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Ricardo Lopes

#11338

Cleaning Stencils | 25 May, 1999

Is it possible to define a fequency for cleaning stencils on Stencil cleaner machines ?

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#11339

Re: Cleaning Stencils | 25 May, 1999

| Is it possible to define a fequency for cleaning stencils on Stencil cleaner machines ? |

40 kHz is the most common frequency used for stencil cleaning. All major manufacturers use this frequency (Aqueous Technologies, PMR, etc.). Many manufacturers (including Aqueous Technologies) use a "sweep" frequency based on 40 kHz.

If you have any other specific questions, feel free to contact me at (800) 218-8128.

Mike

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DNC

#11340

Re: Cleaning Stencils | 25 May, 1999

| Is it possible to define a fequency for cleaning stencils on Stencil cleaner machines ? | Deon Response:

Hello Ricardo,

The frequency of cleaning your stencils has a lot to do with: 1)The evironment that you are in. Hot ,humid, dry etc... 2)The type of paste you are using. 3)Stencil set up.

So keeping these variables in mind it really depends on what works best for your process. I typically have stadardized cleaning of stencils manualy on the machine with a bristle brush diluted a mixture of alcohol and water, if the paste has sat idle for 30 mins. We do not deinstall stencil for full cleaning until the end of shift. In your case, stencil cleaner cycle. Keep in mind if you are printing fine pitch devices >.025" you should wipe under stencil surface after every 2 or 3 print cycles with a lint free cloth or lint free tissue. When performing this operation you can also lightly soak cloth or wipe in alcohol.

Regards,

Deon Nungaray SMT MFG Process Engineer General Monitors USA CA

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#11341

Re: Cleaning Stencils | 25 May, 1999

| | Is it possible to define a fequency for cleaning stencils on Stencil cleaner machines ? | | I hate when that happens´┐Ż you read a question, submit an answer, then re-read the question and realize that you may have misunderstood the question! Is your question based on the frequency (kHz) or the frequency (how often stencils require cleaning)????

Mike

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DNC

#11342

Re: Cleaning Stencils | 25 May, 1999

| | | Is it possible to define a fequency for cleaning stencils on Stencil cleaner machines ? | | | | I hate when that happens´┐Ż you read a question, submit an answer, then re-read the question and realize that you may have misunderstood the question! Is your question based on the frequency (kHz) or the frequency (how often stencils require cleaning)???? | | Mike | | Deon Response:

I agree with Mike. Either way you have some good info. Right Mike!!

Regards,

Deon Nungaray SMT Mfg. Process Engineer General Monitors USA CA |

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#11343

Re: Cleaning Stencils | 25 May, 1999

Just a note about cleaning stencils with a mixture of alcohol and water, especially if you're using no clean paste, it's really not recommended.

Don't take my word for it, you can check with Alpha or most any other solderpaste vendor. What will actually happen is that you'll dry the paste out in the apertures and then it'll be a bear to clean thoroughly. I found out the hard way back when I was working for Zevatech. If any of you have been to any of the NEPCON show over the last few years, you know that Zevatech always builds these little keychain boards with a Tessera MicroBGA on them.

Well, after setting the line up and running a few panels to tweek things in for the exhibits, we needed to clean the stencil for the next day (we were running with Alpha's no clean). Somebody forgot to pack-up any solvent, and so the next best thing (so we thought) was to run to a drug store that was real close to the convention center and get some alcohol. Problem was, is that most rubbing alcohol is only 70% pure and it has emolients in it, the rest is normally water. Dries the paste out in the apertures like you wouldn't believe. Went to try and print some boards and barely and paste came out of the MicroBGA apertures...it all hung up inside the openings.

If you use alcohol make sure it's 100%, or what we finally got at the supply store at the convention center when they opened was denatured alcohol...

-Steve Gregory-

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DNC

#11344

Re: Cleaning Stencils | 25 May, 1999

| Just a note about cleaning stencils with a mixture of alcohol and water, especially if you're using no clean paste, it's really not recommended. | | Don't take my word for it, you can check with Alpha or most any other solderpaste vendor. What will actually happen is that you'll dry the paste out in the apertures and then it'll be a bear to clean thoroughly. I found out the hard way back when I was working for Zevatech. If any of you have been to any of the NEPCON show over the last few years, you know that Zevatech always builds these little keychain boards with a Tessera MicroBGA on them. | | Well, after setting the line up and running a few panels to tweek things in for the exhibits, we needed to clean the stencil for the next day (we were running with Alpha's no clean). Somebody forgot to pack-up any solvent, and so the next best thing (so we thought) was to run to a drug store that was real close to the convention center and get some alcohol. Problem was, is that most rubbing alcohol is only 70% pure and it has emolients in it, the rest is normally water. Dries the paste out in the apertures like you wouldn't believe. Went to try and print some boards and barely and paste came out of the MicroBGA apertures...it all hung up inside the openings. | | If you use alcohol make sure it's 100%, or what we finally got at the supply store at the convention center when they opened was denatured alcohol... | | -Steve Gregory- | Deon Response:

I partialy agree with Steve. If you are using no clean do not use water.I should have pointed that out. If you are using water soluble paste it doesn't matter. I have never encountered a problem with using clean D.I. water diluted with IPA for cleaning purposes of water soluble pastes.

Reagrds,

Deon Nungaray SMT Mfg Process Engineer GMI USA CA

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#11345

Re: Cleaning Stencils | 26 May, 1999

Dear Ricardo, We have a number of published articles on our web site. One of them is titled "Improving Screen Printing Yields" by Richard Clouthier of AMTX stencils (now Photo Stencil). This article appeared in EP&P magizine and also Asian Electronics Engineer magizine. Go to our web site and click on the "Recommended Reading" button. It is the first paper listed. Regards, Bill Schreiber

| Is it possible to define a fequency for cleaning stencils on Stencil cleaner machines ? |

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