Electroless Nickel Bath: Design Rules and Process Limits The electroless nickel bath deposits the nickel layer that carries the gold in an ENIG finish, and its chemistry decides the phosphorus content of that layer. Unlike an electrolytic cell, the bath plates by chemical reduction, so the deposit forms on every…

IMC Growth: 6 Rules for Solder Joint Life IMC growth is the thickening of the intermetallic compound layer that forms where solder meets copper or nickel, and it begins in every solder joint from the moment the alloy melts. A thin layer is what makes the solder joint possible, because…

Laser Drill Taper Control: 5 Rules for HDI Blind Vias A laser drill taper is the difference between the diameter a blind via shows at the copper surface and the diameter it reaches at the bottom of the hole. On a nominal 75 um target the entry may open to…

Solder Dam: 6 Rules Against Wave Bridging A solder dam is a narrow wall of cured solder mask left between two conductive features to stop molten solder from joining them during wave soldering. It is a printed barrier rather than a mechanical one, and it works because solder will not…

Desmear Swelling Step: 5 Checks Before Permanganate The desmear swelling step is the first chemical stage of hole wall preparation, and it decides how much the permanganate that follows can achieve. Its solvents penetrate the resin, soften it and open the structure so that the oxidiser can attack the smear…

PTH Conditioner Bath: 5 Checks Before Activation The PTH conditioner is the first chemistry a drilled hole meets, and its job is to make the hole wall wettable. Without it, the desmeared surface repels the activator, and the palladium catalyst deposits unevenly or not at all on the resin and…

Contact Angle: 6 Rules for Wetting Checks A contact angle is the angle a droplet of liquid makes with a solid surface where the two meet, and it is a direct reading of how well that liquid wets that solid. On a circuit board the liquid is usually water or…

Microsection Preparation: 6 Rules for Clean Cuts Microsection preparation is the sequence of cutting, mounting, grinding, polishing and etching that turns a piece of a board into a surface that can be examined under a microscope and measured. Every step changes the surface, and a mistake in any of them…

Anode Area Ratio: 5 Checks for Balanced Plating Anode area ratio is the relationship between the surface area of the anodes and the surface area of the work being plated, and it decides how the plating current is distributed before any chemistry is considered. A tank with too little anode…

Spray Fluxer: 6 Rules for Flux Deposition A spray fluxer applies flux to the underside of a board as a fine aerosol, and it replaced foam and wave fluxing because it puts down only the flux the joint needs. The spray fluxer is also the part of a wave soldering…