X-Ray Inspection of BGA and QFN Joints Why X-Ray Is Needed A ball grid array hides every joint underneath the package, and a quad flat no-lead part hides its joints under the body edge. Optical inspection sees the package and nothing else, and functional test sees only the nets that…

Thermal Vias: Design and Copper Filling Where the Heat Goes A surface mount power device conducts most of its heat into the board through the thermal pad on its underside, not through the package body into the air. That pad sits on a copper land, and the land has to…

PCB Via Plating Thickness Ratio: The Copper in the Wall Modern electronics depend on boards that are assembled correctly the first time. Every product – a phone, a charger, a medical instrument or an industrial controller – relies on thousands of solder joints that must conduct current for years. This…

Stencil Aperture Design and Paste Volume The Deposit Decides the Joint Every soldered joint on a surface mount assembly begins as a printed deposit of paste, and the volume of that deposit is the single largest influence on whether the joint is sound. Too little paste and the fillet is…

Copper Filling Versus Conductive Paste Via Fill Why Vias Are Filled At All A plated via is a hole with a thin conductive wall and an open middle. That is fine for a signal via in an ordinary board, but it becomes a problem in three situations: when a via…

SMT Reflow Solder Paste Powder Size: The Grain in the Paste Electronics manufacturing has become a discipline of small details. Solder paste volumes, placement accuracy, temperature profiles and inspection limits all add up to the final result. This guide looks at SMT reflow solder paste powder size from the perspective…

OSP Versus ENIG: Surface Finish Selection What the Finish Has To Do The copper on a pad has to remain solderable from the moment the board leaves the plating line until the last joint is made, which may be weeks later and several thermal cycles away. The surface finish is…

PCB Copper Trace Width Control: Keeping the Width on Target Electronics manufacturing has become a discipline of small details. Solder paste volumes, placement accuracy, temperature profiles and inspection limits all add up to the final result. This guide looks at PCB copper trace width control from the perspective of a…

PCB Stackup Design: Layers, Planes and Symmetry Why the Stackup Comes First The stackup is the arrangement of copper layers and dielectric layers that the board will be built from, and it is decided before the routing, not after. Every signal layer needs a reference plane at a known distance,…

Via in Pad: Filling, Plating and Design Why Put a Via in a Pad Placing a via directly in a component pad solves two problems at once. It removes the short stub of trace that would otherwise run from the pad to a via placed beside it, which matters at…