Press Fit Technology

Press fit technology uses a solder-free connection to make an internally powerful, gas-tight connection. At Wurth Electronics Midcom, we rate our connectors up to 10A per pin. This varies on the size of the pin and the part, but the high current technology really just uses a normal through-hole plating.

What is a gas-tight connection?

In the process of cold welding (such as a press-fit connection), two metal surfaces create a gas-tight connection together so that no foreign molecules (water, gas) can fit between them. So on our power elements, the gas tight connection and the cold weld process takes place right on the four corners of a square pin. In this example, the result is an absolutely homogenous connection from brass to copper.

Where is Press-Fit technology used?

High current applications, whether it’s a continuous, peak or spike current, are ideal for press-fit. You can see in the photo that the power element can support a 300A connection, but it is half the size of the 10.16mm terminal blocks, which only handle a 57A current. The high mechanical stability works well for heavy cables. Any torque will get better results from press-fit parts. It also works well for applications with high environmental impact such as temperature, vibration, or harmful gases.

What are the advantages?

The photo shows some of the common disadvantages of soldering such as the melting of plastic that can happen at high temperatures or shorting of pins. While hand soldering can fix these problems on a small scale, it is not ideal for large operations or mass production. Why use press-fit instead of soldering? It is a low-resistance connection with no problems for cold solder joints or even solder bridging. Also there is little heat development on sensitive components. Usually, press-fit is the last process so if you do any reflow solder then you end with press-fit, which results in the large, high-current parts being exposed to less heat. Press-fit is mechanically more stable than other connections with a failure in time, FIT, up to about 30 times better than compared to a surface mount connector. It also cuts down on the thermal stress on the PCB.

What tooling is needed?

Not a lot of special tooling is needed for the press-fit process. A couple standard arbor presses are pictured here. This is needed whether you use a manual style or a pneumatic or automatic foot pedal style, both work great. Press-fit also requires a baseplate and work pieces.

A baseplate is tooling (in this case aluminum) to support the circuit board. When the circuit board has a base like the one pictured, you can press in without seeing any bend or weakness in the PCB. Those cutouts allow the pins to protrude through the bottom because there is a minimum and maximum thickness on the PCB, so it’s important that the pins come through the bottom a little bit. On the right side are the work pieces needed for the press. The brass colored piece would screw onto the press, directly over the top of the power element, just left of the blue circle. In this case, they chose to drill in the pin setting so those could protrude through the baseplate.

Difference in the Pins

Wurth Electronics Midcom offers two different styles of power elements. The newer and more popular is pictured on the left, the massive pin. It is laser cut out of a piece of copper and then plated with tin so it is a one piece solution. During pressing, the via of the circuit board adapts to the pin. The other option is the flexible pin, which is a machined style power element so there are a number of cuts and bends to make this pin. It is a two piece solution so it folds over a square nut on the inside. This pin adapts to the via during the press, opposite of the massive pin.

To view our power elements, visit our online catalog.

Learn more about the processes and applications in our next blog post.

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