Circuit Boards Have Changed.
So Has The Board Test Fault Spectrum.
Over the past several years printed circuit board assembly yields have increased as component and assembly process defect rates have decreased as shown in the figure on the right. In addition, the distribution of fault types typically found on boards during the manufacturing and assembly process has shifted over the past several years as illustrated in the fault spectrum pie diagrams to the right.
Why Does the Shifted Fault Spectrum Matter? Because the Fault Coverage of Traditional In Circuit Testers Is Declining.
The Shifted Fault Spectrum also means that the faults that traditional ICT is adept at finding occur much less frequently—reducing overall tester effectiveness—but not cost.
As a Result
Test engineers have eliminated almost all of the tests traditional ICT was designed to do well—resulting in simple in circuit programs that leave all that “big iron” ICT capability either under-used or unused. This mismatch between today’s fault spectrum and yesterday’s traditional ICT means high overhead costs for unused tester resources in the form of more complicated fixtures and programs and the higher support costs inherent in complex testers.
New Technologies Will Augment In Circuit Test (ICT)
While ICT remains the most economical means to identify manufacturing and component defects, new technologies such as Automated X-Ray Inspection (AXI) and Automated Optical Inspection (AOI) are being integrated into assembly lines to deal with the new defect classes that ICT can no longer—or simply never could—identify.
What Does the Shifted Fault Spectrum Mean For ICT?
If test engineers continue to use traditional “big iron” ICT for every test job, OEMs and contract manufacturers will keep generating unnecessary test costs. For North America alone, CheckSum estimates that more than $250 million annually is spent unnecessarily on testers, tester support, test programs and fixtures by using “big iron” where Low Cost ICT will do the job. Employing Tester Portfolio Management will reduce total ICT cost while maintaining superior fault coverage–and free up budgets to fund the new AOI and AXI technologies that today’s new board technologies also require.