Solder Simplified We still get calls about what solder to use. The following should help answer any questions, and |¢ show what works best. | Solder is specified E oh J by percentage/weight of alloy in accordance with federal law. The des- ignation 60/40 means 60 percent tin and 40 percent lead. The tin content always precedes that of lead, except in the 95/5 designation. The 95/5 designa- tion may be any one of many alloys and must be carefully marked. Plastic and Liquid Temperatures. Every solder alloy has a different melt (liquid) temperature. Example: 60/40 374 degrees F (see chart, page 9) 40/60 460 degrees F (see chart, page 9) Note: Both start to become soft at 361 degrees F. See chart. Plastic Range. Plastic range is the range of tempera- tures between that which a given alloy first becomes soft and the temperature when it becomes liquid. The chart above is designed to show the plastic range on the right hand side and the melting point on the left hand side. This chart is tin/lead combinations. There are many other combinations of composition using silver, antimony, copper, phosphorus, zinc, and no lead at all. No lead will probably be a necessity in the future due to health a n d safety concerns. Notes: 1. When soldering diodes and reg- ulators you must know the temperature range that the solder in the compo- nents can stand or you will be killing the parts and/or the solder connection inside the part you are connecting to. We suggest contacting your parts sup- plier for this information. 2. For soldering armatures your best bet will be 10/90, possibly with some silver. 3. For rotors at least 40/60. 4. For field leads and brushes 15/85, if you can work with it. It would be bet- ter yet to use a silver solder with approx- imately 15 percent silver with a spot welder or resistance soldering machine. 5. For stators to diodes (using a heat sink to protect the diodes and some- times the regulator), at least 40/60 or a lead free solder composed of 96 percent tin, 4 percent silver or 95 percent tin, 4 percent copper and 5 percent silver. Remember Step 1. 6. Solenoid connections should be the same on Step 5. Keep in mind that the higher the melting point of solder you use, the more heat it will take to make the con- nection and the more important flux becomes. We suggest making sure you can work with the solder before you buy a large quantity. A Word About Flux. Principles at work during soldering require that the surfaces of the materials NN to be joined are cleaned of dirt, oxides, or other contaminants for good solder- ing to take place. One function of a flux is to provide final cleaning by chemical reaction with the metal surface. This attack should be slight but effective. Covering the surface with flux is no substitute for prior cleaning procedures. When heated, the flux is activated, cleans contacted surfaces, and protects the cleaned areas from oxidation during soldering. The solder filler metal is applied when the joint has been heated to the soldering temperature. The surfaces are protected by the activated flux during soldering action. When soldered joints have been cooled, some residual flux may be present that needs to be removed to prevent early joint deterioration. Solder purity is very important, so don’t be swayed by low cost. Richard Vensel is owner of Vensel Enterprises, Crystal Lake, Ill. TIN LEAD ~J oy aS DID KN NN | 0 | 5 | | 10 | | 15 | 20 | | 25 | | 40 | | 45 | | 50 | | 55 | 60 | | 65 | 80 | | 85 | 90 | 95 100