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PCB Interconnects and Socket Technology

PCB Interconnects and Socket Technology

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Understamding Horizontal Mount Interconnects - Advantages and Applications

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Junior Member level 3
Junior Member level 3
Aug 11, 2016
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Horizontal mount screw machine pin and socket receptacle interconnects sit parallel to the surface of a printed circuit board. One reason why they’re so advantageous from a product design standpoint is their mating center line is low profile to the PCB. Horizontal mount screw machine pin and socket receptacle interconnects can come in two configurations: surface mount and right angle through-hole.

The primary advantage of surface mount horizontal interconnects is they allow the product designer to utilize both sides of the identical location on a PCB. This doubles the packaging density.

Two common versions of horizontal surface mount interconnects are: the barrel and S-Bend tail. The advantage of the barrel style interconnect is it only requires a small PCB footprint. The advantage of the S-Bend tail, is it allows for greater visibility of the solder joint for inspection and accessibility for rework. Both SMT versions can be packaged on tape and reel.

Typically horizontal SMT connectors should exhibit no greater than .005” variation of coplanarity over a 1 inch strip length. For strips longer than 1 inch, the actual coplanarity will need to be determined.

The primary advantage of through-hole right angle tail interconnects is they are mechanically stronger than SMT connectors, as the pin tail is soldered inside a plated through hole. It is now possible for even through-hole right angle tail interconnects can on tape and reel too.
Mutual to both SMT and through-hole screw machine interconnects is their construction. Screw machine receptacles are precision machined using Brass Alloy.

Screw machine socket receptacles are assembled with a progressive die stamping, made of Beryllium Copper, called a “Contact Clip”. Contact clips characteristically are configured in 3, 4, 6 and 8 multi finger arrangements.. The function of a contact clip is to provide the mechanical and electrical interface to the mating pin.

Because contact clips are heat hardened during manufacturing, they score the surface of the mating pin, this achieves a reliable gas tight connection. However, contact clips are not locking mechanisms for the mated pin. The pin can be pulled out when required. Contact clips come in a variety of pin acceptance ranges each with its own characteristic force parameters

The two piece construction of precision screw machine socket receptacles allows for cost savings to be realized as the shell can be plated tin for improved solderability while the contact clip is plated gold for corrosion resistance. Plating gold only where required results in cost savings.
One little known trick of using a horizontal mount interconnect, is to combine it with a vertical mount interconnect forming space saving, perpendicular orientation on the PCB.

Another little known fact is that screw machine receptacles assembled with contact clips having a pin acceptance range of .030” diameter and .025” square posts, can effectively mate to common .025” square post header strips. This allows the product designer to create mating modules using square post headers with round screw machine socket receptacles.

Horizontal mount screw machine interconnects are typically manufactured with RoHs compliant platings and thermoplastics suitable for RoHs soldering profiles.

As this paper presented in detail, horizontal mount screw machine interconnects have many useful applications and present product designers with cost effective, low-profile solutions.

If you have any questions or would like to learn more about this subject, please feel free to contact me,
I will be happy to help you - Marty

Marty Houlroyd
Principal Engineer

An Example of a Right Angle Horizontal Interconnect Pair

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An Example of a SMT Barrel Interconnect Pair
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An Example of a SMT S-Bend Interconnect Pair

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An Example of combining vertical and horizontal interconnects to create a perpendicular to PCB pair
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