However, which standard should be employed for automotive tests by manufacturers of complex multichips like MCM and SIP? Problems that baffled IC design houses and Tier 1 automotive module manufacturers for a long time could be solved with an official answer-- AEC-Q104 --the newest specification for automotive. As soon as the AEC-Q104 specification released, iST has received relevant inquiries from many international chip manufacturers. This suggests the specification is quite important.

The AEC Q-104 MCM specification, recently released by the Automotive Electronics Council (AEC)-appointed Multichip Modules (MCM) committee, including Lattice, Intel, Infineon, Microchip, NXP, On Semiconductor and TI will eventually eliminate the problem of testing by IC or module specification for complex multichip types including MCM, System in Package (SIP), and Stacked chips. In addition, the AEC-Q104 is the first automotive industry specification of its kind to define Board Level Reliability Test (BLR).

Compare with AEC-Q100, AEC-Q104 is not only the first automotive industry specification to define Board Level Reliability Test (BLR), but also explicitly state on the basic concepts, testing methods, testing items, ESD specifications and the quantity of test samples. Said Allan Tseng, Director of Reliability Engineering Division of iST.

For the basic concepts of AEC-Q104, one rule of thumb is that MCM products shall be subject to just 7 items of AEC-Q104 Group H tests as long as its components include passive components (resistors, capacitors, and inductors), diode discrete components, and ICs that passed the AEC-Q100, 101 or 200 tests before being assembled.

These 7 test items cover 4 reliability tests (temperature cycle test (TCT), drop, low temperature storage life (LTSL), start up and temperature steps) and 3 failure inspection tests (X-ray, acoustic microscopy (AM), destructive physical (DPA)). On the contrary, if the components within MCM products have not passed the AEC-Q100, 101 or 200 tests first, the verification items shall be chosen from all 49 items out of the eight categories based on product application. This, in turn, suggests more verification items would be required. Said Allan Tseng.

For the Board Level Reliability (BLR) test items, Allan Tseng indicated, the BLR is the most common global method to verify IC component solder joint reliability after being mounted on PCB. It has been a routine test item for hand-held devices; however, as more IC components are used in cars which increase the complexity of the automotive electronic system, the BLR has gradually become one of the important test items of automotive electronics.

Tier 1 module makers are making rising efforts in creating proprietary board level tests, including Bosch, Continental, and TRW. More strikingly, the AEC has also come up with the latest AEC-Q104 qualification to clearly define the test items of BLR.

Although the AEC-Q104 covers only Temperature Cycle Test (TCT), Drop Test, Low Temperature Storage Life (LTSL) and Start up & Temperature Steps (STEP), etc., and has not been completely close to the specification of Tier 1 makers; AEC-Q104 is treated as a big step in the BLR general standard. Allan Tseng further indicated.

In addition, the AEC-Q104 adds sequential tests. As an example: you have to test High Temp Operating Life (HTOL) successfully before proceeding with Thermal Shock (TS) but not vice versa. Moreover, The AEC-Q104 adds an "H" group for tests addressing MCM product. In addition, the tests of thermal shock and visual inspection for migration (VISM) are added addressing component level reliability. The qualification condition gets tougher after the sequential tests are required, said Allan Tseng.

Considering the complexity and high costs of MCM components, the AEC-Q100 sets test quantity samples at 77 pieces in each of 3 lots while the AEC-Q104 specification lowers this to 30 pieces in each of 3 lots. Regarding ESD test items: the minimum requirements of the Human Body Model (HBM) are down to 1KV from 2KV defined in AEC-Q100. Regarding Charged-Device Model (CDM): all pins are set to 500V defined in the AEC-Q104.

Allan Tseng suggested, the AEC-Q104 specification is aimed at global automotive IC design houses, and is less likely to meet requirements of vehicle manufacturers and Tier 1 automotive module makers. AEC-Q104 is the entry ticket for suppliers trying to step into the automotive industry. To take a hold in the automotive supply chain the MUST is to comply with the custom specifications of individual car makers.