Making PCB Design a Team Approach Print E-mail
Written by W. Scott Fillebrown   
Friday, 31 May 2013 21:52

Let designers be the specialists they are.

In this era of downsizing, it may seem impossible to create a team approach to design, especially in an organization that never has taken this approach to circuit board layout. However, it is possible to accomplish without adding overhead to your company, and the outcome can produce ROI every CFO dreams of.

First, discuss what “team approach” means to your company and then review the benefits with each team member. Once the marketing team outlines a product’s features and goals, and the mechanical engineers outline the specifications, assemble the board development dream team. Minimally, this team should include physical design, fabrication, assembly, procurement and test professionals, each focusing on their individual field of expertise. This team should be led by the R&D electrical engineer, who makes the final decision when the team members’ opinions conflict.

Now that we know who, let’s discuss how.

Let’s start at the beginning … well almost! The schematic is done and you are ready to lay out the board, when you realize you can buy a suite of PCB layout software cheap and do it yourself, right? Wrong! It has been proven that layout professionals design more producible boards from a fabrication and assembly perspective. This is what they do all day (and sometimes all night!), compared with an engineer who might do layout once a month. Not only should the designers be specialists, but they also should coordinate information between the other specialists. While the final approach decision ultimately comes from the R&D engineer, all approaches should be reviewed with the designer, since that person executes the plan from a design perspective.

You may choose to bring your PCB fabrication expert in at an early stage, perhaps even while the mechanical engineer is reviewing the requirements. Doing so may help with panel utilization and bare board manufacturing. It is more common, however, to bring the bare board expert in as component placement wraps up and before routing begins. Some designs may need little to no review, but, as the complexity increases, the need for their expert perspective increases. They can answer questions about controlled impedance requirements, material type and cost considerations around aspect ratios. This review may take 10 minutes or it may take a day; either way, time and money are saved. Time spent during the fabrication discussions will be recovered when fabrication begins. An informed board shop is prepared and does not suffer from delays while waiting for clarifications.

Often, the design for assembly (DfA) review is overlooked. Yes, typically there is very little wiggle room in the placement of components. Yet there is so much more to review than just the placement on the board. There is a more basic issue that first should be reviewed, and that has to do with the component CAD library. A part with a lead that is too long, short or wide must be caught and fixed. The other critical issue has to do with solder mask between pads. A good DfA review can reduce these issues, dramatically affecting first-pass yield through test. In some cases, it could be the difference between a 50% yield and the more typical 95%-plus pass, which clearly affects throughput and cost.

As early in the process as possible, a complete review of the bill of materials (BoM) should be undertaken, and then redone as revisions occur. This does not have to be a long, drawn-out process. Other than the obvious cost considerations, three basic questions should be asked: First, have alternates been called out wherever possible? Are there extremely long lead parts that must be dealt with sooner rather than later? And finally, are any components doomed to obsolescence within the product’s lifetime? Notice the common theme in the assurance of supply. It does not matter how producible a product is. If you cannot supply the materials for it, you cannot ship them to the customer!

The last area is in regard to test. Most people think of test as a yield issue, and that is part of it. A thoroughly tested product results in both a high yield to the end-customer and a highly reliable product. A complete test plan should be devised using a test engineer as the focal point. The goal for the test engineer should be to use, where possible, an off-the-shelf approach to product testing. The test plan should include both a low power and functional test approach. Of all the issues discussed, nothing will kill a new product faster than shipping low-quality, unreliable goods.

This column has covered a lot; however, one area omitted is the cost of this dream design team. At first glance, this looks like a lot of people power, which equals a significant investment in salaries and benefits. This does not have to be the case. An OEM should rely on those who will produce the product to supply the experts in each of their disciplines. In some cases, the best choice may be a turnkey EMS company that has the entire gamut of expertise; in other cases, each supplier might be independent. Regardless, go with experts you can lean on at little to no additional cost.

W. Scott Fillebrown is president and CEO of ACD ( This e-mail address is being protected from spambots. You need JavaScript enabled to view it ). His column runs bimonthly.

Last Updated on Monday, 03 June 2013 15:52
 

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