Semiconductor devices checked on the production line

Louise Smyth

IXYS UK Westcode is investing in its Chippenham, UK factory to manufacture a new range of power semiconductor devices, which will be marketed alongside the company's long-established Press-Pack Capsules. Nikon Metrology was chosen to supply the all-important X-ray equipment for checking the quality of the reflow soldering process during production.

Power semiconductor devices are used for switching high currents and voltages and are widely used in the rail, wind turbine, mining and petrochemical sectors. Press-Pack capsules are clamped together under high pressure to achieve the required electrical rating, whereas isolated power modules use integrated circuit on DCB (direct copper bonded) substrate technology. The Nikon Metrology XT V 160 is needed because the reflowed solder, which attaches the chips to their contact pads, must be continuous with a controlled level of voids and X-raying is the only way to see if these conditions have been met.

Fiona Lambert, Process Engineer at IXYS UK Westcode commented, "I previously used a smaller Nikon 130 kV X-ray quality assurance (QA) system when I worked at an electronics company in South Wales, so I knew how easy its equipment is to use. After reviewing what else was on the market, it was clear that their more powerful 160 kV model would best suit our application, which involves penetrating thicker and higher density materials to observe solder coverage."

X-raying is carried out at two stages of manufacture. The first is after the chips have been placed on the blank DCB substrate and reflow soldered. After six built substrates have been electrically tested and soldered onto a 5mm thick aluminium-silicon-carbide baseplate, the whole assembly is X-rayed again.

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