5 Myths about Vapor Phase Technology Print E-mail
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Written by Jochen Lipp   
Friday, 28 September 2012 15:09

It’s not a panacea, but with 2,000 installs worldwide, acceptance is widespread for a reason.

RoHS requirements helped restart the conversation on vapor phase a few years ago. However, not all conversations reflect the best information. Machine technology, materials and appropriate applications have changed greatly since vapor phase technology was first introduced in the 1970s. This month, I thought valuable to dispel five common misperceptions.

Voids and tombstoning. Vapor phase technology helps minimize voids and tombstoning. Products are getting smaller, yet consumers want the same power and features. From a production standpoint, that translates to smaller, higher powered components that are densely packed on printed circuit boards. This combination of heavy mass and small components is challenging for conventional convection soldering and very expensive to inspect. Add multiple thermal cycles at a high enough temperature to solder RoHS for PCB assemblies requiring rework, and you have a formula for higher scrap rates. Comparatively, vapor phase technology offers lower temperatures (217˚C to 227˚C), equal heat distribution because the PCBA is immersed in a vapor blanket, and perfect wetting properties due to an inert environment. Custom profiles can reduce the ramp rate to 0.7˚C/sec. after the assembly reaches 200˚C. This limits tombstoning. Some newer machines include vacuum soldering technology. Not only does the vacuum vapor phase machine reduce voids, some machines use profiles that include a thermal soaking zone.

High cost. This is a legitimate conversation. The Galden fluid used in the vapor phase process and the initial machine cost are higher than conventional convection soldering. However, vapor phase lowers a number of additional costs:

  • Nitrogen is not needed because the vapor blanket creates an inert environment.
  • Power consumption is less because 98% of the machine’s heat is focused on heating the PCBA rather than the factory.
  • Many machines have good vapor recovery systems, so loss of Galden fluid is minimal.
  • Machine footprints are often smaller than
  • conventional convection soldering machines, freeing up factory floor space.
  • Preventative maintenance is only required once or twice a year for some machines, which reduces technician workload and increases capacity.
  • The ability to avoid tombstoning and solder joint voids is enhanced, resulting in less time and money spent on inspection and rework.
  • The profile window is broader, and new product profiling can be done quickly, providing a fast changeover option for high-mix production.
  • Temperature-driven profiles reduce the number of profiles required, enabling new products to be run with existing profiles, dramatically reducing production startup time.
  • No changeover time for leaded to Pb-free products.

In short, when total cost savings are considered, vapor phase is a more cost-effective option over the life of the machine.

Fluid unstable and dangerous. Modern vapor phase heat transfer fluids are based on perfluoropolyethers and do not contain CFCs or other harmful ingredients. Galden LS/HS is a line of fluorinated fluids specifically designed for vapor phase soldering. The Galden fluid’s main properties are chemical and thermal resistance, non-toxicity, electric insulation properties, no flash or firepoint, and low viscosity. There is a wide choice of grades with different boiling points. The fluid is noncorrosive and does not deteriorate over time.

The boiling point is application-dependent. Most Galden liquids have boiling points between 200˚ and 235˚C. Fluids with higher boiling points are available, up to 260˚C. The fluid’s boiling point determines the maximum temperature in the vapor phase oven, making overheating impossible.

Suitable only for low throughput production. Vapor phase machines of the ‘70s and ‘80s were highly inefficient. Most machines were batch mode and simply could not process PCBs fast enough for volume production. Also the machines ran on a temperature level mode, which made it difficult to have slow ramping profiles, whereas today’s vapor phase machines run on vapor height level. Today’s machine market includes both batch mode and inline machine options. Miniaturization and RoHS considerations continue to increase the number of inline machines in the field that run continuously in higher volume environments. As mentioned, fluids are safer and longer-lasting. Profiling software is easier to use and can generate profiles in minutes. Broader process windows make it easy to handle high-mix production with just a few profiles. In short, there is a machine model suitable for virtually every type of production volume and mix.

Waning in popularity. Vapor phase technology use decreased dramatically when CFCs were banned. However, improvements in materials and machines have made it a viable alternative to convection soldering systems. RoHS requirements and miniaturization have increased demand, as manufacturers have seen the advantages they offer in terms of lower temperatures and more even heating. Today, there are more than 500 installed in North America, more than 1,000 in Europe and 300 to 500 in Asia. OEMs and EMS companies are adding the technology.

Vapor phase technology is not a solution for every company. However, its applicability to a variety of production requirements continues to broaden. Machine technology and materials improvements have eliminated many former issues. If solder joint quality, tombstoning or heat-sensitive components are a common source of defects, vapor phase technology may be worth evaluating.

Jochen Lipp is CEO of IBL Technologies (ibl-tech.com); This e-mail address is being protected from spambots. You need JavaScript enabled to view it . His column runs bimonthly.

Last Updated on Monday, 01 October 2012 13:07
 

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