Technical Sheets & Articles

HARDWARE SOLUTIONS FOR ELECTRONIC COMPONENTS

No matter how sophisticated or advanced, electronic components must be attached reliably and securely within an end-product if they are to deliver optimum performance. Beyond this universal requirement, particular attachment demands often emerge. Boards will need to be stacked or spaced; multi-wire cables have to remain bundled and in place; power cables must be terminated; installation of a component may have to allow for its removal or replacement; and, in many applications, miniaturization will leave little room to maneuver.

But for every challenge that may arise when incorporating electronic components into an assembly, a hardware solution can be found. As the following examples indicate (and there are many more), the solution can even contribute production and performance benefits over and above a method's intrinsic value in attachment.

Application Challenge: Mounting Wires and Cables

Most conventional mounts to hold ties for wires or cables within enclosures or electronic chassis either tend to exhibit specific problems in service or otherwise have drawbacks.

Plastic adhesive-mounted bases can fail (and release from position) over time and temperature cycling; snap-in or screw-mounted bases will protrude on the side opposite installation and affect backside appearance or clearance; and screw-mounted bases require the use of additional hardware (screws) and more time to install. Other methods, such as lances in sheets, create openings for attachment of ties but open the door for EMI/RFI or contamination of electronics by dust or dirt.

An innovative hardware solution (PEM® TY-DT self-clinching cable-tie mounts) has been designed to circumvent these problems. This "clinch" hardware installs permanently without adhesives or screws to enable the tie-mounts to remain securely in position exactly where specified.

TY-D hardware (in several sizes consistent with industry standards) can be used with steel or aluminum sheets as thin as .040"/1.02mm and as thick as .125"/3.18mm. The hardware's low profile proves advantageous in fitting where space is at a premium.

The simple installation process is accomplished by placing the TY-D hardware through a properly sized rectangular mounting hole and into an anvil at each desired location. A squeezing force is then applied to complete installation. The outside surface remains flush, and ties will slide easily through the hardware's "eye."

Application Challenge: Keeping Screws to a Minimum

Screws are routinely specified in the electronics and computer industries to help ensure sturdiness of assemblies, but they carry their own sets of problems. Screws can fall out of place during fastening or after installation (which potentially can damage delicate circuitry); they tend to strip; and they add to the hardware that must be stocked and handled.

For these reasons, hardware that reduces screw count (without sacrificing the integrity of an assembly) will make a positive contribution. One of our customers (Agilent Technologies, Loveland, CO) has documented a firsthand success story featuring PEM self-clinching standoffs as part of an enclosure redesign.

Agilent redesigned the enclosure using only one screw (for an electrical ground connection), instead of 40 in comparable rack-mounted enclosures. The drastically reduced parts count and overall "screwless" design were enabled by SNAP-TOP® and KEYHOLE® self-clinching stainless steel standoff fasteners.

For this application four SNAP-TOP standoffs attach the unit's power-supply board to the bottom cover and eight KEYHOLE standoffs secure the 17" x 9" motherboard to the bottom cover and hold the front panel in place. Dozens of screws became unnecessary.

SNAP-TOP fasteners utilize a spring action to hold PC boards and subassemblies securely, while allowing for quick attachment and removal with a simple snap-on/snap-off action. KEYHOLE fasteners enable a PC board or panel to be slipped quickly into place or removed easily by sliding the board sideways and lifting it off.

The switch by Agilent to self-clinching standoffs has accelerated unit assembly (and disassembly) without tools and kept hardware to the desired minimum.

Application Challenge: Terminating Power Cables

The potential for "voltage drop" is a typical (but undesired) outcome from most power-cable terminations in low-voltage systems. While even a 10 percent loss of current from a power-cable termination may seem negligible, this loss can prove devastating in systems that may, for example, conduct only 3.3 volts of power. With traditional termination methods (such as standard crimp lugs), users often have had to resort to larger wires in an attempt to compensate and keep current ratings high.

As an alternative to larger wires, Cableco Technologies (Dublin, CA) developed the FusionLugT power-cable termination, which is uniquely designed to deliver a current rating equal to the size of a wire. For one of Cableco's customers, the FusionLug has been enhanced further with PEM self-clinching nuts as a means to reduce the amount of loose hardware and to make final attachment quicker and easier.

In this specific data-storage system application, FusionLugs are included on two cables (each conducting 5 volts of power at 60 amps). They are fabricated from the stranded ends of cable wire, which allows for multiple wire terminations (more than 100 wires can be terminated together in any one application). FusionLugs are extremely rugged, machinable, and formable, according to Cableco, and can be customized (with chamfers, diagonal cuts, and bends) per requirements. A "boot" is molded to fully insulate the metal.

In the customized application, two steel PEM Type "S" nuts (thread size M4) are installed permanently in each FusionLug by inserting them into pre-drilled 5.4mm holes and applying squeezing force using a standard press. A single mating screw for each nut is all that is required for the customer to mount the power termination to board.

Cableco has documented a 25 percent lower voltage drop attributed to the FusionLug termination (compared with standard crimp lug methods) and a termination rating equal to the cable current rating. The PEM threaded hardware retains the largest possible surface area to help keep voltage high.

This application stands as a reminder that hardware solutions for the assembly of electronic components need not be exotic. They can include time-tested parts such as PEM nuts, which were introduced in 1942 as the world's first self-clinching fastener.

Application Challenge: Attaching Non-Ductile Materials

Broaching fasteners in a wide variety of types, sizes, and finishes are among the hardware solutions for component-to-board, board-to-board, and board-to-chassis fastening applications. These threaded or unthreaded fasteners will install permanently in all types of PC boards, as well as in those components made from acrylics or polycarbonates.

As is the case with self-clinching fasteners in thin-metal applications, broaching fasteners for non-ductile materials can similarly reduce the amount of hardware required to attach components.

A broaching fastener is a knurled-shank fastening device that can be pressed into a punched or drilled hole to provide a strong threaded or unthreaded attachment point in non-ductile (non-metal) materials. Specially formed axial grooves around the shank of the fastener "broach," or cut into the material, creating a firm, interference-type fit resistant to rotation.

This category of hardware for non-ductile electronic components covers broaching nuts to provide permanent threads for board mounting; broaching standoffs in threaded or unthreaded types for stacking or spacing components; flare-mounted standoffs for applications where components will be subject to high pullout forces; threaded studs for use either as solderable connectors or as permanently mounted mechanical fasteners with external threads; one-piece board-mount assemblies in which screws remain captive for easy mounting and removal of PC boards without loose hardware; and self-expanding fasteners with a self-expanding shank to ensure positive contact with plated thru-holes.

Application Challenge: Fitting in with Miniaturization

"Size" is one of the most significant design trends impacting on the assembly of electronic components. As components get smaller, available "real estate" shrinks, leaving less room for the placement and installation of fastening hardware. As sheets get thinner, holding power can be jeopardized, unless a way can be found to provide strong threads. In a related trend, hardware must increasingly address the demands emerging from overall lighter designs.

As a solution, miniature self-clinching fasteners will fit into a minimal space and provide strong, reusable threads in metal sheets as thin as .020"/0.79mm. As with all self-clinching fasteners, these types require fewer assembly operations than loose hardware and deliver more holding power than sheet-metal screws. (Miniature fasteners also allow for closer edge distances and are designed to meet all relevant industry standards.)

Regardless of type, miniature self-clinching fasteners install by placing the shank into a properly sized punched or drilled mounting hole and applying sufficient squeezing force until the specially designed knurled collar of the fastener is completely embedded in the sheet. By becoming a permanent part of an assembly, any risk from potentially loose hardware is eliminated, even when components are removed for service.

Despite their small size and precision manufacture, miniature self-clinching fasteners are highly reliable due to the knurled-collar feature. Upon installation, the embedded knurled collar guarantees against rotation of the fastener in the sheet. (Self-locking fastener types deliver added holding power.)

Miniature self-clinching fasteners are typically made from 303 Stainless Steel and are designed for use in aluminum and cold-rolled steel sheets with hardnesses of HRB 70 or less. Thread sizes can range from #0-80 through 1/4-28 and M2 through M6. (For best performance, mating screws should be long enough so that at least two threads project through the fasteners when tightened.)

Of course, these represent just a sampling of the many types and variations of hardware that can prove ideal for electronic components. Others include a complete family of panel fasteners (known as "access hardware") with captive screws to satisfy UL service access requirements; two-part grounding systems (spring-loaded plunger assembly and contact button) for static and EMI and RFI discharge; unique customized hardware designs; and countless more examples.

The scope and diversity of available (or custom) hardware for electronic components suggest that users can benefit by turning to an experienced hardware manufacturer early in the design process to arrive at the most effective solution for an application challenge.

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