Abstract: An enhanced substrate for making a printed circuit board (PCB) includes a silane applied to the ends of glass fibers in via holes. In one embodiment, during a plated through-hole (PTH) via fabrication process, glass fiber bundles exposed in a drilled through-hole are selectively sealed. For example, after the through-hole is drilled in a substrate, the substrate may be subjected to an aqueous silane bath (e.g., an organo trialkoxysilane in an aqueous solution of an acid that acts as a catalyst) to deposit a layer of silane on the exposed glass fiber bundle ends. For example, trialkoxy groups of the silane may react with exposed silanols on the glass to form a siloxane, which is further polymerized to form a silane polymer barrier layer on the exposed glass fiber ends. The barrier layer effectively seals the glass fiber bundles and eliminates the conductive anodic filament (CAF) pathway between PTH vias.

Abstract: An enhanced mechanism for via stub elimination in printed wiring boards (PWBs) and other substrates employs laser resin activation to provide selective via plating. In one embodiment, the resin used in insulator layers of the PWB contains spinel-based non-conductive metal oxide. Preferably, only insulator layers through which vias will pass contain the metal oxide. Those layers are registered and laser irradiated at via formation locations to break down the metal oxide and release metal nuclei. Once these layers are irradiated, all layers of the PWB or subcomposite are laid up and laminated. The resulting composite or subcomposite is subsequently drilled through and subjected to conventional PWB fabrication processes prior to electroless copper plating and subsequent copper electroplating. Because metal nuclei were released only in the via formation locations of the appropriate layers, plating occurs in the via barrels only along those layers and partially plated vias are created without stubs.

Abstract: An enhanced substrate for making a printed circuit board (PCB) includes a silane applied to the ends of glass fibers in via holes. In one embodiment, during a plated through-hole (PTH) via fabrication process, glass fiber bundles exposed in a drilled through-hole are selectively sealed. For example, after the through-hole is drilled in a substrate, the substrate may be subjected to an aqueous silane bath (e.g., an organo trialkoxysilane in an aqueous solution of an acid that acts as a catalyst) to deposit a layer of silane on the exposed glass fiber bundle ends. For example, trialkoxy groups of the silane may react with exposed silanols on the glass to form a siloxane, which is further polymerized to form a silane polymer barrier layer on the exposed glass fiber ends. The barrier layer effectively seals the glass fiber bundles and eliminates the conductive anodic filament (CAF) pathway between PTH vias.

Abstract: An enhanced mechanism for via stub elimination in printed wiring boards (PWBs) and other substrates employs laser resin activation to provide selective via plating. In one embodiment, the resin used in insulator layers of the PWB contains spinel-based non-conductive metal oxide. Preferably, only insulator layers through which vias will pass contain the metal oxide. Those layers are registered and laser irradiated at via formation locations to break down the metal oxide and release metal nuclei. Once these layers are irradiated, all layers of the PWB or subcomposite are laid up and laminated. The resulting composite or subcomposite is subsequently drilled through and subjected to conventional PWB fabrication processes prior to electroless copper plating and subsequent copper electroplating. Because metal nuclei were released only in the via formation locations of the appropriate layers, plating occurs in the via barrels only along those layers and partially plated vias are created without stubs.