Laser-assisted Die Bonding

Finetech's laser-assisted bonding technology is used in C2S and C2W applications with high demands regarding speed, highest accuracy and localized heat input. Especially quick heating reduces the risk of oxidation processes and allows shorter process times in time-optimized production environments. During sequential bonding processes at wafer level, each chip is only heated once. Unlike area heating, the spot heating via laser does not need extensive provisions to avoid thermal expansion.

Depending on the application and materials, two approaches are possible. If the chip/substrate is transparent for the wavelength of the laser (fused silica, sapphire glass etc.), the laser's energy passes through without being absorbed and is used to heat the solder directly. In non-transparent substrate materials (Si, Poly-Si, GaAs etc.), the laser's energy is absorbed and converted into a local heat source used for the bonding process.

Presentation: Laser Assisted Die Bonding – Requirements and Limitations, Advantages and Disadvantages

Using an eutectic process is common when it comes to bond optoelectronic devices such as VCSEL and laser bars on submounts or substrates. However, this process is rather slow, resulting in long cycle times and a low machine throughput. Laser assisted die bonding appears to be a promising approach to overcome this limitation. In addition it makes using formic acid or Nitrogen superfluous.

Despite these obvious advantages, laser assisted bonding has its limitations in terms of substrate and/or chip materials as well as chip size.

In this presentation, general advantages and disadvantages as well as requirements and limitations are described. Also ways are shown how to overcome some of the problems and limitations, which may allow using laser assisted bonding for a broader application range.

The presentation was held by Finetech's own Dr. Carlo Pagano and Hermann Moos during the Micro Assembly Day 2016 in Berlin.

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