A printed circuit board may look perfect and still not function correctly.
That’s why inspection and testing are both important parts of electronics manufacturing. Inspection technologies such as Automated Optical Inspection (AOI) and X-ray can help identify physical assembly issues, but testing answers another critical question:
Does the product actually perform the way it is supposed to?
There are several PCB testing methods, and they don’t all test the same things. Depending on the product, its complexity and its intended application, a manufacturer may use functional testing, in-circuit testing, hi-pot testing, burn-in or a customized combination of methods.
GIC provides a variety of testing capabilities tailored to individual products, including customized functional testing, electronic and mechanical testing, PCBA system testing, in-circuit testing, hi-pot and burn-in.
Understanding what these tests do—and why they are different—can help OEMs develop a more effective quality strategy for their electronic products.
Why Is PCB Testing Important?
The purpose of PCB testing isn’t simply to find defective boards.
Testing can help verify that an assembled product meets its specifications before it moves to the next manufacturing stage or reaches the customer.
That’s an important distinction.
A PCB assembly can pass a visual inspection while still having an electrical or functional problem. Conversely, testing shouldn’t necessarily replace inspection because different quality-control processes are designed to uncover different types of issues.
A comprehensive quality strategy considers how a product is designed, assembled, inspected and tested.
At GIC, testing is customized according to each product’s requirements rather than applying one testing method indiscriminately to every PCB.
What Is Functional PCB Testing?
Functional testing evaluates whether an assembly performs according to its intended requirements.
In simple terms, instead of asking, “Was this PCB assembled correctly?” functional testing asks:
“Does it actually work?”
The specific test depends heavily on the product.
A manufacturer may provide inputs, signals or power and then evaluate outputs or responses against expected results. Because electronic products perform very different functions, functional tests often need to be developed around the individual assembly.
GIC offers customized functional testing and works with customers to develop testing protocols tailored to their products and requirements.
Functional testing can be particularly valuable because it evaluates the PCB in a way that more closely reflects its intended operation.
What Is In-Circuit Testing?
In-circuit testing, commonly abbreviated as ICT, takes a different approach.
Instead of evaluating only the overall operation of an assembly, in-circuit testing is designed to evaluate electrical characteristics at the board level.
Depending on the PCB, test equipment and test strategy, ICT can be used to identify certain problems involving components, connections and electrical values.
The advantage is that testing can potentially pinpoint specific areas of concern rather than simply indicating that the overall assembly isn’t functioning as expected.
GIC lists in-circuit testing among its PCB testing capabilities.
However, not every PCB or production program necessarily requires ICT. The appropriate testing approach depends on factors such as board design, test accessibility, complexity, production quantities and customer requirements.
What Is Hi-Pot Testing?
Hi-pot is short for high-potential testing.
Unlike functional or in-circuit testing, hi-pot testing focuses on electrical insulation and isolation.
A higher-than-normal voltage is applied between designated points to evaluate whether the product’s insulation can withstand the specified electrical stress without unacceptable current leakage or breakdown.
This type of testing can be important for certain products where electrical isolation is a critical requirement.
GIC includes hi-pot testing among the testing capabilities available to its PCB manufacturing customers.
As with other PCB testing methods, whether hi-pot testing is appropriate depends on the design, application and product requirements.
What Is Burn-In Testing?
Some problems don’t appear immediately when an electronic assembly is powered on.
That’s where burn-in testing can be useful.
Burn-in involves operating an electronic product or assembly for a specified period, sometimes under controlled environmental or operating conditions, to help identify problems that may emerge after extended operation rather than during a brief functional test.
GIC provides burn-in testing and has temperature-chamber equipment among its general testing resources.
Burn-in may be appropriate for products where reliability over time is particularly important or where customer specifications require it.
It is not automatically necessary for every PCB assembly, however. The duration, conditions and acceptance criteria should be established according to the product’s requirements.
PCB Testing Methods: Which One Is Best?
There’s no single best PCB testing method.
The better question is:
What do we need to verify about this particular product?
For example:
- Functional testing can help determine whether the product operates as intended.
- In-circuit testing can evaluate electrical characteristics at the PCB level.
- Hi-pot testing can evaluate electrical insulation and isolation.
- Burn-in testing can help identify certain problems that emerge during extended operation.
Some products may require one method. Others may benefit from several.
The appropriate strategy depends on the PCB, its application, customer specifications, applicable standards, production volume and the consequences of a potential failure.
Inspection and PCB Testing Work Together
Testing also shouldn’t be confused with inspection.
In our previous discussion of AOI vs. X-ray inspection, we explained how optical inspection can evaluate visible characteristics of an assembly while X-ray inspection can provide visibility into areas that aren’t readily accessible optically.
Testing provides another layer of verification.
Consider a BGA, for example. X-ray inspection can provide information about hidden solder connections beneath the component. Functional testing, meanwhile, can help determine whether the assembled product performs as intended.
One isn’t necessarily a substitute for the other.
GIC’s manufacturing capabilities include both 2D and 3D AOI and X-ray inspection, while its testing capabilities extend into functional, in-circuit, hi-pot, burn-in and other customized testing.
Together, inspection and testing can provide a more complete quality-control approach.
Test Fixtures Can Be an Important Part of PCB Testing
Testing doesn’t just require the right equipment. It may also require a reliable way to connect the PCB or product to that equipment.
That’s where test fixtures come in.
A fixture can provide repeatable physical and electrical connections between the product being tested and the testing system.
But what happens when an OEM doesn’t already have one?
GIC offers dedicated test fixture design services for customers who require PCB testing but don’t have an existing fixture. GIC can develop a customized fixture or modify an existing one based on the product’s requirements.
This is an important capability because testing should ideally be considered as part of the manufacturing strategy—not as a problem to solve after production has already begun.
Design Your PCB With Testing in Mind
Testing requirements can also influence PCB design.
If a manufacturer will need access to specific test points, for example, that should ideally be considered before the design is finalized.
This connects directly to Design for Manufacturability (DFM) and, more specifically, designing with testability in mind.
Engineers and manufacturers should consider questions such as:
- What needs to be verified?
- What constitutes a passing or failing result?
- Which test points need to be accessible?
- Will a custom test fixture be required?
- Does the finished assembly require functional testing?
- Are there electrical isolation requirements?
- Does the application justify burn-in testing?
- How will test results be documented?
Addressing these questions earlier can help make testing more efficient once the product enters production.
PCB Testing Is Part of a Larger Quality System
Testing equipment by itself doesn’t create quality.
Quality comes from a larger system of controlled processes, documentation, inspection, testing and continual improvement.
GIC’s quality management system is certified to ISO 9001:2015 and ISO 13485:2016. The company also builds to IPC-A-610 Class 2 and Class 3 specifications and identifies J-STD-001, J-STD-002 and ANSI/ESD S20.20 among the standards incorporated into its quality program.
That broader quality framework is especially relevant when evaluating a contract manufacturer.
An OEM shouldn’t only ask, “Can you test my PCB?”
It should also ask how testing fits into the manufacturer’s overall quality process.
Choosing the Right PCB Testing Strategy
Different products have different risks, operating environments and performance requirements. That’s why the right testing strategy should be developed around the product rather than selected from a generic checklist.
Functional testing may be critical for one assembly. Another may require in-circuit testing. A product with specific electrical isolation requirements may need hi-pot testing, while another application may benefit from burn-in.
Some products may require several methods working together.
GIC’s testing capabilities include customized functional, electronic and mechanical, PCBA system, in-circuit, hi-pot and burn-in testing. Its general test equipment includes oscilloscopes, function generators, RF-related equipment, frequency counters, programmers and temperature chambers.
The goal isn’t to perform the greatest number of tests possible.
The goal is to develop an efficient testing process that provides the appropriate level of verification for the product being manufactured.
Put PCB Testing Into the Plan From the Beginning
Testing is most effective when it isn’t treated as the final step before a product leaves the manufacturing floor.
It should be considered during product design, prototyping and manufacturing planning.
By defining requirements early, OEMs and their manufacturing partners can determine which PCB testing methods are appropriate, identify necessary test points, develop fixtures when needed and establish clear acceptance criteria before production ramps up.
GIC provides customized PCB testing solutions as part of its comprehensive electronics manufacturing capabilities. If you’re developing a new product or evaluating the testing requirements for an existing PCB assembly, talk with GIC about developing a testing strategy around your specific application and specifications.