How Proper PCB Pin Selection Improves Product Reliability

Most designers are not familiar with the range of pin options that can be used in a printed circuit board (PCB). Pins are available for board-to-board mounting, wire termination connections in cable assemblies, and mating with female receptacles or sockets. PCB pin selection takes into consideration pin orientation and fit with other parts of an assembly, and because they are individual components they allow for flexibility in layout.

Along with their versatility, PCB-mounted pin connections are among the most reliable electrical and mechanical connections that can be constructed for delivering power, handling thermal fluctuations, enduring mechanical shock and vibration, and providing low contact resistance for signal transmission. Not all assemblies will need PCB-mounted pin connections, but those that do should make reliability an important part of a cost vs. performance comparison.

Important Specifications for PCB Pins

Like any component, PCB pins have several important specifications that affect their performance, namely their dimensions (overall length and largest diameter), ability to handle power, material compatibility for mating with other components, and the mounting/retention method on the PCB. The important specifications for pin selection are shown below.

The process for selecting PCB pins is similar to that for any other connector: determine the important specification and select a group of components that fits. Most often, the top specification for ensuring reliability is mechanical retention method, followed by power handling ability, and overall size. In some settings, such as where an assembly or the PCB pins may be exposed to corrosive substances, the material option may be the first consideration.

Power and Thermal Management

Thermal management of PCBs and PCB assemblies is critical to overall product performance. Because power and heat are directly related, highly conductive PCB pins can be useful in dissipating heat during operation. This is especially important for pins used in power and ground connections. Higher current in general requires physically larger connectors in order to provide both lower resistance — to pass current more efficiently — and higher thermal mass to dissipate heat more effectively.

While there are other off-the-shelf connectors that can handle similar power levels as PCB pins, the use of individual PCB pins brings some additional advantages:

Individual pins allow for freedom in the layout or footprint of the connections. Multi-pin connectors have current and temperature limits governed by the connector housing/insulator. Individual PCB pins have no such limiting factor, which is a typical reason they are used in DC-DC power converters and other power supply modules. Connection can be cyclable if mating to a receptacle or socket. When higher currents are needed, a designer can easily add more pins to expand the number of circuits in the interface and thus the total power delivered via the interface.

Mechanical Stability

For interconnects, mechanical stability most often indicates a demand for a high-strength connection to the PCB which limits vibration and offers a high number of mating cycles.

Mechanical stability in terms of pin construction comes from two aspects of pin design: pin form factor and mounting method. PCB pins can be attached to the PCB via surface mount soldering technology (SMT), through-hole soldering, press-fit, or swage mount.

Modern PCB design incorporates surface mount devices (SMD) as much as possible because it enables maximum component density by utilizing both sides of the PCB. SMT also offers the most efficient placement and assembly option for a PCB, but, in terms of mechanical stability, it will have the lowest level of reliability, as the components do not pass through the PCB. The remaining options (swage, press-fit, or through-hole solder mount) will provide much higher retention forces as the pins are secured through the PCB. For highly reliable power connections, through-hole solder or press-fit options are superior as they can make contact with multiple internal layers in the PCB.

Material Selection

Finally, pin materials play a major role in determining reliability. As is the case in other connectors such as pin headers, PCB pins are coated with a plating material that determines their corrosive resistance and maximum number of mating cycles.

There is also the base material to consider, which is typically a less-expensive metal that can be easily plated and can impact pin durability and current rating.

Among these sets of materials, prioritizing reliability demands selecting the right plating material. The most reliable plating material is gold. It can be deposited on brass, phosphor bronze, and other base materials — typically with a copper and/or nickel underplate — to deliver excellent mechanical stability in terms of corrosion and wear resistance, along with exceptional conductivity.

Mill-Max Delivers Reliability

For high-reliability interconnects in a PCB, the most important specification is usually the mounting and retention method. Many components that meet the mounting requirement are available with multiple plating options, so they could comply with a non-RoHS soldering requirement (e.g., aerospace), or a high corrosion resistance environment (e.g., marine or industrial). Power handling tends to become the next most important specification in PCB pins; choosing larger pins or increasing the number of pins used in parallel can provide higher current carrying limits.

Mill-Max is a leading PCB Pin manufacturer dedicated to ensuring reliability in our customers’ products. Contact us today to get started on your next project.