The Role of Pin Receptacles in Ensuring Electrical Contact Reliability

PCB designers that need a board-to-board or board-to-wire interface will sometimes choose an off-the-shelf set of mating connectors. These connectors have their value, but they can quickly become very bulky and expensive. When a high-reliability board-to-board, board-to-wire, or board-to-device connection is needed, a better option may be pin receptacles, which can mount directly onto a PCB and make a strong electrical and mechanical connection.

Pin receptacles are a proven technology that are simple to incorporate into a PCB. Once the pin receptacle has been mounted to the PCB, the connecting board or device will need to have a corresponding mating pin, lead, or wire. These mating components will insert into the pin receptacle, forming a reliable and secure mechanical and electrical connection that will hold true despite external environmental factors (ex. shock and vibration).

Reliability Factors Related to Pin Receptacles

Pin receptacles are often used to form connections between boards, wiring, and devices/components. When selecting pin receptacles for high-reliability interconnects, some important questions should be addressed in the engineering requirements:

Is the pin receptacle mating with a predetermined pin, lead, or wire?
How much current will the pin receptacle need to pass?
What is the desired termination method of the pin receptacle?
Are there any size limitations the pin receptacle must adhere to?
Will the pin receptacle be mated repeatedly during the lifetime of the product?
Are there environmental factors that could impact reliability of the pin receptacle (e.g. heat, humidity, chemical contamination, shock and vibration)?
Is RoHS compliance required?

Selecting a pin receptacle with an acceptance range to properly engage with the mating pin, lead, or wire should be the top priority. Each pin receptacle has an acceptance range which details the minimum and maximum diameter limits of the corresponding mating component.

When the mating component properly falls within the acceptance range, a robust connection is formed, ensuring electrical and mechanical stability.

SMD or Through-Hole?

SMD mounting versus through-hole mounting of the pin receptacle and its mating pin will be a major determinant of reliability. In general, through-hole receptacles can offer a more robust connection to the PCB, as they have the advantage of being anchored through the PCB. However, SMD mounting is also desirable, as it eliminates the need for mounting holes in the PCB, enabling dual sided population of the board. Both through-hole and SMD termination options are commonly used. Which is ultimately selected would be based on the needs of the application.

Through-hole pins and receptacles come in three versions: solder mount, press-fit, and swage assembly. These are outlined and compared with SMD receptacles below.

Through-hole solder mount receptacle	Strong hold through the PCB provided by large volume of solder encapsulating the receptacle in the hole. Allows for standard board hole tolerances, simple round pad designs and, typically, ample clearance for placement. Can be soldered using wave, intrusive reflow, fountain, or hand methods. Can be hand placed or automated. Packaging can be bulk or tape and reel.
Press-fit through-hole receptacle	Eliminates the need for soldering, although can also be used to secure the receptacle in place prior to soldering. Reliably anchored by press-fit features embedding into the metal layers of plating in the PCB hole. Polygon press-fit features allow for press-fit in multi-layer boards. Receptacles may be pressed in with hand tools, semi-automatic, and fully automatic equipment. Packaging can be bulk or tape and reel.
Swage mount through-hole receptacle	Fastened to the PCB like riveting; part specific tooling is required. Soldering is often performed after swaging. Typically mounted to the PCB using manual placement and swage tooling. Can be automated with specialized equipment depending on the application. Packaging is bulk.
SMD receptacle	Not anchored through PCB. More economical: reduces the number of holes in the PCB; allows double sided component mounting for higher density PCB fabrication; supports pick and place assembly for high volume applications. Compatible with standard reflow processes. Can allow for thinner PCBs. Automatic placement is recommended. Packaging is typically tape and reel.

It should be noted that the termination method for the pin receptacle and the mating pin does not need to be the same. For SMD pins, the pin receptacle could be either a through-hole receptacle or SMD pin receptacle, and vice versa for through-hole pins.

Pin receptacle plating materials will affect many factors related to reliability, both in terms of mechanical reliability and environmental reliability. In terms of total reliability of an interconnect, the pin plating materials will principally affect the number of mating cycles and resistance to corrosion during operation.

Below are some areas where different platings would be used:

High-Durability: Gold preferred
Highly-Corrosive: Gold preferred
Aerospace Qualified: Tin/Lead preferred if RoHS compliancy is not required.
General-Purpose: Gold or Matte Tin for RoHS compliant. Gold, Matte Tin, or Tin/Lead if RoHS compliancy is not required.

Trust Mill-Max Pins and Receptacles

Mill-Max is a trusted partner and supplier of pins and receptacles, ready to partner in your next design. We have the mounting and plating options you need, and the engineering expertise to help you consider all the critical factors that help ensure reliability. Contact us today to get started.