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ELECTRONICS: MATERIALS 


andmaking corrective changes is bad for a number of reasons, not least of which is that each iteration has a potential effect on the product’s EMC performance. Webber explained that there is a set of


design rules that are well established for improving the outcome of board designs. “These design rules are based on standards, experience and experiments,” saysWebber. “They’re not set in stone and could change as densities increase and will certainly becomemore critical.”


AN ENVIRONMENT IN FLUX Changes in densities and the resulting overcrowded EMC environment are certainly creating a challenge to design engineers and prototyping is becoming more important for producing a compliant product. Shielding is essential in reducing


emissions fromnoisy components or protecting these components froma noisy environment. Cans, which cover critical or sensitive components, are an extension of the PCB ground plane, which provides a large surface area to prevent the board frombecoming an antenna for emitting or receiving RF. These shielding cans are able to be surfacemounted or can be attached using the older through hole and wave soldermethod. However, asWebber explained, both of


these techniques are expensive in terms of the amount of solder used and the effort required in reworking and inspecting. To overcome this and to facilitate easier


prototyping,Harwin supplies its EZ- BoardWare Shield Cans as well as its prototyping kits. Using the kits, engineers are able to formtheir own size and shape of shielding can and rework it to achieve optimumperformance before placing an order for production volumes. Using theHarwin can/spring clip


approach to attachment alsomakes it easier to assemble without the use of solder paste or wave soldering processes.


CLIP TOGETHER ASSEMBLIES The wayHarwin achieves its easy assembly board hardware approach is through the use of spring clips. The clips attach to the ground plane of the board to ensure continuous, solid grounding, including the components attached to the clips. The universal spring clips are first


attached to the board using surfacemount pick-and-place equipment and solder paste. The EMC can is then hand pushed onto the clip ensuring ground continuity across the shielding can. There is a range of clips available, which can be supplied with different retention


32 /// Environmental Engineering /// August 2017


forces for hand removal or for solder removal. Sometimes, the hand force removal option is good for final products where service access is regularly required to the component beneath the shielding can. The example used byWebber was on smartmeters. The clips themselves are of a stamped


and plated construction and so they’re very inexpensive. They can also be used on signal contacts fromantennas to boards. The clips come in a wide range of


designs, sizes, compression forces, heights and spring displacements to suit size restrictions and proximity factors fromone component to another. Webber toldme: “Ourmain focus is to


meet the requirements of newmarkets in connected industry through innovative design and so we prioritise product development.” The company produces test reports for


all of its products to give its clients confidence in what they’re purchasing. This doesn’t just extend to EMC but also to vibration response. Vibration can be a significant factor in the reliability of spring contacts.


CABLING Harwin is well known as a connectivity specialist, supplying a wide range of electronic connectors andWebber explained tome that EMC is becoming more significant in cable connection design now. “Signal frequencies are becoming much higher down the cable now and at very high frequencies the wires turn into antennas,” he says. The cables themselves have better


shielding options than ever before but often the connectors are lagging behind. AtHarwin, a lot of design effort is put into the connector design so that the back shell of the connector extends the cable shielding to the connector so that there are no exposed wires that could present an EMC risk. “Well designed back shells provide good protection fromabsorption,” saysWebber.


COMPLIANCE FROM THE START Harwin has invested heavily in the development of products that provide engineers with flexible design options for overcoming the challenges of EMC in crowded RF environments. By employing such products as the prototyping shielding can kit in the early stages of PCB design, product development costs can be reduced as well as the time spent on redesigning and reworking using “permanent” solder technologies. As component densities further increase


and the RF environment becomes even more crowded, such tools will gain even more significance in the future. EE


 To readmore online about EMC testing, scan the QR code or visit http://goo.gl/AjZqxp


 Surface mounted clips attach ground planes together for continuity; spring clips come in a range of heights and compression displacements, below


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