Press Fit Connectors in Assembly What a Press Fit Connection Is A press fit connector is attached to the board without solder. Each pin is a compliant metal shape that is slightly larger than the plated hole it enters, and pressing the pin into the hole deforms it so that…

Castellated Holes for Module Edges What Castellated Holes Are A castellated hole is a plated through hole that has been cut in half at the edge of the board, leaving a plated semicircular channel along the edge. The result is a connection that can be soldered flat onto a pad…

Tented Vias and Solder Mask Coverage What Tenting Means Tenting is the practice of covering a via opening with solder mask so that the hole is sealed by a film of mask rather than by a plug of material. The mask spans the opening and, in a well-made board, adheres…

Via Plugging and Filling Methods Why Vias Are Plugged A via is a hole in the board, and an open hole causes problems after soldering. Solder paste can wick down the barrel and out the other side, leaving a starved joint on the surface and a blob of solder on…

Solder Fillet Criteria for Inspection Why Fillet Criteria Exist The fillet is the visible part of a solder joint, and it is the only part an inspector can see. Criteria exist so that different inspectors, on different shifts, in different factories, reach the same conclusion about whether a joint is…

Solder Pot Maintenance and Dross Control Why Pot Condition Matters The solder pot is the reservoir that feeds every wave or fountain joint on the line, and its condition determines the quality of all of them. Alloy composition, temperature, and cleanliness change over time as the pot is used, and…

Solder Paste Inspection on the Line What Paste Inspection Measures Solder paste inspection examines the printed deposits before components are placed, which makes it the earliest opportunity to catch a defect on the line. The system measures the height, area, and volume of each deposit and compares them with the…

EMI Shielding on Assembled Boards Why Shielding Is Added at Assembly Electromagnetic interference is a system problem, but the first line of defence is often at the board. A shield placed over a noisy circuit keeps its emissions inside, and a shield over a sensitive circuit keeps external fields out.…

HDI Design Rules for Dense Boards What Makes a Design HDI High density interconnect is defined by the use of microvias, laser-drilled holes that are much smaller than conventional plated through holes, combined with finer traces and tighter spaces than a standard board allows. The result is more routing per…

Microsection Analysis of PCB Quality What a Microsection Shows A microsection is a cross-section of a printed circuit board that has been mounted in resin, ground and polished back to a plane, and examined under a microscope. It turns the board’s internal structure into something that can be measured: copper…