Distribution world – EMC is our speciality

Distribution world – EMC is our specialityThe latest software products to hit the market are aimed at helping designers solve EMI problems at the design stage to save time and cost. Many problems can also be overcome by good layout practice. By Paul Gregg
As well as getting involved in their customer’s supply chain management systems, electronic component distributors are being asked to help solve EMI problems. But it is proving to be tough market to satisfy during an economic downturn.
EMI problems are best solved at the design stage in order to avoid fitting filters at a later stage and the extra cost that is incurred. There are new software products are coming onto the market all the time to help designers, but many design problems can be overcome by adopting good layout practice, such as partitioning between analogue and digital circuits. Filters should be placed where signals enter the unit or as close to connectors as possible.
EMC also encompasses protection against electrostatic discharges, surge voltages and transient suppression. Shrinking semiconductor feature sizes are eroding the self-immunity of ICs, and gallium arsenide devices used at microwave frequencies are less tolerant to electrostatic discharges. The increasingly high speed and low capacity of current designs, as well as increased number of channels per package, aggravate EMI problems.
For the most part, design engineers have learnt from experience over the past two to three years, how to ensure those products conform to the EMC regulations. In those instances where no off-the-shelf solution is available, specialist component distributors are gaining a reputation for being able to offer customised filtering solutions at competitive prices. In some cases, this involves combining several standard suppression devices to provide a solution.
When faced with a particular EMI problem in the past, designers had either to go to a filter device manufacturer directly for technical advice or approach a broadline distributor. The drawback is that the device manufacturer may not be interested in customers wanting small quantities, and the broadline distributor cannot always offer a customised solution.
This is where the specialist distributor steps into the picture.
The specialist EMC distributor is in a position to manufacture devices as well as offer design-in support over a wide range of applications that include semiconductors, power systems, as well as analogue and digital circuits. Consumer and telecommunications sectors generally want EMI counter measures at the board level, using low cost inductors and capacitive filters behind the I/O connectors. Dedicated EMC distributors will have already identified emerging markets and stocked up with the most commonly used parts.
Surtech Distribution, based in Basingstoke tries to influence designers into considering feed-through filters in order to reduce their overall component cost and board space. The company’s marketing manager, Mike Collen, said: “For DSP applications, we can supply the multi component EMC solution for balanced lines (X2Y technology), recently introduced by Syfer Technology”.
In the case of military and avionics markets, there are additional military specifications and inter-government standards to be taken into account, and Surtech can offer a retrofit solution from its supplier, Metatech. This is accomplished by placing over the established connector, an elastomeric seal, which links chip connectors or varistors by a web of gold wire bonds and grounds to the shell of the connector.
Another solution is to insert a custom device inside a standard connector. The company can arrange for each pin to be filtered in different ways by placing SMD inductors, capacitors, diodes or varistors on a miniature circuit board, which is then integrated into the connector. Again, this can be lower in cost and quicker than using conventional filter connectors with the added benefit of customisation.
For the industrial market, EMC demands vary, and Surtech offers support for engineers in selecting readily available components to meet their needs. “We have developed small stocks for prototyping applications, and we offer samples to ensure prompt delivery for on-board testing. To a large extent, EMI component selection remains trial and error,” added Collen.
In supplying sample quantities of customised filter devices free of charge for a new project, distributors can expect to secure follow-up orders from customers when volume production commences. But all too often in times of recession, new business means a re-design or a re-issue of an existing product. The designer more or less copies what has gone before and there is no additional business for the distributor.
Except for a few specific sectors, business is seen a generally quiet right now.
According to Component Bureau’s sales and marketing manager, Malcolm Green: “At the moment, market awareness is our problem and getting the catalogue to the right people at the right time. There seems to be very few new projects requiring new components at this time. We are also finding even the pricing of small quantities very competitive.”
Components Bureau launched its new catalogue division, specialising in EMC and suppression products last year.
One distributor that is bucking the trend is specialist power supplier, XP. EMI/RFI suppression component manufacturer Schaffner has awarded XP its EMC Distributor of the Year Award for the second year running.
The award reflects XP’s extensive design-in activities using Schaffner EMI filters. “Compared with recent years, 1998 was a relatively flat for our component distribution network,” said managing director of Schaffner EMC, Michael Lowe. “The one company to buck the trend is XP, with a further 60 per cent year-on-year increase. This proves what is possible for a company prepared to truly add value. XP’s sales of Schaffner components have almost trebled over the last two years.”


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