In Circuit Testing

The printed circuit board assembly or PCB manufacturing is a complex process, which involves various intricate tasks. Most of these tasks are automated, still, they may go wrong at times. To avoid this, today PCB assembly services and OEMs are employing various types of testing methods to ensure the appropriateness of these tasks. In-circuit testing is one of the important types of PCB testing techniques employed by PCB assembly services companies such as Sierra Assembly to detect manufacturing and placement defects of the PCB.

What Is In-Circuit Testing?

In-circuit testing (ICT) is an automated electrical test method used to verify the performance of individual components on a fully assembled circuit board. Also known as PCB electrical testing, this method isolates and evaluates components such as resistors, capacitors, diodes, and integrated circuits (ICs) to ensure they meet design specifications.

At Sierra Assembly, we offer advanced in-circuit testing services designed to ensure the performance and reliability of your printed circuit board assemblies Our ICT process enables rapid identification of electrical faults at the component level, making it a crucial part of any robust quality control process. From prototype verification to large-scale production, our electrical testing capabilities help eliminate manufacturing defects before your boards leave our facility.

Why Choose ICT Testing for Your PCB Assemblies?

• Up to 95% test coverage
• Fast cycle times (ideal for volume production)
• Detection of open/short circuits, reversed components, and solder defects
• Compatible with analog, digital, and mixed-signal boards
• Effective for circuit card assembly testing in regulated industries

Equipment Used for In-circuit Testing

At Sierra Assembly, we utilize the following equipment for testing:

• GenRad 2283 Board Tester
• GenRad 2280S Board Tester

These board testers feature the following:

• Bed of nails with a fixture
• Boundary scan capable
• OpenExpress equipped

The board tester system features a matrix of several sensors and drivers, which may amount to hundreds at a time. They are used to perform the test measurements. The fixture is designed to interface with the board tester system, and the part of the PCB being tested. Comprising several sensors, this fixture is commonly referred to as “bed of nails” due to various contact pins. Each nail is designed to connect to the relevant points on the PCB. Through this connection, it sends information to the tester. These contact pins help speed up the process of testing, and help check the functionality of the product. The tester system is controlled by software. It instructs the type of test to be performed on the board, and allows users to set parameters for a fail or pass. The software is always unique for each assembly to be tested.

Our In-Circuit Testing Process

We follow a rigorous testing workflow that prioritizes quality, traceability, and turnaround time:
1. Design for Test (DFT) Review
We work with engineering team to review your PCB layout and ensure it is optimized for ICT testign pcb. This includes verifying access to test points, ensuring sufficient spacing, and identifying components that need special handling.
2. Test Fixture Development
A custom bed-of-nails test fixture is fabricated based on your PCB design. This ensures consistent electrical contact with test points and components.
3. Test Program Creation
Our engineers develop a test program specific to your PCB using the GenRad software environment. This program defines expected voltages, resistance ranges, signal paths, and other test parameters.
4. Automated Testing
Each board is tested on our in circuit testing systems. The machine checks hundreds (or thousands) of test points to identify any electrical or component-level issues.
5. Diagnostics and Failure Reporting
Defects are precisely logged and flagged. Our systems can pinpoint faults down to individual pins or component leads, streamlining the repair process.
6. Optional Rework and Retest
We offer in-house rework and retesting services to ensure only compliant, fully functioning boards are shipped to your facility or customers.

Benefits of In-circuit Testing

Our advanced capabilities and vast industry experience coupled with following benefits of this testing have helped us assure quality products to clients.

• Offers 100% Coverage: The pcb electrical testing offers 100% coverage, and they are used to detect the following:
  • Part Placement: ICT equipment are designed to check for part placement. They can easily identify substituted or improperly placed components.
  • Condition of Parts or Components: As PCBs are populated with fine components, which are not visible to human eyes. These components may be damaged by electrostatic discharge. The damage may not be immediately recognizable during a visual inspection or standard operational testing of the product. During the testing, our experts measure the reaction of components at various current and voltage values, and this helps them identify and replace damaged components on the circuit board.
  • Perfection of Printed Circuit Board Assemblies: We regularly design several denser printed circuit boards. The individual traces of these circuits may get heavily damaged. ICT helps determine the presence of any short circuits or opens on the board.
  • Electrical Requirements: Our advanced ICT equipment helps identify electrical parameters of the board. They help understand capacitance or resistance of the board, electricity leakages, wrong polarities, and other issues. In short, the equipment enables us to assure if the PCB meets desired electrical requirements of an application.
• Reliability: Owing to the clarity that in-circuit testing assures, it is one of the highly reliable testing methods available. It helps identify different manufacturing defects, design flaws, and faults.
• Can be Used for Testing Ball Grid Arrays: This method enables the testing of ball grid arrays, as well as field-programmable gate arrays (FPGAs), which are difficult to verify with flying probe testers and AOI.
• Saves Time: This testing has helped us identify the defects and minimize the wait times. Thus, we also recommend it to clients who may be working on tight deadlines.

What ICT Testing Detects: Fault Types and Functional Coverage

pcb electrical testing is one of the most powerful methods for early detection of manufacturing and assembly defects. Our in circuit testing systems can detect a wide range of electrical faults and component-level failures that may compromise your PCB's performance.
Here’s a breakdown of what circuit card assembly testing can identify:

Electrical Faults

• Open Circuits: Missing solder, broken traces, or lifted pins that interrupt current flow
• Short Circuits: Unintended connections between traces, pins, or layers due to solder bridges or layout issues
• Solder Bridging: Excess solder forming connections between adjacent pads or component leads

Component-Related Issues

• Missing Components: Components not placed or mounted during assembly
• Wrong Part Values: Incorrect resistor/capacitor values due to pick-and-place errors or BOM mismatches
• Incorrect Part Orientation: Polarized components (diodes, electrolytic capacitors, ICs) installed backward
• Out-of-Tolerance Components: Components that fall outside their specified value range (important in analog circuits)
• Defective ICs or Semiconductors: Broken logic gates, stuck-at faults, or open pins on ICs

Mechanical and Soldering Defects

• Cold or Dry Solder Joints: Incomplete solder wetting that causes intermittent electrical contact
• Cracked or Lifted Pads: Damaged PCB pads due to thermal or mechanical stress
• Floating Pins or Leads: Leads that are not properly soldered and make no contact with the pad

Power and Ground Rail Checks

• Continuity and isolation tests on power and ground planes
• Voltage level checks to confirm power rail integrity
• Detection of power-to-ground shorts, one of the most common and dangerous PCB failures

Being at the forefront of the PCB industry, we are committed to delivering quality products. This commitment has kept us going all these years, and as a result, we have built a huge list of happy and satisfied customers. To know more about our in-circuit testing capabilities, please contact us at the earliest.