Authored By:
Claus Zabel
ASSCON Systemtechnik GmbH
86343 Konigsbrunn, Germany
Summary
Due to the switch to lead-free, high packing density, extreme mix of light/heavy components manufacturers are faced with multiple new challenges. Simple processing, successful soldering for various products, high quality and user-friendliness are the basic requirements that current soldering systems have to provide.
Vapor phase soldering meets these demands. However, individual systems vary greatly when looking at important details. Vapor phase soldering systems feature cutting edge technology with their fully flexible temperature gradient control (DYNAMIC PROFILING), oxidation free atmosphere, low peak temperature (230 degrees C max. lead free), zero delta T.
These systems provide process reliability and repeatability especially for very complex soldering application. Vapor phase soldering was developed by Western Electric, Princeton, in the beginning of the Seventies. Those systems were based on the two-phase-technology. Due to high loss of medium a secondary medium (often CFC) was initiated over the primary vapor layer.
The ban of CFC around 1990 led to the end of these 2-phase-systems and caused success of infrared and convection soldering. However the disadvantages of the infrared and convection technology, such as different warm-up time of components with varying heat requirements, high peak temperatures, oxidation caused this technology to reach its limits for challenging products.
The past years have seen increasingly complex assemblies (e.g. layout, differences in mass) which pose challenges to the soldering technology that are becoming more and more difficult for convection soldering to overcome. Vapor phase soldering was introduced once again. Today backplanes can have up to 96 layers, carbon fibre or metal core, inner cooling layers etc.
The risk of a thermal damage during thermal treatment is always present with convection technology. Todays state of the art single-phase vapor phase provide the solutions needed for lead-free soldering in combination with a very challenging product design and requirements for a void less solder joint.
Conclusions
Modern vapor phase soldering systems based on newest technologies have eliminated the disadvantages inherent to early condensation systems. Vapor phase soldering offers best reflow thermal treatment technology for all kind of high tech soldering application.
By employing saturated vapor not only for the heating but also the pre-heating phase, any risk of oxidization is eliminated. In addition, precise medium temperature settings eliminate overheating of the product in any stage of the soldering process. Variable temperature gradient control provides optimum pre-heat and soldering for any product.
If also a VACUUM or even MULTIVACUUM Process is intergrated into the Vapor phase soldering process best possible and void free quality of soldering is ensured.
Initially Published in the SMTA Proceedings
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