Frequently Asked Questions About Contact Clips & Receptacle Design

What is the "Range" of a contact clip?

This is the specification of the minimum to maximum pin diameter the contact will accept. The minimum pin diameter inserted into the contact will exhibit the lightest insertion/extraction forces. Conversely, the maximum pin diameter inserted into the contact will exhibit the highest insertion/extraction forces. Inserting the largest possible diameter pin into a contact will effectively form the contact fingers and accelerate its fatigue.

What is the ideal Mating Pin Diameter and Pin Insertion depth for a Mill-Max Receptacle?

Ideally, the Mill-Max contact clip selection should have a pin acceptance mid-range, near the diameter of the mated pin. When designing an interconnect always try to select a Mill-Max contact with a mid-range near your pin diameter.  To ensure a reliable electrical and mechanical connection, the mated pin should pass a minimum distance, equivalent to the pin diameter, past the end of the contact clip position inside the shell, so the contact fingers can engage and score the mated pin surface. For complete list of contact clips and their lengths, review our Contact Selector Chart When mating Mill-Max receptacles with square/rectangular shaped leads, we recommend converting the square into a diameter by means of the Pythagorean theorem (a²+b²=c²).  This will ensure the pin falls within the receptacle’s acceptance range. For example, If a square lead is .010”x.020”, it would be calculated as follows: .010²+.020² =  .0005  .0005” = .022360”

What is the "Compliancy" of a contact clip?

This is the resultant loss of the lower contact range, due to forming, when a contact clip is engaged by a near maximum range diameter pin. When designing an interconnect, always try to select a Mill-Max contact with a mid-range near your pin diameter.

The Mill-Max "multi-finger" contact clip exhibits wide compliance, ie: the ability of any single contact to accept a broad range of round pins as well as rectangular or square component leads. This ability is referred to as the contact's "compliancy". The compliancy factor specifies the re-configured operating range after the initial insertion of the largest permissible mating pin. For example: the #34 contact has an initial operating range from .032" (0,813mm) to .047" (1,194mm) diameter pins, and a compliancy of .010" (0,254mm); but after insertion of a .047" (1,194mm) pin, the contact is sized, and the minimum pin acceptance becomes .047" (1,194mm) - .010" (0,254mm) = .037" (0,94mm). Thus, the new operating range becomes .037" (0,94mm) to .047" (1,194mm).

For complete specifications on all Mill-Max contact clips, review our Contact Selector Chart

What is the "Initial" Insertion Force / Insertion Force "2nd Cycle"?

The initial insertion force will always be the highest, because the contact plating is in a pristine state. Subsequent insertions will be a slightly lower force.

The insertion and extraction forces are shown on the force graph for each Mill-Max Contact Clip. This is a mathematical representation of the average force readings found through testing using a polished bullet nose calibrated pin. These numbers should be used for reference purposes only, and are not intended to represent absolute force values. For customers who need to specify insertion/extraction force parameters on their boilerplate drawings, it is highly recommended they test sample receptacles in a simulation of their anticipated working environment.

What is the cycle life of the Contact Clip?

The life cycle of a contact clip is a function of the customer's application. How the clip is engaged / disengaged in the customer's application, will determine how fast or slow the contact fingers fatigue. All metal objects eventually fatigue when exposed to cycling. Fatigue factors include constant contact cycling (pin insertions) over time, deformation damage of the contact fingers by pin misalignment (Figure 1), and/or forming the contact by inserting too large a diameter pin that fall towards the extreme end of the contact range (Figure 2). Mill-Max has customers that achieve thousands of cycles out of our contacts by ensuring the mated pin is a diameter within the mid-range of the contact specification, and not rough surfaced or chisel tipped. They ensure the mated pin is engaged/disengaged concentric to the receptacle opening, usually by incorporating alignment guides on both halves of the connector. For customers who need to specify a life cycle parameter on their boilerplate drawings, it is highly recommended they test sample receptacles in a simulation of their anticipated working environment.

Why is it important to incorporate a "Shoulder" in my receptacle design?

Many Mill-Max receptacles incorporate a "shoulder" at the top of the part. This shoulder serves several functions outlined below:

• Automation - Incorporating a pin shoulder on a receptacle design allows Mill-Max to automate contact clip assembly into the shell.
• Alignment - The shoulder prevents a receptacle from falling through a mounting or plated through hole and also serves to help keep the pin perpendicular to the circuit board during soldering operations.
• Targeting - Incorporating a shoulder allows for a countersink opening providing a larger pin entry to guide the mated pin into the receptacle.
• Strength - If a pin receptacle shell does not have a shoulder, the section of the shell that the contact clip gets press-fit into may bulge up to .003" (0,076mm)