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PCB Interconnects and Socket Technology

PCB Interconnects and Socket Technology

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Beryllium Copper and Stainless Steel Contact Clip Technology

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Junior Member level 3
Junior Member level 3
Aug 11, 2016
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A major advantage of screw machine receptacles is two-piece socket construction. The outer shell is machined, and the internal insert called a contact clip is a beryllium copper stamping.

Contact clips are inserts press-fit into machined shells to make electrical and mechanical contact to mating pins.

Contact clips are stamped and rolled in a progressive die. They are typically conical in shape with multiple fingers (2,3,4,6, or 8). When a pin passes through the receptacle opening, the fingers open like cantilever beams scoring the mated pin surface.

Contact clip fingers apply insertion and withdrawal forces onto the pin

A significant advantage of two-piece socket construction is the cost-savings from selective plating. The outer shell (with the larger surface area) is plated tin. And the internal contact (with a small surface area) is gold plated.

Modifying contact clips is cost-prohibitive as it requires modification of a progressive stamping die.

Review the following when selecting a contact
1. The pin acceptance range
2. The insertion and withdrawal force.
3. The contact length
4. The required shell inner diameter.
5. The current rating of the contact clip.
6. The number of contact clip fingers.

Some barrel-shaped style contact clips are bidirectional, but typically conical-shaped multi-finger contact clips are not.

Do not insert a mating pin with any arrow tip feature, you will pull the clip out of the shell.

Important Guidelines and Tips:
1. Avoid selecting a contact your pin is already
at the maximum or minimum of the clip
acceptance range.

2. Do not insert a pin with an arrow-shaped head.
The clip fingers will lock around the pinhead
and you’ll pull the clip out of the shell during
pin withdrawal.

3. Do not insert a rough-edge or chisel-shaped
pin into the contact clip, you will damage the
clip fingers.

4. Conical shaped contact clips typically do not
mate bidirectionally.

5. Do not allow the solder to wick into an open
bottom receptacle and reach the gold plated
contact clip.

6. Inserting the maximum diameter pin into a
contact clip will “size” it, and you will lose the
lowermost pin acceptance range.

7. The mating pin should extend a minimum of
the pin diameter past the fingers to ensure
good electrical and mechanical contact.

Conical-shaped contact clips are typically stamped using spring tempered beryllium copper alloy. Each finger of the contact clip functions as a cantilever beam applying initial, normal, and retention forces onto the mating pin. Conical-shaped contact clips typically accept the mating pin from the entrance side only. They are not bidirectional. Due to the complexity of the progressive stamping die, modification of an existing contact clip is usually cost-prohibitive.

Make sure the contact clip you select is COTs.

Contact Clip Animation

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