent is a blocked polyisocyanate that upon heating forms a polyisocyanate selected from the group consisting of toluene diisocyanate, isophorone diisocyanate, 1,4-naphthalene diisocyanate, 1,6-hexamethylene diisocyanate, tetramethyl xylene diisocyanate, bis (4-isocyanatocyclohexyl)methane. 
   
   
       18 . A composition in accordance with  claim 1  further comprising a phosphorus containing material, the soluble phosphorus containing material further comprising a hydroxyl group. 
   
   
       19 . A composition in accordance with  claim 18  wherein the phosphorus containing material, under thermal reaction or crosslinking, can polymerize with the phosphorus containing acrylate and polymer binder. 
   
   
       20 . A composition in accordance with  claim 1  further comprising a filler selected from the group consisting of aluminum hydroxide, magnesium hydroxide, zinc borate, micro crystalline cellulose, micro crystalline silicas, clays, alumina, bentonite, kalonites, attapultites, montmorillonites, silicon oxide, titanium oxide, carbon black, zinc oxide, melamine polyphosphate, melamine cyanurate, and ammonium polyphosphate. 
   
   
       21 . A composition in accordance with  claim 20  wherein the filler has a particle size from 5 nanometers to 10,000 nanometers. 
   
   
       22 . A composition in accordance with  claim 1  further comprising a photo-active component. 
   
   
       23 . A composition in accordance with  claim 1  further comprising a photo-active component wherein the photo active component is selected from the group consisting of photo-initiators, photo-sensitizers, photosolubilizers, photodesensitizer, photoinhibitor, phototackifier, photodetackifier, a component that is photodegradable, photochromic, photoreducible, photo-oxidizable, photoadhesive, photoreleaseable, photomagnetic, photodemagnetic, photoconductive, photoinsulative, combinations thereof, and materials that change refractive index upon exposure to actinic radiation. 
   
   
       24 . A composition in accordance with  claim 1  further comprising an adhesion promoter. 
   
   
       25 . A composition in accordance with  claim 1  further comprising an adhesion promoter selected from the group consisting of 2-amino-5-mercaptothiophene, 5-amino-1,3,4-thiodiazole-2-thiol, benzotriazole, 5-chloro-benzotriazole, 1-chloro-benzotriazole, 1-carboxy-benzotriazole, 1-hydroxy-benzotriazole, 2-mercaptobenzoxazole, 1H-1,2,4-triazole-3-thiol and mercaptobenzimidazole. 
   
   
       26 . A composition in accordance with  claim 1  wherein the composition is flame retardant according to UL 94 Thin Material Vertical Burning Test 94VTM-0, UL 94 Thin Material Vertical Burning Test 94VTM-1 or UL 94 Thin Material Vertical Burning Test 94VTM-2.