Head in Pillow Defects in BGA Assembly A head in pillow defect is a ball grid array joint in which the solder ball on the package and the solder paste on the board have each melted and solidified without merging. The two form a shape that looks like a head…

Solder Wick Selection for Board Rework and Cleaning Solder wick is a braid of fine copper strands that removes molten solder by capillary action, and it is the most common tool used in rework after the soldering iron itself. It is simple, cheap and easy to misuse: the same braid…

Non Wet Open Defects Explained A non wet open is a joint where the solder never bonded to the pad at all. The solder may sit on the surface, it may have formed a ball beside the pad or it may appear to have covered it, but the interface is…

Bottom Terminated Components: Placement and Reflow Guide Bottom terminated components cover a wide family: quad flat no lead packages, dual flat no lead parts, land grid arrays and the many power packages whose only connection is a pad underneath the body. They are attractive because they are small and because…

Impedance Controlled Stackup Design Impedance control means that the characteristic impedance of a trace is specified as a number and built to a tolerance, rather than being accepted as whatever the geometry happens to give. It matters for every interface that has a specification attached, from a single ended clock…

Component Placement Accuracy in SMT Placement accuracy is the difference between where a component was intended to be and where it actually landed. It is quoted as a machine specification, but the number that reaches the board is the sum of several contributions, and only some of them belong to…

Thermal Via Design Guide A thermal via is a plated hole whose purpose is to carry heat rather than current. It connects a hot component to an internal or a bottom layer that can spread the heat into a larger area, and it is the cheapest thermal improvement available to…

Taping And Reel Requirements For SMT Components Components arrive at the placement machine on carrier tape wound onto a reel. The tape is part of the packaging, but it is also part of the feeding system, and a defect in either role stops the line. Requirements for taping therefore sit…

Miniaturization Challenges in PCB Design Miniaturization is rarely a single decision. It arrives as a requirement for a smaller enclosure, a lighter product or a shorter interconnect, and it is then translated into a set of board level changes that each carry their own cost. The components shrink, the features…

Copper Plating Thickness Distribution Across a Panel Electroplating does not deposit copper evenly, and no practical plating line removes the variation entirely. The copper is thicker at the edges of a panel and around the rack contacts, thinner in the middle and thinner still at the centre of a deep…