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Eye of needle press fit design

IP.com Disclosure Number: IPCOM000242053D
Publication Date: 2015-Jun-16
Document File: 7 page(s) / 316K

Publishing Venue

The IP.com Prior Art Database

Abstract

Through simulations, it was found that the main reason of this sensitivity is the beam lengths. Shorter beams are good to make the press fit more mechanically stable and less sensitive to tolerances, but the contact area with the PCB hole is decreased.

The problem of sensitivity is solved by adding flexible beams in the middle area. The beams will have a spring function and allow a better control of insertion and normal force (and thus push out force).

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Eye of needle press fit design

Background of the invention

Eye of needle press fit are components that ensures solderless contacts.

Examples are shown in below pictures.

           

This press fit is supposed to be flexible thanks to its two beams and remain elastic enough to ensure a normal force with a PCB hole and thus provides good electrical performance and stability with vibrations.

The picture below shows a cross-section of a needle press fit after insertion into a PCB card.

Below pictures illustrates a variety of shapes exists on the market.

Customers and standard specifications require a maximum value for push-in (insertion) force, and minimum value of push-out force. Such designs of press fit are very sensitive to dimensional variations (e.g. in hole dimension or press fit dimension).

Below figure illustrates the sensitivity of maximum value push-in force and minimum value push-out force on variations in eye length.

In addition to the sensitivity, mechanical performance aren’t well controlled. Push-out may be easily under the minimum specified, and insertion force may exceed the maximum specified by customer or in standard specifications.

Accordingly, several companies developed some designs that may substitute the classic eye of needle.

As illustrated in below figure, examples of such developments are shown. Here, a multi spring and action pin is shown.

These concepts make the press fit more mechanically stable and thus less sensitive to dimensional variations.

 


Description of the invention

Through simulations, it was found that the main reason of this sensitivity is the beam lengths. Shorter beams are good to make the press fit more mechanically stable and less sensitive to tolerances, but the contact area with the PCB hole is decreased.

The problem of sensitivity is solved by adding flexible beams in the middle area. The beams will have a spring function and allow a better control of insertion and normal force (and thus push out force).

Designs 1, 2 and 3, shown below, disclose reinforcement with flexible beams.

These concepts make the beams opposite to each other shorter, which may decrease design sensitivity.

Another idea consists of making multi-eyes press fits (2 eyes or more). Design 4, shown below, disclose a multi-eye design.

This design appears like a superposition of two eye of needle press fits with short beams. The first opening may be seen as the main press fit, while the function of the second one consists on increasing contact area, normal and push out-forces.

The two graphs below show a considerable increase of inserti...