Cleaning SMD Adhesives

Using ultrasonic technology to remove adhesive is normally not that difficult. I do not know who�s machine you are using (perhaps its ours).

In any case, here are some tips for removing adhesives.

1. Heated wash chemistry works better than ambient. If your stencil cleaning system is equipped with heaters, set them to 105 degrees F.

2. You mention that you are using Zestron. May I assume that you are using Zestron�s SC200? If so, are you buying the ready-mix or the concentrate? If it is the concentrate, what percentage are you using? I believe that 20% is the recommend percentage. You can verify the chemical concentration easily by using a hand-held refractometer. This will display the refractive index of your chemical mix. This will determine the percentage. Zestron sells an over-priced refractometer and others are available elsewhere (for less). Be sure to ask Zestron what scale to use. I would also recommend that you contact Zestron (www.zestron.com) (703) 589 1198. There chemicals are expensive but their chemical and process knowledge is very good. They will run tests with your adhesive and provide you with some advice.

3. Was there a time when the chemical worked better than now? If so, the chemical may be loaded. Zestron likes to say that the chemical will last almost indefinitely. Though this may be true in a lab environment, it is seldom true in the real word. If your stencil cleaning system is equipped with a wash-solution filtration system, the chemical will last longer. With the right amount of filtration and chemical attrition, your chemical may last almost indefinitely. Send Zestron a sample of the wash solution. They can determine the chemical loading.

4. Most stencil cleaning equipment have an adjustment on the ultrasonic generators called an amplitude adjustment. This is normally an adjustment of 50% - 100% output power. Be sure that the generator is turned up to 100% amplitude.

5. Make sure that your was solution is properly degassed before you use it. Normally, new wash solution must be degassed before it can effectively be used. Degassing can be accomplished simply by running the ultrasonic transducers for about 45 minutes each time the wash solution is replenished. Without proper degassing, the wash solution will not be effective.

6. How many watts of ultrasonic power does your machine have? The lowest powered machines on the market are equipped with 500 watts of power. Most machines are 1,000 � 1,500 watts. Some are even higher. Too little wattage (500 watts) may be ineffective in tough cleaning application while wattages greater than 1,500 may be too powerful.

7. Try another chemical. Although Zestron�s SC200 is normally very good, so are others. We make an adhesive chemical called StencilWash-AD, specifically for adhesives. Petroferm�s (www.petroferm.com) Hydrex WS series is also good. Kyzen (www.kyzen.com) also makes some very good chemicals.

8. Send me some of your paste and I have our lab test it with a variety of chemicals in an ultrasonic stencil cleaner. Perhaps we can find the right combination.

Mike Konrad Aqueous Technologies www.aqueoustech.com (909) 944-7771

This message was posted the Electronics Forum @

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Dave,

Are you using The DEK plastic stencils with the 3906 or stainless steel? When we were using stainless steel, just about anything worked. It seems that the process for cleaning these *%#*&@" plastic stencils is either the best kept secret in the industry or else everyone is having the same problem I am having.

I even got a direct e-mail from a DEK applications engineer offering to help, but he offered no process. That tells me that either I'm the only one using these DEK stencils, or there is no process that works.

Oh, and our favorite stencil cleaner salesman forgot to change "solder paste" to "adhesive" in #8 of his canned response.

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Interesting. From the reaction we got from DEK, I thought we were the only ones with pumpprint woes. We've tried 1 stencil with Bioact SC10, Hydrex SP&WS, Axarel, and Loctite remover on both Heraeus and Loctite glues. Some we spray, some we work-in manually (unfortunately, never tried ultrasonics). All we got is static build-up, plugged apertures, and a lot of hard work. It doesn't seem possible, but the plastic actually seems to attract adhesives, even emulsified adhesives. Then, we discovered PhotoStencil laminate steel stencils. The plastic stencil is now with the mesh screens and rubber squeegees in the back.

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Hello Carl,

Is the 220-A chemistry from Smart Sonic aqueous or a solvent? What do you plan to do with the waste water (solvent)?

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