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Defence Products > Electronic Assembly > NAFI Interconnection Systems

NAFI Interconnection System

NAFI (Naval Avionics Facility Indianapolis) was developed in the late 1960s for the US Navy for defence and aerospace applications, based on blade and tuning fork interconnection system on a 0.100" x 0.100" grid.

fork pcb These are designed specifically to meet the requirements of MIL-C-28859 and MIL-C-28754.

Advantages:

Ensures a high reliability gas-tight connection
Results in optimum contact retention within the panel
Minimises panel stress and growth, and distortion of the plated through hole.
Enables contacts to be easily replaced, with no loss of reliability.

Albacom Compliant Pin

The compliant interface section of the contact consists of two bow-shaped springs which have a geometry determined in conjunction with the stress characteristics of the contact material.

Upon insertion of the contact into the plated-through-hole in the panel, these springs interface with the sides of the hole and resiliently flex inwards.

This resilience creates an inverse vector force which acts on the contact to maintain it in intimate association with four vertical sections of the hole.

The flexibility of the spring members also enables the contact to be used effectively in holes with a plated-through tolerance of up to + 0.076mm ensuring optimum performance over a range of hole sizes.

The simplicity of the basic design permits each contact to be fabricated as a virtually exact reproduction of every other contact, further ensuring consistent and optimum press-fit performance.

Contact Replacement

Retention of a press-fit contact within a plated-through-hole should be sufficiently high to prevent the contact from being dislodged by an accidental blow or during normal assembly activity, and to produce the desired gas-tight interface. However high retention force should not be obtained via abnormally high insertion force, which may cause damage to the hole.

Press-fit systems which use noncompressable contacts exhibit insertion forces up to 300N and retention forces in excess of 200N. In light of hole damage and difficulty of reliable contact replacement, these forces are considered excessive. With the Compliant Pin System the retention force is typically 100N.

Contact Retention

Because the press-fit contact depends upon interface with the sides of the hole for retention, some abrasion and scoring of the plating is normal.

When the insertion and removal forces are excessive, however, significant breakthrough of the plating will occur.

This breakthrough can damage the hole to the point where subsequent contact replacement is unreliable because of significant changes in the interface characteristics and geometry of the hole.

The compliant spring action of the contact minimises these effects. Its consistent insertion and removal forces create minimum changes in hole characteristics, thus permitting contact removal and replacement up to three times with no sacrifice of reliability.

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