Design for Manufacturing

The majority of new part and assembly introductions happen during research and development. Because the components are new, very few particulars are known, other than the information documented on datasheets or in trade press announcements.

An engineer may have read a magazine or journal article featuring a new design with application notes that highlight a new part. Or perhaps demand for the new part may have come from viewing a competitor's product or having discovered the component at a recent tradeshow. Questions concerning cost and sample or volume availability remain unanswered until the research for the part selection process is complete.

Think design, early on
Manufacturers, distributors, and logistics are standard considerations when it comes to part availability and suitability. But what happens if a component has been designed and prototyped by your company -- to your form, fit, and functional requirements -- and the circuit design, materials, or processes required to build the product are so unique that no other manufacturer has ever seen, much less produced, anything like it?

Unless you can produce the product in-house to meet your projected volume requirements, you have already put yourself behind the virtual eight ball. If you wait until the prototype is built and working before identifying a potential outside manufacturer, your eventual supplier likely will have to climb a pretty steep and costly learning curve to meet the delivery schedule for your finished product.

With custom materials and dimensions, your company may have to underwrite the supplier's tooling. If your product requires unique testing or inspection methods, the supplier may have to purchase or rent test equipment on an expedited schedule. This could add more cost, as well as delays if the equipment is unavailable or has an extended lead time. Training production or test personnel will also add cost and delays.

Working with engineering
If a company wants to minimize both cost and delays, potential suppliers for proprietary parts and assemblies must be identified as early as possible during the R&D process -- as soon as engineering knows and can articulate the particulars of the build and test requirements. The nondisclosure agreements should be comprehensive and put in place ASAP. Potential suppliers should undergo a thorough capability assessment at their premises, including a historical business analysis.

Once the nondisclosure agreements are signed, the supplier or manufacturer should be invited into the design meetings, where the manufacturing particulars can be reviewed and modified to meet the supplier's core competencies and equipment capabilities. The goal of these meetings is to design the product to match the manufacturer's most efficient methods of operation.

The term for this is "design for manufacturing" (DFM). If the manufacturer has input into the build process, the supplier will be up to speed by the time the product is ready for mass production -- with no surprises that can slow down the production cycle.

Hard lessons
Recently, I was part of a design team that developed a board with a 0.004-inch trace width and 0.004-inch trace-to-trace spacing. It wasn't as easy as calling a PCB fab house and sending it the zipped drawings and Gerber files. The first three vendors selected from the requests for quotes said they did not have the technology for such tight trace spacing. That caught us by surprise. We had to go around the block several more times, and we ended up at an out-of-state fabrication house. We had to pay the extra cost for the special service requirements, and we were crossing our fingers that there would be no ugly setbacks due to product quality issues.

In hindsight, as part of our early production planning, we should have identified several fab houses that could handle the 0.004-inch narrow trace. For our first six boards, we paid $659 each for a one-week turn. Our second round of six cost us $354 for the same turn time. The difference was that we had the time to search for another PCB fab facility. This one had been doing narrow traces for more than a year, and it had developed cost-saving techniques that it was able to pass on to its customers.

This was a hard lesson in DFM. In this case, the DFM acronym could have stood for "design forfeiting money." We paid good money that could have covered the cost of two prototype builds had we gone to the correct manufacturer in the first place.

Bring the potential suppliers and fab house into the early product design stages, and save your company a lot of money, time, and grief.

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