Production method for thermoplastic liquid crystal polymer film, circuit board and production method therefor

Abstract

Provided are a method for producing a thermoplastic liquid crystal polymer (TLCP) film having an improved thermo-adhesive property, a circuit board, and a method for producing the same. The production method of the TLCP film includes preparing a TLCP film as the adherend film and a TLCP film as the adhesive film; examining each of the prepared TLCP films for a relative intensity calculated as a ratio in percentage of a sum of peak areas of C—O bond peak and COO bond peak based on the total area of C 1 s peaks in the XPS spectral profile so as to calculate a relative intensity X (%) as for the prepared adherend film and a relative intensity Y (%) as for the prepared adhesive film; and controlling the TLCP film as the adhesive film to have a relative intensity Y by selection or activation treatment of the adhesive film so that the relative intensity X of the adherend film and the relative intensity Y of the controlled adhesive film satisfy the following formulae (1) and (2): 38< X+Y<65   (1) −8.0< Y−X<8.0   (2).

What is claimed is: 
     
         1 . A method for producing a thermoplastic liquid crystal polymer film as an adhesive film to be thermo-bonded to an adherend body of a thermoplastic liquid crystal polymer film (hereinafter referred to as an adherend film), the method at least comprising:
 preparing a thermoplastic liquid crystal polymer film as the adherend film and a thermoplastic liquid crystal polymer film as the adhesive film;   examining each of the prepared thermoplastic liquid crystal polymer films for a relative intensity calculated as a ratio in percentage of a sum of peak areas of C—O bond peak and COO bond peak based on the total area of C1s peaks in the XPS spectral profile so as to calculate a relative intensity X (%) as for the prepared adherend film and a relative intensity Y (%) as for the prepared adhesive film; and   controlling the thermoplastic liquid crystal polymer film as the adhesive film to have a relative intensity Y by selection or activation treatment of the adhesive film so that the relative intensity X of the adherend film and the relative intensity Y of the controlled adhesive film satisfy the following formulae (1) and (2):
   38< X+Y< 65   (1)
 
   −8.0< Y−X< 8.0   (2).
 
   
     
     
         2 . The method for producing a film according to  claim 1 , wherein the controlling is performed by at least one activation treatment selected from the group consisting of ultraviolet (UV) ray irradiation, plasma irradiation, and corona discharge treatment. 
     
     
         3 . The method for producing a film according to  claim 1 , wherein the thermoplastic liquid crystal polymer film as the adhesive film is further subjected to degassing of the film before or after the controlling process of the relative intensity Y (%)
 by degassing the film (i) under vacuum of 1500 Pa or lower for 30 minutes or more,   by degassing the film (ii) under heating at a temperature ranging from 100° C. to 200° C., or   by degassing the film under the vacuum (i) and under the heating (ii) simultaneously or separately.   
     
     
         4 . The method for producing a film according to  claim 3 , wherein the degassing process is carried out by degassing the film under vacuum of 1500 Pa or lower while heating at a temperature ranging from 50° C. to 200° C. 
     
     
         5 . The method for producing a film according to  claim 1 , wherein the thermoplastic liquid crystal polymer film as the adhesive film has a film thickness of 10 to 500 gm. 
     
     
         6 . A method for producing a circuit board comprising a thermoplastic liquid crystal polymer film as an adherend film and a thermoplastic liquid crystal polymer film as an adhesive film, the both films being laminated by thermo- bonding, the method comprising:
 preparing the adherend film and the adhesive film as circuit board materials;   stacking the adherend film and the adhesive film in accordance with a predetermined structure of a circuit board to obtain a stacked material, followed by conducting thermo-compression bonding of the stacked material by heating under a predetermined compression pressure; wherein   the prepared circuit board materials are independently at least one member selected from the group consisting of an insulating substrate having a conductor layer on at least one surface, a bonding sheet, and a coverlay; and   the adhesive film is a thermoplastic liquid crystal polymer film produced by a method recited in  claim 1 .   
     
     
         7 . The method for producing a circuit board according to  claim 6 , wherein the adherend film is an insulating substrate having a conductor circuit on at least one surface, and the adhesive film is at least one circuit board material selected from the group consisting of an insulating substrate having a conductor layer on at least one surface, a bonding sheet, and a coverlay. 
     
     
         8 . The method for producing a circuit board according to  claim 6 , wherein the method further comprises degassing the adherend film and the adhesive film before thermo-compression bonding by degassing the film (i) under vacuum of 1500 Pa or lower for 30 minutes or more,
 by degassing the film (ii) under heating at a temperature ranging from 100° C. to 200° C., or   by degassing the film under the vacuum (i) and under the heating (ii) simultaneously or separately.   
     
     
         9 . The method for producing a circuit board according to  claim 8 , wherein the degassing is carried out under vacuum at a vacuum degree of 1500 Pa or lower for 30 minutes or more at a temperature ranging from 50 to 150° C. 
     
     
         10 . A circuit board comprising a thermoplastic liquid crystal polymer film as an adherend film and a thermoplastic liquid crystal polymer film as an adhesive film, the both films being laminated by thermo-bonding, wherein
 the adherend film has a surface portion to be adhered, the surface portion having a relative intensity X (%) calculated as a ratio in percentage of a sum of peak areas of C—O bond peak and COO bond peak relative to the total area of C1s peaks in the XPS spectral profile;   the adhesive film has a surface portion to be adhered, the surface portion having a relative intensity Y (%) calculated as a ratio in percentage of a sum of peak areas of C—O bond peak and COO bond peak relative to the total area of C1s peaks in the XPS spectral profile;   the relative intensities X and Y satisfy the following formulae (1) and (2):
   38< X+Y< 65   (1)
 
   −8.0< Y−X< 8.0   (2); and wherein
 
   the circuit board shows a solder heat resistance when the circuit board is placed in a solder bath at a temperature of 290° C. for 60 seconds conforming to a method of JIS C 5012.   
     
     
         11 . The circuit board according to  claim 10 , wherein a bonding strength between the adherend film and the adhesive film in accordance with JIS 05016- 1994 is 0.7 kN/m or higher. 
     
     
         12 . The circuit board according to  claim 10 , wherein where there is a conductive material portion between the adherend and adhesive films, the surface area ratio of the conductive material portion existing between the adherend and adhesive films is less than 30%. 
     
     
         13 . The circuit board according to  claim 10 , wherein difference in melting point between the adhesive film and the adherend film is 0° C. to 60° C.