BGA Inspection: X-Ray, AOI and Visual Methods Compared A ball grid array package places its electrical connections underneath the body, which is what makes it efficient and what makes it difficult to inspect. Once the part is reflowed, most of the joints are hidden behind the package and the board,…

Layout Rules and Standards That Prevent Rework A rule that nobody understands is followed until it becomes inconvenient and then abandoned. That is why a set of layout rules is worth more when it is short, specific and attached to a reason. The rules themselves are not complicated; what takes…

Layout Design Steps for a Controller Board Layout design can be described in three steps and then takes years to master. The steps are the schematic, the netlist that carries the connectivity across, and the physical layout itself. Everything else, including the placement rules and the routing constraints, is detail…

Flexible Circuit Board Types: Single, Double, Multilayer, Rigid-Flex Most design guides treat flexible circuits as one category, which is why so many first attempts pick the wrong construction. In practice there are four families, and the cost, the layer count, and the assembly difficulty rise sharply as you move up.…

Flexible Circuit Board Construction and Assembly Notes A flexible circuit board is often described as a thin rigid board that bends, and that description leads to bad decisions. The construction is different in kind, not just in thickness. The base is a film rather than a woven glass laminate, the…

PCB Solder Mask Color: Which One Should You Choose? Ask two engineers why one board is green and another is blue and the answers will usually be tradition and appearance. The choice does affect something real, though: how light behaves at the surface, how easily an inspection system can see…

Pulse Plating vs DC Plating for PCB Copper Copper plating is what turns a stack of laminated layers into a working circuit, and the way the current is applied to the plating bath decides how evenly that copper is distributed. Conventional DC plating holds a steady current; pulse plating switches…

FPC Stiffeners Compared: Polyimide, FR4 and Stainless Steel A flexible circuit is thin, and thin circuits do not tolerate being used as a connector. Where a flex tail has to plug into a connector, carry a component or hold a screw, a stiffener is bonded to the back of the…

Via Treatment for a Rigid Flex Board: Design Guide A rigid flex board combines stiff sections that carry connectors and heavy components with flexible sections that fold into the shape of the product. The vias are the same in principle as on any other board, but the flexible region changes…

Exposed Copper on PCB Pads: Finishes and Solderability Bare copper is the best conductor on the board and the worst surface to leave exposed. It oxidises within hours in a normal room, and the oxide that forms does not wet with solder, does not accept a wire bond and does…