# Solderability

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{{Short description|Metalworking measure}}
The '''solderability''' of a substrate is a measure of the ease with which a [solder](/source/solder)ed joint can be made to that material. Good solderability requires [wetting](/source/wetting) (low contact angle) of the substrate by the solder.<ref>[http://www.tutorialsweb.com/smt/chapter4d.htm#4.5 Solders, fluxes, and solderability] Section 5: Solderability , ''www.tutorialsweb.com''</ref>

__TOC__
==Of metals==

Solderability varies depending on the type of solder alloy under discussion. The discussion that follows applies only to unspecified electronic solders<ref name="efunda"/> (which may include solders that contain [lead](/source/lead), now banned for use in nearly all electronic equipment made or sold in the [EU](/source/European_Union)). Solderability when using lead-free alloys can differ significantly from solderability when using lead based alloys.

[Noble metal](/source/Noble_metal)s may be easy to solder but they have [brittle](/source/brittle) joints. The metals in the good category require a large amount of heat therefore oxidation is an issue. To overcome this a [flux](/source/flux_(metallurgy)) is required. For [carbon steel](/source/carbon_steel), [low alloy steel](/source/low_alloy_steel), [zinc](/source/zinc), and [nickel](/source/nickel) the presence of [sulfur](/source/sulfur) creates a brittle joint; lower temperatures are used to minimize this problem. The oxides on the surface of [aluminium](/source/aluminium) cause wetting issues and special solders must be used to prevent [galvanic corrosion](/source/galvanic_corrosion) issues. [Stainless steel](/source/Stainless_steel) and [high alloy steel](/source/high_alloy_steel) have a low solderability because the [chromium](/source/chromium) alloying element creates [oxide](/source/oxide)s that require aggressive fluxes. The only way that the final category of metals can be soldered is by pre-[plating](/source/plating) them in a metal that is solderable.<ref name="efunda"/>

In lead‑free assembly, studies of selective soldering have shown that prolonged contact times and elevated solder temperatures can accelerate copper dissolution from pads and nozzles, gradually reducing the available solderable surface and impairing wetting and joint reliability.<ref>{{cite web |title=Apollo Seiko Copper Erosion Study
 |url=https://dklmetals.co.uk/wp-content/uploads/2025/12/Apollo-Seiko-Copper-Erosion-Study.pdf |website=DKL Metals |access-date=December 16, 2025}}</ref>

{| class="wikitable" align="center"
|+Solderability of various metals<ref name="efunda">{{Citation | title = Solderability | url = http://www.efunda.com/materials/solders/solderability.cfm | accessdate = 2009-11-30 | postscript =.}}</ref>
|-
! Solderability !!&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Metal&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;!! Remarks
|-
| Excellent || [Tin](/source/Tin)<br />[Cadmium](/source/Cadmium)<br />[Gold](/source/Gold)<br />[Silver](/source/Silver)<br />[Palladium](/source/Palladium)<br />[Rhodium](/source/Rhodium) || Noble metals dissolve easily in solders, resulting in brittle joints.
|-
| Good || [Copper](/source/Copper)<br />[Bronze](/source/Bronze)<br />[Brass](/source/Brass)<br />[Lead](/source/Lead)<br />[Nickel silver](/source/Nickel_silver)<br />[Beryllium copper](/source/Beryllium_copper) || High [thermal conductivity](/source/thermal_conductivity) of these metals requires high heat input during soldering. Oxidizes quickly so proper flux must be used.
|-
| Fair || [Carbon steel](/source/Carbon_steel)<br />[Low alloy steel](/source/Low_alloy_steel)<br />[Zinc](/source/Zinc)<br />[Nickel](/source/Nickel) || Solder joints become brittle in sulfur-rich environments. Avoid higher temperatures in the presence of lubricants (which contain sulfur).
|-
| Poor || [Aluminium](/source/Aluminium)<br />[Aluminium bronze](/source/Aluminium_bronze) || Tough oxides on the surface prevent wetting (formation of the inter-metallic layers). Solders have to be specially selected to avoid galvanic corrosion problems. Tin-zinc solders have proven to be reliable in joining aluminum to aluminum and aluminum to copper.<ref name=KappAloy9>{{cite web|author=Kapp Alloy|title=KappAloy|url=http://www.kappalloy.com/tin-zinc-solder.php|publisher=Kapp Alloy & Wire, Inc.|accessdate=23 October 2012}}</ref> They most often require flux and brushing with a stainless steel brush to break oxide coating to achieve proper bond. 
|-
| Difficult || [High alloy steel](/source/High_alloy_steel)<br />[Stainless steel](/source/Stainless_steel)s || Too much chromium oxide. The surface needs to be cleaned with an aggressive flux.
|-
| Very Difficult || [Cast iron](/source/Cast_iron)<br />[Chromium](/source/Chromium)<br />[Titanium](/source/Titanium)<br />[Tantalum](/source/Tantalum)<br />[Magnesium](/source/Magnesium) || May require pre-plating, or pre-tinning,<ref name=KappaTinnning>{{cite web|last=Kapp Alloy|title=Kappa Tinning Compound|url=http://www.kappalloy.com/babbitt-tinning.php|publisher=Kapp Alloy & Wire, Inc|accessdate=4 April 2013}}</ref> with a solderable metal or will require the use of a specialized solder.<ref name="Kapp GalvRepair">{{cite web|author=Kapp Alloy GalvRepair|title=Kapp GalvRepair|url=http://www.kappalloy.com/tin-zinc-lead-solder.php|publisher=Kapp Alloy & Wire, Inc.|accessdate=23 October 2012}}</ref> 
|}

==Testing solderability==
Both [quantitative](/source/Quantitative_data) and [qualitative](/source/qualitative_data) tests for solderability exist.<ref>[https://web.archive.org/web/20160428230130/http://eesemi.com/solderability-test.htm Solderability Testing] ''www.eesemi.com''</ref>
The two most common testing methods are the 'dip and look' method and '''wetting balance analysis'''. In both of these tests, the soldered pieces undergo an [accelerated aging](/source/accelerated_aging) process before being tested for solderability, to take into consideration the time a component was in storage prior to mounting to final assembly. The dip and look method is a qualitative test. One form of it is specified as Mil-Std-883 Method 2003. On the other hand, the wetting balance analysis is a quantitative test that measures the wetting forces between molten solder and the test surface as a function of time.

==References==
{{Reflist}}

Category:Soldering

{{Metalworking-stub}}

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Adapted from the Wikipedia article [Solderability](https://en.wikipedia.org/wiki/Solderability) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Solderability?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.