Scanning Acoustic Microscopy for Package Delamination Some of the most damaging defects in a plastic package are invisible from the outside and completely transparent to X-ray. A thin layer of air between the mould compound and the die pad, or between a solder mask and a copper plane, changes almost…

SMD Aluminium Electrolytic Capacitor For Reflow A radial aluminium electrolytic capacitor is one of the last through hole components on many boards. It cannot be placed by a machine that expects a flat body with solderable pads, so it is inserted by hand, clinched, and soldered in a wave. That…

Power Thick Film Resistor With Thermal Monitoring A resistor that has to absorb a large amount of energy in a short time, or dissipate a continuous power that a chip resistor cannot handle, moves into a different class of package. The element is printed onto a ceramic substrate and housed…

SMT Assembly Process Overview: From Paste to Test A surface mount line is a sequence of machines that each do one thing well, and the quality of the finished assembly is decided by how well the steps agree with each other. Paste, placement and profile are one system rather than…

FPC Test Clip Connection For Flex Testing Testing a flex circuit during development is awkward in a way that a rigid board is not. The conductors are on a thin, compliant substrate, the pitch at the connector is often 0.2 or 0.3 millimetres, and the gold fingers at the edge…

Active Crystal Oscillator: Preparation, Placement and Process Control An active crystal oscillator packages the quartz blank and the sustaining circuit in one component, so the designer gets a logic level output instead of a raw resonant element. That saves the load capacitors, the feedback resistor and the start up tuning…

Ball Shear and Pull Testing for Solder Joint Strength A solder joint that looks perfect can still be weak. Voiding, partial wetting, brittle intermetallic layers and contaminated pad finishes all hide beneath a smooth fillet, and none of them show up reliably under a microscope. Mechanical testing exists to expose…

Strain Gauge: Design Rules and Process Limits A board can be perfectly soldered and still fail later because the assembly process bent it. Strain measurement is the tool that turns that suspicion into a number. It is used to qualify a new fixture, to compare two depaneling methods, to set…

EDX Analysis and SEM Imaging in PCB Failure Analysis Failures rarely announce their own cause. A pad that lifts after reflow, a joint that cracks in the field, a residue that corrodes a trace months after shipment — each of these leaves chemical fingerprints behind. When a board fails, the…

Repair Strategy: Levels of Repair and Spares Planning How far a repair goes depends on where it is performed and on what the repaired unit must subsequently be trusted to do. A repair at the production line and a repair in a service centre are different operations with different requirements.…