Overview

Our PressFIT technology offers the possibility for solderless mounting of power modules, meeting the demands of lead-free technology. PressFIT is a time-saving possibility for lead-free solderless mounting of power modules. The low electrical and thermal contact resistance makes the contact suitable for a wide range of currents and applications. Environmental tests show that vibration load has no negative influence on contact resistance.

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Background of PressFIT technology

As mentioned above, PressFIT technology enables lead-free solderless mounting of power modules. In addition, it offers the possibility of quicker mounting of the assembly, thus saving process time and costs with the potential of higher output capacity. The possibility of mounting the module on either the soldering or the component side of the PCB provides further flexibility to meet the requirements of modern assembly lines.

Well-merged surfaces in a force-fitting connection

Usually, if two contact faces are assembled, there are only a few spots that are connected (metal to metal) and which carry the current – this is also true for polished surfaces. The minimum radius of such a microscopic metal-metal contact is typically 10 µm. In force-fitting technologies like PressFIT, there is always a necessary plastic deformation on these truly effective contact points within the contact zone. The contact radius increases due to the high contact pressure that occurs since the macroscopic contact force concentrates on a small, microscopic contact area. That means the two faces will be merged.

The effective contact zone will be increased, and a gas-tight contact zone is generated, which is very robust against corrosive environments. The connection principle is the well-known cold-welding effect. Here, free electrons are generated from the plastic deformation of both contact faces. The metal-bond electron cloud links the free electrons and connects them again with the same mechanism as in the basic metal. The bonding force is indeed lower than in the prior grid but is increasing within the first hours of the connection due to recrystallization effects.

Quality of PressFIT modules

Several tests regarding the application of PressFIT technology and its reliability in power modules have been performed according to well-known IEC standards (e.g., IEC 60352-5), but with enhanced conditions. The result of the whole program can be concluded as follows: None of the tests caused any measurable contact degradation. The resistance of the connection, which is the leading indicator of the quality of connection, is very stable during and after several loadings. This means not only that high current can be handled safely over the lifetime, but also the advanced integrated functions with low voltage and current (e.g., current sensing) will be kept stable beyond the lifetime of the system. Due to this, PressFIT technology is well suited to power semiconductor modules – especially for future high-reliability requirements.

Background of PressFIT technology

As mentioned above, PressFIT technology enables lead-free solderless mounting of power modules. In addition, it offers the possibility of quicker mounting of the assembly, thus saving process time and costs with the potential of higher output capacity. The possibility of mounting the module on either the soldering or the component side of the PCB provides further flexibility to meet the requirements of modern assembly lines.

Well-merged surfaces in a force-fitting connection

Usually, if two contact faces are assembled, there are only a few spots that are connected (metal to metal) and which carry the current – this is also true for polished surfaces. The minimum radius of such a microscopic metal-metal contact is typically 10 µm. In force-fitting technologies like PressFIT, there is always a necessary plastic deformation on these truly effective contact points within the contact zone. The contact radius increases due to the high contact pressure that occurs since the macroscopic contact force concentrates on a small, microscopic contact area. That means the two faces will be merged.

The effective contact zone will be increased, and a gas-tight contact zone is generated, which is very robust against corrosive environments. The connection principle is the well-known cold-welding effect. Here, free electrons are generated from the plastic deformation of both contact faces. The metal-bond electron cloud links the free electrons and connects them again with the same mechanism as in the basic metal. The bonding force is indeed lower than in the prior grid but is increasing within the first hours of the connection due to recrystallization effects.

Quality of PressFIT modules

Several tests regarding the application of PressFIT technology and its reliability in power modules have been performed according to well-known IEC standards (e.g., IEC 60352-5), but with enhanced conditions. The result of the whole program can be concluded as follows: None of the tests caused any measurable contact degradation. The resistance of the connection, which is the leading indicator of the quality of connection, is very stable during and after several loadings. This means not only that high current can be handled safely over the lifetime, but also the advanced integrated functions with low voltage and current (e.g., current sensing) will be kept stable beyond the lifetime of the system. Due to this, PressFIT technology is well suited to power semiconductor modules – especially for future high-reliability requirements.

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