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December 2015

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From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Wed, 16 Dec 2015 15:10:06 +0000
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I disagree with the practice. 
The two materials, solder paste and tacky flux, are two different entities and should NOT have the same name without something to tell the difference between the solder paste and the flux used in the paste.
They should be two different part numbers and two different descriptions. There is no reason they can't be.

-----Original Message-----
From: Mike Fenner [mailto:[log in to unmask]] 
Sent: Wednesday, December 16, 2015 7:14 AM
To: 'TechNet E-Mail Forum'; Stadem, Richard D.
Subject: RE: [TN] IPC 7095 and Liquid Fluxes for Rework

Yes, but....
Alpha is not alone in doing this. Many users require the repair material to be the exact same FLUX as the original solderpaste. Others are happy to use a Tacflux which is the same generic type.

--
Regards 
 
Mike
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, December 16, 2015 12:42 PM
To: [log in to unmask]
Subject: Re: [TN] IPC 7095 and Liquid Fluxes for Rework

Also, Alpha uses the same material "name" for their flux crèmes (sticky or tacky fluxes) as they do for their solder pastes, which is a constant source of confusion. 
I don't think they realize just how much confusion and angst this leads to.
There have been several occasions that I am aware of where the operator was told to use a crème or tacky flux and because they were familiar with the solder paste by the same name, they used that instead, which led to disaster.
So give your crème flux a different Company Part Number and identify the material by that and the term "Crème Flux", or "tacky flux", or whatever you want to call it, and teach (train) them to know the difference between that and the different Company Part Number and description for the solder paste.
I am not saying anything good or bad about any of the products I mention here, I just need to cite some examples so everybody hopefully understands what we are talking about.

There is both a WS-609 crème flux and a WS-609 solder paste, for example.
So please don't be confused by that.
Bad dog, Alpha! Noooo doughnut.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, December 16, 2015 6:11 AM
To: [log in to unmask]
Subject: Re: [TN] IPC 7095 and Liquid Fluxes for Rework

Not sure what you mean, Tan, but I am talking about liquid fluxes such as Kester 2331ZX, for example, and tacky flux (also called paste flux or flux
crème) such as Alpha WS-809.
NOT solder paste.
Hope this helps.
dean

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Tan Geok Ang
Sent: Tuesday, December 15, 2015 7:32 PM
To: [log in to unmask]
Subject: Re: [TN] IPC 7095 and Liquid Fluxes for Rework

Paste flux not liquid flux....

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, 16 December 2015 3:32 AM
To: [log in to unmask]
Subject: Re: [TN] IPC 7095 and Liquid Fluxes for Rework

I'm going to come right out and make this statement. You can laugh all you want, but the data proves that liquid fluxes are terrible! 

Not only for BGA rework, but pretty much any type of rework! They form particulates in the solder joints, they run all over, and they like to penetrate and boil. Many people do not realize that is one of the main causes of lifted pads.

Let the screaming and moaning and hysterical laughing begin. I really don't care.

I have been training operators in the companies I work for years and years to use only tacky fluxes for touchup, for simple rework, and for hot air or hot gas rework, as well as for molten solder fountain rework. I have qualified the use of tacky fluxes to replace liquid many, many times. The cleanliness results of both water soluble and cleaned RMA tacky fluxes are several times better than for liquid fluxes. The tacky fluxes seem to promote wetting much better than any liquid flux I have ever used, and I think I have used them all.

Because the tacky fluxes are developed for worst-case conditions (hot gas and solder fountain rework) they actually work much better than any liquid flux I have ever tried.

And they typically are much easier to confine to just the solder joint(s) you are trying to touchup or solder.

And they don't evaporate or burn off before you even reach liquidus.

And for about 10,000 other reasons, but one of the biggest is that once the operators try using tacky flux for all rework and touchup, they never go back.

If the REACH folks decreed that there would be no more liquid flux allowed, beginning yesterday, it would not mean a thing to me. I would say, "Good riddance".

Most liquid fluxes on the market today were developed for wave solder or selective solder use; they were never intended to be used as a benchtop flux. People adapted them for compatibility reasons.

My feeling is that they should be limited to wave or selective solder processes. 

Use a good tacky flux of the same chemistry for everything else. Those from one particular solder company have always worked best for me.  God is the ____ and the Omega.

But always qualify, qualify, qualify. 

dean


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Wettermann
Sent: Tuesday, December 15, 2015 10:40 AM
To: [log in to unmask]
Subject: [TN] IPC 7095 and Liquid Fluxes for Rework

Dear Technetters:

In reviewing the IPC 7095 BGA guidelines I noticed a mention of liquid based fluxes for BGA rework. Has anyone heard of liquid fluxes being robust enough for Sn63 or lead-free rework processes?


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--
Thanks

Bob Wettermann/BEST

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