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SMT Solder paste and wave flux evaluation

Chua

#32304

SMT Solder paste and wave flux evaluation | 28 January, 2005

Hi,

I could like to find out what are the things need to look out if I'm doing a new SMT solder paste ( water soluble & no-clean ) evaluation. And also flux ( spray type ) for wave-solder ( water soluble & no-clean ).

Appreciate for all the input.....

Thanks.

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Chunks

#32310

SMT Solder paste and wave flux evaluation | 28 January, 2005

Your best bet is to do a decision making matrix. Each company has so many different criteria�s it's hard to pick out which one might be important to yours.

Simply pick out your top 5 paste manufactures. Next decide what your "Eliminators" are - things you must have from you paste (i.e. 8 hour tack, global supply, air N2 compatible). If one of your paste vendors doesn't meet one of your eliminators, get rid of em'. Next pick out your "Criteria�s". These are things that you can measure from 0 to 100. Things like over-all look of each solder paste after reflow, max print speed, ICT pin probable etc. Once you have this list, define which one is the most important Criteria all the way to the least one. Assign a weight of 10 to the most important and work your way down to the least. You can assign the same weight value to two different Criteria�s if you feel they both are important. You also do not need to go 10, 9, 8, 7, 6, 5, 4, 3, 2, 1. Especially if you have more than 10 Criteria�s. So you may give 3 different Criteria�s a weight of 10, then the next one a weight of 7, then the next 4 most important ones the same weight of 2 and perhaps you have a half dozen Criteria that you�d only give a weight of 1 too. It�s up to you or your group.

Now since Criteria�s are not Yes/No type of questions, you or your group needs to assign a 0 to 10 point measure on each one. This is where you run all your different pastes and measure the results based on your criteria. So say for example, your top weighted Criteria of PRINT SPEED has a weight of 10 on it. Run all your different pastes and see how they measure. Say the XYZ paste far exceeded your fasted print speed you�d ever need � you decide to give it a 10. ABC paste meets your fasted print speed but will not roll any faster past this speed � you give it a 9. 123 paste couldn�t keep up so well � so you give it a 3. Now multiply the weight of MAX PRINT SPEED which is 10 times the measured scores. For XYZ paste, you gave em� a 10 and so you get a score of 100 for MAX PRINT SPEED. Now do the same for the other pastes; ABC is 10 times 9 which is a score of 90, 123 is 10 time 3 which is 30.

Continue down your Criteria list and get scores for each paste Criteria till you�re done. Now add up the Scores and the highest one meets your Criteria with the best resulting score. You can use one spread sheet with a group of people � or have the group of people do their own spread sheets and then compile a final spreadsheet � it�s up to you.

This would be million times easier to show you with a spread sheet � but we don�t seem to have the technology on this forum. Hmmm, go figure! I can e-mail a completed one I used if you want.

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Bob R.

#32311

SMT Solder paste and wave flux evaluation | 28 January, 2005

We use the exact same method Chunks outlined for evaluating just about anything we're going to roll out worldwide, whether it's a material or a machine. List your factors (print speed, solder spread, etc), assign each a weight, evaluate each paste and give them a score for each factor, then multiply factor weights times scores for each paste and add them up. My experience is you'll have one or two top performers, most will be about the same somewhere in the middle, and a couple will be really poor.

A key point is to test the show stoppers first. For example, SIR testing. Nothing worse than running a whole lot of tests for things of lesser importance then finding out one of your pastes doesn't pass one of your "must have" tests. It saves a lot of effort if you do those first.

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Indy

#32313

SMT Solder paste and wave flux evaluation | 28 January, 2005

That is what we call as good "Problem Solving Skills". :)

This message was posted Add this forum to your site! Click to learn more. the Electronics Forum @

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Chua

#32329

SMT Solder paste and wave flux evaluation | 29 January, 2005

Hi Chunks,

Thanks for your input. Appreciate you could send me a copy of your evaluation list as this type of evaluation is new to me..... Here is my email address :- pgchua@cyberway.com.sg

Thanks.

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Howard Sommerfeld

#32371

SMT Solder paste and wave flux evaluation | 1 February, 2005

I also have a spreadsheet tool for comparative analysis using criterion weighted scoring. It can be used to analyze any decision, and helps groups reach consensus on why a particular alternative is the way to go.

As final steps you can also consider risk of each alternative and then the cost.

If cost is a factor - divide the score by cost for each alternative. This delivers a relative value of points per dollar for each alternative.

If anyone would like the .xls tool just drop me a line at: hsommerfeld@automatedlearning.com

H.

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#32398

SMT Solder paste and wave flux evaluation | 1 February, 2005

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