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Emphasize DFM Checks and Balances

All too often, the basic principles of design-for-manufacturing (DFM) get short shrift due to a CM’s greater attention on meeting delivery dates. Also, in some instances, DFM is an afterthought left for assembly engineers and technicians to deal with. But the reality is effective DFM takes into account the practice and implementation of checks and balances at the right places and at the right times during design, fabrication, assembly, and test.Image

DFM starts with design layout with the PCB designer thoroughly understanding each and every detail of the applicable datasheets ñ details like dimensions, cut outs, slots and pin numbering and sequencing. With PCBs becoming increasing complex, there can be any number of component miscues due to a PCB designer’s inexperience and not properly reading a data sheet, among a host of other reasons. Those include improperly fitting a component on its associated footprint, incorrect or damaged connections into and out of a component, incorrect sequencing or pin numbering, poorly defined pad dimensions, incorrect drill or via holes, as shown in Fig. 1.

To get greater details on efficient DFM, read our article appearing in the June issue of CircuiTree Magazineís PCA Quarterly by clicking here.

Here are some important pointers the PCA Quarterly article discusses, which can be helpful for your next PCB project:

  • Test points must be precisely placed on a board during the design layout phase.
  • Get assurances that fiducials, sequencing and pin numbering, and other associated aspects of your PCB design are correctly performed.
  • Ensure the PCB designer correctly splits your boardís circuitry.
  • Correctly performed fabrication and assembly drawings are critical for effective DFM.
  • For board fabrication, impedance control must be correctly calculated to ensure transmit and return signals are intact.
  • PCB design must maintain communications with the fabrication house to avoid problems.

Also, it’s important to know efficient DFM demands the utmost use of automated equipment with pick and place being the frontrunner. Automation brings to the table a high quality and repeatable product that can be traced back and doesn’t require human interaction and judgment, which can be sometimes questionable.