DFT for the Digital PCB Manufacturing Process

May 28, 2020 , in Blog

One of the most difficult things to do in any business is to allow someone else to perform a task that is very important to you or your mission. As the individual responsible for the success of a project, it can be stressful to place your trust in the abilities, not to mention the dedication, of another. Nevertheless, one of the factors that separate good management from great management is the ability to delegate well. Smart delegation, well-summarized by the SMART framework (i.e. Specific, Measurable, Achievable, Relevant, and Time-bound), is the most effective means of optimizing productivity.

Using delegation to multiply productivity

Smart delegation is required when building circuit boards or electronics systems, as PCBA manufacturing process optimization typically requires the distribution of responsibilities among several companies. For example, the responsibility of transforming intent into a design that meets performance objectives lies with the engineer or PCB designer. Building the board that accurately reflects the designer’s intent is the responsibility of the contract manufacturer (CM), who may outsource fabrication or assembly. Finally, the task of testing and verifying that the board actually functions as intended is generally handed back to the developing company.

Functional testing of PCBAs requires equipment and space found in an electronics laboratory setting. However, there are times when this equipment or environment is not available to the developer, and testing must be outsourced. There are basically two options in these cases: (1) engage a special testing facility or (2) rely on your CM. In either case, including additional data, information, and specificity for testing, commonly referred to as design for testing or testability (DFT), is necessary. Opting to go with your CM can be advantageous, especially if a digital PCB manufacturing process is utilized. Below, we justify why this is true after first discussing the essentials of DFT for PCBA manufacturing.

The Conventional Use of DFT for PCBAs

After decades of isolation between developer and manufacturer, circuit board development is emerging from the dark ages and embracing white-box PCB manufacturing that is based on the effective use of CM-specific DFM. In an effort to provide more comprehensive services, some CMs have added functional testing capability to the more common quality assurance circuit board testing methods. This testing usually consists of one of the following, both of which need DFT specifications, and have the attributes listed (comparatively).

PCBA Tests That Require DFT

  • Flying Probe
    • Attributes
        • Short setup time
        • Slower runtime
        • Higher cost/unit (runtime)
    • Measurements:
        • Open and/or short circuits
        • Passive component values
  • Bed of Nails
    • Attributes
        • Longer setup time
        • Faster runtime
        • Lower cost/unit (runtime)
    • Measurements:
        • Open and/or short circuits
        • Passive component values
        • IC testing
        • Analog and digital data

In order for your CM to perform these tests, DFT specifications (which include all components and parameters to be tested) must be provided by the engineer or board designer as part of the PCB manufacturing file(s). These are in addition to PCB layout items such as test points and adequate spacing.

Why Digital PCB Manufacturing Process Testing?

Circuit boards, particularly IoT PCBs, are enabling the production revolution that is being experienced across virtually all industries. Not only are boards themselves impacted by Industry 4.0, but the PCB construction is also getting smart. All of these advancements are possible by the increasingly more effective usage of software and communications, which is the digital thread at the heart of the digital PCB manufacturing process.

As stated above, when confronted with the inability to perform local board testing, choices include establishing a specialized testing facility or consulting your CM. In the table below, these two options are compared.

Digital PCB Manufacturing Process Testing Versus Specialized Testing 
CM Testing Facility
Collaboration Equipment on hand
Ability to make adjustments/changes Engineering testing expertise
Lower cost

As shown above, there are advantages to both options. However, for prototyping during which functional testing is done, collaboration and the ability to quickly institute changes if necessary are invaluable. Therefore, in most cases digital PCB manufacturing process testing, if available, is probably the better option.

Tempo’s Software-Driven Smart Factory Delivers the Industry’s Leading Custom Turnkey PCBA Manufacturing Services
  • On-demand PCBA Contract manufacturing.
  • Rapid, accurate quotes.
  • DFM support from Day 1 of design.
  • Digital Thread Processing with real-time monitoring.
  • Fastest turnaround times in the industry to maximize ROI.
  • Standard and Advanced QC testing.
  • Worry-free supply chain continuity.
  • Specialization in rapid prototyping and low-volume production.
  • PCBA development optimization for complex critical system industries like Aerospace, Medical Devices, Automotive, and Industrial.

Testing is one of the major stages of PCBA development that is required to ensure that your boards adhere to the performance and operational expectations for which they were designed and built. If this testing must be outsourced, working with a CM that employs a digital PCB manufacturing process, as we do at Tempo Automation, can save you time and money while providing the flexibility to easily and quickly make any necessary changes to meet your design objectives.

And to help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.

If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on DFT for the digital PCB manufacturing process, contact us.

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