What is In-Circuit Testing (ICT)?
The manufacturing of electronic assemblies involves many complex tasks that all carry the potential for something to go wrong. The fabrication of the printed circuit board assembly (PCBA), the placement of components on the board and the integrity of the parts themselves require testing to ensure the resulting end product meets quality standards. The verification process can be expensive and extremely time-consuming. One method that assists original equipment manufacturers (OEMs) and contract manufacturers in consistently meeting defined parameters during production runs is in-circuit testing (ICT).
Hardware Used in In-Circuit Testing
ICT relies on test fixtures, commonly referred to as “bed of nails” because of the multiple contact pins they contain, to speed up the process of testing each finished product for proper functionality. Product design engineers determine how the bed of nails will access the crucial test points for a printed circuit board assembly. Specific pins on the test fixture will be depressed when the test points on the PCB assembly comes into contact with them either through manual pressure or an induced air vacuum.
How Software Plays a Role in ICT
Ideally, engineers who are intimately knowledgeable with the built-in parameters and intended function of the product develop the software required to run the required test on the assembly. The software runs tests designed to identify any potential problems by powering on and off certain areas, measuring electrical parameters and flagging any results that indicate a problem.
Measurable Factors Tested During In-Circuit Testing
By automating the process of testing, ICT allows for acceptable line speeds while increasing overall quality levels. The ability to check each finished product rapidly and consistently helps manufacturers ensure that they are upholding design standards. Some of the parameters and faults that the regular ICT setup checks include:
- Part placement: Even with today’s high standards of manufacturing and heavy reliance on automated assembly, mistakes still creep into the production process. ICT routinely checks for improperly placed or substituted components.
- Printed circuit board soundness: As PCBs become more tightly populated, the individual traces are more vulnerable to damage during the assembly process. ICT determines the presence and isolates any opens or short circuits on the PCB board itself.
- Component condition: An IC damaged by electrostatic discharge may not be immediately noticeable during standard product operational testing. By measuring component reaction at specified voltages and current, technicians can quickly locate and replace damaged components.
- Electrical requirements: ICT can easily measure basic electrical parameters such as resistance and capacitance of the final product to determine if they meet design specifications.
ICT represents a standardized way to verify proper operation of electronic products that are mass-produced. While it is not a perfect method of testing, In-circuit testing is one of the most efficient ways to produce large numbers of products that work as designed.