Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Flux Residues In Lead Free Wave Soldeing Process

Views: 3579

Hi You all We use no clean flux in our lead free wave sol... - Mar 25, 2006 by Smartasp  

#40636

Flux Residues In Lead Free Wave Soldeing Process | 25 March, 2006

Hi You all

We use no clean flux in our lead free wave soldering process and have unacceptable residues. The provile is spot on. If I reduce the flux amount the holes won't be filled and border on the IPC II specs. The customer does not accept partial hole fill even if it is IPC II acceptable and at the same time he does not accept the flux residues as well. Cleaning is out of the question since the cost added is to high.

reply »


Loz

#40640

Flux Residues In Lead Free Wave Soldeing Process | 25 March, 2006

Hi,

sounds unusual if your profile is accurate that you have so many residues. Had a similar problem before with no clean flux and with various flux manufacturers, and all residues were down to excess flux. This does not help your case though. How are you measuring your parameters?

loz

reply »

#40653

Flux Residues In Lead Free Wave Soldeing Process | 27 March, 2006

Is the flux rated for lead free temps?

reply »

#40656

Flux Residues In Lead Free Wave Soldeing Process | 27 March, 2006

When you say "unacceptable" do you mean cosmetically unacceptable? I've always put as much flux (no clean, of course) on the board until the ICT guys start yelling at me. That's how I roll...

Lots of factors with no-clean flux residues...board mask (glossy is worse), flux type (alcohol or water based), and the obvious, flux deposition amounts. We all know, no-clean flux has a low-solids content, has past electromigration testing, etc, and that residues won't harm your product in the field..

The water-based tends to produce "fluxcicles" or white flaky residues, whereas alcohol tends to leave behind a film...

What would Wavemaster Larry do?

reply »

#40682

Flux Residues In Lead Free Wave Soldering Process | 28 March, 2006

Thanks for the input Guys

Yeah the not so knowledgable customer does not like to residues for cosmetic resons. The flux is for lead free process, of the no clean and water soluable type. We have explained to him that technically the residues do not post a problem since it has no impact on the SIR etc. We even provided him with a white paper on the white residue issue. Stil �%*(&/&(//( My test guys of course do not like me either but understand the issue after actually taking the time to listen. The tip regarding the different solder stops confirms what we have noticed as well. It definitally makes a difference. We have not been able to determine axactly what tipe of solder stop is the worst of em all since we do not know the make (no board data available). However we found that solder stop with a smooth (glassy type of finish) give the best results. The rougher tipe seems to absorb the flux like a spongue. This I think dissables the wave to fully "wash" off the flux and therefore more residues remain on the board, which cristalizes after some time especially when exposed to higher huminity after some time. Reducing the amount applied result in bad filling of the vias and specially the THT components. We are lost what to do next and may even loose the customer because of this issue.

I realy look forward to more suggestions from you all.

Cheers smartasp

reply »

#40683

Flux Residues In Lead Free Wave Soldeing Process | 28 March, 2006

Hi Loz

The profile is generatet and verivied with the Latest model of KIC.

Smartasp

reply »

#40684

Flux Residues In Lead Free Wave Soldeing Process | 28 March, 2006

Hi Jdengler

Yes it is. Made sure of that before use.

Smartasp

reply »

#40685

Flux Residues In Lead Free Wave Soldeing Process | 28 March, 2006

Hi Samir

You are spot on. Exept the glossy surface. For us exactly the oposite.

Who is Wavemaster Larry?

Smartasp

reply »


Rob

#40704

Flux Residues In Lead Free Wave Soldeing Process | 29 March, 2006

Larry is an exponent of Newton's third law - the law of reciprocal actions.

You've no doubt heard of the font of all knowledge, well Larry is the equal & opposite of this. (There has also been considerable discussion as to whether he has his own superhero costume.)

reply »

Wave Master Larry

#40723

Flux Residues In Lead Free Wave Soldeing Process | 29 March, 2006

LISTEN thats the problem with the engineers.The engineers at my place of employment always crack that "engineering humor" too and i hate it.Hell Edison had no formal education. I liken myself to Thomas Edison no formal education but lots of practical expereince specially at wave wich Ive done for 12 yrs now. This guy in charge 0f our waves here at my place of employment likes to really put that flux on alot like what that Samire fella is saying but I was taught at Soltec college that the rule of thumb is "less is better'.Plus I hear some fellas talking about how too much flux will form dendrites over time espeicially if theres too much white residue left on the PCB board. The dendrites will act as a conductor causing feild failures thats what our sigma black belt expert has told us anyway. So thats my take on this whole flux residue deal. No knowlege of "Newtons traversing law" needed for that!

reply »

Chunks

#40726

Flux Residues In Lead Free Wave Soldeing Process | 29 March, 2006

After reading that, I have to go bang my head on the wave.

reply »

#40728

Flux Residues In Lead Free Wave Soldeing Process | 29 March, 2006

You better check with Larry to make sure you do it properly!

reply »

steve

#40730

Flux Residues In Lead Free Wave Soldeing Process | 29 March, 2006

"After reading that, I have to go bang my head on the wave."

Promise us you'll let it cool first, eh?

reply »


RDR

#40731

Flux Residues In Lead Free Wave Soldeing Process | 29 March, 2006

He has been doing it for 12yrs now you know!

reply »

#40743

Flux Residues In Lead Free Wave Soldeing Process | 30 March, 2006

Hi Fellas

After bangin my head several times on the cold and hot solder pot nothing improoved. The residues still bother my customer. I agree with less is better but if we apply less we have a cleaner board but the solder won't flow all the way up. Back to the beginning. Thinking of increase the airpressure of the spray fluxer (air velocity) and at the same time reduce the flux volume so to achieve better penetration and yet reduce flux volume applied. Will let you know about the outcome.

Smartasp

reply »

#40748

Flux Residues In Lead Free Wave Soldeing Process | 30 March, 2006

Is your customer hands-off when it comes to what type of process materials you use on their assemblies?? In the world of Contract Manufacturing Hell, you'll have a mixed bag of customers...some, who don't care what materials you use - after all, YOU'RE the CM, and YOU'RE the process expert. They trust that you've done your homework.... Then you got the "Control Freak" customer who has no friggin' clue about anything related to electronics manufacturing...they're usually from the Medical or Automotive industries... they lock you into using a 1980's flux because they want you to "validate" any changes you make - even though they have no idea how to go about "validating" a new flux or solder paste. Okay enough of my rant... If you DO have a hands-off customer, I'd say try a new flux. The new modern VOC-Free formulas make a world of difference, where, yes, you CAN use the "less is better" philosophy. They have nice activators which can survive the chip wave and penetrate nicely into your through holes giving you that nice top-side wetting that everyone wants to see. Search the archives on VOC-Free flux and you'll find lots of good threads in there.

reply »

#40752

Flux Residues In Lead Free Wave Soldeing Process | 30 March, 2006

Hi Samir

I totally agree with you on the customer issue. We have all of them. Where we have free hands we supose to use the flux as specified (one fits all) by our technical guy at the head office in europe. I realy start to question the desicion since we have problems with more than one board. Sure will be digging in the archive. Thanks for all the tips.

Smartasp

reply »


RDR

#40755

Flux Residues In Lead Free Wave Soldeing Process | 30 March, 2006

Does your fluxer provide for very fine atomization of the flux or is it more "droplet like" Great term huh?

reply »

Hoss

#40942

Flux Residues In Lead Free Wave Soldeing Process | 12 April, 2006

Samir - You and I need to go have a beer.

reply »

Larry (not THAT Larry)

#41434

Flux Residues In Lead Free Wave Soldeing Process | 9 May, 2006

Smartasp -

What are your lead to hole ratios like? Dial down the flux and open up the holes, if you can. Keeping at least a 14-20 mil gap between min hole/max lead solves the hole fill problem.

L

reply »

KEN

#41446

Flux Residues In Lead Free Wave Soldeing Process | 9 May, 2006

What is your flux delivery system? Tell us a little more....please.

I'm assuming ultrasonic. You can try to vary your air knife but if your pin / hole ratios are wrong then it may not help. Run a bare fab. If your problem goes away you may need to adjust hole sizes. However, spray pattern, volume and air knife pressure should still be looked at first. Especially, since most customers hate making changes to fabs just because, "you're borderline retarded and can't develop a proper wave process"...or so I was informed by one of our customers Engineers.(true story)

What is your dwell time in wave?

reply »

TimS

#41858

Flux Residues In Lead Free Wave Soldeing Process | 27 May, 2006

Gentlemen I have managed to pull myself together after banging my head. I am not sure the flux volume is the total solution here. All spray processes deposit flux in a similar manner, that is to say the vast majority of material sprayed onto the PCB surface is not sprayed directly on the centerline of a PTH. If this were the case topside wetting would not be a problem, there would be ample flux on the topside of the PCB to obtain picture perfect fillets. As the spray head traverses the PCB the flux is forced into an inverted cone or v shaped deposit pattern. The flux is then impinged into the hole at a moderately acute angle and may only wet the bottom part of the PTH. You can tape a sheet of thermal paper over the top of the PCB and run it through your fluxer be sure to leave the pre-heaters and solder pot off, the flux that reaches the paper will cause a reaction that turns the paper black. This will allow you to fine tune your spray pattern to get the most even flux deposition and may allow you to reduce the volume you use and make your customer happy. Most fluxes are loaded with surfactants that allow them to wet nearly any surface, if the flux is applied in proper volume it will wet to the top of the PTH if given time and provide good filleting. This wetting depends also on the condition of the flux, if you are using a VOC flux you may not want to use forced convection preheats this will drive off the carriers (alcohol) and limit the spread of flux up the barrel. If you are using a VOC free material run your first preheater as low as possible without sacrificing your profile. You may also want to try a faster conveyor speed, remember you only have 1 to 2 percent activators in your flux. These are usually dicarboxilic acids, usually succinic or adipic and the melt at approximately 150 to 189� C. Once these temperatures are reached the flux will complex very quickly and become benign. If this happens prior to the top fillet being formed you will not form the fillet. Oxidation rates double with every 10� C rise in temperature and at or near soldering temps the metal surfaces will reoxidize very quickly. Using a chip wave can be extremely hard on the flux get it through the chip and into the laminar wave as quickly as possible and you may see better results. If this product does not have bottom side SMT parts turn off your chip altogher. Hope this helps.

reply »

GS

#41859

Flux Residues In Lead Free Wave Soldering Process | 27 May, 2006

HI,

just my 0,00001 cents

Which preheat system does your wave solder has?

for instance ?

- IR ? - Bottom only ? - IR + Forced Air ? (bottom) - IR + Forced Air (bottom) IR top ?

PCB thickness ?

Appropriate preheat is important when looking to fill up holes.

Best Regards .......GS

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

reply »

Reflow Oven

PCB Cleaning