Nickel in solder alloy can protect UBM (under bump metallization) layer from dissolution. Indium alloys are expensive and prone to corrosion. Indium lower the melting point, improves ductility, and is used for soldering to gold or for cryogenic applications due to its high resistance to temperature swings. Inhibits growth of tin whiskers.Ĭopper lowers the melting point and improves wetting properties in the molten state. Here are just a handful of examples of alloy additives and what they do:Īntimony increases mechanical strength without reducing wettability while preventing tin pest.īismuth significantly lowers the melting point and improves wettability. To complicate matters further, there are also additives and other metals that may be added to give solder certain properties or enhance its conductivity. Remember the three main materials found in solder: lead, tin, and flux? There are countless varieties of solder available on the market based on the relative ratios of these materials. Acid cores are for metal mending and plumbing, and should not be used on electronics. It also improves the wetting properties of the solder. The flux is released during soldering and reduces (reverses oxidation of) metal at the point of contact to give you a cleaner electrical connection. Lead free solders generally have a higher melting point than conventional solder.įlux core solder is sold as a spool of “wire” with a reducing agent at the core. Tin whiskers can be mitigated by using newer annealing techniques, incorporating additives such as nickel, and using conformal coatings. In the US, manufacturers could receive tax benefits for using lead-free solders. Lead free solder started taking off when the EU started restricting the inclusion of lead in consumer electronics. The higher the tin concentration, the better the tensile and shear strengths. Known colloquially as soft solder, tin is selected for its lower melting point while lead is used to inhibit the growth of tin whiskers. The most common mixture is a 60/40 (tin/lead) blend with a melting point around 180-190☌. Lead based solder was what kicked of the electronics revolution. Fortunately, there are really only three main categories of solder which you can use to narrow down your search: There are so many different kinds of solder available on the market today that it can be daunting picking the right one for your project. The idea of using a lower melting point alloy to bond two or more metals has been around for thousands of years, but today’s solder is typically a blend of tin, lead, and/or flux. low melting point) used to bond metal workpieces together. Solder hails from the middle english word soudur, which derives from the latin word solidare, meaning “to make solid.” It’s a fusible alloy (i.e. Not sure which solder to use for your project? In this post we’ll look at the different types of solder that are out there and how you can choose the right solder for your needs. It’s hard to imagine what modern electronics would be like without this convenient, low-melting point alloy at our disposal. It serves as the conductive glue that sticks components to substrate and brings continuity to the circuit board. Solder on a PCB can be thought of as connective tissue.
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