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Common Errors In Setting Up Manufacturing Tests


When the design of a new product is complete, many people think it is quite simple to transfer the design to manufacturing. The design documents include Gerber Files from which a PCB can be fabricated. So, it seems like you only need to contact a contract manufacturer and send them the files.

Unfortunately, it is much more complex than that. One important need is testing the product after it has been manufactured.

1. Recognizing the Need for Testing

Many people don’t realize how crucial testing is to the product manufacturing process. After manufacturing, each board should be tested to ensure that only good products are shipped. 

Despite excellent quality control at the best contract manufacturers, there can be errors in PCB fabrication, PCB assembly, flaws in procedures (such as loading the code into a device), or even flaws in the design.  

A failure rate of 1% is considered good for an average board prior to testing and would be unacceptably high for high-volume manufacturing. The testing determines if the product satisfies the requirements and is ready to ship.

At Voler Systems, we ensure a smooth, thoughtful transfer either to the client’s internal test group or to partners like Solution Sources Programming for test and production.

2. Leaving Testing as an After-thought can Lead to Expensive Problems

We do design verification testing before manufacturing, including safety, compliance, and regulatory testing, as well as testing over the specified range of environmental conditions. Both manufacturing tests and design verification should be planned from the beginning of the design.  

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3.  Early Testing Decisions Affect the Design of the Board

The testing methodology is essential, as it impacts design considerations on a PCB. By implementing a Design for Test (DFT) phase in product design, we can ensure a smooth transition from design to manufacturing. This DFT plan ensures that each board meets functional and performance requirements.

At Voler, our design checklist helps avoid common problems in transferring a design into production. Some typical common problems we work to avoid are:

  • No access points to test products (no thought into giving access via test points or pads for an electrical connection to probe)
  • Test pads too small to probe (targets too small to accurately probe or touch to make good electrical contact)
  • Test pads too close to probe (center-to-center spacing of test points is too close; therefore, the test probes can short out to each other)
  • Designing boards with no tooling holes (This prevents a board from wandering when being tested; therefore, making the board under test a moving target with a small target to try to make electrical contact.)
  • Putting test points or pads too close to other devices or other non-testable devices such as brackets (This affects the ability to put a probe on a test point, as it’s too close to such devices that it either can’t make contact due to it being blocked or it could short out to a device.)
  • Specifying components that should have “built-in test” capability but not confirming during design that it works.
  • Presuming a board will be re-spun or the layout revised before production; therefore, not designing for testing in the first round of layout (Many times, the first board can be the final version if it is designed for testing.)

4.  Tradeoffs

Early design and testing decisions impact the test methodology and manufacturing cost. There are different types of tests, such as in-circuit tests, functional tests, and flying probe tests. They vary in the ability to find a defect, the time to execute the test, and the development cost. 

The selection of the right test type depends upon the board’s complexity, the manufacturing volume, and the level of concern about a failure. 

Tradeoffs between the type of testing, cost, and the need for calibration can either simplify or add to the complexity of your overall manufacturing and quality processes.

For example:

  • Will code be loaded onto the board?
  • At what point in the manufacturing process will this happen?
  • Can it be done at the same time as testing to avoid a second operation with more handling? (Which is expensive, by the way)
  • Will the device need to be calibrated?
  • Should this be done before testing or after?
  • Can the calibration be done at the same time as testing to avoid an additionaloperation with more handling?

Lastly, the assembly of the device should be carefully considered and documented. Optimizing test and assembly procedures to minimize scrap will help lower the cost of manufacturing products while cutting down on testing, debugging, and repair time.

For example, some signal wires should be routed away from noise-generating parts. Some devices are glued or welded shut. After this step, they cannot be repaired. It is usually desirable to test the device before this step, minimizing scrap.

Partnering for Successful Product Manufacturing Testing

In conclusion, working closely with partners like Solution Sources Programming, often in conjunction with our client’s internal testing group, minimizes testing costs, and cuts debug and rework time. It also saves time in the transfer to manufacturing and helps to ensure reliable and high-quality products.

About Solution Sources Programming

Founded in 1990, Solution Sources Programming, Inc has decades of experience implementing the latest test and measurement technologies from DFT (Design for Testability), Bench-Top Boundary scan, In-Circuit Test, and Functional/System Integration Testing. We design, build and deploy custom automated test solutions to validate boards and products in characterization, qualification, and manufacturing environments.

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