Trends in the design of electronic goods affect the choice of fasteners
Where once it was believed that design would always be predicated on the need to take things apart and repair or recycle them, the fact is that the opposite has increasingly become true. Electronic devices, in particular, have seen a fundamental shift whereby disposability is increasingly considered the norm – even in expensive devices.
Due to their inherent cost, these devices have always been constructed in a way that they could be disassembled for repair should they go wrong. We are familiar with sending these devices to an authorised repairer who would disassemble and replace the faulty component, reassemble, test and return.
According to Dr David Quinn, European R&D director for PennEngineering: "Unbeknown to the consumer, there has been a growing trend over the years that many of the sub-assemblies are being manufactured with a higher propensity for disposal rather than repair. Additionally, the current quality of these components brings increased dependability, making failure during the product's useful life unlikely."
One key element in this change has been the elimination of the need for threaded screws to hold things together. Using traditional fasteners in modern plastic or non-ductile materials involves costs for inserts as well as screws. There are also risks of increased production costs through cross threading, over and under tightening, vibration loosening and others.
Some manufacturers have considered other approaches, including the use of adhesives or the use of rivets instead of screws. In the case of adhesives, they require time to cure, may be affected by temperature and are only useful when using similar types of material and low loads. In the case of rivets, they share some of the same quality issues as threaded fasteners in relationship to the security of the joint, but also suffer from a negative visual impact on the consumer.
In more recent years, there has been a further shift towards making complete devices with no serviceable parts, in addition to the constant drive for smaller, lighter and thinner devices.
Some examples of the technology that we are seeing come to market are wireless broadband dongles, credit card reader attachments for smartphones or medical infusion devices.
What this has meant is a need for fasteners in the global electronics industries that reflect these trend. Says Dr Quinn: "It became apparent that there was a new need in the global electronics industry for a fastener that had the cost-effectiveness and simplicity of a rivet, yet displayed the precision, dependability and quality of a threaded fastener in a product that needed little real-estate or protruded substantially. Because of the nature of material used in electronics, this new type of fastener required the ability to bond different materials – metals, die-cast materials, and non-conductive plastics."
With these requirements in mind, PennEngineering devised a solution to the problem by developing two ranges of non-threaded fasteners to join the existing microPEM range: the TackPin and the Tacksert.
A Type T microPEM TackPin fastener is installed by first preparing properly sized mounting holes in the sheet to be attached and the base panel. After inserting the fastener into these holes, the fastener is pressed into place. The fastener clinches into the base panel and the fastener's head subsequently holds the top sheet as thin as 0.2mm/0.008" firmly and permanently in place. The base panel can be as hard as HRB 45 or less on the Rockwell "B" scale and should be at least 0.89mm in thickness for blind holes or 0.5mm in thickness for thru holes. Upon installation, loosening due to vibration or other factors is not a concern.
During the process, the fastener's tapered tip assists in location, an interference fit eliminates hole-tolerance issues, and the self-clinching action results in full 360° metal contact.
The fasteners can be installed automatically for high-volume applications.
In addition to the TackPin range, TackSert fasteners can be used to attach a top panel of any material as thin as 0.2mm / .008" to a base panel or chassis manufactured from common magnesium die-cast materials such as AZ91D or plastics such as ABS. They have a unique diagonal knurl which effectively holds the top panel to a base panel or chassis by broaching into the base panel/chassis using a simple press-in action, without the use of heat or ultrasonics.
TackSert pins are quick and easy to install using pre-prepared and properly sized mounting holes in the top sheet and base panel. Operatives or machines place the pin through the hole in the top sheet and into the mounting hole of the base panel; sufficient squeezing force is then applied using punch and anvil until the head of the pin contacts the top sheet. During the process, the fastener's tapered tip assists in location and a firm interference fit eliminates hole-tolerance issues.
Designers can specify TackSert fasteners as either a Type TK4 Series stainless steel pin for broaching into castings and similar materials or a Type TKA aluminium pin for broaching into plastic applications.
Also designed for the electronics industry, TR Fastenings' plastic fasteners and fixings range for Printed Circuit Board (PCB) hardware and Cable Management requirements. Plastic fasteners and fixings are set to be a core part of TR's expansive product portfolio, with a comprehensive range available, on demand and competitively priced.
Manufactured in high-performance and incredibly versatile Nylon 6 and Nylon 6/6,
TR Fastenings' new PCB range includes circuit board hardware, rivets, screws, Cable Management and Wiring Accessories. Combining functionality and reliability without compromising on quality, these plastic fasteners feature extensive benefits, which can assist in efficiency and productivity of production processes.
Not only can one plastic fastener be used for a variety of purposes, but they also have other qualities, including ease of use, being formed from a lightweight material, strength at low and high temperature, resistance to impact, abrasion, organic solvents and gasoline, retention of shape and stiffness at high temperature. Furthermore, TR's plastic range meets with the necessary industry standards and sizes, all products satisfy the RoHS compliance (Restriction of Hazardous Substances) legislation, are ISO 14001/2004 compliant and available in flame-retardant versions.
The new moulded Nylon range for PCBs addresses a multitude of application needs, but the range is especially beneficial in the electronics and telecoms industry, such as ATMs, PCs, laptops and mobile phones, as well as in lighting. In such applications, with their closely grouped electrical components, plastic fasteners offer the ideal solution as they are a non-conductive material. Furthermore, TR is introducing an extensive range of Cable Ties, Cable Management products and Wiring Accessories, for effective Cable Management.
Author - Paul Fanning, Eureka Magazine