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Press-fit technology

For making connections, press-fit technology has benefits over mere soldering technology. When evaluating the dependability of different connecting technologies, the term FIT value (Failure in Time) is used and it is 10 times higher with SMD soldering technology and many times higher again with conventional soldering technology (THT) than with the press-fit technology.

Failure in Time (FIT) indicates the number of defects in electronic components/assemblies that occur during a specific period of time.

Originally, the automotive electronic area especially relied on this technology. Meanwhile more and more applications in industry are carried out using this connection technology. Press-fit technology is not only highly reliable but also extremely economical. Using appropriate press-fit tools you can press-fit multiple components simultaneously, often even all the power elements of an assembly in a single operation.

The design of the circuit board is important in press-fit technology. The drill hole diameters and copper layer thicknesses in the metallization must be according to specifications.

The press-fit procedure with solid press-fit pins creates a mechanically very stable, gas-tight connection between pin and sleeve that at the same time has an extremely low electrical resistance. Solid press-fit technology is thus especially suited for use with high currents and under harsh ambient conditions.

History

During the 1970s the rapid development of electronic components and increasing complexity of applications, particularly in telecommunications technology, resulted in ever greater demands on connection technology. Bus systems like VME or the IED bus started to be used when it became possible to manufacture multi-layer circuit boards. The limitations of existing connection technologies such as wire wrap technology and solder connections became apparent. Multipole bus connectors in particular had to create a low-resistance connection with the circuit board. Soldering such connectors securely was a problem. This was the birth of the press-fit technology. After some developmental cycles, a large number of flexible and solid press-fit zones came into use, and some of them are still commonly used today.

During the 1980s Würth Elektronik ICS focused primarily on manufacturing backplanes. The company made its own circuit boards. Connectors were purchased from outside sources. Over a period of years the company acquired considerable experience in using and processing solder-free connection technology.

As backplanes have become larger, a new problem arose: the power supply!

Würth Elektronik power elements

Connection technologies that enable currents of more than 100 amperes to be fed to the circuit board with a single connection were not available. Würth Elektronik ICS rose to this challenge and developed power elements with solid press-fit pins - the Würth Elektronik power elements. Well-known manufacturers quickly authorized use of these power elements. It soon turned out that a considerable number of other problems can be solved with these high-current contacts, not merely feeds, whether just as mechanical connection, board-to-board connections or for connecting components such as IGBTs, or even to pressing copper bus bars with circuit boards.

Basics of solid press-fit technology

The solid press-fit technology is extremely easy to use; the manufacturing step can be integrated seamlessly into the process chain. As already mentioned, the cross-section of the press-fit pins must match the plated drill hole in the circuit board. The metalized hole in the circuit board and the base material absorb the deformation energy of the press-fit pins. A gas-tight connection is created between pin and the metalized sleeve. This is what makes this technology so unique and gives it its outstanding mechanical and electrical properties. A pin with a diagonal of 1.60 mm has a contact resistance to the hole sleeve of 0.1mΩ to 0.2mΩ. The press-fit pin contacts directly with the conductor track via the sleeve. A power element with 36 press-fit pins has 144 of these direct connections. The number of connections is multiplied because there are connections across multiple layers of the circuit board. It is thus not surprising that currents of several 100A can be supplied. The bottleneck generally is not in the connection with the circuit board but in the layout or connection area.

Millions of power elements by Würth Elektronik ICS are used in our own manufacturing processes and by our customers.