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Evolving Semiconductor Assembly Challenges in 2019

As i see it, 2019 will be a year of increased innovation in semiconductor packaging as global uncertainty on political and economic fronts plays out. Also contributing will be the impact of the perceived 2017/2018 “bubble” (from higher memory prices) in the semiconductor industry, which will leave engineers potentially with a little time to experiment.

In 2019, we will see Qualcomm and Intel 5G modems in cellphones, and a smattering of 5G infrastructure will be built out in major metropolitan areas; however, due to its short range, the vast majority of the world will remain on 4G or 4.9G for the foreseeable future. This may be a fringe benefit in the 20s for the SAE (Society of Automotive Engineers) level 4 autonomous driving (AD) vehicles running 5G as it will essentially geo-lock these local Uber-like services witnin specific urban areas by simple availability of low latency, high bandwidth RF connectivity.

Advanced processors and memory: The assembly and packaging of thinned 7nm die are now becoming more complex and process-sensitive. By necessity, assembly of these advanced devices is becoming a more fab-based, post-back-end-of-line process, with the major semiconductor manufacturers strongly leading. Indium Corporation’s ultra-low residue and water-soluble flip-chip fluxes are enabling both 3D and 2.5D assembly processes for advanced processor and 3D TSV memory stack flip-chip attach. We are increasingly differentiating ourselves with specialty ultra-low and near-zero residue (ULR/NZR) fluxes, which are inherently compatible with both molded underfills and capillary underfills without cleaning. Laser-assisted bonding (LAB) is an increasingly viable alternative to standard thermocompression bonding (TCB) and mass reflow processes. It promises to be higher throughput, yet with precise temperature control, and we are finalizing our work with several OSATs and wafer fabricators with fluxes to suit, which are expected to roll out in 2019.

Thermal interface materials for advanced processors:  Ideally suited for large logic die operating at high power, Indium Corporation’s breakthrough M2TIM™ (metal to metal thermal interface material) technology enables a reliable, compliant, and highly thermally conductive die-backside TIM interface. The patent-pending material set and its application require no die-backside metallization, allowing a unique, highly-effective functionality with reduced die processing costs.

Panel-level packaging (PLP):  Indium Corporation has been working with the John Lau/ASMPT-led PLP consortium to develop ball-attach fluxes suited to finer pitch (0.3mm and below) arrays. These halogen-free water-soluble fluxes are designed to print without slumping and to be compatible with RDL (redistributed layers) polymers without swelling, yet clean at room temperature using only DI water.

High-temperature applications: AI and ancillary systems for ADAS-enabled automotive and also for high-end server applications are running at higher thermal junctions for longer periods, so Indium Corporation has been developing new solder alloys to allow reliable operation at higher temperatures. We will continue to expand our portfolio of high-tin (Sn) -based solder alloys, such as Indalloy®276, as well as standard offerings, such as SnSb5 and SnSb10.

This alloy approach is also working well for large-area die-attach and DBC/heat spreader-attach. Our patented InFORMS® engineered solder allows for an extremely well-controlled bondline thickness with no tilt, ideally suited for large, thin (<50um), high-current-density die, such as are used in IGBT modules, as well as in DBC (AMB) substrate to heat-spreader attach.

Discrete and small module: The usage of high-Pb solders in smaller discretes and modules is not likely to be curtailed by the European Union (under the current ELV/RoHS legislation) in 2019. Specific emerging failure modes caused by increasing component lifetime needs, the usage of higher current density wide band-gap semiconductors (especially SiC), and failures of devices using thinned die due to alpha emissions will continue to drive customers away from standard high-Pb offerings toward high UPH “drop-in”  (i.e., no capital expenditure) assembly processes using Indium Corporation paste materials:

  • Alternative, more resilient high-Pb alloys (under development)
  • Low-alpha standard high-Pb alloys (available now)
  • A unique high-melting Pb-free BiAgX® solder paste (available now)
  • New, dispensable high UPH QuickSinter(TM) rapid sintering materials (print and dispense versions being launched in Q1 2019)

Very high-temperature applications: Die-attach for RF and similar applications that use gold-based metallizations often suffer from voids that are caused by excessive gold in the final solder joint. By developing new alloy processing techniques, Indium Corporation is now able to offer significantly lower gold (lower cost) AuSn alloys in any form and reduce the occurrence of intermetallics, and hence, minimize voiding in the final reflowed solder joint.

Quantum computing: Finally, as the age of quantum supremacy becomes reality in the 2020s, we will see the large-scale implementation of liquid helium-cooled quantum computers operating at a fraction of 1K, and running as isolated islands in data centers, bringing to mind H. G. Wells’ “vast and cool” intelligences. Specific and unique assembly needs of the quantum chips themselves are proving to be a challenge, and we are currently working to resolve these issues with major customers, with results and materials sets clearly delineated in 2019.

I hope to see many of you again in 2019!
Cheers!  Andy