mechanically strongest soft solder?

[coppercone2]

I want to solder on some stuff to a copper block, that also has resistors soldered to it.

Is there a solder that has similar melting point to lead or lead free electronics solder but is stronger mechanically despite decreased electrical performance?

It has to be in the same ballpark as electronics solder melting point. But this would be for mounting hardware, where no current should go and EMI is not relevant.

Also, it can't be gold bearing, because its way too expensive.

70/30 solder is a hair stronger. But that's not worth it.

[coppercone2]

idk the specification of PSI

They seem to compare it that way on tables. used for glue also

and I don't care if it leaks or not its just a bracket

[coppercone2]

I am thinking either kappzapp 3.5
https://www.kappalloy.com/solder-alloy/kappzapp-solders/kappzapp3-5a/

or bridgit
https://www.rhsupplyco.com/buy/product/harris-products-group-bridgit-lead-free-solder/136763


I used bridgit before, the eutectic nature of kappzapp 3.5 seems preferable to this application since I am not filling a gap.

kappzapp 7 is slightly stronger, but I think I prefer the eutectic.

Anyone got any other ideas for similar melting point range for copper to copper or copper to brass? can we get 20k psi?

[bdunham7]

Eutectic silver solder will probably give you the most reliable strong joints at temperatures near normal solder.  There won't be a huge difference, however solder is actually pretty strong if it is done right--which it often isn't.  A jewelers silver solder will be stronger but will have much higher melting point and may contain cadmium in some cases.  The advantage of using something like that is you can do the mechanical soldering first and subsequent electrical soldering won't remelt it.

can we get 20k psi?

IDK, that's pretty ambitious for a regular copper block to some random bracket with a flat joint.  Where did you get the 20ksi figure? 

[coppercone2]

but its already brazed. It needs both a electronic mod and a mechanical mod.

AND I am 100% sure I can do this with regular solder I don't need the strength I just feel like shopping. I was gonna buy another roll of bridget because I am down to about 3 inches, but I don't mind buying something new. OFC bridget is 1/4 the price

[jpanhalt]

@coppercone2

Are you sure that brazing is less conductive than leaded or lead free solder?  Your data or citations would help. I suspect brazing will give both more strength and equal or better conductivity per volume of fill.

[coppercone2]

THe thing is brazed already I need mods that involve attaching a bracket and attaching parts. I want the best thing to attach. I am not going to mess around rebrazing this thing.

Braze is better in every way but I am not going to get this that hot


However i did notice bridget is 460F and lead is much lower. If I attach the bracket with bridget I have quite a temp range before I have to solder on the parts. So I can break up the job.

With 420F and 360F that is a bit close. Feel alot better about 100F vs 60F. That should hold even with dodgy temperature control. That is 50C vs 33C difference, which is pretty solid.

and you can make repairs more comfortably on the electronic parts with the extra margin.

[T3sl4co1l]

Soft solder maxes out around 5k PSI, mostly tin with a bit of copper and silver, maybe antimony.  Whatever alloy designations those include, but SAC305 isn't bad, mechanically.

Epoxies are comparable, the longer-cure and industrial kinds anyway.  Surface prep is paramount.

No lead alloys are particularly strong, AFAIK.  More or less for similar reasons, as tin and lead aren't very strong crystals (low binding energy gives low melting point and low shear strength, even when slippage planes are frustrated by alloying), though tin happens to be the stronger of the two.  (Also, this kinda despite both having rather high boiling points, but I mean it's not everything, materials are complex.)

Brazing takes place at higher temperatures.  There aren't really any alloys of importance, for these base metals, until you get to silver-based ones that work around red heat and up.  They are very strong in comparison, often stronger than the base metal (certainly compared to the yield strength of pure copper), comparable to lower steels.  (Note that the base metal ends up annealed after brazing; you can't do much heat treatment, nor any mechanical working of it.)

There are zinc alloys, which are best suited to aluminum; but zinc tends to be a bit brittle.  A lot of "brazing" alloys for aluminum, tend to be more like shallow welding: say, Al-Si eutectic plus fluoride flux, with melting point just barely below the base metal -- not really usable by hand, but common in industrial processes.

Because soft solders are weaker than base metal, they're best used in large, wide joints; lap joints, pin-in-socket joints, etc.  Prevent peeling failure by suitable joint design

Tim

[coppercone2]

What do you mean 5K PSI?

The link for that solder I linked says 14K. The bridgit datasheet is like 13K.

The Zapp soft solder (420F melting) lists 15K for Copper and 28K for stainless steel joints.

Is there some kind of fraud going on like with compressor CFMs?

Tensile Strength (Copper):
   

14,000 psi

Tensile Strength (Stainless Steel):
   

25,000 psi

Shear Strength:
   

11,600 psi

[coppercone2]

I was also hoping someone knows some exotic brand that has even better specs (gold does, its like 40k)

[T3sl4co1l]

Maybe I remember a bit low? Lemme see here.

Basic Sn63 around 5, well, 6: https://www.matweb.com/search/DataSheet.aspx?MatGUID=9e382af924de44ffb4eb42027ca1436d
Sn62Ag2 about the same, 6.2: https://www.matweb.com/search/datasheet.aspx?MatGUID=15b6a001052c4ec98896e839da7f5b75
Clearly, one of these is wrong: https://www.matweb.com/search/DataSheet.aspx?MatGUID=7f7fb170f75d480ca183c17a4c7574a7
Not very many of the results in their database seem to have tensile strength listed.

Kind of an odd article, not sure what it's written for, or how well supported it is, but discusses the process some at least:
https://www.osti.gov/servlets/purl/1347531
Seems to suggest joints can be stronger than the base metal but doesn't really discuss either thing.

This article is more in line with my expectations: http://files.aws.org/wj/supplement/WJ_1976_10_s323.pdf but doesn't mention joints can be stronger, or, seem to find them stronger than base filler at all.

The impression seems to be that joints can be stronger than the base metal, but I'm not seeing a reference supporting that.  But go figure, Google is terrible; a top result is a Quora question that's mostly bot-generated (and the possibly-not-bot-generated content wholly lacks insight into the matter).  We can go to a horse's mouth and see some data,
https://lucasmilhaupt.com/Lucas/Technical-Documents1/Silvabrite100TDS2018English.pdf
I *think* they mean 1/2" tube (0.5" actual), which will have a 1/2" overlap area, which comes to ca. 10 MPa.

Harris doesn't appear to give any, like actually zero technical data at all, on their Bridgit product.  Composition and temperature, sure, but strength?  You'd think, you know, claiming it's stronger than anything else, they would proclaim prominently what the actual number is?  In the absence of such data, I can only assume it's because it's not actually any better, and as far as I should be concerned, it's marketing fluff, no different from any other alloy of comparable mixture.

Incidentally, this raises an important point, solder creeps and must be loaded quite gently to last a long time.  It's possible there are larger numbers due to intermetallic reactions, basically cementing the joint together (think of how hard it is to wrench copper pipes apart by reheating them -- often by heating far too much, exacerbating intermetallic growth!), at the expense of going brittle.  But this will also depend strongly upon joint fitness, as the IM layer is only some microns thick normally.

Tim

[coppercone2]

the bridget is in the TDS
https://www.rsd.net/assets/prod/745.pdf

I am inclined to believe harris numbers because their only job is like to prevent stuff from breaking. I don't think they care about anything else lol

[coppercone2]

Lol what kind of results would just tugging on the wire give? I mean taking solder and seeing when it rips. maybe their just yanking it

but harris makes tons of welding shit. I assume they might use the same machines for testing welding and brazing and soldering because its cheaper. I don't think they are allowed to bullshit data like that for something like structural rod welding. But a pure electronics manufacturer.... hmmmm  can we trust them to buy a pull tester and actually solder a 1 inch area joint.. ?

I feel like if they specify both shear and tensile, that means it must be tested on some pretty specific setup. Tugging pipes apart is shear I think.

[coppercone2]

There is also this thing
https://xdevs.com/doc/_Materials/Chemistry/solder_alloy_directory_brochure_97720_r2.pdf


But its indium corp. I don't like them. I think they need to allow their employees to socialize because I swear they write all their stuff up so you have to give them a call. Perhaps they should do some company outings, give some PTO, because seriously they have
1) tons of critical information that is deleted from the website after I saw it there before, like something about a galium coated nickel felt
2) absolute crapshoot on what you can buy and what you need to call for
3) they wanna get to know your whole family before they will sell you some crap that you can make in a crucible. Or the nanofoils. But that is just w/e.. you could make something 100 times more potent with a god damn file and a old car (thermite). It's not nuclear ordinance.

I seriously think there is like a PR directive there that says "make every effort to confuse the customer so they contact us. make sure they need to contact the entire company leadership, and fill out paperwork, so they can join two random objects together". The other school of thought is that if something is easy to get, people talk about it, and it sells itself.


The only company more insane then them is that EMC place that wants your social security number to order metal stampings!!!!! You might get that from your boss if he smokes a fat crack rock before you ask him, because aint no one in america gonna give you that shit for a online order!!!!!!!!!!!

[Doctorandus_P]

You can use epoxy. It is mechanically quite strong and you don't have to heat it at all. It is however quite terrible at electrical connections 

Maybe you can use a combination. Solder the joints for the electrical connection, and use epoxy (or some other glue) for mechanical strength.

[T3sl4co1l]

Well, sure. Give or take creep.  But down at 1 mm^2 say, that's all of 8 lbf, or 40N say.  That's not much, I can pull that with one finger.

And maybe you want the safety factor to be 4, so it's barely enough to hold up, oh Idunno, a modest size transformer or something?  Factor could easily be 20 or more to account for mechanical shock.  Plus twisting/bending moment.  Clearly you'd want a stronger joint than that, and more contact points to distribute the load over.  Something like a PCB, doesn't have nearly as strong laminate/peel strength anyway, so you need quite a bit of soldering area, which is, well, how we normally do things, so there's that.

Anecdote: the bracing on my homebrew LED strip, that I have hanging over a closet door frame, started to look dangerously loose over the last couple of years; I finally took it down and redid the joints this year.  It was... how to put it, something of a tee joint, between two pieces of copper clad, one flat (base board), one perpendicular (the brace), with maybe a 5mm-long solder joint at the base on both sides.  The brace was subject to some leverage, as it sits at an angle; it was clearly pulling out of the solder joint and had displaced by several degrees.  This is over a good ten years or so, and fabbed with Sn63 solder.  I put it back up by doubling up on solder joints (the brace is resting against a cross-member that it previously wasn't soldered to), and adding another brace (a square to reinforce the cross-member from the backside, to prevent it bending).  At this rate, and given the reinforcements, it's probably good for 20 or 30 years, in which time the power supply, and probably current set of LEDs, will have long since expired.

Tim

[jonpaul]

I would not  depend  on  solder joint to hold mechanically,

It is only for electrical conduction.
 the conductors need to be fixed  independent  of the solder.

Eutectic has least crystalizaton and lowest MP.

63 /37 Tin/Lead.

j

[johansen]

Stay brite 8 has a tensile of 15,000 psi. Its just silver and tin.

[coppercone2]

Do you think the nickel might make it tougher or more resistant to creep with bridgit? Because nickel is tough as hell compared to tin and silver.  But they do say nickel is ductile.

Or the antimony. Antimony is hard and brittle. Does this bring down creep in an alloy? Can you make connections like that?

[T3sl4co1l]

Stay brite 8 has a tensile of 15,000 psi. Its just silver and tin.

Citation needed.

Horse mouth says 10.6 KSI,
https://ch-delivery.lincolnelectric.com/api/public/content/e521e75f45b741e58940da1988c2976d?v=a156575a
but again I'm dubious about method or how it's actually measured (no standard cited, and not that ASTM standards are generally publicly available anyway).

Indium Corp seems to suggest closer to 7,
https://www.matweb.com/search/DataSheet.aspx?MatGUID=19662ece2a4a4bb2bbe7aa522f916185
though the alloy is slightly different, but again, no mention of method.

Do you think the nickel might make it tougher or more resistant to creep with bridgit? Because nickel is tough as hell compared to tin and silver.  But they do say nickel is ductile.

Or the antimony. Antimony is hard and brittle. Does this bring down creep in an alloy? Can you make connections like that?

There's hardly any in it.  It's most likely present as a dispersion of microscopic particles.  These will frustrate slippage planes as any other hard inclusion, but in such small amount, mostly the solder will still slip around itself I think.  Think of forming pure clay, vs. forming clay with a few percent of coarse gravel in it, or marbles.  That's an imperfect analogy, because crystals have preferred slippage planes, whereas bulk clay is randomized (clay itself is lamellar, but only retains that grain when formed or deposited appropriately.)   Let's see... Ni3Sn4 seems to be the relevant intermetallic.  Very low solubility.  The other thing is it may act as a nucleation site for Sn grain growth, leading to finer crystal size, more grain boundaries, less weakness due to them; but this is a minor contribution I think.  The stuff like precipitation hardening in that other paper I found would do well, though still ultimately limited by strength of the matrix, and creepage mechanisms give or take.  I'd need to see more and better papers to have some idea what that ultimate strength might be.

Tim

[coppercone2]

The problem with hardly anything in alloys is that there are alloys that benefit from hardly anything. I.e. superalloys have ingredients added by 0.05%. They even have germanium doped solder for some reason... they call it doped. There is some PDF about it but I don't really understand much there, it looks like adding very small amounts of nickel halfs some problem parameter and then doping amount of germanium half it again.

I got the quartz crucible so I can try to make some of this stuff and test it. Easy enough to hang it on near overload with some weights. If I get around to it in the next 10 years

that is too much for me to understand with boundaries.

the expensive part appears to be the rolling machine for making wire. All the elements are pretty cheap apart from silver and gold. The machine looks like a 500 dollar investment at least But you can make square solder using a butchers knife and a body hammer I think

[Berni]

Regular leaded electronics solder might not be very strong compared to welding, but it can still hold a lot of force. Go ahead and solder two wires together and then try to pull them apart and see for yourself how strong solder can be.

Whatever bracket you are trying to solder on, just design the bracket in a way that it has a lot of surface area for the solder to flow between and grip onto. While you could improve strength by using stronger solder, you could easily make the existing solder hold 4x more force by simply giving it 4x more surface area to grab onto. That is likely a larger improvement than you would get from using some exotic low temperature solder.

[coppercone2]

its a heat exchanger so I need to be reasonable

[coppercone2]

https://link.springer.com/article/10.1007/s10854-023-10704-3

i wonder what else you can add

https://patents.google.com/patent/US4588657A/en
calcium

https://www.harrisproductsgroup.com/en/Products/hpg-na-sterling



selenium

[Coordonnée_chromatique]

Hello,
Consider the mechanical "strongness" of a metal by its tensile strength is like considering the power ability of a transistor by its case size only.