SALT I: Soldering Aluminium at Low Temperatureat

Certain Aluminium alloys can be successfully soldered using low melting solders. Read here how we do it.

I. Challenges and objectives

Joining of Aluminium and its alloys represents a specific challenge due to the presence of the tenacious oxide film at the metal surface. Successful joining of any Aluminium alloy requires a surface modification action, leading to removal of the native surface oxide film, which can be done through mechanical abrasion or chemical etching or photon absorption.

The surface modification action must be capable of displacing the oxide film barrier during joining, stabilization of the obtained surface, prevent the alloy surface from re-oxidizing, and allow the solder metal to flow freely to form the desired joint shape.

Normally in industry Aluminium parts are joined through brazing using near-eutectic AlSi filler at temperatures around 600°C . Various aluminum alloys have different solderability: the 1xxx, 2xxx, 3xxx, 4xxx, and 7xxx series are easier to solder than the 5xxx and 6xxx series alloys. It is the objective of the SALT project to develop a Pb-free joining technology for local soldering aluminium components with a suitable low temperature solder. Low temperature is defined as soldering below 300°C.

II. Technical goals

Local removal of oxides through chemical etching or mechanical abrasion or laser ablation
Stabilisation through working in a protective ambient or under a liquid
Render Aluminium solderable through local modification of the surface of the Al-alloy, e.g. through eless Ni(P) plating or Ni electroplating or an alternative
Local heating through a strongly focused light /laser source
Deposition of the solder through a solder deposition equipment (yet to be defined)

III. Expected impact

Products that can be realized through the new technology, range from the small RF ID tags to large interconnect in light to electricity converting devices
Aluminium is a low cost environmentally compliant metal, fitting well within the circular economy
Aluminium is environmentally stable in the sense that it does corrode over time
Soft soldering below 300°C requires far less energy than brazing at 600°C.

Back-scattered electron image of the Al-substrate/SnBiIn(Ag)-solder interface. The formation of the -phase during soldering procedure is clearly visible.

IV. Author

C. van Veen

Download the pdf file here.


More Posts

Send Us A Message

Post Form
Would you like to know what we can offer you?

Copyright © 2023 Mat-Tech-All Rights Reserved

Mat-Tech B.V.
Ekkersrijt 4302
5692 DH Son
The Netherlands

Mat-Tech B.V. Production
Ekkersrijt 4508
5692 DM Son
The Netherlands

Mat-Tech Joining Technologies LTD
A2, Douglas Park, Stone Business Park
Opal Way, Stone
ST15 0YJ
United Kingdom