DN Staff

August 30, 2010

3 Min Read
Micro Fasteners Adapt to New Electronics Design Requirements

The trend toward smaller, lighter and thinner designs overthe years has presented particular challenges for fastener manufacturers. Hardwaremust fit extremely restrictive design envelopes, parts counts must often bereduced, all while reliable performance in service remains essential. Thisreality is particularly evident in compact electronic devices, such as cellphones and tablet computers, where the specified hardware to attach componentsultimately must help - and not hinder various design and function objectives.

One solution available to designers to address thesesmaller, lighter, thinner design trends is threaded micro screws. Designers nowcan select from a variety of micro-screw materials, head styles, and drivertypes to satisfy and advance application objectives. Threaded micro screwsoften serve as standard hardware in many applications where size and spacematter.

But micro screws were just the beginning of the trend towardextremely small fasteners. A new generation of self-clinching micro fasteners(some threaded and some not) has been introduced offering performance,production, and serviceability advantages.

Clinching Fasteners

Clinch fasteners become permanently retained in thin metalsheets via a displacer and an undercut in their design. When the fastener ispressed into a properly sized hole, metal from the edge of the hole is forcedby the displacer to flow into the undercut around the circumference of the partbeneath the fastener's head. The fastener is then securely locked in place andwill not loosen or fall out.

Among other benefits, self-clinching fasteners of all sizesinstall permanently where designed to do so and can reduce the amount of hardwarerequired since only a mating part is required for final component attachment.This fact can also help streamline the production process.

Micro Fasteners Adapt to New Electronics Design Requirements

Micro Fasteners Adapt to New Electronics Design Requirements_A

Examples of newly developed micro versions of clinchingfasteners include threaded self-clinching micro standoffs to space internal components; non-threaded self-clinching microlocating pins creating posts or pilots for locating, positioning, and/oralignment; and threaded micro metal inserts,which can be considered similar in benefits to clinch fasteners since theyall install permanently into plastic host panels.

Not Just Miniature

The specialty design and engineering behind micro fastenersunderscores that they are not simply scaled-down versions of their largercounterparts. As fastener types are downsized to lengths as short as 2 mm,thread sizes as small as M1.0, and diameters of 1mm, issues relating to tighttolerances and performance values become magnified. Unique features engineeredinto the fastener become critical.

For example, self-clinching micro tack pins can enable permanent attachment of twopanels for such applications as anchoring internal divider plates. In additionto this fastener's displacer and undercut (which are characteristics designedinto every self-clinching fastener), clinch tack pins incorporate a taperedpoint and tangential interference band. These work together both to guide thepart into the small-diameter and shallow hole in the panel and create a slightinterference fit between the hole and the fastener at the interference band. Thiscreates minimal stresses in the host sheet and absorbs any tolerance betweenthe diameter of the hole and the diameter of the clinching pin.

Micro Fastener Future

Looking ahead at the evolution of micro fastener technology,more types can be expected on the horizon offering capabilities and functionsthat can contribute to extended and expanded application potential. Some willdeliver production economies, too, as demonstrated by the forthcoming surface-mountfasteners.

Surface mount fastening eliminates the need to manuallyplace the hardware on a populated printed circuit board. Instead, the hardwaresupplied on tape and reel is positioned while a board is being processed andthen installed with the other electronic components using conventional surfacemounting equipment. Quality issues related to board cracking and misalignmentare expected disappear with the use of this new fastener, since the hardwareinstalls automatically with the same pick-and-place robotic equipment used for aboard's electronic components. In addition, because the fasteners are packagedon tape and reel, different parts will not inadvertently get mixed in.

For more information, go to http://www.pemnet.com.

Sign up for the Design News Daily newsletter.

You May Also Like