no-clean flux

Off-the-Shelf Connectors or Pogo Pins? What's Best For Your Design

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Standard connectors, such as pin headers and socket connectors, are ubiquitous in electronic designs due to their simplicity and proven effectiveness. They provide reliable electrical connections and are available in a variety of configurations, making them suitable for a wide range of applications. However, their performance can be compromised under conditions of mechanical stress, such as vibration or shock, and they may be susceptible to environmental factors like corrosion or dust, which can degrade the electrical contact over time.

In contrast, pogo pin/receptacle pairs represent a more specialized solution that offers several advantages over traditional connectors, particularly in high-reliability applications. Pogo pins are spring-loaded contacts that ensure a consistent, reliable electrical connection by maintaining constant pressure against the receptacle. This design allows for better mechanical stability and ensures high connectivity reliability under various conditions, including vibration and thermal expansion. The spring mechanism in pogo pins also provides a self-cleaning effect during connection and disconnection cycles, which helps maintain the integrity of the electrical contact throughout the lifespan of the product.

High Reliability Connectors

High reliability standard connectors, such as ruggedized pin headers and socket connectors, are specifically engineered to meet the stringent demands of applications where failure is not an option. These connectors are superior versions of standard models, designed to enhance durability and performance under extreme conditions.

Key features of high reliability connectors include:

  • Materials: Constructed with robust materials capable of withstanding higher temperatures, mechanical stress, and corrosive environments. Metal pins are often made from superior alloys for better conductivity and resistance to fatigue, while bases are crafted from high-performance thermoplastics or thermoset materials for enhanced heat and chemical resistance.
  • Design Enhancements: Features such as locking mechanisms and retention clips ensure a secure and stable connection, crucial in environments with high vibration or shock, such as in aerospace, military, and automotive electronics.
  • Contact Surface Plating: Frequently plated with high-grade materials like gold or palladium to improve conductivity and protect against corrosion, ensuring low-resistance electrical contact throughout the connector's lifespan.

High reliability connectors with locking, retention, keying, and rugged construction are often used in aerospace & defense, automotive, industrial systems, and robotics. These enhancements make high reliability standard connectors indispensable for these application areas, where ordinary connectors might fail, providing dependable performance in challenging environments and maintaining consistent functionality under extreme operational demands.

 

ruggedized connector

Selection of ruggedized connectors from Amphenol.

 

Why Pogo Pins

Pogo pin/receptacle pairs represent a specialized solution in the field of PCB connectors, designed to offer enhanced reliability and performance. Named for their resemblance to pogo sticks, these pins feature a spring-loaded mechanism that allows for consistent, resilient contact.

Pogo pins are cylindrical pins containing a spring that compresses and expands to maintain constant electrical contact with a mating receptacle. This design ensures a reliable connection even under conditions that might disrupt other types of connectors, such as movement or thermal expansion.

 

pogo pins

Selection of ruggedized connectors from Wiselink.

 

The integration of pogo pins into PCB designs is straightforward, requiring corresponding receptacle designs on the connecting board. This feature is particularly beneficial in high-density designs where space conservation is crucial. Additionally, the choice of plating materials for pogo pins, such as gold or palladium, enhances their durability and resistance to wear and corrosion, making them ideal for applications where long-term reliability is critical.

Regarding routing for power, a set of simple rules can be applied for pogo pins:

  • Power routing into pogo pins primarily uses copper pour regions to make the required pin connection
  • Apply a thermal relief if the pin connection is into a plane layer or into a very large pour region; some assembly process testing may be required
  • If heavier copper (>1 oz./sq. ft.) is used, make sure the finished hole wall size is specified (see more below on pads and holes sizes)
  • Ensure the surface plating used in the bare PCB is compatible with the pin material for soldering in order to form strong intermetallics
  • If required for high power, use multiple rails in parallel (on multiple layers) to route into the pin, and apply thermals on each when rails are very large

Thermal reliefs on through-hole pogo pins can be very important for ensuring formation of a strong solder joint whenever the pin attaches to a large copper pour. For example, see the image below from an Altium Designer project.

 

No-clean flux study

Thermal relief for surface-mount components shown in Altium Designer.

 

For signals, pogo pins require some level of qualification, which often demands simulation and testing to ensure compliance with a particular signaling standard. Typically pogo pins are not used for high-speed signals and instead a specialized connector would be preferred. There are many factors that drive signal integrity in PCBs that use pogo pins, and it is difficult for pin vendors to guarantee performance for every signaling standard.

Hole/Pad Sizing in PCB Footprints

Every component in a PCB layout needs to have a footprint, including pogo pins. Surface-mount and through-hole land sizing is specified in IPC-7351 (for surface-mount parts) and IPC-7251 (for through-hole parts); these provide guidance on conductor sizing in order to comply with other IPC standards related to performance, qualification, and acceptance (e.g., IPC-A-610 or IPC-6012).

The recommended pad sizing for through-hole parts depends on the density level of components in the PCB, which is specified using three levels (A, B, and C). The above standards, as well as the design guidance for rigid boards in IPC-2222, give the following requirements for pad and hole sizes:

  • Through-hole pins
    • Level A:
      • Pad diameter = Min hole size + 0.1mm + 0.60 mm
      • Min hole diameter = Max lead diameter + 0.25 mm
    • Level B:
      • Pad diameter = Min hole size + 0.1mm + 0.50 mm
      • Min hole diameter = Max lead diameter + 0.20 mm
    • Level C:
      • Pad diameter = Min hole size + 0.1mm + 0.40 mm
      • Min hole diameter = Max lead diameter + 0.15 mm
  • Surface-mount pins
    • Pad diameter follows maximum, minimum, or normal material conditions
  • Press-fit pins
    • Same as through-hole, although tighter drill tolerance may be required

These requirements outline the basic pad sizing for lands on the surface layer and are applicable to SMD pin/receptacle pairs and SMD connectors. Through-hole pogo pins or connectors would have the same pads applied internally if non-functional pads are kept in the design, which would help anchor the plated through-hole to the internal PCB layers.

For through-hole pogo pins, the annular ring size requirement in some cases, such as Class 3/3A products for high-reliability systems, may demand an increase in the pad size by a small amount depending on the fabricator's Producibility Level. Many fabrication houses can examine this point regarding Class 3/3A compliance during an engineering review prior to fabrication.

Ultimately, the choice between standard connectors and pogo pin/receptacle pairs should be guided by the specific requirements of the application, including the expected mechanical and environmental stresses and the need for space efficiency. Pogo pins offer a robust alternative for ensuring high reliability and durability in challenging conditions.

 

Whether you're designing high-speed PCBs for mil-aero embedded systems or a complex RF product, you should work with a design and development firm that can ensure your product will be reliable and manufacturable at scale. NWES helps aerospace OEMs, defense primes, and private companies in multiple industries design modern PCBs and create cutting-edge embedded technology, including power systems for high reliability applications and precision control systems. We've also partnered directly with EDA companies and advanced ITAR-compliant PCB manufacturers, and we'll make sure your design is fully manufacturable at scale. Contact NWES for a consultation.

 



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