How to do it : Soldering Tips & Tricks


Soldering is done in electronics constructions to join the components with the tracks of the PCB. The working performance of the circuit depends on the accuracy and perfection in the soldering. It is an art to make a good circuit. Soldering requires skill and practicing the good soldering methods will help you to make a good working circuit. Here explain the methods of good soldering. Soldering requires Soldering Iron, Soldering Lead and Flux along with a PCB and component layout diagram.

Selection of Good Soldering Iron:

Soldering Iron
Soldering Iron

Selection of the Soldering Iron is very important. Soldering Iron is the electric device that heats the solder lead and makes the joint. Many types of soldering irons are available, so select one with 15-25 watts. If the wattage of the Iron is too high, it may destroy the heat-sensitive components or causes detachment of PCB tracks. Choose the Iron with a 3 pin cord. The earth connection is important to remove the stray current that accumulates in the iron tip. This is very important while soldering static-sensitive components like CMOS ICs and MOSFETs.

Use the Better Soldering Wire:

Soldering Lead
Soldering Lead

Solder lead joins the component leads with the PCB contacts firmly. The quality of the solder lead should be good enough to, make the soldering process perfect. Rosin core solder is a good choice. Do not use the Acid core solder used to solder electrical contacts and plumbing metal joints since the acid content will corrode the copper tracks of the PCB. Good solder contains 60% Tin and 40% Lead. Solder with 0.75 to 1mm diameter is good. Some makes of solder contain a core of flux inside.

Use Little Soldering Flux

Soldering Flux
Soldering Flux

Soldering flux is usually applied to the solder joints before soldering. The flux reduces the melting point of the lead so that the solder lead will melt easily and spread uniformly on the solder joint. Liquid type flux is better since it will not leave dirt after soldering. Fumes from the flux are toxic so do the soldering work in a well-ventilated place and use an exhaust fan in the room.

A well-maintained Tip can make the soldering easy

Dry Joint



Good soldering requires a clean soldering iron tip. If the soldering Iron is a newly purchased one, first apply a layer of lead before starting the soldering. This is called Tinning which will helps to transfer heat easily. After prolonged use, the tip will become dirty which will make the soldering process difficult. So before starting the soldering, clean the tip using a File or Sandpaper and make it glowing. After cleaning, wipe the tip with moist cotton or sponge. Since the soldering process is intermittent, keep the soldering iron tip on a heat sink. An old porcelain fuse carrier can be used for this or purchase one soldering iron stand with a heat sink.

Watch the following video to get good practical Knowledge on soldering Process:



Top Tips in Soldering Process:

The following tips will help you to practice good soldering methods:

  1. First, clean the PCB joints well using a blade or knife to remove dirt and corroded materials. If the joint is dirty, the solder joints will be loose.
  2. Clean the leads of components before placing them on the PCB.
  3. The leads will project out from the copper track side of PCB. Place resistors slightly projecting from the surface of PCB to dissipate heat.
  4. First solder resistors, then capacitors, diodes, etc and finally transistors and ICs.
  5. Apply very little flux in the solder joints and make the soldering. The soldering lead and the iron tip should be at an angle of 45 degrees so as the make the solder flow easily.
  6. Do not keep the soldering iron tip more than 3 seconds on the soldering joint when soldering CMOS components.
  7. After soldering, check the solder joints carefully. Use a hand lens if needed. The joints should be conical, uniform, and shiny.
  8. If the solder joint is Dry, that will considerably affect the working of the circuit. So double-check all the joints and re-solder if necessary.
  9. Cold solder is the term used to describe the solder joints without firm connection. The cold solder will appear as a ball over the solder joint. So if it appears to remove the excess solder with the hot iron tip.
  10. Trim the excess leads of the components with a Trimmer.
  11. If static sensitive components are used, touch the soldering iron tip to a metal object before soldering to remove the static charge accumulated at the tip.
  12. Wires should be soldered firmly to prevent loose contact. Before soldering the wires, clean the bare wire with a blade to remove rust or dirt. Apply some solder to the wire tip and make the soldering.
  13. After completing the soldering, double-check the joints for any shorting of leads. This is essential for the transistors and ICs.
  14. Clean the solder side of PCB using Spirit or PCB cleaning solution.
  15. After connecting the power supply, just touch on the components. If heat develops, disconnect the power supply immediately and check for any shorting.
  16. If AC is used in the PCB, do not touch any points when connected to mains.
  17. As a safety measure, wear rubble footwear during soldering. It is better to use a plastic sheet on the floor so that the foot will rest on the insulated sheet while soldering.

Soldering Safety tips:

Soldering is an essential part of circuit construction. Soldering is the process by which two metal parts are joined together using a metal alloy. The metal alloy used in soldering is the mixture of lead and tin. To make the solder evenly spread over the joints, soldering flux is applied which removes the oxidation remnants in the metal joints and makes the contact form. The flux also reduces the melting point of lead for easy melting. The soldering process requires proper care to avoid hazardous situations. The following are some possible hazards during soldering and the tips to avoid them.

Shock hazard

Soldering iron is an AC device used for heating the iron tip. There is a heating element in the iron which heat up when current passes. To connect the soldering iron, a three-pin socket with proper earth connection is a must. Check the metal part of the iron using an AC tester for any leakage before using it. Also periodically check the plug, cord, etc for any insulation break. Always wear rubber footwear during the soldering work. It is better to place a rubber sheet on the floor of the workroom so that the feet will rest on it during the work.

Skin Burning

Soldering iron becomes too hot when it is connected to mains. Avoid touching it with the body parts to prevent burning. The molten lead also causes burning injury. It is better to wear a spectacle during soldering to protect the eyes because sometimes the solder bubble may explode and there is a chance for falling into the eyes.

Health Hazards

The lead and the flux used for soldering contain toxic materials that will come out in the form of fumes and gases. When heated, the soldering lead will emit lead oxide which is highly toxic if inhaled in excess. Once entered into the body, it will be absorbed through the mucous membrane of lungs, stomach and then enters into the bloodstream. Symptoms of lead poisoning include loss of appetite, indigestion, nausea, vomiting, constipation, headache, abdominal cramps, nervousness, insomnia, etc.

Soldering Lead
Soldering Lead

Flux is the cleaning agent used in conjunction with the solder to remove the oxidation from the metal joints. It improves the overall flow and effectiveness of the solder. The commonly used flux is the Rosin based flux. It is made from the extracts of pine tree sap. Colophony is the base product of flux. It is translucent amber-colored rosin obtained when turpentine is distilled from pine trees. It is composed of 90% resin acid and 10% neutral material. When flux is heated, the colophony generates fumes that contain aliphatic aldehydes like Formaldehyde. It also emits gases containing benzene, toluene, phenol, isopropyl alcohol, etc. Inhalation of flux fumes causes short term problems like nose, sinus, eyes and throat irritation, skin rashes, and long term problems like asthma and dermatitis.

Soldering Flux
Soldering Flux

To avoid the health hazards from the toxic fumes, it is advisable to do the soldering work in a well-ventilated area preferably with a fan. It is also better to install an exhaust fan in the room. If a local exhaust system (a small exhaust fan fitted in the work table) is properly designed, it will capture and control lead particles at or near the source of generation.