Coverlay for high-frequency circuit substrate

Abstract

To provide a coverlay for a high-frequency circuit substrate, that uses polyimide film and fluororesin, has excellent mechanical properties and heat resistance, and can increase workability during the manufacture of high-frequency circuit substrates. Resolution Means: The coverlay for a high-frequency circuit substrate including a polyimide film and a fluororesin bonded together, and an adhesive strength between the polyimide film layer and the fluororesin layer being greater than 3.0 N/cm.

What is claimed is: 
     
         1 . A coverlay for a high-frequency circuit substrate, the coverlay comprising a polyimide film and a fluororesin bonded together, and an adhesive strength between the polyimide film layer and the fluororesin layer being greater than 3.0 N/cm. 
     
     
         2 . The coverlay as described in  claim 1 , wherein a thermal shrinkage thereof at 260° C. for 30 minutes is less than ±0.1%. 
     
     
         3 . The coverlay as described in  claim 1  or  2 , wherein the fluororesin has a melting point of 200° C. or less. 
     
     
         4 . The coverlay as described in any one of  claims 1  through  3 , wherein the fluororesin is a fluorine-containing ethylenic polymer, and the fluorine-containing ethylenic polymer contains a carbonyl group. 
     
     
         5 . The coverlay as described in  claim 4 , wherein a quantity of carbonyl groups contained in the fluorine-containing ethylenic polymer totals 3 to 1000 groups per 1×10 6  main-chain carbon atoms. 
     
     
         6 . The coverlay as described in any one of  claims 1  through  3 , wherein the fluororesin is made up of fluorine-containing ethylenic polymer that has at least one type selected from a group made up of carbonate groups, carboxylic acid halide groups, and carboxylic acid groups totaling 3 to 1000 groups per 1×10 6  main-chain carbon atoms. 
     
     
         7 . The coverlay as described in any one of  claims 1  through  3 , wherein the fluororesin is one or more types of fluorine-containing ethylenic monomer selected from a group made up of tetrafluoroethylene, vinylidene fluoride, chlorotrifluoroethylene, vinyl fluoride, hexafluoropropylene, hexafluoroisobutene, monomers represented by the following formula (X):
   CH 2 ═CR 1 (CF 2 ) n R 2   (X)
 
 (wherein R 1  represents H or F, R 2  represents H, F, or Cl, and n is a positive integer in a range 1 to 10), and perfluoro(alkyl vinyl ethers) having 2 to 10 carbon atoms, or a fluorine-containing ethylenic polymer made by polymerizing the fluorine-containing ethylenic monomer and an ethylenic monomer having 5 or fewer carbon atoms. 
 
     
     
         8 . The coverlay as described in any one of  claims 1  through  3 , wherein the fluororesin is a copolymer made by polymerizing at least the following (a), (b), and (c);
 (a) 20 to 90 mol % of tetrafluoroethylene, 
 (b) 10 to 80 mol % of ethylene, and 
 (c) 1 to 70 mol % of a compound represented by the formula:
   CF 2 ═CFR 3   (Y)
 
 
 (wherein R 3  represents CF 3  or OR 4 , and R 4  represents a perfluoroalkyl group having 1 to 5 carbon atoms). 
 
     
     
         9 . The coverlay as described in any one of  claims 1  through  8 , wherein the polyimide film is made up mainly of one or more aromatic diamine components selected from a group made up of paraphenylene diamine, 3,4′-diaminodiphenyl ether, and 4,4′-diaminodiphenyl ether, and one or more acid anhydride components selected from a group made up of pyromellitic acid dianhydride and 3,3′,4,4′-biphenyl tetracarboxylic acid dianhydride.