Supplier Selection Key to Assembly Reliability

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Defining terms is always a good point to start, and from a practical standpoint, reliability can be simply defined as performance to both the design intent for the expected life cycle of the product.

When asked to discuss supply chain strategy, EMS and OEMs often respond with something like, “Yes of course, we have a purchasing department.” Supply chain management has progressed far beyond the old school purchasing mentality to become a key component of the modern business organization. We are all just pieces in the supply chain puzzle that is responsible for getting the ultimate customer’s product to market.

The first step in developing an SCM program is to identify all purchased materials (and services) into two categories, standard and critical. Suppliers of critical materials are the ones that need to be controlled; you probably don’t want to spend too much time managing your supplier of stationary and paperclips. A raw PCB supplier is a perfect example of a critical material, both from a technology complexity standpoint as well as a risk level. It only takes one defective $25 printed circuit board to destroy $2,500 worth of perfectly good electronic components.

Qualification Criteria

Strategically, deciding how to qualify new suppliers is the most critical step in the process. Of course, there must be an overriding strategy governing supplier identification and selection, but that would be a whole other column. The underlying tool should be an audit/survey that measures the quality system, financial viability and technology. Audits are frequently based on ISO 9000, which would be preferable if ISO registration is another qualification criterion (which is highly recommended). There should be a re-audit frequency established and some provision for the supplier to provide demonstration of continued capability for the time period between audits. This could be in the form of quarterly Cpk reports, ISO surveillance audit summaries, etc.

What is found too often are that suppliers have been grandfathered onto an AVL because they have always supplied materials, and that no one has ever audited the facility. Or, the only existing control is a self-audit that the supplier completes with no verification (which is probably ok since we all know that no one ever embellishes on their capabilities when filling out one of these!).

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Editor's Note: This article originally appeared in the January 2014 issue of SMT Magazine.