Sales & Service to the PCB Industry
 
 
Vapour Phase Reflow - Lead-Free Reflow Soldering
 
     
  Does Pb-free = problems?

Are you confident you can comply with the new legislation?
Should you re-think your reflow?
Should you cast out convection?
Has the time come to reconsider your options?
Is there a process which can help you to alleviate reflow problems Pb-free will create?

An IBL Vapour Phase machine can solve your problems.
 
     
 
The EU's Restriction of Hazardous Substances (RoHS) directive, effective from 1st July 2006. Presenting challenges to Electronics Manufacturers.
 
INCREASED REFLOW TEMPERATURES
Lead-free soldering is performed with alloys different to those used for decades, and to which PCB manufacturers are familiar; when changing to lead free the required melting points are higher. Typically, lead-free soldering alloys have a melting point of about 220ºC (Sn-3.5Ag 221ºC or Sn-3.5Ag-0.7Cu 217ºC). Theoretically, soldering with lead-free materials can be undertaken in every solder machine that is able to produce sufficient heat.
 
However, with the increased reflow temperatures required for lead-free, manufacturers will find that some components, such as surface mount connector bodies, are susceptible to the heat. Selecting reflow temperatures and profiling to suit all components may require careful consideration. Too little heat and reflow is incomplete, too much and the components could overheat or burn and the body of the device could melt.
 
A convection reflow oven temperature profile peaking at 210ºC for tin lead may peak at 250ºC or as much as 270ºC for SAC. (SnAgCu - tin, silver copper - recent industry data would appear to indicate that this alloy is the popular choice for SnPb-free)
 
When using Vapour Phase solder reflow for lead-free alloys (e.g. SnAgCu), that have a melting point of about 220ºC, a fluid with a boiling point of 230ºC would be used. It is impossible for the temperature of the vapour to exceed the boiling point of the liquid, consequently there is no risk of overheating. Additionally, due to the extremely efficient heat transfer of a vapour, reflow soldering in a vapour phase system ensures even reflow irrespective of component size or thermal mass. Even assemblies with a large thermal mass, such as back-planes and motherboards, pose no problem to vapour phase. Using Vapour Phase solder reflow the Delta T will always be less than 5ºC.
 
Vapour Phase soldering offers the best thermal environment with optimum solder joint quality. The very uniform heating is also particularly well suited for soldering complicated products that have complex shapes, and for applications where assemblies must operate in more stringent environments.
 
WETTING PROBLEMS OF LEAD FREE ALLOYS
Lead-free alloys do not wet as well as SnPb, an inert atmosphere will be more important to employ the best possible soldering conditions to help overcome this problem. When using convection reflow the use of a nitrogen atmosphere will improve solder joints, but for low cost manufacturing the added cost of using nitrogen may not made it a viable solution. To cut short-term costs you can solder without nitrogen, however, long-term your product reliability could be jeopardised.
 
Vapour Phase reflow soldering automatically provides a 100% inert atmosphere, without adding nitrogen (and without adding additional cost), to guarantee the best possible soldering conditions, and the best possible long term reliability, for all your production every time.
 
GREATER RISK OF VOIDS
As plastics are hygroscopic, humidity will get into the body of these components (e.g. BGAs). When reflow soldering this can lead to high pressure of the moisture trapped inside the molded components, which is converted into steam and forced out under pressure during reflow. This can cause delamination of the substrate or 'pop-corning'. The higher the reflow temperature the greater the risk of pop-corning, therefore a maximum reflow temperature of 230ºC is desirable.
 
As there is absolutely no danger of heating above a maximum of 230ºC Vapour Phase reflow, this provides a lower risk of pop-corning.
THE CHALLENGES OF LEAD-FREE PROCESSING EXHIBITS THE ADVANTAGES OF VAPOUR PHASE SOLDER REFLOW
 
 
IBL Vapour Phase machines have all the important features that are required for lead-free reflow. They provide what is probably the definitive answer to the question: How to change to lead-free technology, overnight and problem free.
 
NO MODIFICATIONS - NO ADJUSTMENTS - NO ADDITIONS
 
A 100% inert gas atmosphere guarantees the best possible wetting for all solder alloys.

The maximum board temperature for lead-free soldering can be limited to 230ºC.

At this temperature, everything will be soldered, even large BGAs on double sided boards.

All components and materials, like FR4, that are in use today can be used without the danger of overheating.

All IBL Vapour Phase machines, available NOW, can be used for lead free soldering IMMEDIATELY
 
NO MODIFICATIONS - NO ADJUSTMENTS - NO ADDITIONS
 
 
With industry opinion now voicing its concern, and doubts, about the capability of some of today's components to withstand the increased temperatures and stress that lead-free processing using IR or Convection reflow will exert. Vapour Phase with its ease of application, and simplicity of use, makes it an extremely viable reflow option, which will solve many of the challenges now facing the assembly industry.
 
Reflow temperatures with the vapour phase process are strictly governed by the laws of physics, and the user is absolutely assured that there can be no variations in the process. The uniform repeatability of the heat transfer applies for both SnPb (Tin-Lead) and lead-free solders. Although temperatures required for lead free pastes are higher than SnPb the heat transfer of the condensing vapour is very controllable, and a sufficient melting point can be achieved at temperatures lower than those required for other reflow methods resulting in a reduction in thermal stress, and virtually no risk of delamination or pad lift-off.
 
The 100% saturated vapour phase atmosphere ensures good wetting even with lead-free solder pastes. The maximum soldering temperature for lead-free materials is reliably limited to 230ºC. Repeatable, reliable soldering can be performed at this temperature. Today's typical components and FR4 printed circuit boards can be used without the need to make any modifications to existing vapour phase machines.
 
Using Vapour Phase and either SnPb or Lead-Free materials, every board can be soldered, and irrespective of size and no matter how complicated it is, without being overheated. IBL have already had machines installed and operational in 100% lead free production environments for over two years.
 
 

Several temperature profiles, measured on one board with different set-up of machine parameters.

Depending on the complexity of the board and the need for high quality production,
the board temperature can be controlled to be either faster or slower.
This is especially important for PBGAs.
 
 
Not only does this process enable you to work with lead-free solders, it is the only process which allows users to change to lead free without the risk of overheating the board or damaging the components, and to use one machine for both SnPb and Lead-free without making any machine modifications.
 
The 100% inert gas atmosphere ensures good wetting, even with lead-free alloys.