Electronics > Projects, Designs, and Technical Stuff
Vapour phase Soldering
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mrpackethead:

--- Quote ---And you dont have to learn some awkward tool. Works perfectly fine for me !

--- End quote ---

I guess once you've learned the quirks of Altium, you've got no brain cells left.
mrpackethead:
Difference between HT230 and LS230

According to Matweb.com there are some very minor differences between LS230 and HT230. Heres the comparison


The LS230 exhibits slighlty ( 2% ) higher Heat of Vaporisation,  and slighty higher Specific Heat Capacity.   ( 1.5% )

For all practical purposes Galden HT230 and Galden LS230 appear to be very very similar and for this application i don't think its going to be an issue.
I've found three commercial systems that specify Galden HT230 as their working fluid, as well as several DIY projects.

That being the case, I propose that getting some HT230 seems to be ok.       



mrpackethead:
And then there was this.  This is the 'official' word From the people who make it.

"Solvay Solexis understands that Galden® HT Grades are used as Soldering Fluids in Vapor Phase Soldering Equipment. These fluids have a wider molecular weight distribution and are designed for use as Heat Transfer and working fluids in closed systems. They consist of a mixture of elements belonging to the same chemical family of perfluoropolyethers having varying boiling points, including those with boiling points lower than the nominal values. These low boiling components preferentially evaporate during the operation of the Vapor Soldering Machines. This phenomenon leads to higher losses of the fluids as well as a shift towards higher vapor temperature with time – temperature shift.
As a result, the cost of the vapor phase soldering process and the fluid emissions to the environment increase. The latter defeats the purpose of moving towards lower environmental friendly lead-free soldering.

We believe that Vapor Phase Soldering produces the best quality soldered joints. In addition, it is the most economical, environmental-friendly and the safest soldering process compared to other technologies such as convection ovens that operate at higher temperatures due to the poor heat transfer efficiency of air and other gases.
The Galden® LS and HS fluids are specifically designed with very narrow molecular weight distribution for the Vapor phase Soldering process by a stricter control of the molecular weight distribution during their production. This eliminates the above mentioned problems.

In addition, in order to improve the performance of the Galden® HT grades in closed loop systems, Solvay Solexis has decided to modify the specifications of Galden® HT grades with emphasis on the properties specific to these uses, such as viscosity.

This would make the Galden® HT grades even less suitable for use in Vapor Phase Soldering Process. Solvay Solexis will not be guarantee to provide technical assistance
?to problems arising out of the wrong use of our Galden® HT grades in Vapor Phase Soldering Equipment.

At the same time Solvay Solexis will be at our customer disposal to make the transition form Galden® HT grades to Galden® LS and Galden® HS grades as smooth as possible.
Solvay Solexis also guarantees the supply of the Galden® LS and HS grades for current and future requirements..
We request you to kindly inform your customers of these changes and help them to move to a better process with lower fluid losses and lower emissions."

PDF attached,  what do you make of this.. Is this a marketing thing, or is this for real.
IanB:

--- Quote from: mrpackethead on January 26, 2015, 03:23:35 am ---PDF attached,  what do you make of this.. Is this a marketing thing, or is this for real.

--- End quote ---

It seems to me like it's for real. As a chemical engineer, everything you quoted from Solvay Solexis makes logical sense.
jeremy:
Ok, but to play devils advocate here:

Weller and others recommend HT. So it legitimately performs well. HT is 1/2 the price of LS. Let's assume that solvay doesn't have bigger margins on the LS product, but that might not be true given that they have no competitors (they do in heat transfer though: fluorinert, krytox, etc). If you have a sealed batch vapour phase system, then it is effectively a closed loop system so you should expect basically no losses except what sticks to the board.

I can see the that the LS would be better for an inline system which is perpetually open, but will the losses offset the savings from using HT in a batch oven?

I also think that having some lower boiling point fluids would be better; it will make the temperature gradient of the vapour cloud much less steep.

Can anyone shed any light on why fluid viscosity really matters in a batch oven? I can't think of anything.

Also a lot of this kind of reeks of marketing:
"The latter defeats the purpose of moving towards lower environmental friendly lead-free soldering."
This makes sense superficially, but it doesn't really make technical sense. The lead-free soldering move had nothing to do with ozone or CFCs. We can of course argue all day if it is actually better for the environment ;), but lead free (afaik) uses the same amount of fluxes, generates the same amount of gas, etc if not more due to the higher temps required.

The actual fluid losses aren't quantified. I'm pretty sure if it was a huge amount, they would use the figure to make their argument. They have a technical audience after all. Something like "in our testing, we found that HT losses were 250% greater than LS at 230C". After reading the technical detail in the PDF, I'd be willing to bet that they've done the test and didn't see an enormous difference.

In the slides, they state that Galden is not a CFC, not toxic, accidental spills/release is ok (even on food!), etc. But when it comes to LS vs HT, HT is pretty nasty stuff for the environment? Um  :-//

tldr; do the losses by using HT really account for a doubling in price? My guess is no, or they would have been a little more technical about the whole thing.
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