King Sun PCB

Electric soldering iron is the most common welding tool used by electronic engineers.Good at use of electric irons will save us a lot of time. This article will detail the use of electric soldering irons through preparation, welding and soldering techniques, and, of course, key welding techniques.

(I) The preparatory work

1. Use finesand paper to polish the iron head and heat the electricity before using the new iron, After dipping the rosin, contact the solder wire with the head edge of the soldering iron to make the iron head evenly coated with tin.In this way, it is easy to weld and prevent the surface of the iron head from oxidation. If the old iron head is blackened by severe oxidation, the steel can be depressed and removed to the surface oxide, so that it can be plated again after being exposed to the metallic luster.

Electric iron to use 220V AC power, user should pay special attention to safety. The following should be conscientiously done:

• Plug the electric iron preferably with a three pole plug. Make sure the casing is properly earthed.
• Before use, should carefully check the power plug, power cord damage. And check if the iron head is loose.
• The electric iron can not be struck with force. To prevent falling. When the soldering iron is too long, wipe it with cloth. Don’t throw it away in case it burns others.
• In the process of welding, soldering iron can not be everywhere. When stopsoldering, it should be placed on the iron rack. Note that the power cord can not be attached to the iron head, in order to prevent burning insulation and accidents.
• Should promptly cut off the powerafter using, unplug the power plug,then return the electric iron to the tool box after cooling.

2. Soldering and soldering flux

Soldering and soldering fluxes are needed for soldering

• Soldering: welding electronic components, usually using rosin cored solder wire. The solder wire has lower melting point and contains rosin flux and is extremely convenient to use.
• Flux: the commonly used flux is rosin or mineral spirits (rosin soluble in alcohol). The use of flux can help remove the metal surface oxides, easy for welding, and can protect the iron head. Solder paste can also be used for welding larger components or wires. But it is corrosive, and should be removed in time after welding.

3. Auxiliary tools

In order to facilitate the welding operation often used pliers, tweezers and partial knife as auxiliary tool. Proper use of these tools should be learned

(II) Prewelding treatment

Before welding, Should take pre-treatment for the component pins or circuit boards.

1. Remove the oxide layer on the weld:

A knife can be made of broken saw blades. Scrape off the oxide layer on the surface of the metal lead so that the pin is exposed to metallic luster.

Use spinning paper polish the copper foil of printed circuit board and coated with a layer of rosin alcohol solution.

2. Components tin

Tin plated on a scraped lead wire. After the wire is dipped in the rosin alcohol solution, the hot iron tip with tin is pressed on the lead and the lead is turned. A thin layer of tin can be uniformly plated on the leads. Before the wire is welded, the insulating skin should be stripped off, and then treated by the above two items before welding. If multiple strands of wire wire, after polishing should be screwed together, and then tin.

A layer of tin is uniformly coated on the scraped oxide layer.

(III) Welding technology

After welding is done, the welding can be carried out formally.

1 . Welding method

Welding,checking, short cut

• Right hand holding electric iron. The left hand use pliers or forceps clamping elements or wire. Before soldering, the electric iron should be fully preheated. Soldering tin on the edge of the iron head, with a certain amount of solder.
• Press the edge of iron head on the spot. The electric iron is approximately 60 degrees from the horizontal plane facilitate tin is melted flows to solder joint from iron head,the time that the soldering iron stays at the solder joint is controlled for 2~3 seconds.
• Lift the soldering iron head. Left hand still holds the component,loosen hand till the tin at the solder joint cooled and solidified.
• Turn the lead with tweezers, make sure it is not loose, then cut out the excess lead with a side pliers.

2. Welding quality

• When welding, make sure that each solder joint is well welded and in good contact. Welding quality must be guaranteed.
• Good solder joints should be bright tin points, smooth without burrs and moderate tin. Tin and welded joints are fused firmly. There should be no missing welding and false welding.
• Missing welding means only a small amount of solder joints, causing poor connection, on and off working. Fake welding means that the surface is soldered, but it is not soldered. Sometimes the wire can be drawn out of the solder joint by hand. These two situations will bring great difficulties to the debugging and maintenance of electronic manufacture. Only through a large number of serious welding practice can we avoid these two situations.
• When soldering a circuit board, be sure to control the time. Too long, the circuit board will be burned or cause copper foil to fall off. When the component is removed from the circuit board, the electric iron head is attached to the solder joint and the component is drawn out after the tin on the solder joint is melted.
• When welding flux (rosin and soldering paste is the key, fresh rosin) and non corrosive solder oil can help you complete a good welding, and can make the surface smooth beautiful, you can use a little more flux.

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