... has helped to establish these two laser types as industry workhorses in applications from prototyping to full production runs. For manufacturers, the key to | PRINTED WIRING BOARDS INDUSTRY | cost-effective, high-volume microvia formation lies in understanding the unique capabilities of these two lasers (Table). Comparison of Laser Capabilities Laser Type UV DPSS RF CO2 | PRINTED WIRING BOARDS INDUSTRY | Compatible Dielectric Types FR-4, RCF, Polyimide, PTFE, Aramid FR-4, RCF, Polyimide, PTFE, Aramid Microvia Diameter in Production 25 mm to 150 mm 80 mm to | PRINTED WIRING BOARDS INDUSTRY | 250 mm Typical Drilling Speed 30-mm diameter via at 100 holes per second (copper + dielectric) 100-mm diameter via at 450 holes per second (dielectric | PRINTED WIRING BOARDS INDUSTRY | only), 170 holes per second (copper + dielectric) Direct Copper Drilling Speed 30-mm diameter via at 100 holes per second 100-mm diameter via at 200 | PRINTED WIRING BOARDS INDUSTRY | holes per second (specially treated copper) Decreasing sizes of semiconductor devices will require smaller via holes on PCBs. As the number of I/Os on devices | PRINTED WIRING BOARDS INDUSTRY | increases into the thousands, routing ...
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... utilised by designers trying to maximise board real estate by increasing the density of lines and pads. However, many manufacturing and design issues must | PRINTED WIRING BOARDS INDUSTRY | be addressed before adventuring down this path. Due to the many additional oper- ations, the cost of a blind or buried via board is significantly | PRINTED WIRING BOARDS INDUSTRY | higher than that of a multilayer of the same layer count. | BURIED VIAS | A buried via is a copper-plated hole, imbedded in the | PRINTED WIRING BOARDS INDUSTRY | board, that interconnects two internal layers. The buried via process starts by drilling holes on thin core laminate. These cores are then metallised, imaged and | PRINTED WIRING BOARDS INDUSTRY | etched before being laminated. Individual manufactuer´s method of fabricating multilayer boards mast be understood before designing bboards with buried vias. Designed an manufactures layer sequence | PRINTED WIRING BOARDS INDUSTRY | must match | BLIND VIAS A BLIND VIA | is a copper-plated hole that interconnects a board's external layer to one or more internal layer(s) | PRINTED WIRING BOARDS INDUSTRY | but not through to the other external layer. There are two ...
[ Printed Wiring Boards Industry ]


... Smear Removal Before direct metallization, the drilled holes on multilayers have to be desmeared. The main purpose of this treatment is to remove any | PRINTED WIRING BOARDS INDUSTRY | epoxy smeared onto the edge of the inner layer copper pads whilst drilling. The smear is the result of a hot drill melting the epoxy | PRINTED WIRING BOARDS INDUSTRY | resin and spreading it across the hole wall during its up and down motion. The epoxy smear causes poor and in some cases non electrical | PRINTED WIRING BOARDS INDUSTRY | continuity to the innerlayers as well as poor adhesion of the plated copper to the hole wall. In desmear, the chemical attack is designed to | PRINTED WIRING BOARDS INDUSTRY | remove only the surface smear of resin from the hole wall, without attacking the wall structure itself. For most needs desmearing is sufficient whilst for | PRINTED WIRING BOARDS INDUSTRY | some military applications it is necessary to etchback 75mm for what is referred to as 3 point contact. Etchback is a stronger chemical attack than | PRINTED WIRING BOARDS INDUSTRY | desmearing. It is designed to remove not only the smeared resin, but also additional resin from the wall structure and ...
[ Printed Wiring Boards Industry ]