The trend toward smaller, lighter and thinner designs over
the years has presented particular challenges for fastener manufacturers. Hardware
must fit extremely restrictive design envelopes, parts counts must often be
reduced, all while reliable performance in service remains essential. This
reality is particularly evident in compact electronic devices, such as cell
phones and tablet computers, where the specified hardware to attach components
ultimately must help - and not hinder various design and function objectives.
One solution available to designers to address these
smaller, lighter, thinner design trends is threaded micro screws. Designers now
can select from a variety of micro-screw materials, head styles, and driver
types to satisfy and advance application objectives. Threaded micro screws
often serve as standard hardware in many applications where size and space
But micro screws were just the beginning of the trend toward
extremely small fasteners. A new generation of self-clinching micro fasteners
(some threaded and some not) has been introduced offering performance,
production, and serviceability advantages.
Clinch fasteners become permanently retained in thin metal
sheets via a displacer and an undercut in their design. When the fastener is
pressed into a properly sized hole, metal from the edge of the hole is forced
by the displacer to flow into the undercut around the circumference of the part
beneath the fastener's head. The fastener is then securely locked in place and
will not loosen or fall out.
Among other benefits, self-clinching fasteners of all sizes
install permanently where designed to do so and can reduce the amount of hardware
required since only a mating part is required for final component attachment.
This fact can also help streamline the production process.
Examples of newly developed micro versions of clinching
fasteners include threaded self-clinching micro standoffs
to space internal components; non-threaded self-clinching micro
locating pins creating posts or pilots for locating, positioning, and/or
alignment; and threaded micro metal inserts,
which can be considered similar in benefits to clinch fasteners since they
all install permanently into plastic host panels.
Not Just Miniature†††
The specialty design and engineering behind micro fasteners
underscores that they are not simply scaled-down versions of their larger
counterparts. 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 tight
tolerances and performance values become magnified. Unique features engineered
into the fastener become critical.
For example, self-clinching micro tack pins
can enable permanent attachment of two
panels for such applications as anchoring internal divider plates. In addition
to this fastener's displacer and undercut (which are characteristics designed
into every self-clinching fastener), clinch tack pins incorporate a tapered
point and tangential interference band. These work together both to guide the
part into the small-diameter and shallow hole in the panel and create a slight
interference fit between the hole and the fastener at the interference band. This
creates minimal stresses in the host sheet and absorbs any tolerance between
the 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 functions
that can contribute to extended and expanded application potential. Some will
deliver production economies, too, as demonstrated by the forthcoming surface-mount
Surface mount fastening eliminates the need to manually
place the hardware on a populated printed circuit board. Instead, the hardware
supplied on tape and reel is positioned while a board is being processed and
then installed with the other electronic components using conventional surface
mounting equipment. Quality issues related to board cracking and misalignment
are expected disappear with the use of this new fastener, since the hardware
installs automatically with the same pick-and-place robotic equipment used for a
board's electronic components. In addition, because the fasteners are packaged
on tape and reel, different parts will not inadvertently get mixed in.
For more information, go to http://www.pemnet.com.