... for high-volume microvia formation over a broad range of materials and operating conditions. In fact, their adaptability has helped to establish these two laser | MULTILAYER BOARD | types as industry workhorses in applications from prototyping to full production runs. For manufacturers, the key to cost-effective, high-volume microvia formation lies in understanding the | MULTILAYER BOARD | unique capabilities of these two lasers (Table). | COMPARISON OF LASER CAPABILITIES | Laser Type UV DPSS RF CO2 Compatible Dielectric Types FR-4, RCF, Polyimide, | MULTILAYER BOARD | PTFE, Aramid FR-4, RCF, Polyimide, PTFE, Aramid Microvia Diameter in Production 25 mm to 150 mm 80 mm to 250 mm Typical Drilling Speed 30-mm | MULTILAYER BOARD | diameter via at 100 holes per second (copper + dielectric) 100-mm diameter via at 450 holes per second (dielectric only), 170 holes per second (copper | MULTILAYER BOARD | + dielectric) Direct Copper Drilling Speed 30-mm diameter via at 100 holes per second 100-mm diameter via at 200 holes per second (specially treated copper) | MULTILAYER BOARD | Decreasing sizes of | ...
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... webbing, and so forth. For instance, most | FAB SHOPS | want the largest possible clearances in a solder layer so that mask doesn't | MULTILAYER BOARD | end up on pads. On the flip side, copper is not supposed to be exposed. The two requirements - no mask on pads and unwanted | MULTILAYER BOARD | exposed copper - must be balanced. It is not easy to do. How can the designer help? Devise a standardized clearance, or set the clearances | MULTILAYER BOARD | at 1:1, and let the shop do the soldermask enhancement. Here's another issue: | THE SOLDERMASK | webbing between pads on fine-pitch surface mount devices. | MULTILAYER BOARD | Most masks can go to 0.003" without the resist flaking off. However, if the pads are so tightly grouped that the dams between them are | MULTILAYER BOARD | less than 0.003", it's better to construct a mask opening over the entire group. That will make the fabricator's life much simpler. Bear in mind | MULTILAYER BOARD | that a | FABRICATOR'S | spacing tolerances likely differ from yours. For example, take the drill data. When laying out a board, you usually work | MULTILAYER BOARD | with finished ...
[ Multilayer Board ]


... planes swell exponentially, bog down CAM systems, and crash photoplotters. After the basic prep work is completed, step into the fabrication analysis arena, where | MULTILAYER BOARD | the game is one of checks and balances. You've got your design rules; fabricators have theirs. Checks and balances can resolve any conflicts between the | MULTILAYER BOARD | two. Take soldermask layers, for instance. Often, these layers are not "intelligent" layers within a CAD tool; that is, there is not much in the | MULTILAYER BOARD | way of capability checking within the tool. As a result, these are among the more troublesome layers for fabricators. The solution here is a fabrication | MULTILAYER BOARD | analysis tool that can handle such issues as clearances, coverage, webbing, and so forth. For instance, most fab shops want the largest possible clearances in | MULTILAYER BOARD | a solder layer so that mask doesn't end up on pads. On the flip side, copper is not supposed to be exposed. The two requirements | MULTILAYER BOARD | - no mask on pads and unwanted exposed copper - must be balanced. It is not easy to do. ...
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