Nitrogen: Preparation, Placement and Process Control A reflow oven filled with nitrogen reduces the oxygen available to the joint while it is molten. The consequence is better wetting and less oxidation, and the size of the benefit depends on the paste and on the joint being formed. What the Oxygen…

PCB Tolerance Stack-Up for Connector Mating A connector mates reliably when the two halves arrive within a range of positions that the contact design can absorb. The board contributes part of that variation and the housing contributes the rest, and the only way to know whether the budget is met…

Reflow Oven Maintenance and Verification A reflow oven is a machine with heaters, blowers, a conveyor and sensors, and each of them degrades with use. Maintenance keeps the machine capable, while verification proves that the capability has been restored. The two are often combined into a single activity, and the…

Assembly Ergonomics and Workstation Design A workstation determines how well an operator can see, reach and handle the product, and those three factors decide both the defect rate and the rate at which the person tires. Ergonomics is therefore a quality subject rather than a comfort subject. The design is…

PCB Depanelising Tooling Selection Depanelising is the step where the finished boards are separated from the panel, and it is also the step that damages more assemblies than any other mechanical operation. The tooling choice determines the edge quality, the stress on the components and the cycle time. The decision…

Tombstoning Root Cause Analysis A tombstoned component stands on one end, lifted off the second pad with its unmetallised side in the air. It is one of the most recognisable defects in surface mount assembly and also one of the most misdiagnosed, because the visible result is produced by several…

Adhesive Cure Control in PCB Electronics Assembly Guide Adhesives hold together more of an assembled board than most people realise: they attach components before wave soldering, they stake heavy parts against vibration, they underfill area array packages, and they seal connectors and housings. In each case the adhesive only does…

Laminate Moisture Control Before Lamination Laminate absorbs water from the air, and the amount it holds depends on the resin system, the humidity and how the material has been stored. When a stack is laminated with that water still inside, the press turns it into steam, and the result is…

Calibration and Measurement Traceability in Assembly A measurement is only useful if the instrument that produced it is known to be correct. Calibration establishes that, and traceability establishes that the correctness is anchored to a reference that others can also reach. Which Instruments Need It Instruments whose readings decide acceptance…

Reflow Defect Troubleshooting Flow A reflow defect that appears without warning usually has a cause that has been present for some time, either as a change in the product or as a drift in the process. The troubleshooting sequence exists to find it in a defined order rather than by…