Effect of sintering density on thermal reliability by non-pressure sintering die-attach

The evolution of the transient liquid-phase sintered (TLPS) Cu–Sn skeleton microstructure during thermal aging was evaluated to clarify the thermal reliability for die-attach applications. The Cu–Sn skeleton microstructure, which consists of Cu particles connected with Cu–Sn intermetallic compounds partially filled with polyimide resin, was obtained by the pressure-less TLP sintering process at 250 °C for 1 min using a novel Cu-solder-resin composite as a bonding material in a nitrogen atmosphere. Experimental results indicate that the TLPS joints were mainly composed of Cu, Cu6Sn5, and Cu3Sn in the as-bonded state, where submicron voids were observed at the interface between Cu3Sn and Cu particles. After thermal aging at 150, 175, and 200 °C for 1000 h, the Cu6Sn5 phase fully transformed into Cu3Sn except at the chip-side interface, where the number of the submicron voids appeared to increase. The averaged shear strengths were found to be 22.1 (reference), 22.8 (+3%), 24.0 (+9%), and 19.0 MPa (−14%) for the as-bonded state and specimens aged at 150, 175, and 200 °C for 1000 h, respectively. The TLPS joints maintained a shear strength over 19 MPa after thermal aging at 200 °C for 1000 h because of both the positive and negative impacts of the thermal aging, which include the transformation of Cu6Sn5 into Cu3Sn and the formation of submicron voids at the interface, respectively. These results indicate an excellent thermal reliability of the TLPS Cu–Sn skeleton microstructure.

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Thermal reliability of SiC device with Cu sintering die-attach processed at 250°C in N2 gas

Additional Conferences (Device Packaging HiTEC HiTEN & CICMT) ◽

10.4071/2380-4491.2017.hiten.193 ◽

2017 ◽

Vol 2017 (HiTEN) ◽

pp. 000193-000196

Author(s):

Shijo Nagao ◽

Hiroki Yoshikawa ◽

Hirofumi Fujita ◽

Akio Shimoyama ◽

Shinya Seki ◽

...

Keyword(s):

High Reliability ◽

High Strength ◽

Life Time ◽

Industrial Applications ◽

Junction Temperature ◽

Thermal Reliability ◽

Excellent Thermal Stability ◽

Power Semiconductors ◽

Die Attach ◽

Micron Particle

Abstract Thermostable die-attach method alternative to soldering with Pb content is urgently required for utilizing wide-bandgap power semiconductors like SiC or GaN with a high maximum junction temperature TJ. Ag nano-or micro particle paste sintering attracts wide attention for this purpose, but Cu paste has also being developed mainly because of the cost pressure. Recently Cu sub-micron particle paste dispersed polyethylene Glycol solvent has demonstrated low temperature sintering at 250°C in N2 gas, resulting in high strength of die-attach. In the present study, the developed Cu paste die-attach has accepted to SiC Schottky barrier diode in TO-247 standard packaging with highly thermostable mold materials. The produced sample devices are subjected to high temperature storage tests at 250°C and thermal cycling tests between −50°C and 250°C. The device including the novel die-attach structure exhibited excellent thermal stability. Furthermore, power cycling tests has been conducted, and the results appear prospective for long life time and high reliability with high TJ exceeding 250°C. The presented study thus conclude that Cu submicron paste sintering is a promising candidate of power device die-attach usable for heavy industrial applications.

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Heat-Resistant Microporous Ag Die-Attach Structure for Wide Band-Gap Power Semiconductors

Materials ◽

10.3390/ma11122531 ◽

2018 ◽

Vol 11 (12) ◽

pp. 2531 ◽

Cited By ~ 2

Author(s):

Seungjun Noh ◽

Hao Zhang ◽

Katsuaki Suganuma

Keyword(s):

High Temperature ◽

Oxide Layer ◽

Morphological Evolution ◽

Void Formation ◽

Wide Band ◽

Thermal Reliability ◽

Power Semiconductors ◽

Die Attach ◽

Ag Paste ◽

Sintered Ag

In this work, efforts were made to prepare a thermostable die-attach structure which includes stable sintered microporous Ag and multi-layer surface metallization. Silicon carbide particles (SiCp) were added into the Ag sinter joining paste to improve the high-temperature reliability of the sintered Ag joints. The use of SiCp in the bonding structures prevented the morphological evolution of the microporous structure and maintained a stable structure after high temperature storage (HTS) tests, which reduces the risk of void formation and metallization dewetting. In addition to the Ag paste, on the side of direct bonded copper (DBC) substrates, the thermal reliability of various surface metallizations such as Ni, Ti, and Pt were also evaluated by cross-section morphology and on-resistance tests. The results indicated that Ti and Pt diffusion barrier layers played a key role in preventing interfacial degradations between sintered Ag and Cu at high temperatures. At the same time, a Ni barrier layer showed a relatively weak barrier effect due to the generation of a thin Ni oxide layer at the interface with a Ag plating layer. The changes of on-resistance indicated that Pt metallization has relatively better electrical properties compared to that of Ti and Ni. Ag metallization, which lacks barrier capability, showed severe growth in an oxide layer between Ag and Cu, however, the on-resistance showed fewer changes.

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Comparison of Au-In Transient Liquid Phase Bonding Designs for SiC Power Semiconductor Device Packaging

Additional Conferences (Device Packaging HiTEC HiTEN & CICMT) ◽

10.4071/hiten-paper6-bgrummel ◽

2011 ◽

Vol 2011 (HITEN) ◽

pp. 000077-000083 ◽

Cited By ~ 1

Author(s):

Brian Grummel ◽

Habib A. Mustain ◽

Z. John Shen ◽

Allen R. Hefner

Keyword(s):

Liquid Phase ◽

Semiconductor Device ◽

Bonding Temperature ◽

Transient Liquid Phase ◽

Wide Bandgap ◽

Thermal Reliability ◽

Power Semiconductor ◽

Tlp Bonding ◽

Die Attach ◽

Order Of Magnitude

Transient liquid phase (TLP) bonding is an advanced die-attach technique for wide-bandgap power semiconductor and high-temperature packaging. TLP bonding advances current soldering techniques by raising the melting point to over 500 °C without detrimental high-lead materials. The bond also has greater reliability and rigidity due in part to a bonding temperature of 200 °C that drastically lowers the peak bond stresses. Furthermore, the thermal conductivity is increased 67 % while the bond thickness is substantially reduced, lowering the thermal resistance by an order of magnitude. This work provides an in-depth examination of the TLP fabrication methodology utilizing mechanical and thermal experimental characterization data along with thermal reliability results.

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Effect of Sintering Density on Thermal Reliability by Non-pressure Sintering Die Attach

2021 IEEE 71st Electronic Components and Technology Conference (ECTC) ◽

10.1109/ectc32696.2021.00105 ◽

2021 ◽

Author(s):

Takamichi Mori ◽

Masatoshi Okuda ◽

Ryo Katou ◽

Suguru Hashidate ◽

Junichirou Minami ◽

...

Keyword(s):

Thermal Reliability ◽

Die Attach

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Power cycle reliability of SiC devices with metal-sinter die-attach and thermostable molding

International Symposium on Microelectronics ◽

10.4071/isom-2017-tp12_024 ◽

2017 ◽

Vol 2017 (1) ◽

pp. 000008-000012 ◽

Cited By ~ 1

Author(s):

Shijo Nagao ◽

Hirofumi Fujita ◽

Akio Shimoyama ◽

Shinya Seki ◽

Hao Zhang ◽

...

Keyword(s):

High Temperature ◽

Cooling System ◽

High Reliability ◽

Life Time ◽

Industrial Applications ◽

Junction Temperature ◽

Power Devices ◽

Thermal Reliability ◽

Device Structure ◽

Die Attach

Abstract Metal paste sintering die-attach is recently attracting much attention as an alternative to Pb containing high temperature solders, particularly required for power device packaging with post-Si wide band-gap semiconductors. For high voltage and high power devices, which are used in electric vehicles, railway trains, or power grid systems, SiC MSOFET/SBD devices are emerging replacing Si IGBT devices. These SiC devices have two prominent advantages to traditional Si based devices: fast switching and high maximum junction temperature TJ. The excellent characteristics serve for miniaturization of the device module; the former allows to use smaller capacitor and reactors because of the high frequency, and the latter excludes cooling system without affecting the device life time. However, the thermal reliability should be critically tested before used in industrial applications. We have hence conducted comprehensive reliability tests using several types of metal sintering die-attach including Ag and Cu. High temperature storage tests at 250°C certify that the device structure is truly thermostable, and thermal cycling between −50°C and 250°C indicates that the thermomechanical stress caused by device package design is the key for high reliability of power devices. Power cycling demonstrates the usefulness for effective acceleration tests to estimate the device life time. Our results conclude that present metal paste die-attach is ready for use in the product instead of high temperature solders.

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High Thermal Stability of SiC Packaging with Sintered Ag Paste Die-attach combined with Imide-based Molding

International Symposium on Microelectronics ◽

10.4071/isom-2015-wp15 ◽

2015 ◽

Vol 2015 (1) ◽

pp. 000349-000352 ◽

Cited By ~ 1

Author(s):

Shijo Nagao ◽

Takuo Sugioka ◽

Satoshi Ogawa ◽

Teruhisa Fujibayashi ◽

Zhang Hao ◽

...

Keyword(s):

Lead Frame ◽

Thermal Cycles ◽

Thermal Reliability ◽

Molding Process ◽

Sem Images ◽

Transfer Molding ◽

Die Attach ◽

Ag Paste ◽

Thermosetting Composite ◽

Sintered Ag

We report that ultra-high thermal reliability can be achieved by combining Ag paste sintering die-attach and injection transfer molding with imide-based mold composite. Test specimens of SiC SBD in TO247 discrete-package are prepared; SiC dies bonded on Cu lead frame, Al ribbon wiring from electrode of SiC Schottky barrier diode (SBD) chip to the Cu leads, and injection transfer molding process. The hybrid nano+micro flake Ag paste realizes a low temperature bond process of 250°C in air, die-shear stress recorded 23 MPa without intensive pressure. The thermo-mechanical parameters like glass transition temperature, Young's modulus and CTE of the thermosetting composite are carefully tuned for both the manufacturing process targeting the device operating temperature of 250°C. The test pieces are tested by harsh thermal cycling between −50°C to 250°C, and compared with the other specimens made with usual Pb-5Sn soldering die-attach with the same molding composite. Interface failures are investigated by scanning acoustic tomography (SAT), and the electric properties of SBD are checked by I-V measurements. The sintered Ag die-attach survived over 500 cycles without any failures around the interfaces of SiC die, Cu lead-frame, and mold materials, and no obvious change is found in electronic properties. However, Pb-Sn die-attach joints are gradually damaged with increasing thermal cycles causing degraded I-V property. The SEM images indicate the microstucture of sintered Ag layer is unchanged after the thermal cycles, because of the impregnated imid-matrix into the porous Ag. Our results demonstrate that the combination of Ag sinter paste die-attach and imide-based thermosetting composite can be a massproduction-ready packaging technology to realize the high operation temperature of post-silicon power devices.

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Analysis of Two Electrical Failures Caused by Die Attach of Exposed Pad Package

ISTFA 2014: Conference Proceedings from the 40th International Symposium for Testing and Failure Analysis ◽

10.31399/asm.cp.istfa2014p0184 ◽

2014 ◽

Author(s):

Jinglong Li ◽

Motohiko Masuda ◽

Yi Che ◽

Miao Wu

Keyword(s):

Bonding Process ◽

Die Attach ◽

Die Bonding ◽

Generic Analysis

Abstract Die attach is well known in die bonding process. Its electrical character is simple. But some failures caused by die attach are not so simple. And it is not proper to analyze by a generic analysis flow. The analysis of two failures caused by die attach are presented in this paper.

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