Thermal Emission System for Circuit Board Troubleshooting
Why EL is Needed
Increasing Board Complexity
The complexity of PCB manufacturing has increased dramatically over the last three decades, progressing from straightforward double-sided boards with 100% through-hole technology to highly complex multi-layer PCBs with mixtures of through-hole, surface mount and chip-on-board configurations. Board layouts have consequently increased in density with tighter tolerances and decreased distances between electrical contacts. With this increase in complexity, the possibility of manufacturing defects has increased.
Conventional Test Limitations
Increasing board complexity places limits on the effectiveness of conventional inspection and test strategies. AOI does not have the ability to discern if a component is defective or if a board has a hidden short. ICT often cannot test an entire board due to limited access to test points. Critical sections of the board, such as the integrity of hidden solder joints under a BGA, often cannot be tested using conventional test methods. Furthermore, neither ICT nor AOI can detect latent component defects such as resistive shorts, delaminations, and thermal management problems. A particularly difficult problem is the inability to identify stressed components using conventional test technologies. Stressed components can pass ICT and FCT only to fail early in the field.
Thin Operating Margins
Because the cost saving demands by OEMs require contract manufacturers to operate with razor-thin operating margins, there is a need for efficient and cost-effective failure analysis.
Because lead-free alloys melt at higher temperatures, their application can unduly stress ICs and components and can lead to increased solder related defects such as bridging, poor wetting, and voids. Engineers may not yet have a full understanding of the variety of defects and failure modes that the implementation of a lead-free solder process.
How EL Can Help
EL is a combination of inspection and test technologies and bridges the gaps between conventional test technologies. EL is fast, easy-to-use, cost effective, and provides long-term advantages. Board failures are often symptomatic of problems within the manufacturing process or with the design itself. The sooner a defect can be identified, the more quickly the underlying cause can be rectified. For example, if a defect stems from design problems rather than the assembly process, a contract manufacturer can recommend a simple redesign to their customers.
EL can be used at every stage of the production and debugging process. In the design phase, EL can help create designs that avoid heat concentration and optimize thermal distribution, enhancing reliability and life span. When implemented after conventional tests, EL can identify defects, such as resistive shorts and stressed components, that these tests may have missed. When used for board debugging, EL can dramatically reduce repair time.
Increased competition and shorter product life cycles are forcing OEMs to get their products to the end-user as quickly as possible. In such cases, there may not be adequate time availaibe to setup and program traditional inspection systems. The short deployment time for EL can help improve the speed and frequency of new product launches.
Failure Modes Detected
- Interlayer, hidden, and resistive shorts
- Faulty components
- Stressed components
- Latent defects
- Heat sink and die attach problems
- More complete fault coverage
- Improved reliability in the field by screening latent defects
- High return on investment
- Eliminate scrap piles
- Reduce repair times in the rework cycle
- Improve yields on the production line
- Improve process quality
- Short setup time
- No programming or custom tooling required