New Developments in PCB Test and Measurement Techniques

Any type of electronic product, even when they have been designed properly and built meticulously, are prone to problems. In the prototype stage, electronic products can have bugs and issues, and the designers must troubleshoot them before they can build the final product. However, if something is left unnoticed, it can mean huge problems for the company if the product goes out in the field. Therefore, Rush PCB Inc insists on testing electronic products, especially the printed circuit board, on preventing carrying over problems. Not only does PCB test and measurement improve PCB products, but it is also necessary to evaluate PCBs.

Why Test PCBs

Testing is an important part of the manufacturing process for PCBs. PCB testing, when conducted throughout the production cycle, can help to save money and prevent issues at later stages.

Designers often resort to design analysis techniques during the early stages of design. This helps to minimize several issues during later stages. However, there is a wide range of PCB testing methods that manufacturers perform on physical boards. They mostly run these tests on prototypes or small-scale assemblies. These tests look for potential shorts, opens, solder joint issues, and functionality of the board. This ensures that each PCB undergoing the test will function as intended.

Benefits of PCB Testing

Most companies consider PCB testing as absolutely necessary because of the advantages testing provides. For instance, the top advantages of PCB testing are as follows:

Identification of Issues

This is the primary benefit of testing. It helps to identify potential problems in PCBs. It is immaterial whether the issue lies in manufacturing, functionality, or elsewhere, PCB tests can identify issues in a board and its layout, allowing the designer to adjust for it accordingly.

Time Saving

In the prototyping stages, PCB testing can identify major issues. Rectifying the issues at the early stages of design can help to prevent a major catastrophe later on. Using thorough testing at early stages, designers can determine the root causes of each problem and rectify them easily and quickly.

Cost Reduction

With PCB testing, it is possible to prevent the production of faulty products. Repairing faulty products is not only more expensive than preventing these faults at prototype stages, but it also prevents wasting time to market. By ensuring the design is as faultless as possible before going into production, the designer ensures that the production will also move forward smoothly, keeping production costs significantly low.

Fewer Returns

Products failing in the field are typically returned for repairs. This is an additional cost to the company. By testing PCBs before they go out, it is possible to weed out failures long before they reach the field, thereby reducing returns as far as possible.

Increased Safety and Reliability

PCBs go into many types of electronic products, including medical instruments. Failure of these PCBs can be a major issue for the people using these products. It may even prevent an organization from providing essential services. The defective product can lead to an electric shock or fire, and the people nearby can be in danger. Testing during manufacturing can ensure that neither machines nor humans face any danger due to an improper design or production process.

PCB Testing Methods

PCB testing typically involves a large range of PCB testing methods to ensure the board meets standards. PCB testing can be classified into two broad categories, bare board testing, and functional testing.

Bare Board Testing

These tests ensure the quality of the board before it is assembled. It includes tests like –

Lamination

Testing the lamination quality ensures the lifespan of a PCB. For instance, if the laminate peels easily, the functionality of the board can have issues. Lamination tests typically involve its resistance to peeling by application of heat or force.

Copper Plating

Manufacturers laminate the copper foil on the substrate to provide conductive layers. Testing the copper plating involves checking its tensile strength and elongation.

Solderability

Electronic components are soldered on to copper pads on the PCB. It is essential to ensure the components are firmly attached to the board. Testing for the solderability prevents soldering defects. The most common test for solderability is wetting, and this tests how well liquid solder can cover the PCB surface.

Hole Wall Quality

PCBs require vias and through holes to electrically interconnect different layers on multilayer PCBs. Unless the quality of the hole wall is good, these electrical connections may be intermittent, causing problems in functionality. Testing the hole wall quality involves analyzing them in environments of cycling heat and humidity to check their response to thermal stress.

Electrical Conductivity and Insulation

Tracks on a PCB must provide electrical conductivity between two pads which they connect, while there must be good insulation between unconnected tracks and pads. Improper etching and plating can disrupt this by providing inadvertent electrical connections between unconnected traces. Testing for continuity and insulation before assembling the board can help identify these problems and ensure their rectification.

Cleanliness

It is essential that the PCB surface is bereft of any unclean material. The presence of unclean material on the surface, such as oil, fingerprints, etc. can lead to solderability issues and electrical leakage when operating. Testing for cleanliness can detect these issues before they disrupt production schedules.

Functional Testing

Most of the functional testing methods are applicable to boards that have undergone complete assembly. Many functional tests are necessary as no single test will uncover all problems. It is necessary to consider each testing method closely to determine if the board meets the specific requirements. Most popular testing methods involve:

In-Circuit Tests

This is a popular PCB testing method capable of detecting more than 98% of faults. It requires a special type of testing equipment, containing a matrix of pins that connect to various test points on the board.

The test pins connect to an electrical circuit in the in-circuit tester. When activated, each pin provides important information to the in-circuit tester, which analyzes the input and decides whether the board is defective or not. The in-circuit tester may have software for conducting the analysis.

In-circuit testers help the manufacturer test individual components, measuring their performance, and assessing their functionality. They can also test for conductivity, opens, and shorts.

Flying Probe Tests

Where In-circuit testers use a dedicated fixture for a PCB assembly, flying probe testers do not need any dedicated fixtures. As there is no dedicated fixture, time and cost savings are substantial. The flying probe tester uses a simple fixture to hold the board while a computerized arrangement moves the flying pins around the board, connecting to relevant points on the board.

While flying probe tests can handle almost all the tests conducted by in-circuit testers, they are faster and more versatile as they can adapt to almost any board quickly. The only time-consuming effort in using flying probe testers is that required for programming the tester.

Functional Circuit Tests

These are helpful in determining the functional performance of an assembled board. Functional testers interface with the components on the board, simulating inputs to the board to assess whether the outputs from the board follow a known pattern. Typically, functional circuit tests ascertain the product’s functionality as a whole.

Conclusion

Regardless of the method of testing, Rush PCB Inc considers PCB testing an essential step in the PCB design and development process. It can help to save the business substantial amounts of money, time, and goodwill by preventing issues from reaching the field.