The manufacture of solder paste stencils for the application of solder paste during the assembly of components onto PC boards traditionally used an etching process. One of the leading suppliers was Pretoria-based Stencils. Stencils has been in the etching business for more than 14 years and while the process was very suitable for use with conventional lead technology, the impending requirement of lead-free technology, as well as the technological requirements for greater accuracy and consistency has seen the company re-think its strategy. Currently, many local companies are changing to laser cut stencils that are imported from Europe at high cost and with times from order to delivery in the region of 10 to 12 days. This delay in delivery can be very frustrating for the assemblers and their customers.
Donovan Jeffery of Stencils recognised that the traditional etching process was on its way out, as the accuracy of pasting and placement of components is much more critical in terms of lead-free processes. Indications are that aperture sizes will be reduced by about 30% - not always possible with etching. As of May this year he established a new company known as Laser Stencil Technology, which is located in Randburg. Although etching will continue to be offered while demand still justifies it, Laser Stencil Technology will have laser cutting of stencils as its core business. After much research into the technology and equipment available, the company has invested in a state-of-the-art multimillion rand laser stencil cutter from Germany, the supplier being the market leader in this type of equipment. The cutting system, after extensive training of the company's staff, became fully operational at the beginning of June this year.
Laser Stencil Technology believes that with this machine it will be able to satisfy the total demand of local industry and will expand as the demand requires. The accuracy of the system is 4 µm and it is capable of cutting stainless steel up to 300 µm thick. A major benefit of the fully configured system is that it makes use of a camera system that allows the stencil to be accurately realigned to, for example, cut new apertures that were omitted from the original design. This capability means that in many cases, re-working of prototype stencils with new holes will also be possible. Stencils will be available to fit all frame types from stretched to pre-mounted etc.
The laser cutter has the capacity to cut 6000 apertures per hour and will address the requirement for high volumes of BGA apertures. The device also has a turbo-cut capability that can be used when only round apertures are required and this increases the rate to 25 000 per hour. The hardware and software is very comprehensive and will be able to handle automotive parts and specialised components. To streamline the process for regular customers, a universal pneumatic frame will be available as an option (once-off cost) and will be supplied by the company. The use of this frame will also eliminate the problems sometimes encountered where the stencil is mounted upside down.
Laser Stencil Technology will offer a standard turnaround time of between two and three days and a premium service will also be on offer. This will allow a same day turnaround, the company being prepared to operate 24 hours a day if necessary to achieve this goal. Pricing is also intended to be very competitive with overseas costs, where several intermediaries, shipping, insurance etc, add significantly to the delivered cost. The company will deliver finished stencils directly to customers in the greater Gauteng area while other customers will benefit from overnight courier delivery. What customers new to the laser cutting process need to understand is that the stencils will be more expensive than those produced with the conventional etching process. The reason is, of course, that while the chemical milling process ensures that all apertures are etched simultaneously, the laser has to cut each of these separately so pricing is related to the number of apertures required.
As the end-users of the stencils use many different technologies, Donovan Jeffery wants to be able to provide a locally-based service where the assemblers can be helped to solve pasting problems. This service will extend to the development of custom stencils that best suit their particular requirements.
Laser Stencil Technology says it is currently the only laser-based high accuracy stencil cutting facility in Africa.
For more information contact Laser Stencil Technology, 011 793 1318, 072 901 0453, [email protected]
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