Design an experiment to optimize the PCB solder reflow profile

[peacewong]

Hello All,

I have a difficulty about the PCB defect in reflow. Could somebody provide an example of DOE to optimize the reflow profile? Thanks a lot.

 

[D.Scott]

Re: Design an experiment to optimize the reflow profile

Hello All,

I have a difficulty about the PCB defect in reflow. Could somebody provide an example of DOE to optimize the reflow profile? Thanks a lot.

I'm not sure what you are looking for with this question but I will try to get us on the right track.

I am answering here and closing the duplicate thread so we don't have input scattered all over.

First, a DOE is typically defined based on alternative elements of a process. The experiment would then illustrate the effect each option has on the process and a "best" action can be determined. In order to do that, you must outline all the alternatives and "design" the experiment.

For example, in your reflow profile you are "having trouble with the PCB defects". I assume you are having problems with the temperature gradient across the PCB? Your DOE should include a comparison of convection versus IR ovens; the length of your soak zone and other contributing factors you may identify.

There are some pretty good articles on reflow profiles on the Internet. Check this one before you run an experiment. It may have your answer already.
http://www.tkb-4u.com/articles/soldering/reflprofadjust/reflprofadjust.php

Good luck with the DOE. Please share your results with us.

Dave

 

[peacewong]

Thanks a lot. In fact, I'm badly in need of a DOE example for reflow profile as a Six Sigma project.

 

[Tim Folkerts]

I doubt you will find a competed DOE for this topic with all the data & analysis you might need. The article Dave Scott linked to is actually close ... the results of a designed set of experiments (a "DOE") to optimize the heating profile. ITt gives the basic results as well as some of the basic graphs that would be produced.

If you want to do your own DOE from scratch, you need to decide what you want to learn (and how big of a budget you have). I am not an expert on reflow profiles, but from the article, it appears that some key parameters are
* initial ramp rate
* soak temperature
* soak time
* peak temperature
* cooling rate

Since you said you wanted to "optimize" the process, then a RSM (response surface methodology) approach would be called for. With 5 factors, you would need 30-50 individual trials to complete a standard DOE. From the results of these trials, you would then perform the analysis to determine the optimized parameters.

As an alternative, you might consider an EVOP (evolutionary operations) approach. Here you make minor adjustments to an existing process and see what the results are. The disadvantage is that it might take longer to optimize the process. the advantageis that you can continue with normal production as you do the experiments.


Tim F

 

[harry]

Hello All,

I have a difficulty about the PCB defect in reflow. Could somebody provide an example of DOE to optimize the reflow profile? Thanks a lot.

I believe you are dealing with lead free solders - which had caused a flurry of discussions and studies because of different characteristics.

There are a number of discussions in google and some specialized forums (such as smt forum). You may be able to get some ideas from this page.