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Minimize or Avoid ECOs

Engineering change orders or ECOs have been around for as long as one can remember. Itís gotten to the point that ECOs are like a way of life for OEMs, contract manufacturers (CMs) and EMS providers. People have just come to accept ECOs.

Fig. 1

But, the one saving grace is a highly conscientious group of PCB design engineers in our industry who make it a point to do everything in their power to avoid ECOs.

These PCB designers focus on seven key areas that are most likely to create ECOs. Those seven are component selection, memory, moisture sensitivity levels or MSL, design for test or DFT, cooling methodologies, heat sinks, and coefficient of thermal expansion or CTE.

Click on this link and check out our article in EE Times/Embedded.com to find out more about avoiding ECOs.

Here are some tips and hints on some of the ways to avoid ECOs:

  • Poor component selection is probably the biggest ECO magnet. This means the PCB designer needs to conduct a thorough research on the set of components used on your PCB project.
  • Everybody wants to use the newest, greatest, most powerful component or IC. But it is highly prudent to check out the specs first to see how the chipís characteristics relate to the PCB design.
  • Find out how far the PCB designer goes to check out manufacturing aspects as they relate to your component package types.
  • The experienced PCB designer depends on good heat dissipating techniques to avoid overheating and solder mask de-lamination, as shown in Fig. 1 (see image above).
  • Also, the savvy PCB designer places special attention on design for test (DFT) and placing at the right places on the board the test probing points.
  • Careful with the inexperienced PCB designer when it comes to heat sinks. It the right heat sink isn’t specified, then an ECO is created.

It’s also worth putting more attention on component selection as the one area that generates more ECOs. The main cause behind this is simply due to the fact an inexperienced designer inadvertently chooses the wrong or least effective component. These designers who donít have a great number of designs under their belt can choose a component that appears perfect with the availability, cost, and reliability they seek.

However, if they took extra time to take a closer look at that component, they might find that the reliability data currently available is not that extensive or sufficiently detailed. A selected component might only be on the market for a few months and only available in small sample quantities. Consequently, there is not a considerable amount of reliability and quality assurance data.