August, 2015
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Reflow Soldering: With or Without Vacuum?
V
acuum is an emptiness that can be fulfilling, especially for electronics production and
reflow soldering. It was when Galileo Galilei (1564-1641) posed the ques- tion of the existence of absolute emptiness (from the Roman latitudi- nus vacuus) that the concept was first brought from the philosophical realm into the field of science. Today, 368 years after the generation of the first artificial vacuum by Torricelli, vacuum technology is an important and well-established part of process engineering. Low vacuum (from 300mbar to
1mbar) is widely used for a variety of purposes, in particular in electronics production. The most important of these applications include drying, dispensing, gas ex change, and vacu- um soldering. Void-free solder joints are increasingly required for power electronics and high-reliability com- ponents. These void-free joints are produced when the still molten sol- der is subjected to a vacuum process immediately after the creation of the solder joint.
Void content of less than 2 percent can be realized with a vacuum between 100mbar and 10mbar.
Rehm offers a variety of reflow
sol der systems with different VisionXP+ options for soldering with or without vacuum. The same new vacuum-capable soldering system enables convection soldering process- es with or without vacuum. The company has established a
history of applying vacuum technolo- gy in the soldering of electronic com- ponents and printed-circuit boards (PCBs), starting with the first vacu- um soldering system, the VAC400 system, brought to market in 1999. Shortly afterwards, condensation soldering technology (vapor-phase soldering) was combined with suit- able vacuum technology to provide condensation soldering by means of a Rehm Condenso series soldering system. When performing condensation
vacuum soldering with one of these systems, the vacuum can be applied in the process sequence for optimal results, as a pre-vacuum process component and/or as a final vacuum process component. Along with supe- rior heat distribution, the Condenso soldering system offers the opportu- nity to use dry pastes and to achieve production solder joints with void content of less than 2 percent. Motivated by customer require-
ments for higher production through- puts with enhanced integration of surface-mount-device (SMD) compo- nents, vacuum technology was part- nered with convection soldering. By combining a VisionXP+ convection reflow solder system with a vacuum chamber, Rehm created a new option for this type of production soldering system. The VisionXP+ reflow solder
system with vacuum option uses the vacuum capability to reliably remove solder voids and gas emissions, as soon as the solder is molten and
By Paul Wild, Research & Development, Rehm Thermal Systems GmbH
while the solder is still in this opti- mum molten state. Void content of less than 2 percent can be realized with a vacuum between 100mbar and 10mbar. For an exact setting of the
This is a VisionXP+ Vac convection soldering system with vacuum chamber.
process parameters for the Vision - XP+ Vac, the vacuum level is meas- ured not on the vacuum pump but directly in the process chamber. The pressure gradient and speed of the vacuum process can be set individu- ally and saved as profile parameters for each board processed. The
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