Hand Soldering A Crystal Oscillator Without Hidden Damage A quartz crystal that oscillates correctly on the bench can still fail weeks later because of what happened during soldering. The damage is rarely a visible crack or a lifted pad. It is a slow shift in frequency, a rise in equivalent…

Test Limits and Guard Bands: Setting an Acceptance Window A test limit that is set equal to the design specification will fail good units. The measurement has its own uncertainty and the process has its own spread, and both must be accounted for before a limit is written into a…

ESD Protection Devices: Selection and Placement A protection device that is not on the board, or that is on the board but a centimetre from the connector, provides much less protection than its data sheet implies. The selection and the placement are one decision. What the Device Must Do The…

Laser Marking Serial Numbers on PCB Assemblies: Practical Notes A serial number marked on the board is what allows a field failure to be traced back to a manufacturing lot, and laser marking has become the usual way of applying it because nothing touches the surface and nothing is consumed.…

PCB Teardrop Application: From Prototype to Volume Production Buyers and engineers often focus on the finished product and forget the production line behind it. In practice, most field failures can be traced back to process decisions made during assembly. Understanding PCB teardrop application gives you a practical advantage when you…

Production Test Strategy: Choosing Between ICT, Flying Probe and Functional Every test method detects a subset of the possible faults and costs a certain amount per board. A test strategy is the choice of which methods to use, in which order, and what to do with what they find. What…

In-System Programming in Production: Setup and Control A board that leaves the assembly line without firmware is not a product. Programming has become part of the assembly process, and it introduces its own requirements on the layout, the test and the traceability. Where Programming Fits Programming can be performed before…

In-Circuit Test Versus Functional Test: Choosing the Right Gate In-circuit test and functional test answer two different questions, and the argument about which one to use is usually resolved by deciding what the factory needs to know when a board fails. One test tells you which component is wrong, and…

Reflow Preheat and Soak Zone Control for SMT Assembly The first half of a reflow profile decides most of what happens in the second half. Preheat brings the assembly up to temperature without stressing it, and the soak zone gives flux time to activate and clean the surfaces before the…

PCB Blind and Buried Vias: From Design to Repeatable Production 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 blind and buried vias from the perspective of a…