In May, a new project was started with the IGF project No. 21868 N, in which a gentle TLP joining process (LowTemp-TLP) is to be developed by using ternary systems.
In May, a new project was started with the IGF project No. 21868 N, in which a gentle TLP joining process (LowTemp-TLP) is to be developed by using ternary systems.
The first meeting of the project monitoring committee has already taken place. Details and the current status were presented there. The aim is to reduce the process temperature for TLP bonding to below 150 °C.
Transient liquid phase bonding (TLP bonding for short) is a bonding technology for high-temperature applications that enables the low-stress assembly of microsystems such as sensors. This is because the process temperature in TLP bonding is below the melting point of the resulting connection.
The TLP process runs as follows for the two-phase Ag-Sn system:
- Application of pressure
- Application of heat
- Melting of Sn and diffusion into Ag
- Maintaining the temperature until isothermal solidification takes place (alloy formation)
- Homogenization of the bonding compound
However, the current TLP process temperatures of well over 200 °C are too high for many materials. For example, there is a risk of degradation or even complete destruction of resins in printed circuit boards or plastics in components. This was the motivation for a research project for a gentler technology.
A ternary system of silver, indium and tin (Ag, In, Sn) can be designed in such a way that at process temperatures below 150 °C a compound of intermetallic phases is created that is temperature-stable up to over 300 °C. This has several advantages. This has several advantages. The low process temperatures and thus the lower temperature difference to room temperature lead to lower mechanical stresses in the structure, so that the structures have better properties than with comparable joining techniques, in particular greater reliability. In addition, commercially available bonding devices can be used. LowTemp-TLP is suitable for joining individual components, individual chips or even entire wafers. The required layer systems can be provided both as films and by direct (electrochemical) coating.
The research institutes Hahn-Schickard-Gesellschaft für angewandte Forschung e. V., Villingen-Schwenningen (in charge), the Research Institute for Precious Metals and Metal Chemistry (fem), Schwäbisch Gmünd, and the Institute for Microsystems Technology (IMTEK) at the University of Freiburg as well as industrial partners are involved in the project.
The first meeting of the project support committee took place in June in the form of a video conference. After welcoming and introducing the participants, a detailed project presentation took place, focusing on the structure and the planned solution. The work programme is divided into several work packages (WPs), some of which will be implemented in parallel/overlapping and some in succession. These and the persons responsible for them (in brackets) are
- WP 1: Specification with the aim of defining the processes, materials, alloys, temperatures, applications and test methods to be used in consultation with the companies on the project support committee (all)
- WP 2: Investigation of the ternary system In-Sn-Ag (fem)
- WP 3: Electrochemical production of films and direct coatings (fem, HS)
- WP 4: Develop joining process technology (IMTEK, HS)
- WP 5: Production of test objects (IMTEK, HS)
- WP 6: Characterization using different methods (all)
- WP 7: Production of functional samples (all) to demonstrate the application of TLP bonding on one or more specific components
The funding project will run until October 31, 2023, and the milestones are planned accordingly:
- M1 (after 12 months): TLP layer systems or InSn alloys available as foils and coatings
- M2 (after 21 months): Test objects characterized
- M3 (after 28 months): Functional samples produced and characterized
Meetings of the project support committee are also planned every 6 months. Further points of the first meeting were the current status of the work, i.e. the TLP bonding tests with InSn foils and the result of the company survey on applications as well as the discussion and determination of the next steps. The IGF project 21868 N is funded by the Federal Ministry for Economic Affairs and Energy via the AiF as part of the program for the promotion of joint industrial research (IGF).
