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Viscometer - paste or glue measurements

morefun

#6697

Viscometer - paste or glue measurements | 25 May, 2001

Is anyone out there is the contract or the OEM sections using viscometers to check solder paste or glue for acurate process definitions. By this I mean check the materials viscosity over a period of time and measure the degradation of performance, then instruct operators that upon meeting the following condition(s) time;temp;humidity that the associated viscosity of the material non-conforming for..eg. less than 25mil print for paste / or less than 17.5 mil wide apertures.

The reason I am asking this is that I wanted to purchase some spare parts for a Brookfield Viscometer and asked for the approval. I was asked "why would we want to do this?", and something to the affect of "no one else is".

Take it easy on me Dave F. Read as "smackdowns" are accepted, but dang they hurt. I am fairly new at this, but after reading this forum for over a year, I know I am supposed to check the archives = 1 hit appeared (maybe it was covered in the old lost ones)

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#6698

Viscometer - paste or glue measurements | 25 May, 2001

We don't measure the viscosity of paste or epoxy as a proces control method. Look here http://www.smtnet.com/Forums/index.cfm?fuseaction=view_thread&CFApp=1&Thread_ID=1559&mc=12

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morefun

#6700

Viscometer - paste or glue measurements | 25 May, 2001

Thanks Dave, you were pretty quick on that response, and it was well taken. Cal or Wolfgang any thoughts or should I go find a rock to climb under?

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#6704

Viscometer - paste or glue measurements | 27 May, 2001

Listen, you can figure this-out from your particular situation.

Do this: 1 Talk to your operators and determine if they see viscosity changes in your materials. 2 Talk to the people doing viscosity measurements and determine if they see viscosity changes in your materials. 3 Chart the viscosity measurements you've already taken on these materials. [If you have worn-out the machine, you probably have boat loads of data. The question is: "What have you been doing with the data?"]

With this information, you can determine if you need repacement parts or refinement of your application of SPC methods. [And maybe size yourself for the rock you mentioned. Or rather, can you take advantage of the situation and review other useless process measurements that your making?]

Bottom line: If you see a substantial amount of variation or excessive R, you need to either (1) notify your suppler that their performance needs improvement or (2) get a new supplier. Their process is just not in control.

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#6709

Viscometer - paste or glue measurements | 29 May, 2001

Why not find a rock to climb on instead of under ?

You may find that it needs TRUST in your safety equipment ( harness, rope, slings, partner .... ) and concentration on your part to succeed that task.

I haven�t checked those proposed parameters but well chosen my supplier of the equipment I work with and up to now there has been no reason to complain (except for bare boards ;-( ) . If something kept me from reaching the summit it was my fault or lack of necessary ability.

If it turned out that a piece of equipment didn�t act the way it should be I replaced it or chose another brand.

As I see it, trust is a must for me in this job because I can�t control everything, I�ve to look for my own performance.

Hope that you get what want and for me that I get what I need

Wolfgang

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#6716

Viscometer - paste or glue measurements | 29 May, 2001

No body really does these days - unless they work for someone who believes in duplicating what the vendor has already done. It used to be a good think to do in the past, cause most pastes and adhesives where kind of sensitive, but today most materials are pretty tuff. Most vendors of paste and adhesive will supply you with all the data you need by each lot you receive, so why try to duplicate it? Plus, I've found that when you do, you can start to quarantine a lot of material and cause yourself some headaches just cause someone ran the viscosity test wrong. So trust your vendor's data. I find making a yearly visit to actually see them doing the test is not only fun, but pretty informative too! A round of golf doesn't hurt either! I just wish more paste and adhesive vendors shipped out of Hawaii!

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Dreamsniper

#6781

Viscometer - paste or glue measurements | 5 June, 2001

I don't understand why you wanna do this. The vendor has done this part for you and actually they have a recommended glue / solder paste life on the stencil or pcb (e.g. 6 hrs, 8 hrs.). If you will stick with their recommendations you won't be lost provided you monitor and maintain your factory temp. and humidity.

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blnorman

#6788

Viscometer - paste or glue measurements | 6 June, 2001

We do it because we have had problems in the past. We accept the viscosity certs sent from the vendor, but we run a check on a sample sent in. We have had problems in the past with material sent from the factory sitting on a loading dock or somewhere else and the consistency of the paste changed when it got to our receiving dock. We wouldn't run a test on the line, what we see from the line is that with the normal pressure, the paste is too runny or there's not enough paste being dispensed. We then run the viscosity check and usually we find that it's out of our spec range.

Personally, I believe in incoming inspection. Too many times we've lost boards and time because the materials coming in weren't what the certs said they were.

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