Thermal Management
impregnated resins on glass cloth carriers (FR4). These materials are low cost, easy for FR4 manufacturers to adapt their current production processes and aimed at the bottom end of the thermal scale. With laminated materials the surface
area compared to the dielectric mass on a resin glass matrix will be very high so moisture can easily be absorbed if the material is not baked and all moisture removed before solder level, otherwise an intense heat shock could result in vapour pressure from moisture release leading to delamination. In our experience the cheaper materials may require additional in process baking during assembly and this adds time, leading to a false economy. LEDs are sold on a 50,000 hour life span and only a handful of metal substrate materials have been around long enough to have real life data and proven quality. The reliability of the ‘me too’ laminates flooding the markets is a real concern. It is therefore important that we understand which material, from the now wide range available, is the best suited to you and your application. The LED lighting market offers the opportunity to enter the arena and sell new material on price alone, unlike Power Electronics where understanding the materials and function is an absolute, the lighting manufacturers as a rule don’t understand or care… if it’s seen to work then it must be ok!
This explains why the industry is spawning partnerships where PCB fabricators align themselves with one of the laminate companies. This provides
these PCB fabricators with the technical support and sales leads they lack but at a cost of their ability to be independent, as it ties them to a single source offering. Another dubious practice is laminate rebranding.
Although the growth continues in both LED and backlight TV markets where these materials are most frequently found, the ability of the industry to support the influx of new materials is questionable, dissecting the material costs, taking metal prices and the cost of production into account its difficult to see it going any lower. We will see many more entering this market in the coming years, which will offset those that are exposed having had to leave.
Street lighting is a prime example of a
product where lights set at angles provide the beam coverage required - traditionally individual modules need to be wired together however, with a formable dielectric, a circuit can be produced as a one piece solution removing interconnection and failures associated with this.
The answer is in the dielectric chemistry - the ability to bend without losing the properties of electrical isolation. Once again though, it has been a year since the product was launched and already other suppliers are entering the market with the claimed ability to bend as a selling feature, but this is rarely backed up by the test data.
Metal based PCBs are the principal weapon in the fight to remove heat from electronic components as quickly as possible.
The future will no doubt present many new challenges to match the developments and growth in LED technology and, until this aspect of the lighting market matures, we will see both good and bad solutions being promoted.
DK Thermal Solutions |
www.dkthermal.co.uk
Dave Hunton is Technical Manager at DK Thermal Solutions
pickering
www.cieonline.co.uk
Components in Electronics March 2012 13
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