During the 200°C to 350°C curing process involved in metallization, significant quantities of vapour and smoke are produced which must be reliably exhausted from the process chamber in order to avoid contamination and yield loss. However, since there is a wide variation in paste compositions associated with solar metallization, it is not always possible to customise a suitably effective filter or condenser to manage the released vapour or smoke. As a thermal management specialist, Rehm has been engineering solutions to the challenge of residue contamination for many years. Now, as part of its advanced series of drying systems for PV metallization, the company has introduced the technology into the solar industry, along with its ability to substantially reduce the process’ condensate-forming potential.
Thermal oxidation is a process during which the volatile organic constituents and the hydrocarbons (VOCs) in the metallization pastes react with oxygen, and are decomposed. The goal is to burn the long-chain molecules in the vapour or smoke and transform them into readily volatile, non condensable substances. These are then easily discharged from the system, to significantly reduce the potential of condensation and in turn, minimise system maintenance. Due to the arrangement of the heater and the granulate pack in Rehm’s RDS Drying Systems results in a very compact, thermal reactor which requires little additional energy to reduce energy consumption even further.
Rehm’s thermal oxidation process involves heating the gas to a temperature greater than 500°C. The molecules cracked at these high temperatures and combine with atmospheric oxygen which is present within the system. In order to oxidise hydrocarbons in an energy-efficient manner at low reaction temperatures of nearly 500°C, catalyzers are installed downstream from the heating chamber. This results in a thermal reactor which is dimensioned for solar dryers such that a gas exchanger of greater than 40-fold assures reliable removal of the vapour or smoke which occurs in the process chamber. Rehm recently detailed its pioneering approach to residue management in a new technical paper entitled ‘Controlling Damaging Contamination in PV Metallization’.
About Rehm Thermal Systems
Rehm Thermal Systems (www.rehm-group.com) is an international supplier to the photovoltaic and electronics industries, specializing in curing, drying and firing technologies as well as convection and condensation soldering. Rehm operates vertically integrated manufacturing facilities in Germany, China, and Russia, and technical support facilities throughout Europe, Asia and North America.