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Why is NC the prefer process for BGA mounting? why not WS?

mugen

#17279

Why is NC the prefer process for BGA mounting? why not WS? | 21 August, 2001

SMT community, My Fellows,

1) why is No-clean (NC) the preferred process, for BGA mounting by SMT?

2) why is water-soluble (WS) not a hot choice?

3) All I know, *is in layman terms*, that BGA has tendency to trap water, should WS process be the choice, and trapped water mingles with flux residue, to cause testing reliability problems, as reflected circuit shorts......

4) Being inqusitive bunch, and extremely technical in background, my end-customer is asking why NC? and they want to use WS process......

5) can some one *out there* help, this buggy question, and answer from a technical point of view, pls?

Thanks in advance...

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#17280

Why is NC the prefer process for BGA mounting? why not WS? | 21 August, 2001

Mugen,

are you sure you get all of the WS residues out from underneath the BGA with your equipment ?

I think testing that will be quite difficult.

Wolfgang

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CAL

#17281

Why is NC the prefer process for BGA mounting? why not WS? | 21 August, 2001

A) The standoff height of some uBGA components does not allow water to penatrate under the component. B)Water soluable may dilute the flux and not remove it all together. This can be tested with Ion Chromatography. C) Water soluable in some cases needs more heat (How ever you want to call it slow conveyor, Higher temps, longer soak time) to activate the flux. D) Some balled packages are auto underfilled thus traping moisture, flux, contaminates under the component. Caldon W. Driscoll ACI USA 610-362-1200 cdriscoll@aciusa.org

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#17292

Why is NC the prefer process for BGA mounting? why not WS? | 21 August, 2001

1) why is No-clean (NC) the preferred process, for BGA mounting by SMT?

Probably the same reason NC is the preferred process for mounting non-area array SMT components.

2) why is water-soluble (WS) not a hot choice?

There�s not reason not to use WS. Cleaning of assemblies featuring BGA devices may seem at first consideration to be fairly easy due to the large standoff height achieved by the balls. The difference between fine pitch QFP and BGA devices is that it is initially difficult to get any cleaning solution under the parts and then remove it. This is due the leads preventing easy passage of the solution. The package standoff height from the board for a QFP is normally between 0.005"-0.015", which is not normally a problem. In the case of BGA the standoff height is 0.020", but the balls then obstruct the easy passage of the cleaning solution under the device and also impede its exit.

A simple trial to examine this effect involved mounting different types of BGA components on a glass plate then passing them through a batch cleaning unit. Visual examination then showed the effectiveness of solution penetration and removal. Trials repeating this experiment using a spray can show that flux can easily be flushed out from under the devices. Video taping this experiment provided a good indication of the cleaning potential. As the parts increase in size the effective drying of water based products may be more difficult but can easily be assessed using this technique. The use of cleanliness testing equipment to monitor ionic residues may also be used with very few problems. If required, parts may be attached to a piece of glass with flux placed under the device. This may then be tested to see the effectiveness of the test method. Using a specific quantity of sodium test solution would allow a specific reading to be obtained which could provide evidence of the equipment's ability to detect contamination. [Most of the fore-going is from comments made by Bob Willis, years ago.]

3) All I know, *is in layman terms*, that BGA has tendency to trap water, should WS process be the choice, and trapped water mingles with flux residue, to cause testing reliability problems, as reflected circuit shorts ......

Well, hopefully the water that�s loitering around under the BGA is not sitting in a puddle of flux res. Generally, the plan is to squirt enough water under the BGA that these flux res are flushed down the drain, euphemistically speaking of course.

Next, hopefully the air knife on the washer drying section moves the clean water that�s loitering around under the BGA out from under the BGA and reunites it with its aqueous brethren and sistern, not cistern, in the wash tank.

4) Being inquisitive bunch, and extremely technical in background, my end-customer is asking why NC? and they want to use WS process ......

Well, use NC if you like whining about voids in your BGA balls after soldering.

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mugen

#17294

Why is NC the prefer process for BGA mounting? why not WS? | 22 August, 2001

For appetitizers, Cheers everyone for respective reply...

For mains, everyone get this straight, we wanted technical ref to why NC is, the more common choice of BGA mounting, and not helluv bunch of wordy opinions.....

Can someone pls ref some tech-journals, for this topic???

For pudding, wellz, everyone gets a complimentary, lemon pie splat-in-de-face, for not answering to the question....

Dumping my lousy ungrateful attitude aside, thanks to all participants in smtnet.com, appreciate your honest answers....

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CAL

#17295

Why is NC the prefer process for BGA mounting? why not WS? | 22 August, 2001

For one MUGEN Your original point number 5 asked for a technical point of veiw not any reference documentation. You get what you ask for.

Your appreciation is shallow, everyone that posted to your topic took time out formulate a responce.

So with that said I have lost the sudden urge to supply you with what you are looking for.

Cal

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#17297

Why is NC the prefer process for BGA mounting? why not WS? | 22 August, 2001

I doubt that you�ll find a technical journal article that chronicles why a company selected one flux type over another. You might find some thing that sketches-out points to consider.

As Cal says just because you ask an answer here, that doesn�t mean we have the answer, want to give the answer, have time to find the answer, or see any pay-off in working for nothing when some dead-butt is too lazy to do the research themselves. If it�s fairly painless, you get what you asked for. If not, then you have to work.

Oh, and my pie, pack-it.

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#17299

Why is NC the prefer process for BGA mounting? why not WS? | 22 August, 2001

From the perspective of someone that seldom contributes unique knowledge to the forum but asks a lot of questions, I find this "You're all a bunch of mouthy know-nothings, but thank you sincerely." attitude pretty friggin' puzzling.

Considering what you paid for the use of the forum, you hardly should be whining that you got what you asked for, instead of what you really wanted.

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#17300

Why is NC the prefer process for BGA mounting? why not WS? | 22 August, 2001

Mugen,

well, your offer of lemon pie for pudding ... even in the way it is anounced to be served ... was well received here. We might look forward to a date for this dinner, having a bit of small talk about technical issues, the way problems are to be solved etc. Sorry that my financial background doesn�t allow for waiving of expenses.

;-)

Wolfgang

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Michael Parker

#17305

Why is NC the prefer process for BGA mounting? why not WS? | 22 August, 2001

Lookit here, Mugwump,

The SMT community at large is composed of a vast array of expeiences, some barely with SMT 101 behind them to others who have probably already forgotten more than you'll ever learn. Without direct, personal contact of any one poster here at the 'net, it is sometimes hard to gauge to what level of technical savvy to appropriately respond with. What are you really looking for? Some epistle to plagarize that will dazzle your customer with brilliance to further inflate your own ego that you are a legend in you own mind? I personnally do not need to brag to my compatriots about my PH.d - they all know what it is really used for (that would be Post Hole digger - a clam shell shaped excavation implement to extract terra firma) You gotta know - sometimes the best answer is the one that is plain and simple. *KISS* (Keep It Simple, Stupid) I have noticed that a majority of your communications here are laced with a tinge of sarcasm. You would be well served to tone it down or find yourself persona non gratis, technically speaking. And have I got a pie for you, one with the edges so finely crimped, a crust so flaky it falls apart with each fork full, filled with the freshest, steamiest of meadow muffins, by George- YES - it's a moose turd pie, have a bite and get grounded with the rest of us Plebs!

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#17311

Why is NC the prefer process for BGA mounting? why not WS? | 22 August, 2001

I can send you a DOE I did on WS vs NC on BGA�s, but the results were..

NC = Had significantly less voiding both in number of voids and size of voids. A longer soak time (reflow oven) resulted in less voiding both for NC and WS.

Mike

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mugen

#17317

Why is NC the prefer process for BGA mounting? why not WS? | 23 August, 2001

Looky here people,

1) did imply *my* APPRECIATION for the replys posted herein...

2) If *me* appears to have no contribution to the forum, hope someone out there vaguely recalls some infrequently posted info *me* posted, that did get some joy & thanks....

3) suppose being a relative newie to smt manufacturing, in pale comparision to all my seniors, I do seem abit too big for my boots, apologizes for stepping on ur toes, mates....

4) as for being sacarsm inclined, and being "too lazy" to do my own homework, wellz, that certainly ain't no deterrent excuse, for anting to post *my* messages, and appearing to be a ignorant fool....

5) do ya think, i'd damage my "fragile" ego, and professional dignity, and ask for help from a bunchcha helpful fellas? *completely certified experts in ur own right* if i KNEW the answers myself? as the late henry ford was somewhat-quoted,

" I do not need to know all things *abt making cars*, I just need to know where to find it *mfg info*".....

6) no smartie *me*, just a regular guy struggling in this lousy economy, and trying to find answers to questions, folks either dun know, or dun care *its-not-my-jurisdiction symdrone*....

Once again, thanks for the help mates.... I never had a easy life, and dun expect charity from others, and, i do believe strongly in good karma, and that good deeds will have positive returns, suppose thats why lotsa folks participate herein forum, *nyak* Cheers!!!

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mugen

#17318

Why is NC the prefer process for BGA mounting? why not WS? | 23 August, 2001

Mike,

1) NC process = less BGA voids & void-size

2) longer soak times...

Heyz, thanks mate :)

~~~~~~~~~~~~~~

Dave F,

tot u were inclinded to the school of thought, that NC process hath higher chance for whining abt voids?

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mugen

#17319

Why is NC the prefer process for BGA mounting? why not WS? | 23 August, 2001

Ha!

I too have a P.h.D......

Mine is a certified, "PASS. Highschool *with* .Difficulty".... so which rock did you crawl from under??

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mugen

#17321

Why is NC the prefer process for BGA mounting? why not WS? | 23 August, 2001

Thanks, for pointing out my lack of, precision inquiry methodology....

I'll keep it in mind, and stay on my toes, next time I post a forum question...

Regards

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