Heat Sink Mounting and PCB Thermal Design Adding a heat sink to a hot component is the obvious answer to a thermal problem, and it is often the wrong one. The heat sink is only the last element in a chain that runs from the silicon junction, through the die…

Reflow Profile for Boards With Mixed Thermal Mass A board with a heavy connector at one end and a fine pitch package at the other cannot reach the same temperature everywhere at the same time. The single profile that suits both is a compromise, and understanding the compromise is what…

Level Shifter Interface Circuit Design Modern boards mix logic families, and a 3.3 volt processor often has to talk to a 5 volt peripheral or a 1.8 volt radio. Connecting them directly risks both damage and unreliable operation, so a level shifter is inserted between the two domains. The circuit…

Solder Mask Printing: Process Steps And Controls Solder mask is applied over the whole panel and then patterned, which means the printing step is only one part of a sequence. Getting it right depends on what happened before the ink touched the board and what happens after it is exposed,…

Where to Put a Stiffener on a Flexible Printed Circuit A stiffener is a patch of rigid material bonded to a flexible circuit to give it local rigidity, and it is what allows a connector, a component or a screw hole to survive on a board that is otherwise designed…

Comparator Hysteresis and Interface Design A comparator converts an analogue level into a logic decision, and the decision is only as good as the circuit around it. A comparator with no hysteresis will switch repeatedly when the input passes slowly through the threshold, and the resulting burst of edges is…

Assembling MEMS Flow Sensors on a Production Line A micro electro mechanical flow sensor measures the movement of air or gas across a small heated element or a diaphragm. The sensing structure is on the scale of tens of micrometres, and it is packaged in a cavity that has to…

Assembly Data Preparation: BOM, Placement File and Rotation Errors The assembly machine is programmed from data, and the data arrives from several sources that must agree. When they do not, the result is a board that is built exactly as instructed and is nevertheless wrong. What the Data Set Contains…

SMT Component Identification: Packages and Markings Surface mount parts are identified by their package, their marking and their position on the board. The information is small and often abbreviated, and being able to read it quickly is what keeps an assembly line moving and a repair from turning into a…

Battery Tab Welding: Welding Battery Tabs, Connecting Plates and Terminals A battery pack is assembled from cells that are joined to each other and to the outside world through tabs, connecting plates and terminals. Those joints carry the full current of the pack, they are made from dissimilar metals in…