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When connecting one circuit to another, designers can choose from a wide range of connection methods, all of which have their own advantages and disadvantages.
Screw terminals are a common connection method that utilizes a screw to compresses a wire and secure the connection. This connection method is permanent, it can also be adjusted. Unfortunately, screw terminals can suffer from reliability issues when used in mechanically stressful environments (i.e., vibration) and requires careful torque selection when tightening the screw.
Soldering is another connection method that provides a permanent bond between two circuits, with the benefit of a mechanically strong connection. However, soldering is permanent, and is not ideal if future changes to connectors or wires become necessary. Soldering also suffers from issues related to joint quality, joints that are made poorly can damage cables and connectors as well as the PCB.
Wire-wrap is a connection method in which a wire is tightly wrapped around a pin. The flexibility of wire-wrapping makes it ideal for prototyping; however, the non-permanent nature of the connection is not ideal for mechanically stressful environments. Disconnections may result in damage to the end of the wire.
Connectors are one of the most common methods used by designers and provide many advantages over the previous methods. To start, connectors support more than one cable, and so they are ideal for connecting data buses across boards. Connectors also support mechanical polarity, allowing only a specific orientation and preventing incorrect connections. Connectors can support both power and data simultaneously and can have mechanical fittings (such as screws) to ensure that they are secured. However, connectors can be expensive, have a limited number of mechanical cycles, and can be easily damaged by environmental factors such as dust, chemicals, and moisture.
Fortunately, there is an alternative connection method that is mechanically secure, is ideal for both prototyping and final product, has a simple installation, and is applicable in both power and data applications: PressFIT pins.
What is PressFIT technology?
PressFIT technology is a well-established connection method that utilizes a pin with a bowed body. When inserted into a correctly sized and plated PCB through-hole, the pin is compressed, which creates the electrical connection while providing mechanical stability. PressFIT does not rely upon soldering or any other connection method to keep pins in place.
Advantage 1: Simplicity
The design of PressFIT connectors allows for simple and efficient instillation which does not require tightening, specialized equipment, or multiple operations. In the case of the new Wolfspeed WolfPACKTM power modules, the pins are aligned with holes on the PCB, and the module is pushed into place. Once inserted, the module is secured mechanically and connected electrically.
Advantage 2: Higher power transfer
The secure mechanical connection formed between the plated through-hole and the pin allows for greater current transfer than some other connection methods. PressFIT also has better thermal characteristics, including heat dissipation. Both the increased current capacity and thermal performance are beneficial in power module applications. As such, the Wolfspeed WolfPACK power modules are ideal for implementation in various converter topologies, such as active rectifier, buck, and boost circuits.
Advantage 3: Low failure rate
PressFIT connectors offer one of the lowest failure rates relative to other connection methods. PressFIT has a typical failure rate of 0.005 FIT (whereby 1 FIT is one failure in 109 component hours), while screw terminals and solder connections have a failure rate of 0.5 FIT. PressFIT is an optimal solution for applications that require high reliability. By extension, this makes the Wolfspeed WolfPACK modules ideal for applications with such reliability requirements, such as renewable energy power conversion, grid tied converters, industrial motor drives, and more.
Advantage 4: Prototyping
Because modules using PressFIT pins can be simply installed by being inserted into a PCB, they are fast to install and easy to deploy in prototypes. What’s more, because the connections can be removed, the module can be reused in other projects, designs, or configurations. As such, the use of PressFIT pins in Wolfspeed WolfPACK modules substantially simplifies the prototyping process.
Despite the ease of installation, PressFIT pins form a reliable connection suitable for use in a final product. Therefore, prototypes which use the Wolfspeed WolfPACK modules will closely resemble the end product. In addition to reducing development stages, this fact also allows engineers to better understand the mechanical and electrical functionality of the end product during the prototype phase.
Advantage 5: PCB fabrication
One important advantage of PressFIT pins is their comparability with plated through-holes. Unlike connections that require specialized parts, PressFIT pins are directly compatible with PCBs. Therefore, Wolfspeed WolfPACK modules do not require specialized connectors, which can have long lead times.
The PressFIT pins also reduces installation time by only requiring the module to be oriented to the PCB and pushed into place. In addition to reducing installation time / cost, PressFIT pins improve reliability as the modules cannot be inserted incorrectly. The compatibility with PCB plated through-holes also reduces the overall system cost as, other than the holes manufactured during PCB fabrication, no additional components or assembly steps are required.
Conclusion
PressFIT technology provides many advantages to power electronic systems, including high reliability, excellent electrical and thermal properties, and a simple installation. The mechanical compression of the pins creates strong connections, while the use of PCB plated through-holes makes PressFIT pins easy to implement in designs. Finally, the reusability of PressFIT pins streamlines prototyping, alterations, and module replacements by removing the need for soldering, wrenches, and specialized tools.
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