Heraeus at ECTC 2018

Visit Heraeus at ECTC 2018 and find out more about our materials and material solutions

May 29 - June 1, 2018
San Diego, CA
Booth 506

Come and meet our experts during the exhibition, and find out how we can assist you in optimizing your process for better results.

Visit our expert presentations at ECTC 2018

Pressure-less sintering of large dies using infrared radiation and optimized silver sinter paste

Wolfgang Schmitt speaks at CIPS 2018
Wolfgang Schmitt

Wednesday, 30 May 2018 - 13:30 – 13:55
Oral Dialogue Sessions, Room Nautilus 5
Wolfgang Schmitt, Project Leader Paste Development at Heraeus Electronics

Typical pressureless sintering profile carried out in a convection oven takes approximately 4 hours long to complete, which if shorten, increases attractiveness to adopt pressureless sintering. Additionally, the long process time required pressureless sintering to perform under nitrogen atmosphere in a convection oven to prevent oxidation of the substrate surfaces or chip metallization.

The main objective of this study was to investigate using IR radiation to reduce the total sintering process time.

We found out that with this new alternative process, it is possible to sinter dies with sizes up to 50 mm² under air atmosphere with the total process time of less than 2 hours. Scanning acoustic microscopy images demonstrate that delamination was not observed in the sintered joint of the samples sintered by IR after 48 hours pressure cooker test with conditions of 100% RH at 110°C and 100 thermal cycles with a condition of -40°C/+125°C. Cross section of sintered layer obtained by IR sintering and conventional pressureless sintering was performed in this study and the images illustrate that a more homogeneous sintered layer was achieved by IR sintering.

Authors: Wolfgang Schmitt, Ly May Chew, Robert Miller

Micro-silver sinter paste developed for pressure sintering on bare Cu surfaces under air or inert atmopshere

Ly May Chew speaks at ECTC 2018
Ly May Chew

Wednesday, 30 May 2018 - 16:45 – 17:10
Oral Dialogue Sessions, Room Harbor Island 1
Ly May Chew, Project Leader Paste Development at Heraeus Electronics

In this study, we observed the average initial die shear strength for Ag metallized substrate is higher than that for Au metallized and bare Cu substrates.

This observation points to the self-diffusion of Ag is faster than the interdiffusion between Ag and Au as well as between Ag and Cu. SEM-EDX results demonstrate that silver/copper interdiffusion occurred during the long term storage at 250°C where Cu from the substrate diffused into the silver sintered layer and concurrently Ag from the silver sintered layer diffused into the Cu substrate generating strong interface joints between silver sintered layer and Cu substrate. The increase of bonding strength of sintered joints by thermal cycling are verified by die shear strengths and bending tests. Good sintered joint was obtained for all the sintered samples in this study as we observed no voids, drying channels and delamination even after 2000 thermal cycles with conditions of -40°C/+150°C.

The results obtained in this study show that our properly formulated micro-silver sinter paste is suitable for pressure sintering under air atmosphere on precious metal surfaces as well as on bare Cu surface.

Authors: Ly May Chew, Wolfgang Schmitt, Christian Schwarzer, Jens Nachreiner

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