Process and Product Development

Fraunhofer IZM is currently pursuing the following research and development in this area:

• Reflow soldering: Development of soldering processes for Sn-based solder and for completely residue-free Au/Sn solders. Examples of applications include bonding optical components or chips that have to remain contaminant-free for subsequent wire bonding.
• Soldering of thin die attach solder joints: Interconnection of transistors and diodes in power electronics requires planar and preferably non-porous joints. Here, we are developing special soldering processes that produce joints with minimal pores for preforms and paste processes.
• Transient liquid phase bonding: Development of novel processes and pastes for transient liquid phase bonding. This technique is extremely important in the design of applications that have to withstand high temperatures. As the melting point of the materials to be joined (parent materials) is so high, conventional solder techniques cannot be applied. Instead, the parent materials are joined by a solder or paste that diffuses at a much lower temperature, spreading to form a non-porous bond between the two temperature resistant materials, without inducing melting of the latter.
• Self-aligning flip-chip bonding: The key to this highly precise assembly technique is the development of low surface-tension solders, which induce a self-alignment mechanism.
• Miniaturized solder joints: Here, we are reducing thermal resistance by miniaturizing the size of solder joints from the current standard of 25 µm to 10 µm and thicknesses from currently approx. 50 µm to 5 µm. 
• Solder for hermetic seals: Here, special soldering techniques for hermetic encapsulation are being developed.
• System-in-package and 3D integration: New techniques are being investigated that expand the possibilities of sequential reflow soldering and collective hot-bar soldering.

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