Processes for manufacturing printed wiring boards

Abstract

Methods of manufacturing printed wiring boards including electrically conductive constraining cores that involve a single lamination cycle are disclosed. One example of the method of the invention includes drilling a clearance pattern in an electrically conductive constraining core, arranging the electrically conductive constraining core in a stack up that includes B-stage (semi-cured) layers of dielectric material on either side of the constraining core and additional layers of material arranged to form the at least one functional layer, performing a lamination cycle on the stack up that causes the resin in the B-stage (semi-cured) layers of dielectric to reflow and fill the clearance pattern in the electrically conductive constraining core before curing and drilling plated through holes.

What is claimed is: 
     
       1. A method of constructing a printed wiring board including an electrically conductive constraining core, where the electrically conductive constraining core comprises a base material and an insert material, where the electrically conductive constraining core is a functional layer of the printed wiring board, and where the printed wiring board includes at least one additional functional layer using a single lamination cycle, comprising:
 removing at least one section of a base material, and replacing the at least one removed section with at least one insert material, wherein the aggregate of the base material and the at least one insert material defines the structure of the electrically conductive constraining core;  
 drilling a pattern of clearance holes in an the electrically conductive constraining core; 
 arranging the electrically conductive constraining core in a stack up that includes B-stage [semi-cured] (semi-cured) layers of dielectric material on either side of the constraining core and additional layers of material, where the electrically conductive constraining core, the B-stage [semi-cured] (semi-cured) layers of dielectric material, and additional layers of material are arranged so that lamination of the stack up forms the functional layers of the finished printed wiring board; 
 performing a lamination cycle on the stack up that causes the resin in the B-stage [semi-cured] (semi-cured) layers of dielectric to reflow and fill the pattern of clearance holes in the electrically conductive constraining core before curing; and 
 drilling through holes through the laminated stack up and plating the through holes to create at least one electrical connection between the electrically conductive constraining core and one of the at least one additional functional layers. 
 
     
     
       2. The method of  claim 1 , further comprising:
 extracting from a printed wiring board design information concerning the locations of plated through holes that are not intended to be in electrical contact with the electrically conductive constraining core; and 
 determining the pattern of clearance holes using the information concerning the locations of plated through holes that are not intended to be in electrical contact with the electrically conductive constraining core. 
 
     
     
       3. The method of  claim 1 , wherein the electrically conductive constraining core has two major surfaces and can conduct electricity directly from one major surface to the other. 
     
     
       4. The method of  claim 3 , wherein the electrically conductive constraining core has a dielectric constant greater than 6 at 1 MHz. 
     
     
       5. The method of  claim 3 , wherein the electrically conductive constraining core is constructed using fibrous material impregnated with resin. 
     
     
       6. The method of  claim 5 , wherein the fibrous material is carbon fiber. 
     
     
       7. The method of  claim 6 , wherein the carbon fiber is metallized. 
     
     
       8. The method of  claim 3 , wherein the electrically conductive constraining core is constructed from a thick metal layer. 
     
     
       9. The method of  claim 8 , further comprising screening resin into the pattern of clearance holes in the electrically conductive constraining core prior to lamination. 
     
     
       10. The method of  claim 1 , further comprising:
 stacking a plurality of electrically conductive constraining cores; 
 drilling the pattern of clearance holes in the stack of electrically conductive constraining cores; and 
 creating lamination tooling holes in the electrically conductive constraining core. 
 
     
     
       11. The method of  claim 10 , further comprising printing and etching the electrically conductive constraining cores to remove debris prior to lamination. 
     
     
       12. The method of  claim 1 , wherein:
 the B-stage [semi-cured] (semi-cured) layers of dielectric are prepregs; and 
 the stack up includes layers of electrically conductive material. 
 
     
     
       13. The method of  claim 1 , wherein the B-stage [semi-cured] (semi-cured) layers of dielectric include at least 70% by volume resin content. 
     
     
       14. The method of  claim 1   wherein regions of the electrically conductive constraining core are constructed using a base substrate material and at least one region of the electrically conductive constraining core is constructed using an insert substrate material.   
     
     
       15. The method of  claim 14 , further comprising:
 selecting a base substrate material;   removing a section of the base substrate material;   selecting an insert substrate material;   cutting a piece of the insert substrate material that can be contained within the removed section of the base substrate material; and   arranging the base substrate material and the piece of the insert substrate material as part of the stack up.   
     
     
       16. The method of  claim 1 , wherein drilling a pattern of clearance holes further comprises:
 determining the location and required width of a clearance channel from a printed wiring board design; 
 determining the distance between notches that are likely to be created when a selected drill bit and drill pitch are used to drill the channel; and 
 selecting a drill bit and drilling pitch so that the distance between the notches closest to a plated through hole is not less than a predetermined clearance diameter. 
 
     
     
       17. The method of  claim 16 , further comprising:
 identifying a plated through hole that creates an electrical connection with the electrically conductive constraining core, which is closest to the clearance channel using the printed wiring board design; 
 determining the distance between the clearance channel and the identified plated through hole; 
 selecting the drill bit and drilling pitch so that the resulting channel does not overlap the location of the identified plated through hole. 
 
     
     
       18. The method of  claim 16 , further comprising:
 determining the height of the notches; and 
 selecting a drill bit and drilling pitch so that the height of the notches is less than 3 mil. 
 
     
     
       19. The method of  claim 18 , further comprising selecting a drill bit and drilling pitch so that the height of the notches is less than 1 mil. 
     
     
       20. A method of constructing a printed wiring board that includes at least one constraining core, the constraining core comprising a base material and an insert material, and at least one functional layer, using a single lamination cycle, comprising:
 removing at least one section of a base material, and replacing the at least one removed section with at least one insert material, wherein the aggregate of the base material and the at least one insert material defines the structure of the constraining core;   arranging the constraining core, comprising a base material and at least one insert material, in a stack up that includes B-stage (semi-cured) layers of dielectric material on either side of a respective constraining core and at least one functional layer of material; and   performing a lamination cycle on the stack up that causes the resin in the B-stage (semi-cured) layers of dielectric to reflow and bind adjacent layers within the stack up.    
     
     
       21. The method of claim 20, wherein at least one of the insert materials includes carbon.  
     
     
       22. The method of claim 20, wherein at least one of the insert materials is a carbon plate.  
     
     
       23. The method of claim 20, wherein at least one of the insert materials includes carbon fibers.  
     
     
       24. The method of claim 20, further comprising drilling a pattern of clearance holes in the at least one constraining core.  
     
     
       25. The method of claim 24, further comprising screening resin into the pattern of clearance holes in the at least one constraining core prior to lamination.  
     
     
       26. The method of claim 24, wherein drilling a pattern of clearance holes further comprises:
 determining the location and required width of a clearance channel from a printed wiring board design;   determining the distance between notches that are likely to be created when a selected drill bit and drill pitch are used to drill the channel; and   selecting a drill bit and drilling pitch so that the distance between the notches closest to a plated hole is not less than a predetermined clearance diameter.    
     
     
       27. The method of claim 24, further comprising drilling through holes through the laminated stack up and plating the through holes to create at least one electrical connection between layers within the laminated stack up.  
     
     
       28. The method of claim 20, further comprising:
 stacking a plurality of constraining cores;   drilling a pattern of clearance holes in the stack of constraining cores; and   creating lamination tooling holes in at least one constraining core.    
     
     
       29. The method of claim 20, wherein the B-stage (semi-cured) layers of dielectric are prepregs.  
     
     
       30. The method of claim 20, wherein the B-stage (semi-cured) layers of dielectric include at least 70% by volume resin content.  
     
     
       31. A method of constructing a printed wiring board including an electrically conductive constraining core, where the electrically conductive constraining core comprises a base material and an insert material, where the electrically conductive constraining core is a functional layer of the printed wiring board, and where the printed wiring board includes at least one additional functional layer, using a single lamination cycle, comprising:
 removing at least one section of a base material, and replacing the at least one removed section with at least one insert material, wherein the aggregate of the base material and the at least one insert material defines the structure of the electrically conductive constraining core;   arranging the electrically conductive constraining core in a stack up that includes B-stage (semi-cured) layers of dielectric material on either side of the electrically conductive constraining core and additional layers of material, where the electrically conductive constraining core, the B-stage (semi-cured) layers of dielectric material, and additional layers of material are arranged so that lamination of the stack up forms the functional layers of the finished printed wiring board;   performing a lamination cycle on the stack up that causes the resin in the B-stage (semi-cured) layers of dielectric to reflow and bind adjacent layers within the stack up; and   drilling through holes through the laminated stack up and plating the through holes to create at least one electrical connection between the electrically conductive constraining core and at least one additional functional layer.    
     
     
       32. The method of claim 31, wherein the electrically conductive constraining core has two major surfaces and can conduct electricity directly from one major surface to the other.  
     
     
       33. The method of claim 32, wherein the electrically conductive constraining core has a dielectric constant greater than 6 at 1 MHz.  
     
     
       34. The method of claim 32, wherein the electrically conductive constraining core is constructed using fibrous material impregnated with resin.  
     
     
       35. The method of claim 34, wherein the fibrous material is carbon fiber.  
     
     
       36. The method of claim 35, wherein the carbon fiber is metallized.  
     
     
       37. The method of claim 32, wherein the electrically conductive constraining core is constructed from a thick metal layer.  
     
     
       38. The method of claim 31, wherein the B-stage (semi-cured) layers of dielectric are prepregs.  
     
     
       39. The method of claim 31, wherein the B-stage (semi-cured) layers of dielectric include at least 70% by volume resin content.  
     
     
       40. The method of claim 31 wherein at least one insert material includes carbon.  
     
     
       41. The method of claim 31 wherein at least one insert material is a carbon plate.  
     
     
       42. The method of claim 31 wherein at least one insert material includes carbon fibers.  
     
     
       43. A method of constructing a printed wiring board including a constraining core, comprising:
 providing a base substrate material;   removing at least one section of the base substrate material;   providing an insert material for at least one section of the base substrate material removed, wherein each insert material can be contained within a respective removed section;   placing each insert material in a respective removed section to form a constraining core layer;   arranging the constraining core layer in a subassembly stack up that includes B-stage (semi-cured) layers of dielectric material on either side of the constraining core layer and at least one additional layer of material;   laminating the subassembly stack up;   arranging the laminated subassembly in a stack up that includes B-stage (semi-cured) layers of dielectric material on either side of the laminated subassembly and at least one additional layer of material; and   performing a lamination cycle on the stack up that causes the resin in the layers of dielectric to reflow and bind adjacent layers within the stack up.    
     
     
       44. The method of claim 43, wherein at least one insert material includes carbon.  
     
     
       45. The method of claim 43, wherein at least one insert material is a carbon plate.  
     
     
       46. The method of claim 43, wherein at least one insert material includes carbon fibers.  
     
     
       47. The method of claim 43, wherein the constraining core is electrically conductive.  
     
     
       48. The method of claim 47, further comprising drilling a pattern of clearance holes in the laminated subassembly.  
     
     
       49. The method of claim 48, further comprising drilling through holes through the laminated stack up and plating the through holes to create at least one electrical connection between the electrically conductive core and at least one additional layer of material.  
     
     
       50. The method of claim 49, wherein drilling a pattern of clearance holes further comprises:
 determining the location and required width of a clearance channel from a printed wiring board design;   determining the distance between notches that are likely to be created when a selected drill bit and drill pitch are used to drill the channel; and   selecting a drill bit and drilling pitch so that the distance between the notches closest to a plated through hole is not less than a predetermined clearance diameter.    
     
     
       51. The method of claim 50, further comprising:
 identifying a plated through hole that creates an electrical connection with the electrically conductive constraining core, which is closest to the clearance channel, using the printed wiring board design;   determining the distance between the clearance channel and the identified plated through hole;   selecting the drill bit and drilling pitch so that the resulting channel does not overlap the location of the identified plated through hole.    
     
     
       52. The method of claim 51, further comprising:
 determining the height of the notches; and   selecting a drill bit and drilling pitch so that the height of the notches is less than 3 mil.    
     
     
       53. The method of claim 52, further comprising selecting a drill bit and drilling pitch so that the height of the notches is less than 1 mil.  
     
     
       54. A method of constructing a constraining core for use in a printed wiring board, comprising:
 providing a base substrate material;   removing at least one section of the base substrate material;   providing an insert material for at least one section of the base substrate material removed, wherein each insert material can be contained within a respective removed section;   placing each insert material in a respective removed section to form a constraining core layer;   arranging the constraining core layer in a stack up that includes B-stage (semi-cured) layers of dielectric material on either side of the constraining core layer and at least one additional layer of material; and   performing a lamination cycle on the stack up that causes the resin in the B-stage (semi-cured) layers of dielectric to reflow and bind the layers.    
     
     
       55. The method of claim 54, wherein at least one insert material is includes carbon.  
     
     
       56. The method of claim 54, wherein at least one insert material is a carbon plate.  
     
     
       57. The method of claim 54, wherein at least one insert material includes carbon fibers.