Blowholes during wave soldering

Joris

We don�t know the maximum period to store the boards without having problems with blowholes. Too many variables to determine. We prefer to just fix the problem, but understand that you have stock that you need to build-down.

Determining moisture content:
* Use a very accurate balance (X.XXX) with enough range to weigh your board. Handling residues (such as hand oils) can influence weight measurements. The transfer/dwell time for the weight measurement can affect your readings.
* Our ol� friend Bob Willis gives us a nondestructive test for outgassing in bare boards here: http://www.trafalgar2.com/troubleshooter/wave_pin_blow_hole.htm

reply »

Aren't the solder balls a result of the blowholes? you know the solder that came from the blowholes is now the solderballs on the resist!

hahaha :-)

Russ

reply »

Hi Dave - You are correct that I was not clear in my comments. I assumed Joris had seen the usual solder balls accompanying his blowholes.
Nevertheless, Joris, my first two recommendations still stand. Increasing the dwell time of your leads in the wave may cure your blowholes very quickly, simply and thoroughly. And, adjusting your preheat, keeping in mind all of the caveats, may also help. You have understandably focused on stock time because that is the variable most evident. These suggested wave solder process adjustments might relieve you of the need to worry so much about the logistical cures like adjusting stock time. Put differently, it's possible you'll find it much easier to try these process adjustments before you worry about instituting new stock time specifications. If they work - and it shouldn't take more than an hour to adjust and test your process - your in great shape. Easy investment, big payoff. If they don't work, you're back to stock time.

reply »

Hi Shrek - Not sure why you think adjusting dwell time and preheats is a sales pitch, but I do appreciate your candor. These are proven, widely used techniques for attacking, eliminating and preventing the recurrence of blowholes. Since it is so easy and quick to see if different dwell times and temperature windows can reduce blowholes, why not do this first before changing other manufacturing systems? And, if a more optimal dwell time or temeprature window is identified, it can be measured subsequently to ensure it is maintained each time the the board type in question is run.
Of course, there are different steps one would take for other types of wave solder defects, such as bridges or insufficients.
About your comments on wave soldering as an artform, no doubt you are an experienced and very good quality engineer, so that your instincts lead you to control the wave solder process. Yet behind what you have termed an artform is both knowledge and measurable, quantifiable data. This can be captured and responded to methodically, thus demystifying the wave solder process.
Such an approach is certainly critical to those engineers and process managers less experienced than yourself, but is also useful to those, like you, who can quickly take advantage of it because of their strong background.
There are specific, step-by-step procedures for identifying the optimal wave solder process parameters when new boards come into a plant, optimal being the measurable parameters for that specific board type that generate the fewest, if any, defects. It's possible that your expertise makes such procedures less vital to you, but in my experience most facilities, when first introduced to them, embrace them as new and vital based on the results they see.

reply »