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Mixing no-clean solder with activated



Mixing no-clean solder with activated | 18 June, 2001

Hi, I put this on the technet forum, and I know some of the same people are here, but I thought I might catch others here as well.

We have PCB's which are populated at the CM level with no-clean solder paste. However in house we use a solder wire such as Kester "44" RA solder to finish some hand assembly of our products or to do rework or repair.

We have a customer that is concerned with mixing the two on our assemblies and specifically mentioned the possibility of dendritic growth due to this mixture.

We do not actually mention any preference to our CM on what type of solder paste to use, other than to state 60/40 tin-lead. I am fairly recent in a brand new position in the company, of manufacturing engineer, and I am trying to clear up some of these oversights in our documentation.

Does anyone have any insight or concerns to raise about mixing them? Any recommendations which way we should go, if we should decide to go all to one way? I have already checked the archives and gotten some info on possibly switching to no-clean.

Your input is much appreciated.

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Mixing no-clean solder with activated | 18 June, 2001

It's possible that combining these two fluxes is benign, you sure can't say your customer is wrong, can you????

So, what is the intent of leaving these two different flux materials on your board? What is the residue remaining on your board as your customer takes it from the packaging just prior beginning their processing on your product? Will this residue affect the reliability of their product?

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Mixing no-clean solder with activated | 19 June, 2001

We don't actually leave the residue on the board, even though the Kester spec sheet says it is ok not to clean - we do spot hand cleaning with Safety Wash.

Kester also said that there shouldn't be any problem with mixing RA with no-clean, although watch out if mixing with water soluble.

The customer would not actually see the components in a finished product, as it is fully shielded on one side and a heatsink applied to the other side of the board.

However, the customer is picking thru our process control with a fine tooth comb and zooming in on anything that appears to be out of normal industry standards.

I have to admit it has been good for us to see ourselves from the outside world point of view but a little bit tough on the pennypinchers when it means spending a little extra cash to clean up our process control. We used to just slap a bandaid on a problem when it showed up, but we're getting too big for that. We now need to avoid the problem before it starts.


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Mixing no-clean solder with activated | 19 June, 2001

So, they want you to talk through a justification for mixing fluxes? That's GREAT, if you can get away with it!!!

Tell us more about Safety Clean.

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Mixing no-clean solder with activated | 20 June, 2001

Fluxes that have been properly heat activated are insulative (non-reactive) during operation in the field and during environmental testing. If you are also performing a cleaning operation, the possibility of growing dendrites is so remote that it can't be considered.

However, if your customer is convinced otherwise, you will either need to change your process, or convince them with your own evaluation (environmental stress screening).

Good luck.

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Mixing no-clean solder with activated | 20 June, 2001

M.G. Chemicals "Safety Wash Cleaner Degreaser". A primarily ethanol / methyl alcohol product. Part number "405". Brushes, Kim Wipes, or cotton swabs have all been used from time to time to apply it to the PCB.

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Mixing no-clean solder with activated | 23 June, 2001

OK, to reopen this and muddy the water a little more, What is the difference between REL0 and ROL0 solder. The solder paste that more than one of our suppliers is using is AIM293+ - this is REL0

The no-clean solder wire we use in house is ROL0, made by Kester.

These are both no-clean, so we could meet our customer's req't to use only no-clean (yes we agreed to do that, instead of fighting for the RA solder) with this, but are we asking for other problems?

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Mixing no-clean solder with activated | 25 June, 2001

According to J-STD-004 "Requirements for Soldering Fluxes", fluxes are classified by their chemical composition, activity level and halide content. In this scheme, each flux type is identified by a 4-character designator, where: * First two characters are determined by the chemical composition of the non-volatile portion. I.e. RO for rosin, RE for resin, OR for organic and IN for inorganic based fluxes. *Third character indicates the activity level: low (L), moderate (M) and high (H). * Last character - 0 or 1 - indicates the absence or presence of halides, respectively. The combination of the last two characters describes the corrosive or conductive properties of the flux or flux residue.

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Mixing no-clean solder with activated | 26 June, 2001

Yes I have read that standard, but it doesn't tell me what I need to know. Both have the same activity level and halide rating (L0) The AIM technical guy told me RO is a natural gum rosin, while (RE) Resin has more processing or something (maybe some other additives), done to the rosin before it is used for the flux. And he said as far as he was aware there wasn't really any difference between them and didn't know why there really needed to be separate classes. It didn't really inspire a lot of confidence in me.

Is there a concern with mixing them? I know RO means rosin and RE means resin but like the AIM guy said, why are there two separate classes if they are fairly interchangeable, and equivalent and there is no concern with mixing them?

There has got to be a reason for separating them out.


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Mixing no-clean solder with activated | 26 June, 2001

Rosin. A hard, natural resin, consisting of abietic acid [and pimaric acids in Europe] and their isomers, some fatty acids, and terepene hydrocarbons. Rosin is extracted from pine tree stumps. It�s an organic material distilled from oleoresin in pine tree sap.

Resin. (1) In solder fluxing: a chemically synthesized rosin. (2) In water processing: an ion exchange product, usually organic polymer beads used in softening and other ion exchange processes to remove dissolved salts from water. (3) In adhesives: an organic polymer which, when mixed with a curing agent, crosslinks to form a thermosetting plastic.

In military applications, all activated fluxes need to have their residues removed by a suitable cleaning agent. So, J-STD-004 classifies fluxes according to the nature of their main constituent: * Natural rosin. * Synthetic resin. * An organic substance. * An inorganic substance.

Turning this screw a bit, for those in Euroland ISO-9454-1 takes a slightly different, but similar, but like something else approach, where: FLUX TYPE: 1 Resin; 2 Organic; 3 Inorganic FLUX BASIS: 1 Colophony [rosin]; 2 Non-colophony [resin]|||1 Water soluble; 2 Non-water soluble|||1 Salts; 2 Acids; 3 Alkalis FLUX ACTIVATION: 1 No activator added; 2 Halide activated; 3 Non-halide activated|||1 With ammonium chloride; 2 Without ammonium chloride|||1 Phosphoric acid; 2 Other acids, amines and/or ammonia FLUX FORM: 1 Liquid; 2 Solid; 3 Paste

Then ISO-9454-1 describes halide levels through: CATEGORY: W; W; X; Y; Z % HALIDE: LT 0.01 [non-activated]; LT 0.05 [activated]; LT 0.15; LT 1.0; GT 1.0 ACTIVITY: Low; Low; Mild; Medium; High

See, don�t you feel better already?

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Mixing no-clean solder with activated | 27 June, 2001

OK....I now fully understand the difference in chemical makeup between rosin and resin.

But....can you, or would you, mix them without any concern? Could you or someone please just give me a straight yes or no answer? Please?

Of course,... I would like to know why, as well.

Thanks. Sorry for dragging this out. I kind of feel like I've been trying to pull hen's teeth getting this answer.


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Mixing no-clean solder with activated | 27 June, 2001


Earth to Genny: Hellooooow!!! No one knows the answer. We�re guessing that it might not be a problem, but we don�t know!!! We are not holding-out to drill you. We�d tell you, if we knew, honest. ;-)

The people that are goofy enough to do what you are doing are so goofy, they never realize to potential / lack of potential for a problem. ;-) Further, most people, even most of the goofy ones, would just change the flux, because they don�t have a good reason not to change. Well, other than saving time and money and not messing with the Safety Wash that is. ;-)

If history is any measure, I sense that the above will not be sufficient. ;-) So, here�s an alternative to consider. * Build five of your boards according to your normal process. * Build five of your boards according to your normal process, but don�t mix fluxes. Use the same flux as your contractor. * Send all the boards to a top flight commercial test laboratory, like Robisan Laboratories: or Contamination Studies Laboratory: * Have the lab analyze the residues on the boards using ion chromatography. [Although IC might not be the preferred test, because it discriminates only ionic contaminants, will require expert opinion by the laboratory personel on the criticality of the levels of the contaminants, and is not well suited in predicting the reliability of your product; it will allow you to compare the ionic res resulting from the two processes and certainly prepare you to respond to the dendrite red herring.] * Evaluate the res and make your decision. * Report back to us.

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Mixing no-clean solder with activated | 28 June, 2001

Thank you. I'm sorry if I came across frustrated or anything, but I wasn't sure if people were ignoring the one question I kept asking or if, as you said, they just didn't know.

Here's the deal. We are a small company rapidly growing into a larger company. There are many things we still handle like a small company while CM's are asking us to start planning like a large co. Taking 6 mos. to jump thru all the hoops to implement an ECO on a product like the Cisco's of the world require is totally foreign to us. Our documentation is minimal at best, that we provide to outside suppliers. And we haven't even realized until recently, some of the things we could control or should control, as you may have seen from some of my other posts like the gold finger thickness.

"Tell the board stuffer what solder paste to use? Why? Let them do their thing and we'll do ours..." As these things are found I'm trying to tighten them up, but I don't know where to begin sometimes.

I'll see what I can do about running a trial and getting lab testing. Thanks for the info.

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Mixing no-clean solder with activated | 2 July, 2001

Any reply yet from the Lab? we eagerly await for news...

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Mixing no-clean solder with activated | 3 July, 2001

No, I haven't even gotten around to formulating my test plan (what PCB to use, what lab to use, etc, etc, nauseum), let alone convince my company that we need to do it. I also got caught up in another extremely tight deadline project and haven't had time to go back to this.

I'll repost in a couple of months when I get back to working on this. At this point, we haven't noticed any problems we can directly link to these processes and only one company raised any stink about our mixing practices, and most of our products are not OEM. So I know this is a copout, but I will stick my head in the sand for a little while longer, and ignore the possible implications.


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