Reflow for Metal Core PCBs

How does the reflow process for a MCPCB (metal core PCB) differ from a FR4 laminate PCB? We have never processed MCPCBs before and I would be grateful for any useful advice?

P. B.

Expert Panel Responses

I assume that with metal core, we are looking at very heavy PCBs. These offer a number of interesting differences to normal PCBs during reflow. Due to the mass of metal, it normally takes more energy to warm up the circuit boards in the oven, so more energy may be required at the early stage to heat up the board. However, once it is heated up, it stores the hot for a longer time. Therefore, care has to be taken with heat sensitive components to ensure they are not damaged. Generally, more energy at the start of the reflow profile will heat the PCB more quickly. Maybe you should use the last zone if you have enough reflow zones to start the cooling process. Reducing the temperature in the last zone to approx. 200 centigrade can help to start the cooling process.

Doug Dixon
Marketing
360-Biz

Douglass Dixon is the Chief Marketing Officer for 360 BC Group, a marketing agency with offices throughout the US. 360 BC specializes in consulting and implementing successful marketing programs that utilize the latest in marketing, sales and technology strategies. As an electronics veteran, Dixon has worked in the industry for over 30 years for companies like Henkel, Universal Instruments, Camelot Systems, and Raytheon. Dixon's electronics industry experience includes a broad skill set that includes engineering, field service, applications, product management and marketing communications expertise.

The fundamental reflow process for a MCPCB is the same as for a FR4 PCB. You have to identify the oven recipe that processes the board within the tolerances required by the chosen solder paste, components, and substrate.

This recipe can be found by traditional profiling, and either a trial and error procedure or by utilizing modern process optimization software.

A metal core PCB will likely, due to its larger thermal mass, require either higher zone temperature settings or a slower conveyor speed.

Bjorn Dahle
President
inspīre solutions LLC

Bjorn Dahle is the President of inspīre solutions LLC. He has 20 years experience in the electronic manufacturing industry with various manufacturing equipment companies covering pick & place, screen printers and thermal process management.

MCPCBs usually use aluminum as their base material, which absorbs a lot of heat. Thus the reflow process will have to be slower, unless you have a longer reflow oven, and able to set at higher temperatures (eg. 350 deg C to 400 deg C). A more effective cooling is also necessary, compared to normal FR4 reflow process.

EH Lim
Managing Director, Asia Pacific
ECD

EH Lim has been in the PCB Assy industry since 1985, starting at Thomson/Singapore for 5 years before moving to Electrovert Asia Pacifc. Lim was Sales Director for Vitronics Soltec prior to joining ECD in 2007 as Managing Director for Asia Pacific.

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