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IMDES CREATIVE SOLUTIONS
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1.3 Introduction to Condensation soldering:
Condensation soldering also known as "Vapor Phase Reflow Soldering” is the use of hot vapor, submitted by a
special heat transfer medium, to transfer heat using the condensation principle on to a PCB with SMD components,
which then will be reflowed
Condensation soldering is a known technique that was first applied in the early eighties when the SMD technique
was introduced.
The heat transfer medium applied in those days had many disadvantages, mainly the chemical used were harmful
to health and the environment.
As a result, the condensation soldering lost popularity and infrared soldering became the standard.
By the arrival of
Perfluorpolyeter *,
the condensation soldering was rediscovered as an alternative to the
infrared "reflow" soldering.
Perfluorpolyeter * is manufactured and marketed by the company Solvay Solexis under the trade name
Galden
.
1.4 HOW DOES IT WORK?
The heat transfer medium is the chemical and electrical neutral liquid
Perfluorpolyeter *.
In a closed space is a chemically inert and electrically neutral liquid heated to the boiling point.
When the liquid temperature exceeds the boiling point, it starts to evaporate and forms a saturated vapour above
the liquid with practically the same temperature as the boiling liquid.
When the assembled printed circuit boards is brought into this space, the vapor will condense on the surface,
because the circuit board has a lower temperature than the saturated vapor, and transfer the vapor’s temperature
to the PCB. This will happen until the entire surface of the circuit board will have the same temperature as the
vapor.
After that, the covering hot liquid will evaporate again. This is the same principle as if someone with glasses from
the cold outside air enters a warm room. At first the glasses will be covered by condensation than drops gradually
will evaporate.
The soldering alloys which have a lower melting temperature than the temperature of the vapor will melt and then
become entirely liquid.
When the heat transfer medium cools down, the solder solidifies, and then circuit board can be removed carefully
from the process chamber.
****Perfluorpolyeter
* liquid polymers, which are exclusively built of carbon (C), Fluor (F) and oxygen (O)
atoms.
The connections present in the molecules are very stable. They belong to the most stable connections in the realm
of carbon chemistry.
1.5 Features:
High temperature resistance.
Under normal circumstances, inert to all chemicals, and does not react with acids alkaline or strong
oxidizers (substances that cause oxidation).
Tolerates all known plastics, metals and elastomers.
Highly resistant to reactive chemicals.
The Fluor atoms bound in the polymer chain in the framework of the display helps protect sensitive C-C
connections against chemical and thermal attack.
Good dielectric properties.
Low vapor pressure.
No flash point.
