Get the Scoop on True DFM
For the record, the acronym DFM, which stands for design-for-manufacturing takes into account PCB design, fabrication, and assembly. So, it goes beyond DFA or design-for-assembly, which is also highly important in its own right. But for DFM, you’ve got to factor in checks and balances at the right places at design, fabrication, assembly and test. You’ve got to do that for highly effective DFM. BTW, be looking for CircuiTree Magazine’s June PCA Quarterly to get the scoop on true DFM.
PCBs are increasingly becoming more complex with high populations of advanced components like microBGAs, QFNs, and CSP devices. Consequently, the real estate on a board is constantly shrinking posing major challenges at the design, fabrication, and assembly stages. Therefore, it is important to have a good handle on DFM to assure your product is highly reliable. Here are some key points to know to ensure your CM or EMS provider provides you effective DFM.
Check on the level of experience the PCB designer has. Even minor miscues from an inexperienced designer can have major consequences at fabrication or assembly.
- Make sure your PCBís circuitry is split correctly.
- Double check component placement is properly performed.
- Precise placement of test points is ultra critical. Experience plays a key role here.
- Assure that boundary scan for test purposes is also correctly performed on the board.
- To correctly fabricate the board, a PCB designer must correctly calculate impedance control properly so that all transmit and return signals are intact.
- Check to see the PCB designer produces an exact fabrication drawing.
- Frequent and detailed communications are maintained between the PCB designer and the fabrication house to assure board accuracy and correctness.
At assembly, 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 doesnít require human interaction and judgment, which can be sometimes questionable. AOI and x-ray also play key roles. Not using AOI machine means final QC time is increased because an effort wasnít made initially to check the inspection process, especially if a PCB is being populated with BGAs, CSPs, and QFNs.