Ball grid array package substrate with through holes and method of forming same

Abstract

In accordance with an embodiment, there is provided a substrate of a ball grid array package that includes a first layer including reinforcement fibers. The reinforcement fibers reinforce the first layer such that the first layer has a higher tensile strength relative to a layer in the ball grid array package that is free of reinforcement fibers. In an embodiment, the substrate comprises a second layer disposed adjacent to the first layer with the second layer being free of reinforcement fibers. In an embodiment, the substrate also includes a through hole penetrating each of the first layer and the second layer. The through hole penetrates each of the first layer and the second layer based on each of the first layer and the second layer having been drilled in accordance with a mechanical drilling process.

What is claimed is: 
     
         1 . A method of making a substrate of a ball grid array package, the method comprising:
 providing a first layer having (i) a first planar surface and (ii) a second planar surface substantially parallel to the first planar surface, wherein the first layer includes reinforcement fibers, and wherein the reinforcement fibers reinforce the first layer such that the first layer has a higher tensile strength relative to a layer in the ball grid array package that is free of reinforcement fibers;   applying a second layer disposed adjacent to the first surface of the first layer, wherein the second layer is free of reinforcement fibers;   applying a third layer disposed adjacent to the second surface of the first layer, wherein the third layer is free of reinforcement fiber; and   mechanically drilling a through hole that penetrates each of (i) the first layer, (ii) the second layer and (iii) the third layer.   
     
     
         2 . The method of  claim 1 , further comprising:
 forming a circuit pattern on the first layer; and   forming a circuit pattern on the second layer,   wherein the through hole permits the circuit pattern of the first layer to be electrically coupled to the circuit pattern of the second layer.   
     
     
         3 . The method of  claim 2 , wherein:
 the second layer includes
 (i) an inner surface adjacent to the first surface of the first layer, and 
 (ii) an outer surface substantially parallel to the inner surface; and 
   forming the circuit pattern on the second layer comprises forming the circuit pattern on the second layer such that the outer surface of the second layer includes the circuit pattern having a number of lines.   
     
     
         4 . The method of  claim 3 , wherein forming the circuit pattern on the second layer comprises forming the circuit pattern such that at least a portion of the number of lines of the circuit pattern on the outer surface of the second layer have a width of no greater than 20 microns. 
     
     
         5 . The method of  claim 3 , wherein forming the circuit pattern on the second layer comprises forming the circuit pattern such that a spacing between at least a portion of the number of lines of the circuit pattern on the outer surface of the second layer is no greater than 20 microns. 
     
     
         6 . The method of  claim 1 , wherein mechanically drilling the through hole comprises mechanically drilling the through hole such that a diameter of the through hole is at least 80 microns. 
     
     
         7 . The method of  claim 1 , wherein mechanically drilling the through hole comprises mechanically drilling the through hole such that a diameter of the through hole is within a range of 100 microns to 150 microns. 
     
     
         8 . The method of  claim 1 , wherein a tensile strength of the second layer is no greater than 125 MPa. 
     
     
         9 . The method of  claim 1 , wherein a tensile strength of the first layer is at least 250 MPa. 
     
     
         10 . The method of  claim 1 , wherein the reinforcement fibers of the first layer comprise one of (i) a glass-containing material or (ii) a cotton-containing material. 
     
     
         11 . The method of  claim 1 , further comprising providing a fourth layer, wherein the fourth layer includes a glass-containing reinforcement material. 
     
     
         12 . The method of  claim 1 , wherein mechanically drilling a through hole that penetrates each of the first layer, the second layer and the third layer comprises mechanically drilling a plurality of through holes that each penetrate each of (i) the first layer, (ii) the second layer and (iii) the third layer. 
     
     
         13 . A method of making substrate of a ball grid array package, the method comprising:
 providing a first layer including reinforcement fibers, wherein the first layer has a first surface and a second surface substantially parallel to the first surface, and wherein the reinforcement fibers reinforce the first layer such that the first layer has a higher tensile strength relative to a layer in the ball grid array package that is free of reinforcement fibers;   applying a second layer adjacent to the first surface of the first layer, wherein
 the second layer is free of reinforcement fibers, and 
 the second layer includes (i) a first surface disposed adjacent to the first surface of the first layer and (ii) a second surface substantially parallel to the first surface; 
   forming a circuit pattern on the second surface of the second layer, wherein the circuit pattern includes a number of lines, and wherein at least a portion of the number of lines has a width less than 20 microns;   applying a third layer adjacent to the second surface of the first layer, wherein the third layer is free of reinforcement fibers; and   a through hole penetrating each of (i) the first layer, (ii) the second layer and (iii) the third layer.   
     
     
         14 . The method of  claim 13 , wherein the first layer is one of a plurality of core layers of the substrate, each core layer of the plurality of core layers including reinforcement fibers. 
     
     
         15 . The method of  claim 13 , wherein at least one of (i) the first layer or (ii) the third layer includes a halogen. 
     
     
         16 . The method of  claim 13 , wherein forming a circuit pattern on the second surface of the second layer comprises forming a circuit pattern on the second surface of the second layer such that the width of the at least a portion of the number of lines is included in a range of 8 microns to 16 microns. 
     
     
         17 . The method of  claim 13 , wherein forming a circuit pattern on the second surface of the second layer comprises forming a circuit pattern on the second surface of the second layer such that a spacing between adjacent lines of the number of lines is no greater than 20 microns. 
     
     
         18 . The method of  claim 13 , wherein the reinforcement fibers of the first layer comprise one of (i) a glass-containing material or (ii) a cotton-containing material. 
     
     
         19 . The method of  claim 13 , further comprising providing a fourth layer, wherein the fourth layer includes a glass-containing reinforcement material. 
     
     
         20 . The method of  claim 13 , wherein mechanically drilling a through hole that penetrates each of the first layer, the second layer and the third layer comprises mechanically drilling a plurality of through holes that each penetrate each of (i) the first layer, (ii) the second layer and (iii) the third layer.