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IONIC CLEANLINESS SPEC FOR BARE PWBs

HI can anyone tell me if they ask there board houses to h... - Dec 05, 2002 by Casimir Budzinski  

#22603

IONIC CLEANLINESS SPEC FOR BARE PWBs | 5 December, 2002

HI

can anyone tell me if they ask there board houses to hold to a max amount of contamination NaCl per sq /in on there incomming bare boards, I have a Ionograph 500SMD and have been testing some of the bare boards comming in to stock, some are much higher than I would like to see but can not find a spec for max amout of NaCl per Sq in

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EW

#22604

IONIC CLEANLINESS SPEC FOR BARE PWBs | 5 December, 2002

It is an interesting topic. This will tell you if they are cleaning the boards well(Di). We typically warn our fab houses if we see them head up or over 4 micrograms per square inch. On occasion we have seen upwards of 20, and "rejected" I think the max for the IPC recommended is 10.07 after you convert from cm2....but check this in either IPC 610 or 600. There is a conversion chart in the mil specs, but I don't think you need that anymore. I'll check. What are your readings? Give me a few days I'll see if I can't find something.

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Kris

#22606

IONIC CLEANLINESS SPEC FOR BARE PWBs | 5 December, 2002

Hi,

Is the limit for " 10.07 " for assemblies ? I guess we need to calculate how much ionic residue the boards see after assembly and cleaning. and then calculate back to the board spec if i am not mistaken ?

For bare fabs we have to access the limits becuase the amount of residue left will differ based on the amount of solder used on the board

Correct me

T

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#22607

IONIC CLEANLINESS SPEC FOR BARE PWBs | 5 December, 2002

While J-STD-001 specifies an upper limit for acceptance of assembly, we use Resistivity Of Solvent Extract testing as a process control. In truth, this "LT 10.07 �gm/sg in NaCl equivalent" measurement has substantial limitations, not the least of which is that it was developed for assessing boards soldered with rosin flux.

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#22609

IONIC CLEANLINESS SPEC FOR BARE PWBs | 6 December, 2002

Bare board cleanliness is still primarily measured by resistivity of solvent extract (ROSE) using instruments such as Omegameters and Zero Ions. What is considered as "acceptable" cleanliness varies between specification and from company to company.

For bare boards, the obsolete MIL-P-55110 allowed a level of 6.5 by the ROSE method. Companies use anything from 1 to 8 by ROSE.

Solvent extract tests are chemical characterization tests. The measure of board cleanliness by surface insulation resistance [SIR], such as for Bellcore, is another issue entirely. Bellcore GR-78, chapter 14.4 shows how clean a fabricators process need to be for telecommunications stuff.

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Mike Konrad

#22610

IONIC CLEANLINESS SPEC FOR BARE PWBs | 6 December, 2002

Military and most commercial standards requires post-soldered boards to measure less than 10 �g/in of NaCl (14 when using an Omegameter, 20 on a Ionagraph, and 37 on a Zero-Ion).

As Dave stated, 6.5 �g/in of NaCl is called out in Mil-P-55110 for bare boards. Obviously, 0.0 is the best number. Although specifications allow higher amounts of contamination, it is important to understand how ionic contamination testers work, before determining a pass/fail number.

All ionic contamination testers are capable of determining the total volume of contamination on a board, then, based on the board�s area, calculating contamination per square inch (or cm). Ionic contamination testers are not capable of telling you where the contamination is or what the contamination is. Although a tester may indicate a contamination level of 5.5 �g/in of NaCl, don�t assume that the contamination is evenly spread throughout the board. A result of 5.5 may actually be a result of an extremely high amount of contamination in small area of the board (which will cause solderability problems) while the rest of the board is clean. As a manufacturer of ionic contamination testers, I recommend that our customers NOT breathe a sigh of relief if the cleanliness result is a few points under the maximum allowed. Use a high test result as a flag and conduct additional testing such as ion chromatography (CSL Labs or American Competitiveness Institute conduct such tests). If an ionic contamination tester indicates a low level of contamination (less than 2 �g/in of NaCl) then odds are good that your board is clean.

Personally, I would not accept an incoming board that measures more than 0.5 �g/in of NaCl. It is perfectly acceptable to expect incoming boards to be very clean.

Mike 800) 218-8128

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MA/NY DDave

#22620

IONIC CLEANLINESS SPEC FOR BARE PWBs | 9 December, 2002

Hi

Well you already got good answers with some diversity, yet from what I read they are giving you the answers for Assembled PWBs, i.e. post solder or PWAs.

I don't remember ever doing this for raw boards. For most of the current pwb finishes it seems odd that you would have an Ionic contamination problem. YET if you do have a good talk with your supplier.

MA/NY DDave

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EW

#22625

IONIC CLEANLINESS SPEC FOR BARE PWBs | 9 December, 2002

I have seen the 6.5 ug/sqin and we have a fab house using 6.4, but I have no definitive answer for today. I see some interesting discussion here which I can also follow up on.

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Kris

#22626

IONIC CLEANLINESS SPEC FOR BARE PWBs | 9 December, 2002

Mike wrote : "Personally, I would not accept an incoming board that measures more than 0.5 �g/in of NaCl."

Would your recommendation be valid for an IONOGRAPH tester ? Did you perform any reliability study that you can share that drove you your conclusion?

T

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MA/NY DDave

#22632

IONIC CLEANLINESS SPEC FOR BARE PWBs | 9 December, 2002

Hi

I kind of agree without any reliability studies.

Where are the Ionics coming from? After Soldering depending on chemistry I think we agree?

Yet these are bare boards after many processes and even testing that should scrub out or off the Ionics. I am thinking we have an entrapment of process solutions problem that is rearing its head.

With most current day processes Ionics should be Zippo. Yet one never knows the fall back into long ago, overcome difficulties.

YiE, MA/NY David

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CAL

#22641

IONIC CLEANLINESS SPEC FOR BARE PWBs | 10 December, 2002

The EMPF has published a paper/ study on this topic, one of there better pieces of work.

http://www.empf.org/html/empfset.htm www.empf.org Doccument number rroo13

Best regards, Cal

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MikeF

#22645

IONIC CLEANLINESS SPEC FOR BARE PWBs | 10 December, 2002

From personal experience, if the PWB vendor is cutting costs and doing their final rinse with tap water instead of DI you will get ionic contaminants left on the board.

You might consider having CSL, or one of the other independent labs mentioned earlier, do some additional testing on some of the bare PWB's that are testing high. They can do a different test to find out exactly what the contaminant is, which gives you more info in dealing with your PWB vendor. In my case, CSL was able to identify different contaminants from the PWB vendor, the assembler that built up the cards, and the other company that potted them into a housing.

Mike F

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#22683

IONIC CLEANLINESS SPEC FOR BARE PWBs | 12 December, 2002

Considering only Ionic residues is very dangerous, most heat transfer fluids that are extremely hygroscopic are also non ionic especially those used in HASL / Roller Tinning fluids. Also consider if the resist is cured or in fact porous which absorbs PWB chemistries and Assembly chemistries both ionic and non ionic. Huge problem here in Europe at present with Solder balling, SIR,bridging and electromigration and of course not forgetting peeling solder resist over wave soldering (MUST BE YA FLUX - yeh yeh yeh) Scope Labs in Chicago are good at this analysis work speak with Jim Hevel and ask for IR Extraction.

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Kris

#22684

IONIC CLEANLINESS SPEC FOR BARE PWBs | 12 December, 2002

Hi Mike

Why is there a difference in readings on the Omega meter and the Ionograph ? Is it because that the IONOGRAPH is a closed loop extraction mechanism while the Omegameter is not ? Can you explain

T

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MA/NY DDave

#22687

IONIC CLEANLINESS SPEC FOR BARE PWBs | 12 December, 2002

Hi

I am wondering about your reply,

Please continue.

YiE, MA/NY DDave

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gabriele

#28500

IONIC CLEANLINESS SPEC FOR BARE PWBs | 9 May, 2004

> Military and most commercial standards requires > post-soldered boards to measure less than 10 > �g/in of NaCl (14 when using an Omegameter, 20 > on a Ionagraph, and 37 on a Zero-Ion). > > As Dave > stated, 6.5 �g/in of NaCl is called out in > Mil-P-55110 for bare boards. Obviously, 0.0 is > the best number. Although specifications allow > higher amounts of contamination, it is important > to understand how ionic contamination testers > work, before determining a pass/fail > number. > > All ionic contamination testers are > capable of determining the total volume of > contamination on a board, then, based on the > board�s area, calculating contamination per > square inch (or cm). Ionic contamination testers > are not capable of telling you where the > contamination is or what the contamination is. > Although a tester may indicate a contamination > level of 5.5 �g/in of NaCl, don�t assume that the > contamination is evenly spread throughout the > board. A result of 5.5 may actually be a result > of an extremely high amount of contamination in > small area of the board (which will cause > solderability problems) while the rest of the > board is clean. As a manufacturer of ionic > contamination testers, I recommend that our > customers NOT breathe a sigh of relief if the > cleanliness result is a few points under the > maximum allowed. Use a high test result as a > flag and conduct additional testing such as ion > chromatography (CSL Labs or American > Competitiveness Institute conduct such tests). > If an ionic contamination tester indicates a low > level of contamination (less than 2 �g/in of > NaCl) then odds are good that your board is > clean. > > Personally, I would not accept an > incoming board that measures more than 0.5 �g/in > of NaCl. It is perfectly acceptable to expect > incoming boards to be very clean. > > Mike 800) > 218-8128

Hello Gents, I learaned a lot by reading your treads.

I would ask you please to clarify better for me this point: ------------- Military and most commercial standards requires post-soldered boards to measure less than 10 �g/in of NaCl (14 when using an Omegameter, 20 on a Ionagraph, and 37 on a Zero-Ion). ---------- Does it mean when I read 10 ugr/in using ROSE (performed by LAB) I have to consider same as 14 ugr/in when using Omegameter (ie. 600SMD), 20 ugr/in when using Ionograph and 37ugr/in when using Zero-Ion ?

It seams the answer should be YES, but I have seen plenty of people in trouble comparing readings from different instruments used, an mainly all of them where looking all for 1,56 ugr/cm2 even if using different instruments like ove mentionned.

Other question please: when using ie: Omegameter to detect ionic presence on PWA (double sided SMT plus TH, what area (surface) is better to consider ? Top Side Plus Bottom Side? or just a Sigle Side the most populated one ? And what about when large Components (BGA, TQFP, Connectors) are located on the PWA (all of the togheter means a considerable surface ) ? do I have to extimate also the total surface of componenst to put into the formula ?

Thank you very much in advance for your answer

Best Regards Gabriele

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#28507

IONIC CLEANLINESS SPEC FOR BARE PWBs | 10 May, 2004

Yes

These instruments are intended for process control. So, it's unrealistic to attempt to correlate readings between machines. Read the EMPF report that Cal recommends here in this thread: http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=22641

On measuring board area, search the fine Smtnet Archives for background, for instance: http://www.smtnet.com/forums/Index.cfm?CFApp=1&Message_ID=19905

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gabriele

#28521

IONIC CLEANLINESS SPEC FOR BARE PWBs | 10 May, 2004

Many Tnks Dave, always helpful is your support.

I am not familiar how to access EMPF, I have tried already last wk but I was able to read only the abstract of RR0013. Is the access for free or it necessary to be a registered SMTA member ?

Regards Gabriele

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#28522

IONIC CLEANLINESS SPEC FOR BARE PWBs | 10 May, 2004

Hi Gabriele

Has the snow melted up there, yet?

No, SMTA membership, while good in its own right, is not a prerequiste to ordering documents from EMPF. Select "order technical publications" here: http://www.empf.org/html/empfset.htm

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gabriele

#28561

IONIC CLEANLINESS SPEC FOR BARE PWBs | 12 May, 2004

Hi Dave, I've got it, many thanks.

Snow ? My village is located latitude GMT + 1 hour,and about 45� north longitude. 30 Km north the mountains are still fully covered by snow. Sea is about 3 hrs driving down. My Job?, EMS'engineer (ex) now scrapped like an old tool after plenty years of work done. So now I spent my time waiting for some air balloon flyng above my village and try to be helpful in case of the balloonist get lost (but not even the Goodyear one is no more flying around !!!). It is very sad to throw away skill and experience !! Positive side of this my situation is that I have plenty of time to follow this Fantastic Forum and this makes me happy because every day I learn plenty of interesting things. ( before no time avaialble for it)

Thanks to all of the "Treatters".

Best Regards.........Gabriele PS: I apoligize for not talking of tech stuff.

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E Wolf

#28646

IONIC CLEANLINESS SPEC FOR BARE PWBs | 18 May, 2004

I'd like to follow the thread discussed on assembly. Hope Everyone is ok with that. I do run into the problem (have it now) that Ionic cleanliness is requested by print on a no-clean assembly. My intention is to use the no-clean to skip the aqueous wash because of the number of boards involved at low complexity. Saves effort to not clean them. I am concerned about the cleanliness spec. being used for a no-clean. Anyone have a suggestion, it would help.

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#28663

IONIC CLEANLINESS SPEC FOR BARE PWBs | 18 May, 2004

Ionic cleanliness is pretty much meaningless, when discussing nc flux residues. If you do the good solder routine and measure the boards, you'll be in the out-house, because the water in your resistivity of solvent extract tester will turn the res on the boards white.

As an alternative, which still maintaining the good solder routine, check with your customer to see if you can either: * Sacrifice a board * Ship a board with white flux res * Test a scrap board without components

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