Reworkable encapsulant

Abstract

The present invention provides an improved fluorinated polymer encapsulant for protectively coating electronic devices in an electronic device module. Also provided is a method for applying and reworkably removing the same to and from the electronic device module. In one embodiment, a coating of a fluorinated polymer solution is applied to at least a portion of an electronic device module. The module is then baked to operably fix to it the fluorinated polymer coating.

I claim as follows:  
     
         1 . A method for encapsulating an electronic device module, the method comprising: 
 (a) applying a coating of fluorinated polymer solution to at least a portion of an electronic device module; and    (b) baking the module to operably fix to it the fluorinated polymer, which serves as a protective coating.    
     
     
         2 . The method of  claim 1 , wherein the act of applying a coating of fluorinated polymer solution includes applying a coating of HFIP fluorinated polymer solution.  
     
     
         3 . The method of  claim 2 , wherein the act of applying a coating of HFIP fluorinated polymer solution includes applying a coating of 12F-PEK polymer.  
     
     
         4 . The method of  claim 1 , wherein the fluorinated polymer solution includes a solvent, and the act of baking the device includes the acts of pre-baking within a first temperature range the device to drive off solvent from the solution prior to baking the device within a second temperature range that is higher than the first temperature range.  
     
     
         5 . The method of  claim 4 , wherein the act of baking further includes ramping the baking temperature from within the first temperature range to within the second temperature range.  
     
     
         6 . The method of  claim 5 , wherein pre-baking within the first temperature range includes baking within a temperature range of 90° C. to 120° C.  
     
     
         7 . The method of  claim 6 , wherein baking the device within the second temperature range includes baking the device within a range of 180° C. to 220° C.  
     
     
         8 . The method of  claim 7 , wherein ramping from within the first temperature range to within the second temperature range includes ramping the temperature within a rate range of 5° C. to 10° C. per minute.  
     
     
         9 . The method of  claim 4 , further comprising the acts of (1) applying to the device a second coating of the fluorinated polymer solvent solution after pre-baking the device, and (2) again pre-baking the device to drive off solvent from the second coating.  
     
     
         10 . The method of  claim 9 , wherein the acts of applying a second coating and again pre-baking are performed prior to baking the device within the second temperature range.  
     
     
         11 . The method of  claim 1 , wherein the act of applying the coating includes the act of spraying the coating onto the electronic device module.  
     
     
         12 . The method of  claim 11 , wherein the act of spraying the coating onto the module includes the act of spraying the coating onto a chip-on-board module.  
     
     
         13 . An electronic device module that is encapsulated according to the method of  claim 1 .  
     
     
         14 . A method for reworkably removing fixed fluorinated polymer coating from an electronic device module, the method comprising: 
 (a) dissolving the fluorinated polymer with a solvent; and    (b) sufficiently removing the dissolved fluorinated polymer coating from the module in order to rework it.    
     
     
         15 . The method of  claim 14 , further comprising the act of drying the module.  
     
     
         16 . The method of  claim 15 , wherein the act of drying includes drying the module with compressed nitrogen gas.  
     
     
         17 . The method of  claim 14 , wherein the dissolved fluorinated polymer is removed by rinsing the module with a solvent rinse.  
     
     
         18 . The method of  claim 17 , wherein the act of rinsing includes rinsing with isopropanol.  
     
     
         19 . The method of  claim 14 , wherein the act of dissolving the fluorinated polymer includes immersing the coated device in the solvent.  
     
     
         20 . The method of  claim 19 , wherein the act of dissolving the fluorinated polymer includes dissolving the fluorinated polymer in xylene.  
     
     
         21 . An electronic device module having an improved protective coating, comprising: 
 (a) a substrate;    (b) at least one electronic device operably connected to the substrate; and    (c) a fluorinated polymer encapsulant protectively adhered about at least a portion of the at least one electronic device.    
     
     
         22 . The module of  claim 21 , wherein the substrate is a printed circuit board.  
     
     
         23 . The module of  claim 21 , wherein the substrate and the at least one electronic device comprise a chip scale package.  
     
     
         24 . The module of  claim 21 , wherein the substrate and the at least one electronic device comprise an opto-electronic device module.  
     
     
         25 . The module of  claim 21 , wherein the electronic device is a flip-chip having an interconnect side facing the substrate.  
     
     
         26 . The module of  claim 25 , wherein fluorinated polymer is used as underfill between the substrate and the interconnect side of the at least one flip chip.  
     
     
         27 . The module of  claim 21 , wherein the fluorinated polymer includes an HFIP bearing thermoplastic.  
     
     
         28 . The module of  claim 27 , wherein the fluorinated polymer encapsulant comprises two or more layers of the HFIP thermoplastic.  
     
     
         29 . The module of  claim 21 , further comprising an epoxy encapsulant sandwiched between the at least one electronic device and the fluorinated polymer encapsulant.  
     
     
         30 . The module of  claim 21 , wherein the fluorinated polymer encapsulant includes microscopic inorganic particles for making the thermal expansion characteristics of the encapsulant closer to those of the at least one electronic device.  
     
     
         31 . The module of claim  30 , wherein the inorganic microscopic particles comprise silica.