(Rhymes with Doddering) Soldering! (Rhymes with Doddering) S.R.Norr, UMD

Definition: Soldering A process in which two or more items (usually metal) are joined together by melting and putting a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. The intent is to create a strong MECHANICAL joint In electrical soldering, electrical conductivity of the joint is equally important

Composition of Electrical Solder Lead is great! But Lead is also BAD (poisonous)! 60/40 Solder, comprised of 60% Tin and 40% Lead, is a great general purpose solder 63/37 Solder is eutectic, having a sharp phase transition from liquid to solid Different alloys have different melting points and different mechanical strength Under the RoHS Directive (Restriction of Hazardous Substances), Lead is banned from modern electronics Most lead-free solders are SAC – Tin, Silver and Copper alloys Avoid using Lead alloys with components that are silver coated Flux Core (Rosin Core or Acid) – Many solders have flux inside the wire, to improve adhesion to the joint by chemically cleaning the surfaces

The Rules of Soldering The first Rule of Soldering club is, “Don’t talk about.. NO. The first Rule of Soldering is, “Keep your Tip Clean!” Clean the soldering tip by washing it in solder, then dabbing it on a wet sponge or brass shavings This serves two purposes: It minimizes contamination in the solder joints (carbon, etc) It prevents the tip from oxidizing (IMPORTANT) The second Rule is that solder flows toward heat. Get your parts hot with the tip, then bring your solder into the heat. If your parts aren’t hot enough before the solder arrives, you’ll get poor adhesion.

General Rules of Thumb 1. Less is more – Use just enough solder to cover the joint. You’ll notice that excessive solder will “bead up”. The correct amount will tend to lay flat. 2. Pay attention to mechanical strength – Don’t expect solder to be the primary mechanical fastener for parts that receive a lot of wear and tear 3. Most soldering is very quick, a few seconds to heat up a joint and apply the solder. If you have a lot of connections on a single part, it will get hot. Try to alternate the locations on the part and/or take a break to let things cool down. Consider a heat sink on the part to delay the temperature rise.

Soldering Temperature Temperature is important You must have a temperature high enough to get your parts hot enough to attract solder You want to avoid temperatures higher than necessary to protect your parts and reduce oxidation of the solder and your tip A general purpose temperature is 350 Celsius (660 F)

Soldering Irons: 15 Watt Pencil 70 Watt Station

The TIP: “B” Series – general purpose, Needle tip – Fine work, chisel tip – Parts Removal

Joining Two Wires: The Western Union Splice: Then tin it with solder Then cover with heat shrink electronics.stackexchange.com

Soldering Through-Hole Components: electronics.stackexchange.com angelfire.com dansdata.com

De-Soldering – A Nasty Business Solder Suckers Wicking Braid pakronics.com.au starwarsbulgaria.com

Surface Mount Components Soldering of surface-mount parts is usually performed with automation Soldering paste is applied to a printed circuit board, usually using a stencil or screen printing Parts are placed on their proper pads (covered now with paste) with a “pick and place” robot The board is inserted into a Re-Flow Oven and baked to make the solder paste liquify and adhere to the parts and board