What Is PCBA Functional Testing and Is It a Must?

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Fri, Apr 09, 2021

functional test for PCB assembly

A functional test (FCT) can identify if a PCBA is working correctly and if it is proper to be distributed.

Is it necessary for you to add a functionality test to the PCB assembly?

Imagine this:

A PCB assembler doesn’t process the functional test to your boards. When you get them, suddenly, an error occurs, your device has to be returned to the PCB assemblers to check and troubleshoot the error.

But this is a tough task, as AOI testing can locate only the assembly’s surface issues, and even a specific crew of the assemblers can hardly locate the error within the PCB in such a circumstance.

Both you and the manufacturer are unhappy, as no one knows if the problem is with the assembler, the components, or the circuit designers. Things go into a dilemma.

This is unfortunate, and what's worse, it happens in the PCB industry.

So, I would say yes, applying the functional test is necessary, which makes sure the assembly quality to the highest degree.

What is a Functional Testing to PCB Assembly

A functional test (FCT) happens after the assembly and before the thermal aging test. It stimulates the working condition to check the PCBA’s functionality performance.

This is how PCBONLINE processes a functional test:

  • First, our senior test engineers use LabView to do the test programming.
  • Then, a test technician connects the PCB assembly to the PCBA tester, opens the test program, and powers on the PCBA. (our testing system is configured in visual basic)
  • Next, the technician operates the PCBA tester to take the signals from the PCB chips and routes the test points.

In this way, the voltage value, signals, and other important parameters are loaded on an oscilloscope. The oscilloscope is connected to a computer, whose screen displays OK if the PCBA is good, or otherwise, displays NG (not good), so that our technician can verify the signal integrity and know if voltages run properly.

All test process data are recorded. If the computer says OK, the PCB assembly goes to the next procedure, which is IC programming or thermal aging test. If the computer says NG, our engineers debug them, and all PCBA testings start again.

Usually, we advise customers whose PCB's area larger than 3 square meters to add the functional test. It reveals any open connections, defective components, solder shorts, and anything that isn’t okay with the PCB. Through it, PCBA manufacturers make sure the assembly quality to extreme precision.

Free Functional Test for PCB Assembly

Generally, if you ask a PCB assembler to process functional testings before delivery, you need to pay additional costs.

Things to Take Note of

Very few manufacturers perform overall FCT to verify the PCB’s full functionality, but PCBONLINE does. If your order amount is over $5,000, we provide free functional testings. Plus, free complete PCBA samples.

PCBONLINEis a one-stop PCB manufacturer that can provide free functional testings. We offer advanced PCB, PCB assembly, box builds, and design. We accept large volumes, small-batch, and prototypes.

The functional test is not the only free test at PCBONLINE, here are other free tests and services: a design for excellence, one-to-one engineering support, Gerber and BOM check before manufacturing, and first article test for PCBA. Plus, you can enjoy $100 off coupons for online purchases once you register on our website.

You can take a look at the complete PCB assembly process at PCBONLINE below:

Benefits of Performing FCT for Your PCB Assembly

You can get these benefits from FTC:

  • The FCT saves money for the customer to buy equipment to find issues or ask a testing company to do so, which is much more expensive.
  • It eliminates the necessity for performing systems tests.
  • It includes most of the PCB’s sections such as resistance, voltage, communication protocols, and anything that could cause issues with the PCB.
  • It is also the stage where manufacturers are able to add additional serializing factors, such as serial numbers and calibrating factors.

During the FTC, the whole operational environment inside the PCB is cleansed of any errors. Responses are monitored at specifically chosen points to ensure the product’s functionality and guarantee it won’t malfunction. This is quite important for the average customers who might not be able to troubleshoot the issue by themselves.

Besides FCT, There Are Other Different PCB Testings

These different testings for a PCB can be:

  • Micro-sectioning analysis
  • PCB contamination test
  • X-ray inspection
  • PCB solderability test
  • Peel test
  • Solder float test
  • Time-domain reflectometer test, or TDR

Here you can take a look at details for some of them:

PCB X-Ray Inspection Service

The PCB X-Ray inspection, also known as AXI, mainly involves 3D digital images that specifically show every single layer of the PCB board. The procedure allows the examiner to take a look at the workings of the entire board, no matter how small they could be.

The main advantages of the X-Ray inspection are the possibility of Inside View and the chance to troubleshoot Complex PCBs.

Micro-Sectioning Analysis

The specific chore the micro-sectioning analysis does is to take a 2D sample that will expose the inner working of the PCB. The components that the test will identify: shorts, opens, solder reflow, thermo-mechanical problems, and defective components.

Micro-sectioning can be truly destructive for a device that is under the test. But the components that aren’t working correctly can be removed from the PCB, placed into a curing epoxy, entirely exposed by any means of abrasion, and then compared with the functioning component. With a closer look, via micro-sectioning analysis, an experienced technician will be able to spot: failure of solder joints, the thickness of the plate, and the intermittent thickness of any metallic layer throughout the PCB.

PCB Contamination Test

A PCB can definitely be contained in more ways we are willing to admit, such as flux residue, human byproducts, handling, and reaction product.

Essential results of the contamination tests can show the significant activity of Corrosion, Degradation, and Metalization. Each non-tested product could significantly interfere with the customer’s usage of the PCB and can lead to unwanted issues.


Bottom Line

Now you have a good understating of the PCBA functional testing. If something stops the whole PCB from working, it can be quite a painful experience for the customer. The FCT simulates the operating environment of the circuit board and helps you prevent any errors you might struggle with in the future.