In a technology landscape that changes by the day, the integrated circuit industry keeps looking for innovation and breakthroughs to meet the challenge of Moore's law approaching its limits. Multi-chip module (MCM) technology, which integrates several independent chips into a single package, has become a key force driving the industry forward. It improves overall system performance and offers an effective answer to the miniaturisation and high efficiency demands of modern electronic devices. With the wide adoption of MCM technology, however, its reliability has become a growing focus of the industry.

AEC stands for the Automotive Electronics Council, an American organisation founded in 1994 by Chrysler, Ford and General Motors. Its membership now spans major vehicle makers, automotive electronics companies and semiconductor manufacturers worldwide. Components meeting AEC specifications can be adopted by all three founding carmakers at the same time, which encouraged component makers to exchange product characteristic data and promoted standardisation of automotive parts, laying the foundation for rapid growth of the automotive component market. AEC-Q is the automotive reliability test standard issued by the AEC organisation and is an important ticket for component makers entering automotive electronics and the tier-one supply chain.

AEC-Q104 is the entry threshold for automotive-grade multi-chip modules

To ensure the reliability and safety of automotive MCMs, the Automotive Electronics Council created a dedicated reliability test standard, AEC-Q104. It applies to MCMs designed to be soldered directly to printed circuit board assemblies and verifies through a series of strict stress tests whether an MCM achieves the expected quality and reliability in practical use.

Its full title is Failure Mechanism Based Stress Test Qualification for Multichip Modules (MCM) in Automotive Applications.

AEC-Q104 was first published in 2017 and its scope is deliberately narrow. It explicitly covers LED modules, MEMs, solid state drives (SSD) and MCMs with connectors. Because dedicated provisions and test procedures may be needed, AEC-Q104 explicitly excludes IGBT and power MOSFET modules.

An MCM is a module made up of several components and in a sense amounts to a small part, except that the chips and devices are combined into an independent package whose external connection may be pads or a connector. The standard currently applies only to MCMs designed to be soldered directly onto a printed circuit board.

Besides MCM, AEC-Q104 also provides guidance for system in package (SiP). AEC-Q104 was developed by the AEC together with Intel, Infineon, Microchip, NXP, OnSemi and TI, and it is the industry's first standard applicable to MCM and SiP that defines board level reliability (BLR) testing.

As vehicles become more electrified, intelligent and driver-assisted, component level qualification used the AEC standards and part level qualification used ISO/IEC standards, but there was no applicable standard for MCM and SiP.

An MCM or SiP package contains several chips and devices, so do the individual chips and devices still need their own AEC-Q testing? The standard offers guidance: the original AEC-Q100, AEC-Q101 or AEC-Q200 qualification data of the components in the MCM can be used to simplify AEC-Q104 qualification.

Because an MCM experiences a composite environment in real automotive use, AEC-Q104 adds sequential testing, which makes qualification harder to pass.

AEC-Q104 is divided into eight groups, A to H. One key principle is that if every component used on the MCM - passive devices such as resistors, capacitors and inductors, discrete diodes and the ICs themselves - has already passed AEC-Q100, AEC-Q101 or AEC-Q200 before assembly, the MCM product only needs the seven tests within Group H of AEC-Q104. These comprise four reliability tests, namely TCT temperature cycling, drop, low temperature storage life (LTSL) and start up and temperature steps (STEP), and three failure inspections, namely X-ray, acoustic microscopy (AM) and destructive physical analysis (DPA).

If the components on the MCM have not previously passed AEC-Q100, AEC-Q101 and AEC-Q200, then test items must be selected from the 49 tests in the eight groups A to H of AEC-Q104 according to the product application, which means far more verification work.

Product scope of AEC-Q104 testing

Hybrid integrated amplifiers such as preamplifiers, pulse amplifiers and high frequency amplifiers; power assemblies such as DC/DC and AC/DC converters and EMI filters; power assemblies such as power amplifiers, motor servo circuits and power oscillators; digital to analogue and analogue to digital converters; synchro to digital converters including resolver to digital and double speed converters; and signal processing circuits such as sample and hold and modulation and demodulation circuits.

AEC-Q104 defines an MCM precisely: within a single MCM package, multiple active and/or passive sub-components are interconnected to create a single complex circuit intended to be attached to a printed circuit board by reflow soldering. The sub-components may be packaged and/or unpackaged (bare die) combined into a single hermetic or non-hermetic package.

MCM types not covered by AEC-Q104 include:

- Two assembled components or MCMs assembled onto a system by a tier-one or original equipment manufacturer (OEM).

- Light emitting diodes (LED), which are covered by AEC-Q102.

- Micro-electro-mechanical systems (MEMS), which are covered by the AEC-Q103 qualification document.

- Power MCMs, which may need specific considerations and qualification test procedures beyond the scope of AEC-Q104. A power MCM consists of several active power devices (that is, IGBTs, power MOSFETs and diodes) and, where necessary, additional passive devices such as temperature sensors and capacitors integrated on one substrate.

- Solid state drives (SSD).

- MCMs with external connectors that are not soldered to a board or other assembly.

Under AEC-Q104, for MCMs with embedded firmware the firmware is considered part of the MCM. It is therefore qualified as part of the overall system approach, depending on the type of MCM. In other words, standalone qualification of the firmware itself is outside the scope of AEC-Q104.

AEC-Q104 test method options

Like AEC-Q100, AEC-Q104 imposes requirements on the assembly lot of the samples. The same assembly lot is defined as a batch of MCMs combined through the same process steps, that is, using the same combination of materials on the same machines through to completion of the MCM. The assembly lot covers all process and test steps, and the same combination of materials includes the combination of multiple traceable sub-component lots.

Where feasible, the reliability test methods for MCMs may draw on existing guidance established in AEC-Q100, AEC-Q101 or AEC-Q200. Additional testing in accordance with Group H of AEC-Q104 must be considered, however, and the overall AEC-Q104 test flow is shown in the figure below.

Note that system in package (SiP) is an assembly of electronic components and their interconnections in a package configuration intended to be used as a single chip package component. It can therefore be qualified in accordance with Section 2.1 of AEC-Q100. One example of a SiP is multiple chips in a BGA package assembled in a stacked or side-by-side configuration.

AEC-Q104 test groups

Group A - accelerated environmental stress tests (PC, THB/HAST, AC or UHAST or TH, TC, PTC, HTSL): 6 tests.

Group B - accelerated lifetime simulation tests (HTOL, ELFR, EDR): 3 tests.

Group C - package assembly integrity tests (WBS, WBP, SD, PD, SBS, LI, BST): 7 tests.

Group D - die fabrication reliability tests (EM, TDDB, HCI, BTI, SM): 5 tests.

Group E - electrical verification tests (TEST, HBM, CDM, LU, ED, FG, CHAR, EMC, SC, SER, LF): 11 tests.

Group F - defect screening tests (PAT, SBA): 2 tests.

Group G - cavity package integrity tests (MS, VFV, CA, GFL, DROP, LT, DS, IWV): 8 tests.

Group H - module specific tests (BLR, LTSL, STEP, DROP, DPA, X-RAY, AM): 7 tests.

Group H contains the test requirements specific to MCMs and is the main difference between AEC-Q104 and AEC-Q100. The finer differences are shown in the figure below.

Differences between AEC-Q104 and AEC-Q100

NTEK testing capability against AEC-Q104 requirements

AEC-Q104 breaks the reliability testing of large scale integrated circuits into accelerated environmental stress reliability, accelerated lifetime simulation reliability, package reliability, wafer fabrication reliability, electrical parameter verification, defect screening and package integrity, and test conditions must be selected according to the temperature grade the device can withstand. Note that it is difficult for a third party to complete AEC-Q104 verification independently; wafer suppliers and assembly and test houses must work together, which places greater demands on overall control of the qualification programme.

About NTEK

NTEK Group was founded in 2009 and is headquartered in Shenzhen. The group provides quality research and technical services covering R&D verification, inspection and testing, failure analysis, simulation and market access for intelligent connected vehicles, electronic communications and new energy.

NTEK has extensive experience in automotive-grade electronic certification and has helped more than 100 companies pass AEC-Q series certification. Driven by the need of vehicle makers to localise automotive-grade chips and supported by the domestic semiconductor industry, NTEK provides comprehensive testing and certification services, applying AEC-Q automotive standards to control the safety and quality of automotive chips, supporting the growth of domestic automotive-grade chips and adding new momentum to the intelligent vehicle safety system.