Homepage » Technology » Products »

Catalytic thermal oxidizer keeps clean

Impressive reduction in maintenance of the reflow oven
Catalytic thermal oxidizer keeps clean

The Catalytic Thermal Oxidizer (CATHOX) is an advanced system for keeping SMT reflow ovens clean and free of contamination. A nanomaterial-based catalyst system thermo-chemically decomposes organic materials outgassed from solder paste, bare boards and components. The nanotechnology makes it possible to change the chemical composition at temperatures around 200 ºC. It is very effective in removing volatile compounds from the process tunnel during reflow.

In thermal oxidation, organic vapors are converted to carbon dioxide and water; little or no char is produced. This invention enables the installation of catalyst units in each individual zone of the oven, and temperature optimization. In addition to the catalyst, a bed of ceramic spheres promotes catalyst activity as a consequence of their unique pore size distributions and their stability to thermal, hydrothermal, and acidic conditions. The invention is filed at the European Patent Office under number EP15153866.7

Reflow process contamination
Since the introduction of lead-free alloys, the composition of solder paste chemistries have changed. More and varied components have been added to meet the higher temperature requirements of lead-free reflow soldering. Due to the different chemistries, the composition of the flux residues has changed as well over the years. Filter systems that were effective in the past may perform poorly today.
Additionally, PCB assemblies have undergone a continuous trend towards miniaturization of PCB, components, and SMD pad dimensions, resulting in higher density of solder joints per square inch, and consequent higher concentrations of reflow-generated contaminants. The risk of oven contamination with reflow residues also increases where pin in paste reflow replaces traditional wave or selective soldering applications for through-hole components. Miniaturization has also meant smaller alloy powder particle size in solder paste, with a higher flux content of the paste needed to minimize potential oxidation of the solder powder.
Traditional flux management systems that were successful for SnPb paste used heat exchangers to condense flux residues. These tacky residues could then be removed and additional filters were able to clean the gas properly.
Every PCB assembly loses, on average, 0.25 grams of weight in the oven. Solder paste is 10 % flux, of which approximately 50% remains on the board after soldering. A high volume SMT line (24/7) will be contaminated with approximately 2 kg per week. Flux management systems in today’s ovens will use heat exchangers and filter systems to condense the flux at temperatures of up to 20 ºC. Chillers or factory water coolers are required to enable condensation and filter boxes need to be cleaned frequently; the more condensation, the more frequent the maintenance requirement.
Benefits of an individual zone catalyst
The primary cleaning concepts in reflow oven flux management are pyrolysis and filtration after condensation. In a condensation system, the temperature of nitrogen/air from the zones requires cooling from 250 ºC down to below 40 ºC. The heat exchangers require a high amount of energy to achieve this. For the Pyrolysis units, the nitrogen/air is heated to ignition at approximately 500 ºC. For this thermochemical decomposition, the exhaust gas runs through the unit and granulates before returned to the oven. The new concept deploys a catalyst unit for each individual zone. It is also possible to combine two or three zones with one catalyst; and each individual zone may have its own preferred settings. The catalyst utilizes the same thermochemical process as pyrolysis, but at much lower temperatures. Typical catalyst temperatures are 185–250 ºC; i.e., temperatures that are identical or close to the gas temperature in the reflow zones. The catalyst is mounted on top of the heating zones, so there is no extended tubing involved. Because the catalyst process temperatures are so close to the zone settings, the energy consumption for operation is small. Very little additional heating is required to control and maintain temperature.
Apart from energy savings, the reduction in maintenance required is impressive. This means increased throughput (higher volumes) and productivity. The catalyst eliminates the need to clean the heat exchangers and filters of the flux management system. In high volume lines, these parts needs to be cleaned every two weeks, which involves downtime and dirty, sticky flux residues. Conversely, the catalyst and ceramic balls don’t require any maintenance for a much longer period. Typically, servicing only once a year is sufficient. The pollutants are generally hydrocarbon-based and when destroyed via thermal combustion, they are chemically oxidized to form CO2 and H2O. The benefits of applying this invention include the following:
  • Clean heating zones
  • Less energy required
  • Slash downtime by eliminating filter/heat exchanger cleaning
  • No waste
  • Higher throughput through less downtime or production interruptions
  • CATHOX catalyst study and implementation
  • The catalyst project began two years ago (2013 )with a wide-ranging laboratory study of different zeolites and granulates. Soon, different catalyst options were included before the test was finished on the lab scale. For the second phase of the project, a large catalyst module was installed in a reflow oven between the heating zones and the flux management system. Flux from solder paste was used in high volumes to accelerate oven contamination for enhanced study of cleaning performance (Study presented at APEX, S05–01 in San Diego, February 2015). The third phase of the project included alpha testing of the catalyst in a 24/7 high volume production line during July 2015. This unit runs in the SMT line of a large renowned well known German manufacturer, where oven contamination is monitored every week.
CATHOX is an option on new ovens, but can also be retrofitted to existing ovens. The system can replace a gas recirculation system and has its own software that communicates with SMEMA to the SMT line. Software measures and controls catalyst temperature. Heaters are PID controlled, will trigger alarms and will even stop the line if necessary.
productronica, booth A4-554
Current Issue
Titelbild EPP EUROPE Electronics Production and Test 11
Issue
11.2023
READ
Newsletter

Subscribe to our newsletter now

Webinars & Webcasts

First hand technical knowledge

Whitepapers

Find all current Whitepapers here

Videos

Find all current videos here


Industrie.de Infoservice
Vielen Dank für Ihre Bestellung!
Sie erhalten in Kürze eine Bestätigung per E-Mail.
Von Ihnen ausgesucht:
Weitere Informationen gewünscht?
Einfach neue Dokumente auswählen
und zuletzt Adresse eingeben.
Wie funktioniert der Industrie.de Infoservice?
Zur Hilfeseite »
Ihre Adresse:














Die Konradin Verlag Robert Kohlhammer GmbH erhebt, verarbeitet und nutzt die Daten, die der Nutzer bei der Registrierung zum Industrie.de Infoservice freiwillig zur Verfügung stellt, zum Zwecke der Erfüllung dieses Nutzungsverhältnisses. Der Nutzer erhält damit Zugang zu den Dokumenten des Industrie.de Infoservice.
AGB
datenschutz-online@konradin.de