Component Package Selection Guide Component package selection happens early and is decided by whoever is buying the parts, the engineer who designed the circuit, or the person who has to fit it on the board. The choice sets the footprint, the thermal path, the parasitic inductance and the supply risk,…

Solder Sphere Quality and Ball Diameter Control for BGA The solder sphere is the smallest component in a ball grid array package and the one that decides whether the package can be assembled at all. Diameter variation, poor sphericity and surface oxide all surface later as bridging, opens or voids,…

Moisture Sensitivity Level: Design Rules and Process Limits The moisture sensitivity level of a package is a number from one to six that describes how long it can be exposed to air before it must be baked. It exists because a plastic package absorbs moisture from the air, and at…

Drill Bit Regrind And Hit Count Management A carbide drill bit for a printed circuit board is a precision tool made to a tolerance of a few microns, and it wears out long before it breaks. The cutting edge rounds, the margin wears, the diameter changes and the surface of…

Copper Voids And Plating Quality In PCB Barrels The copper that lines a plated hole is deposited atom by atom from a bath, and it is possible for the deposit to grow with a gap inside it. A copper void is a cavity in the plating, usually at the corner…

Vacuum Lamination And Void Control In Multilayer Boards A multilayer board is made by pressing several layers of copper and prepreg together until the resin flows, fills the gaps around the copper and cures into a solid block. If the resin does not fill a gap, the result is a…

Solder Joint Inspection Methods Guide Solder joint inspection is a chain of methods rather than a single test. Each one sees a different part of the joint, and each one is blind to something that another can see. A visual check finds a bridge on a lead and misses a…

Solder Paste: Design Rules and Process Limits Solder paste is a mixture of metal powder and flux, and both halves of that mixture have to be chosen for the board rather than picked from a catalogue. The alloy sets the temperature at which the joint forms and the mechanical behaviour…

PCB Coupon Design Guide A pcb coupon is a structure that is built onto the production panel but is not part of the product. It exists so that something can be measured, cut, or cycled without destroying a board. A panel without a coupon is a panel whose process can…

Ionic Contamination Testing On Assembled Boards Cleanliness is invisible, so it has to be measured rather than judged by appearance. A board with a heavy rosin residue may be perfectly clean in the electrical sense, while one that looks spotless may carry enough ionic material at a connector to promote…