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Water Quality Requirements to wash boards

Winnie Chan

#19472

Water Quality Requirements to wash boards | 11 April, 2002

I was wondering what the water quality requirements are to wash PCBs? For example, the specific details including resistivity, pH, etc.

In addition, can you also explain why DI is preferred? What is the scientific explanation behind that?

Thank you very much for your attention.

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#19474

Water Quality Requirements to wash boards | 11 April, 2002

Search the fine SMTnet Archives for the background you seek. For instance, two extremely well written and thoughtfully composed postings are: * http://www.smtnet.com//forums/index.cfm?fuseaction=view_thread&CFApp=1&Thread_ID=1632&#Message6832&

* http://www.smtnet.com//forums/index.cfm?fuseaction=view_thread&CFApp=1&Thread_ID=665&#Message3611&

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ianchan

#19506

Water Quality Requirements to wash boards | 15 April, 2002

On a more layman's terms (am not a expert), here goes :

1) resistivity of DI rinse must be greater than 10M-ohms (some say greater than 16M-ohm?), dunno what is the FIX industrial standard?

2) DI water rinse usually is the end zone rinse, before the DI zone (in a aqueous cleaning machine) usually comes plain old industrial water that is filled up with chlorines and what/not other chemicals... so DI water is to neutralize the ion buildup that results from "normal" tap water rinse. Think its term "dendrite growth", result of flux not wash away properly by DI rinse.

(anyone out there who can further elaborate or correct any misconception I may have displayed, is all the more welcome to share your corrections with us all!)

Thanks for the sharing, from you DI water rinse experts!

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#19512

Water Quality Requirements to wash boards | 15 April, 2002

Hesitating after your shout-out for �DI water rinse experts�,

Q1: �What is the FIX industrial standard?� A1: Never heard of �the FIX industrial standard�. There is no standard in the US electronic industry. The issue: * Is NOT the cleanliness of your water. * IS the cleanliness of your boards.

Q2: Can �anyone out there who can further elaborate or correct any misconception�? A2: It�s entirely possible that 10M is necessary to obtain the required cleanliness of your board to meet customer requirements, but that level seems extremely high. The Ion Pure salesman must love you [and by default your customer]. Look here for background � http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=19474

Since you apparently declined to read the background in the fine SMTnet Archives, is suggesting that you read AC-62A � �Aqueous Post Solder Cleaning Handbook� silly?

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ianchan

#19520

Water Quality Requirements to wash boards | 15 April, 2002

Dave F, Hi Expert,

You are too modest, if anyone can qualify as expert so far, its you...(silent homage to the other unsung experts).

Coming back to "FIX", apologizes, meant to term it "fix" as in "established specifications". and yep, seems the focal point is on "clean boards" and not "clean water". As a nagging point, I had a customer auditor give us a rough time, and one item was that we must monitor the resistivity of the water to assure the "clean water" levels???

although we din exactly agree to that "observation", as it was a penalty item under their fancy checklist, we juz played along and setup a daily monitor c-chart for the ??M-hom. Which leads to the question, just exactly is an acceptable ??M-ohm level???

Hey, you R right. The salesman loves us very muchie...

Knock on the head, makes me wanna go read the fine SMTnet archives to fatten up that mushy muck...

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#19521

Water Quality Requirements to wash boards | 15 April, 2002

Regarding your customer suditor, it would have been nice if you said something like ...

Routinely, our testing shall be less than 1.56 microgram/cm^2 NaCl equivalent ionic or ionizable flux residue, according to TM-650, Method 2.3.35 'Detection And Measurement of Ionizable Surface Contaminants'. Certainly this a boardly accepted cleanliness level, but we will monitor the cleaning process for your boards to any standard you like. [smooch, smooch]

Assuming you truly did something like that.

Check J-001 for the basis of this blathering.

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JamesL

#19571

Water Quality Requirements to wash boards | 18 April, 2002

We do cleanliness testing each morning using a Zero Ion tester. Our pass/fail number is set at 37ug/square inch NaCl. We are rarely above 10ug/square inch NaCl. We use Aqueous flux. Our inline washer has a prewash (70psi@130 degrees F), wash (?psi), DI rinse and air knife drying sections. The DI water resistivity has gotten as low as 50K and our boards still pass cleanliness testing. We have never had a customer complaint for ionic contanimation.

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Dason C

#19573

Water Quality Requirements to wash boards | 18 April, 2002

The industrial standard is follow the R.O.S.E test as a guideline per J-STD-001 and the limit is 10ug/sq. inch.

Different tester with different equivalent factor with the ROSE and you can refer back to the manual, the Zero Ion tester with equivalent factor of 3.7 therefore you can set your control limit to 37 and the Alpha Ionograph with equivalent factor of 2 and we need to change the limt to 20.

Rgds.

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ianchan

#19576

Water Quality Requirements to wash boards | 18 April, 2002

Hi,

what model and make is your "Zero Ion Tester" (is that the brand make?)?

Is yours a portable unit? who's the OEM supplier?

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Dason C

#19589

Water Quality Requirements to wash boards | 19 April, 2002

Zero Ion is from Aqueous Technologies.

Check their web site, http://www.aqueoustech.com/Zero-Ion.htm.

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ianchan

#19617

Water Quality Requirements to wash boards | 21 April, 2002

Hi Dason,

thanks. have sent em' a P.O request.

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ianchan

#19618

Water Quality Requirements to wash boards | 21 April, 2002

Hi Dason,

thanks. have sent em' a online Purchase inquiry.

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