Ultra high-temperature plastic package and method of manufacture

Abstract

A package for microelectronic circuits includes a frame made of a high molecular weight plastic material, such as a liquid crystal polymer (LCP), attached to a flange, or leadframe. The plastic material is injection molded to the flange. Initial polymerization of the plastic material can occur in a liquid state and results in an intermediate material having an initial melting temperature. After the frame is injection molded, the frame is heated and undergoes further (secondary) polymerization, thereby lengthening polymer chains in the plastic material. These longer polymer chains have higher molecular weight, and the resulting final material has a higher melting temperature, than the intermediate material. The resulting ultra-high molecular weight polymer can withstand high temperatures, such as those encountered during soldering. Thus, after the further (secondary) polymerization, a die can be soldered to the flange, without damaging the plastic frame.

1 . A liquid crystal polymer material comprising polymers that have been further polymerized by secondary polymerization after molding of the material into a shape, the material having a melting temperature greater than about 420° C. or having a molecular weight greater than about 30,000 gm/mol. 
     
     
         2 . The material of  claim 1  having an elongation greater than about 2%. 
     
     
         3 . The material of  claim 1  having a tensile strength greater than about 25,000 psi. 
     
     
         4 . The material of  claim 1  comprising an average of at least about 200 repeating monomeric units per polymer. 
     
     
         5 . The material of  claim 1  comprising one or more monomeric units selected from the group consisting of hydroquinone, bisphenol, isophthalic acid, p-hydroxybenzoic acid, terephthalic acid; and 2-hydroxy-6-naphthoic acid. 
     
     
         6 . The material of  claim 5  comprising p-hydroxybenzoic acid. 
     
     
         7 . The material of  claim 1 , wherein the material has been shaped by injection molding. 
     
     
         8 . The material of  claim 1  which is a thermoplastic material. 
     
     
         9 . The material of  claim 1  which is a thermoset material. 
     
     
         10 . A liquid crystal polymer material produced by a method comprising the steps of:
 synthesizing a first polymeric material having a first melting temperature;   injection molding the first polymeric material into a shape;   heating the molded first polymeric material in its molded shape at a first rate of between about 0.1° C. per hour and about 10° C. per hour to a first predetermined temperature below the melting temperature of the first polymeric material; and   heating the first polymeric material in its molded shape at a second rate of between 0.1° C. per hour and about 10° C. per hour to a second predetermined temperature higher than the melting temperature of the first polymeric material.   
     
     
         11 . A liquid crystal polymer material produced by a method comprising the steps of:
 injection molding a polymeric material into a shape;   increasing the temperature of the molded polymeric material at a rate of between about 0.1° C. per hour and about 10° C. per hour until the temperature of the polymeric material reaches a first temperature between about 10° C. and about 30° C. below an initial melting temperature of the polymeric material;   maintaining the temperature of the molded polymeric material between about 10° C. and about 30° C. below the initial melting temperature of the polymeric material for at least about one hour; and   increasing the temperature of the molded polymeric material at a rate of between about 0.1° C. per hour and about 10° C. per hour until the temperature of the polymeric material reaches a second temperature between about 40° C. and about 50° C. below a desired melting temperature of the polymeric material which is higher than the initial melting temperature of the polymeric material.   
     
     
         12 . A liquid crystal polymer material comprising polymers that have been further polymerized by secondary polymerization and having a melting temperature greater than about 420° C. 
     
     
         13 . A liquid crystal polymer material comprising polymers that have been further polymerized by secondary polymerization and having a molecular weight greater than about 30,000 gm/mol.