... melting the epoxy resin and spreading it across the hole wall during its up and down motion. The epoxy smear causes poor and in | PRINTED CIRCUIT BOARDS MAKER | some cases non electrical continuity to the innerlayers as well as poor adhesion of the plated copper to the hole wall. In desmear, the chemical | PRINTED CIRCUIT BOARDS MAKER | attack is designed to remove only the surface smear of resin from the hole wall, without attacking the wall structure itself. For most needs desmearing | PRINTED CIRCUIT BOARDS MAKER | is sufficient whilst for some military applications it is necessary to etchback 75mm for what is referred to as 3 point contact. Etchback is a | PRINTED CIRCUIT BOARDS MAKER | stronger chemical attack than desmearing. It is designed to remove not only the smeared resin, but also additional resin from the wall structure and the | PRINTED CIRCUIT BOARDS MAKER | remaining protruding glass fibres. There are various methods of desmearing and etchback available to multilayer manufacturers. Permanganate works on the principle of oxidising the epoxy | PRINTED CIRCUIT BOARDS MAKER | smear. Advantages are its predictability, its wide operating window and its ability ...
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... by encapsulation, polishing, etching, staining, etc. | MID | (3-D) 3-dimensional molded interconnect devices | MINIMUM ANNULAR RING | The minimum width of metal, | PRINTED CIRCUIT BOARDS MAKER | at the narrowest point, between the edge of the hole and the outer edge of the terminal area. This measurement is made to the drilled | PRINTED CIRCUIT BOARDS MAKER | hole on internal layers of multilayer printed boards and to the edge of the plating on outside layers of multilayer boards and double sided boards. | PRINTED CIRCUIT BOARDS MAKER | | MINIMUM ELECTRICAL | Spacing The minimum allowable distance between adjacent conductors that is sufficient to prevent dielectric breakdown or corona or both, between the | PRINTED CIRCUIT BOARDS MAKER | conductors at any given voltage and altitude. | MINIMUM PLATED-THROUGH HOLE | Size A hole size equal to the specified hole size before plating, less | PRINTED CIRCUIT BOARDS MAKER | the manufacturing tolerance, less four times the minimum plating thickness. | MISREGISTRATION | The lack of dimensional conformity between successively produced features or patterns. | | PRINTED CIRCUIT BOARDS MAKER | MOUNTING HOLE | A hole used for the ...
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... baths call for a great deal of analysis and supervision due to the narrow processing slit. The process of solder mask coating as well | PRINTED CIRCUIT BOARDS MAKER | as de- oxidation of bare copper surfaces (activation) must perfectly match the gold plating. To prevent the risk of poor metallic deposition on the gold surface, | PRINTED CIRCUIT BOARDS MAKER | vias must be completely free of solder mask coating or be completely closed by means of a special filling process. Curing of the solder mask | PRINTED CIRCUIT BOARDS MAKER | coating must also concur with that of the chemical gold plating as it is exposed to hydrogen in the 90° C nickel baths. One has | PRINTED CIRCUIT BOARDS MAKER | the choice between an expensive coating system or a subsequent infrared solidification which, in turn, also calls for further investment in facilities. THE POTENTIAL For | PRINTED CIRCUIT BOARDS MAKER | a lead free altenative provided the PCB manufacturer ensures optimal conditions for immersion nickel gold coating, the results of wave soldering are equally good to | PRINTED CIRCUIT BOARDS MAKER | solder levelling. Good storage ability is also achieved by covering the pad and smd sides ...
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