Transfer molding process for encapsulating semiconductor devices

Abstract

The present invention relates to an improved transfer molding method for encapsulating semiconductor, electrical and optical devices with epoxy or other thermoset resins wherein liner film is provided over the surfaces of the package cavities, runners, and pot prior to inserting the preform tablet in the pot and the devices in the package cavities.

What is claimed is: 
     
       1. In a transfer molding method of encapsulating devices which utilizes apparatus which comprises a mold, said mold having a top portion and a bottom portion, either of said portions including at least one pot and a plunger in each said pot, package cavities, and runners connecting said package cavities with said pot, each of said pots, plungers, package cavities, and runners having surfaces, wherein a device is inserted in each of said package cavities, a preform tablet of encapsulating composition is inserted in each said pot, and wherein said encapsulating composition becomes soft and said plunger is used to force the soft encapsulating composition along said runners and into said package cavities; the improvement comprising using a preform tablet of encapsulating composition having a density Of at least 90% and a water content of 0.1% or less, providing a liner film over the surfaces of said package cavity, runners, and pot prior to inserting said preform tablet in said pot and said device in said package cavity, wherein said liner film is provided for each of said top and bottom portions so as to line all surfaces which come into contact with said soft encapsulating composition, and wherein vacuum is applied to form the liner film to all resin transfer surfaces of the top and bottom portions.   
     
     
       2. Method according to claim 1 wherein a gang-pot mold configuration is used. 
     
     
       3. Method according to claim 1 wherein the liner film is used for one molding cycle and then is replaced with new liner film for each subsequent molding cycle. 
     
     
       4. Method according to claim 1 wherein an application of liner film is used for two or more mold cycles. 
     
     
       5. Method according to claim 1 wherein the liner film is not separated from the molded parts, and is used as a wrap to store or ship said parts. 
     
     
       6. Method according to claim 1 wherein the preform tablets are not pre-wrapped in film. 
     
     
       7. Method according to claim 6 wherein said preform tablets are cylindrically shaped.