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Wave Soldering Flus Selection



Wave Soldering Flus Selection | 14 June, 2001


I read an article that says "Flux selection usually depends on the following factors":

a) Solderability of pcb base metal or coating b) Corrosivity of vapours and residues c) electrical resistivity of residues d) Ease of removal of residues e) Soldering Temperature

Now, can someone explain to me regarding the above factors on "Why flux selection depends on the above 5 factors. Is that all I need to have a look when selecting flux for our Process ?

Thanks in advance.

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Wave Soldering Flus Selection | 15 June, 2001

Dear Greg H

On this link there is some usefull information about the choise of flux for wavesoldering.


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Wave Soldering Flus Selection | 15 June, 2001

In response No that�s not all you need to think about, but lets look at each and then talk of others.

a)The condition of the solderable surface on boards (and components) degrades over time or can be supplied in poor condition (to thin or thick HASL,Cleanliness etc..) all of which effect solderability. If you have good suppliers and turn material rather quickly you may be able to get away with a less aggressive flux. If you are a contact manufacture and have very little control you will want to use the most aggressive flux you can (and your customers allow).

b)The more aggressive (higher solid content) the flux the more corrosive it will be and vise versa. If you have a good cleaning process you can get away with using an aggressive flux but you better be monitoring it.

c)Again the higher the solid content the more conductive it will be.

d)The easier it is to remove the cleaner the boards will be with less effort which means less $$$. for example noclean is very easy to remove as you can leave it on!! no extra cost. RMA's can be Di washed, this adds cost equimpment,manpower maintenance, time.

e)Soldering temps may very between flux types some need a longer soak than others to burn off the alcohol or water. you would care about this if your products could not withstand the necessary time or temp. Or if your equipment couldn�t heat your product to the necessary temp within the needed times.

Of on to more variables.

1) Are you performing ICT if so be careful with the selection of any nocleans fluxes. Some are probable and others are not. If selecting a material that will be washed off don�t worry. 2) Can your current equipment support the flux. Spray or foam, some fluxes especially nocleans are easier to spray than foam. Can the preheaters heat high and long enough to burn off all of the alch/water prior to Pot. Washing if using a material that needs to be washed can the equipment clean it to your specified levels. 3) If this is not your own product what do your customers require or allow? 4) Does the material fit your process, If the boards being processed are mixed technology what type of flux is being used it your SMT process. If using noclean at SMT I dont think you would want to use a water sol at Wave.

Rather long I know but I hope it helps.

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Wave Soldering Flus Selection | 18 June, 2001

ICT probe problems, appearance of res on the boards, and unexpected interactions in RF applications.

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Wave Soldering Flus Selection | 19 June, 2001

Oooo, I just thought of something else. Consider the capability of the fluxer on your wave solder machine when selecting fluxes.

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Wave Soldering Flus Selection | 21 June, 2001

Yano, at lot this discussion is kinda school boy theory. Other issues are: * Soldering time * Corrosion [did we say that already?] * Safety [ie, personnel, plant, environment] * Cost of ownership

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