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Shimadzu Corporation, through joint research with the Joining and Welding Research Institute at Osaka University (Ibaraki City, Osaka Prefecture; Professor Masahiro Tsukamoto) and DOWA POWER DEVICE Co., Ltd. (Shiojiri City, Nagano Prefecture), a group company of DOWA HOLDINGS Co., Ltd., has successfully brought copper-aluminum nitride (Cu-AlN) substrates manufactured using the multi-beam additive manufacturing method into practical use. This is the world’s first technology for directly coating an aluminum nitride (AlN) substrate with copper electrodes by simultaneously feeding copper powder onto the substrate and irradiating it with a blue diode laser, without using silver, which can cause insulation failures. In addition to power semiconductor devices, the technology is also anticipated for use in a wide range of other fields, such as optical communications, communication satellites, AI servers, and medical lasers.

As high-performance power semiconductor devices continue to be developed, technologies for efficiently managing the heat they generate are increasingly needed. Cu-AlN, in which copper is bonded to aluminum nitride, combines excellent thermal conductivity and electrical insulation properties and is mainly used as an insulating heat-dissipation substrate for power semiconductor devices. Conventional bonding methods generally use high-temperature bonding with silver-containing brazing materials. These methods have presented challenges, including lengthy manufacturing times, residual stress*1, and the impact of silver migration*2 on insulation reliability.

New bonding process (right) based on multi-beam additive manufacturing successfully put into practical use
Unlike the conventional bonding method using active metal brazing (left), the new method can bond copper directly without using brazing material

The three partners have been engaged in joint research since November 2022, where Shimadzu was in charge of developing the copper coating system with blue diode lasers and the fabrication processes. The multi-beam additive manufacturing method developed by Shimadzu and the other partners enables copper circuits of any shape to be bonded directly to ceramics without using silver, achieving strong bonds with low residual stress. Blue diode lasers are well-suited to processing pure copper because metals absorb blue laser light highly efficiently. In addition to high heat-dissipation performance, its heat-cycle durability*3 is more than three times that of conventional substrates. Furthermore, 3D additive manufacturing technology enables the formation of fine-line patterns and complex circuit shapes. In addition to power semiconductor devices, we will also evaluate its use in a wide range of fields, including optical communications equipment and AI servers, where high-density wiring and miniaturization are required.

• *1 The force that remains within a material after bonding or processing. Excessive residual stress can cause substrate warpage, cracking, and delamination at bonded areas.
• *2 A phenomenon in which silver migrates under high-temperature, high-humidity, or high-voltage conditions, forming unintended conductive paths. This can reduce the insulation reliability of electronic components and substrates.
• *3 The ability of substrates and bonded areas to withstand repeated exposure to low and high temperatures without degradation. It is an important indicator for evaluating the long-term reliability of heat-dissipation substrates in power modules.

Process for coating an aluminum nitride (AlN) substrate with copper electrodes using a blue diode laser to produce a copper-aluminum nitride (Cu-AlN) substrate

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