This PCB assembly soldering video from Z-AXIS of Phelps, NY examines the importance of thermal profiling in soldering operations.
Measuring the unique thermal profile for each printed circuit board assembly (PCBA) design during pre-production lets us create an optimal program for the solder process. We use this program in production to achieve high quality and lower solder defect rates.
Video Transcript
Today we’re going to talk about the use of thermal profiling in soldering operations.
As printed circuit board assemblies go through solder reflow or wave solder, every area of the board has to reach the right temperature for soldering and remain there for the right amount of time.
You can’t heat the board too quickly, or you can get splatter and solder balls. You can’t heat it too slowly, or the flux can dry out before a good solder joint forms. Overheating damages components, and insufficient heating gives you bad solder joints.
A printed circuit board’s thermal profile shows its temperature over time during soldering. It’s affected by the number of layers: More layers mean more copper and a greater amount of heat absorbed.
Different sections of the same board can have different profiles: Areas like this with lots of copper heat up more slowly than areas like this.
You can optimize solder machine settings to get the profile right for each board. To do this we use a Datapaq – data acquisition hardware in a heat-shield case. Temperature probes from the Datapaq are attached in several places to the board to be profiled. Where there will be larger, heavier components, we add an appropriate mass to mimic the local impact on heating.
The Datapaq goes through the solder oven with the bare board, recording board temperatures the entire time. When removed, it gives us time vs. temperature graphs for different areas of the board. We analyze these graphs to ensure:
- that no area of the board exceeded the maximum temperature ratings for the components
- that we didn’t exceed the maximum rate of heating
- that all areas of the board reached the right temperature and held it for the right amount of time for preheating and reflow, as specified by the solder data sheet.
If we need to, we change the rate of heating by independently adjusting several different temperature zones in the solder machines.
When we get the profile right, we store the settings by board part number in the memory of the solder oven or wave solder machine. Then for each production run, we enter the board’s part number and automatically pull up the settings to optimize soldering for that board.
Not a lot of high-mix manufacturers do this. Most simply create three or four standard profiles, based mainly on number of layers, and run all their jobs using one of these “close enough” standard settings.
But by measuring, optimizing and recording the unique thermal profile of each board design during pre-production, we achieve lower solder defect rates in manufacturing.
It’s another way we improve quality while reducing costs for our customers.