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Taking On The High Road For Hi Rel PCBs

In this day and age, hi rel PCBs demand extra steps be taken at design, fabrication, and assembly to ensure each and every end product is safe and secure under harsh and rugged environments, as well as highly operational under mission critical conditions. However, the contract manufacturer (CM) or EMS Provider must at all times consult the OEM to explain the significance of increasing PCB specifications and get permission to proceed with adding those extra steps by revising original OEM specs.

As the chart shows, making sure there are added tolerances built into processes and procedures is at the foundation of high reliability PCBs. Put another way, it’s going above and beyond the regular ones applied to commercial PCBs. The savvy CM or EMS Provider injects additional reliability at those three stages with various key steps at each stage getting an extra five to 20 percent reliability factor.

Check out EE Times/Embedded.Com editor Bernie Cole’s recent newsletter that features our article on this crucial topic. Click on this link to get more details on beefing up your hi rel PCB.

In the meantime, here is a list of tips to help navigate you to a more robust PCB project and end product.

  • Increase board specifications beyond minimal engineering ones and even after complying with MIL-P-55110 fabrication and assembly IPC 610 Class 3 Rev. E Standards.
  • If your PCB is rated at five amperes, it’s best to add a 30 to 40 percent buffer or kick it up to six, seven amps.
  • Also, if that board is six layers, a good idea is to add two more layers, thus providing extra ground planes.
  • Pump up board traces with extra current ñ for instance, if initial specs call for 0.5 milliamps (mA), give it another 25 percent to at least 0.75 mA current capability for those traces.
  • Even if your PCBs are not for mil/aero applications, deploy mil standards for layout, fab, and assembly to achieve higher reliability and yields.
  • Make sure your CM or EMS Provider is providing your hi rel PCBs three to four iterations of first article inspection (FAI) to assure a perfect thermal profile is created for your project.

The OEM must be vigilant and cast a wary eye on the processes and procedures CMs and EMS Providers institute at those three product phases — design, fabrication, and assembly — to ensure his product is indeed highly reliable. A majority of these techniques and steps are based on a CM’s experience and proven track record since virtually none of them are found in textbooks.