Over the past months, Hauzer daughter company Bernex has developed an important upgrade to their systems to increase the temperature control in their Chemical Vapour Deposition (CVD) machines. Bernex upgraded their control approach significantly, by using more precise thermocouples and control hardware. Hristo Strakov, Head of Technology at IHI Bernex, discusses the upgrades and their benefits.
New Temperature Control Approach
“On a CVD machine, temperature is one of the major factors for the process,” explains Hristo. “Too much fluctuation in temperature behaviour means significant deviations of coating thickness and properties. With our new temperature control system, we are able to adjust the temperature in the reactor to be much more homogeneous during the entire coating process. Deposition temperatures, which used to oscillate by max. 7°C over time, now only oscillate by about 3°C.”
From now on, the new temperature control will be installed and delivered with any new Bernex system, but it has also already been installed on several existing CVD machines. This improvement is attractive to anyone working in the CVD field, especially for customers who need to meet the strict specifications of the tooling markets and aerospace business.
Meeting the RATMC5 S 2750F Aerospace Standard
In aerospace, the AMS 2750F requirement incorporates the control and monitoring of temperature ranges during the whole treatment and deposition process. AMS 2750F is part of the essential NADCAP certification that is used in the aerospace business. Two Bernex Chemical Vapour Aluminizing (CVA) systems now meet this challenging requirement: the Class 2 on Bernex CVA 190 BL with a 360 mm useful reactor diameter and the Class 4 on Bernex CVA 440 BL with a 800 mm useful reactor diameter.
“The breakthrough of this new temperature control approach,” says Hristo, “is that it allowed us to fulfil this crucial certification even for larger reactor diameters, where temperature uniformity is even more challenging. This is proof that our new control approach can be applied even on really demanding applications. With this upgrade, our 190 BL and 440 BL CVA machines fully meet the aerospace requirements.
Faster Heat-up Time
An additional benefit of the new temperature control system is that the heat-up phase of a CVD reactor can be shortened by up to 30%. Consequently, this reduces the total process time and increases the uptime of the whole system over the year. “What is most appreciated is the fact that this shorter heat-up does not lead to temperature overshooting anymore,” Hristo explains. “This is good news for any of our aerospace business partners, as the lack of temperature overshooting is a further objective of the AMS 2750F standards. It serves the critical function of securing the integrity and final quality of the products, which may not be able to withstand higher temperatures than those indicated for the CVA process.”