Kester 245 vs Kester 275 for SN63PB37

[Asad]

For my work, I currently use 60/40 solder wire and it seems to work fine with regards to finishing. I have had some problems with inconsistent cleaning of the residue. I want to move to a no-clean variant of solder wire. I haven't had the occasion to use 63/37 wire before.

We use leaded solder wire for long term product reliability and to prevent whisker growth related issues with lead free Ag based wire. Soldering is primarily done manually (hand soldering) with little to no automation since production volumes are typically low. Chipquik no-clean leaded flux is used to aid with setting and soldering SMD components. Compliance with RoHS and lead free regime is not an immediate concern for now.

I looked up no-clean Sn/Pb options from Kester (for no reason other than having heard and read more about it than others) and found 245 and 275 series with SN63PB37 combination of wire in various diameters between 0.3-0.8mm to match my requirements. If there are other equally good or better options from other brands, please do chip in. I have read lots of positive reviews of 63/37 245 series wire but very few of 275 series.

My confusion, and hence the reason for this thread, is related to following issues:

1 - What percentage of flux is recommended for solder wire to allow adequate whetting for SMD components (smallest size being 0805 resistors, TQFP-80, TQFP-100 ICs, etc) and solder flow with through-holes but not too much which may cause a mess with residue. I see 1.1%, 2.2% and 3.3% options being available for both series.
2 - Datasheets show the 275 having higher leakage resistance than 245 after soldering but I am not sure what flux percentage it is valid for. What is the difference between the 245 and 275 series in practice?
3 - What difference should I expect with regards to workability and finishing (shine, flow, etc) of 63/37 vs 70/30 and 60/40?

If you have got hands-on experience with both series, I would appreciate it if you can share your experience.

I plan to order a sample roll to test before committing to any particular brand/series. Please also share recommended procurement sources for your wire recommendation in the US. I have found Digikey and Mouser pricing to be way too expensive. 

[nanofrog]

Looking at datasheets both are equivalent to RMA, but 275 has better wetting characteristics (361 vs. 348 for 245). Also got the impression 275 would be a bit harder to clean (presume greater solids content).

Take a look at the following suppliers:
All-Spec
Techni-Tool
Stanley Supply

[David Hess]

1 - What percentage of flux is recommended for solder wire to allow adequate whetting for SMD components (smallest size being 0805 resistors, TQFP-80, TQFP-100 ICs, etc) and solder flow with through-holes but not too much which may cause a mess with residue. I see 1.1%, 2.2% and 3.3% options being available for both series.

Long ago I tested 63/37 245 1.1% (no clean) and 63/37 331 3.3% (organic flux water clean) versus the 63/37 44 3.3% I prefer.

I did not like the organic flux water clean solder at all.  It tended to spatter.  The 245 no clean was acceptable for production with clean parts and boards but not for rework.

3 - What difference should I expect with regards to workability and finishing (shine, flow, etc) of 63/37 vs 70/30 and 60/40?

I have never noticed any significant difference between 63/37 and 60/40.

[Asad]

Thanks for the replies!

Looking at datasheets both are equivalent to RMA, but 275 has better wetting characteristics (361 vs. 348 for 245). Also got the impression 275 would be a bit harder to clean (presume greater solids content).

Take a look at the following suppliers:
All-Spec
Techni-Tool
Stanley Supply

You mean the higher the wetting (the level of activation of the flux), the more difficult it is to clean it off?

Thanks for the supplier recommendations. I will look up their prices and inventory.

Edit: Found some pertinent info on Allspec's blog:

http://blog.all-spec.com/2014/03/kester-245-vs-275-solder-wire-how-to-pick-the-right-one/

Both Kester 245 and 275 no-clean solder wires can be used in either lead bearing or lead-free soldering, leaving a clear, non-corrosive and non-conductive residue. So which is best for your application? Read on to discover what makes them different.

Kester 245 is engineered to complement low-residue fluxes used in electronics production.  Proper use results in a clean assembly with clear residue – yet the soldering quality is equivalent to that of mildly activated rosin flux.

Kester 275 was developed to offer superior wetting performance for hand soldering in electronics production, and to reduce spattering typical of other core fluxes. The results are an extremely clear post-soldering residue with no cleaning.

Kester 245 and 275 solder wires are available in a range of alloys, wire diameters and flux percentages to meet your application demands. You’ll find them both online and in-stock at All-Spec for less.   ­­­

[Asad]

1 - What percentage of flux is recommended for solder wire to allow adequate whetting for SMD components (smallest size being 0805 resistors, TQFP-80, TQFP-100 ICs, etc) and solder flow with through-holes but not too much which may cause a mess with residue. I see 1.1%, 2.2% and 3.3% options being available for both series.

Long ago I tested 63/37 245 1.1% (no clean) and 63/37 331 3.3% (organic flux water clean) versus the 63/37 44 3.3% I prefer.

I did not like the organic flux water clean solder at all.  It tended to spatter.  The 245 no clean was acceptable for production with clean parts and boards but not for rework.

3 - What difference should I expect with regards to workability and finishing (shine, flow, etc) of 63/37 vs 70/30 and 60/40?

I have never noticed any significant difference between 63/37 and 60/40.

I am not interested in organic fluxes. The requirements to clean immediately post soldering is not feasible. Also, I am not sure all soldered components will be ok with being dipped in water. 

If 245 is not suitable for rework, which solder would you recommend for rework? Or would increasing the flux percentage with 245 deem it suitable for use in rework?

[David Hess]

I am not interested in organic fluxes. The requirements to clean immediately post soldering is not feasible. Also, I am not sure all soldered components will be ok with being dipped in water. 

I just mentioned the 331 organic water clean flux to be complete and thorough.

If 245 is not suitable for rework, which solder would you recommend for rework? Or would increasing the flux percentage with 245 deem it suitable for use in rework?

The 245 flux cored solder with a 66 core size, 3.3%, should be a lot better but the idea at the time was no cleaning so I tested the extreme.

For rework, a separate application of rosin flux could be used with any rosin cored solder.  I usually just dip the wire solder into liquid flux if necessary coating the outside but I find it easier just to do rework with 44 flux cored solder since I plan on cleaning afterwards anyway.

[Asad]

I just mentioned the 331 organic water clean flux to be complete and thorough.

I figured but just stated it since it wasn't explicitly mentioned in the OP. 

The 245 flux cored solder with a 66 core size, 3.3%, should be a lot better but the idea at the time was no cleaning so I tested the extreme.

For rework, a separate application of rosin flux could be used with any rosin cored solder.  I usually just dip the wire solder into liquid flux if necessary coating the outside but I find it easier just to do rework with 44 flux cored solder since I plan on cleaning afterwards anyway.

Does the 44 series wire you use have 3.3% flux core?

I do have Chipquik and their low temp rework alloy sticks in addition to their tacky flux. I reckon that should be sufficient if and when rework is needed.

[David Hess]

Does the 44 series wire you use have 3.3% flux core?

It does.  All of the spools of solder with 44 flux that I have are 3.3%.

[Asad]

Thanks for all the help.  Much appreciated!   

I placed order for a couple spools of 245/0.02/58, 245/0.031/58 and 44/0.025/66 from Technitools. I will check them out before ordering more spools.

[ThomasCee]

I realize this is a thread resurrection from a long time ago, but very helpful info. Just ordered some garbage solder, and looking to get some Kester stuff and was bewildered by all the options they supply. (now searching this site for all the solder topics I can find : ) Tnx

[FrankE]

Some of the 44 solder wires have 1.1% or 2.2%, 4.4/%. Depends on the alloy and the size.
It's a ROM flux core, therefore not suitable for some [critical]applications. [edit@ ROM flux core should be fine for hobby and much professional selective soldering use]

It's hard finding decent 62 Tin silver-loaded, IEC ROL0 /ISO 29454 1.1.1-flux-cored in the UK.
The solders on the UK resellers tend to be quite similar, giving the illusion of choice and can have more aggressive fluxes, which rules out their use on some applications where standards are basedon the materials not the outcomes. Mil-STDs tend to be migrating towards output standards than precisely defining the input (material) standards.
 
25 reels min for Kester 24-7150-8834-ND (245 ROL0 flux) at Digikey plus a sicknote from my mum pleading the USGov to allow DK to sell it to me and explain myself why I'm using it. Nope.
Mouser has it at £119.20 

There's chip quik at Digikey SMD3SW.020 8OZ in smaller quantities 1@£17.57. less that half their price of SMD3SW.020 1LB (1@£51.48)
2.2% flux though.

Silver-loaded is still eutectic, covers you for leaching of silver from components and silver-coated hook up wire eg the Alpha PTFE-insulated stuff. If you don't have to follow a standards body a ROL1 flux, ROM0 or ROM1 gives you more choice of solders.
62 Ag-loaded won't tarnish as much as 60/40 or 63/37 but be aware solders have a shelf life so it's not worth buying a big 500g or 16oz reel. I've an old roll of 60/40 which has dulled considerably. The joints are filthy. Even pros buy solder in those little tubes as they are using a number of different solder wires, pastes, ingots and balls in different sizes on a variety of substrate materials and sizes.

[ThomasCee]

Very nice and interesting. Yes, it is all for hobbist usage, so my quantity of usage will be low, despite being relatively picky on it's performance.

I decided to give the Kester 24-7150-0018, (listed as rosin activated standard Core Wire Solder) 62/36/2ag. Maaaan it's shiny. It was pretty expensive, but I'm going to eBay 10' chunks of it for $3 or so till I knock the overall price down I got the .025 size, and it's perfect for the very small stuff I seem to be working on more and more lately. Ain't nuth'in getting bigger these days only smaller it seems...

I should post some usage pictures on the "Best Solder" thread sometime. It's really a treat to work with.