Electrostatic discharge is a serious concern throughout the printed circuit board assembly process, and that includes test activities.

ESD can not only cause immediate failure of semiconductors, but can also cause damage that introduces latent faults that do not materialize until later, when the product is in the hands of customers. We are therefore used to controlling ESD during manufacturing, both in the factory environment and also in the tools that come into contact with boards.

Sometimes overlooked, this also includes test fixtures. The probe plates of bed-of-nails style fixtures are often made from plastic materials, and have the potential to generate high static charges. Phenolic and fiberglass materials are usually low risk, but low-cost fixtures sometimes use acrylic, acetal (Delrin), polyamide (Nylon) or other plastics that are not. ESD-safe versions of these materials exist, made by adding carbon black, but may be too conductive to be suitable.

Merifix low-cost fixtures use medium density fiberboard (MDF) for the probe plate. This is strong, rigid, easily and accurately machinable, dimensionally stable, and does not pose an ESD risk. Handling the material does not give rise to static charges, and the surface resistivity is low enough to dissipate any that are present from other sources. Functionally, the bulk material is a good insulator so leakage currents are not an issue, even for closely spaced test probes.

It is important to consider ESD throughout all stages of the manufacturing process to ensure product quality, and reduce costs associated with rework, scrap and returns.