Soldering technology points
As an operating technology, manual soldering is mainly through practical training to master, but follow the basic principles, learning from the experience accumulated by previous generations, the use of the correct method, you can master the operating technology with half the effort. The following points are essential for learning welding technology.
I. Tin soldering basic conditions
1. solderability
Not all materials can be soldered to achieve the connection, only a part of the metal has a good solderability (strictly speaking should be the nature of the soldering), in order to be connected by tin soldering. General copper and its alloys, gold, silver, zinc, nickel, etc. with good solderability, and aluminum, stainless steel, cast iron, etc. Solderability is very poor, a
Generally need to use special fluxes and methods to solder.
2. qualified solder
Lead and tin solder composition substandard or impurities exceeding the standard will affect the quality of solder, especially some of the impurity content, such as zinc, aluminum, cadmium, etc., even if it is 0.001% of the content will also significantly affect the solder wettability and mobility, reducing the quality of welding. And then the smart chef can not use poor-quality raw materials processed out of delicious food, the reason is obvious.
3. flux appropriate
Welding different materials to choose different flux, even if it is the same material, when the welding process is different at the same time often use different flux, such as manual soldering iron welding and dip soldering, post-soldering cleaning and no cleaning will need to use different flux. For manual soldering, the use of rosin and active rosin can meet most of the electronic product assembly requirements. It should also be pointed out that the amount of flux must also pay attention to, too much, too little are not conducive to soldering.
4. reasonable solder joint design
Reasonable solder joint geometry, to ensure the quality of soldering is critical, such as Figure I (a) shown in the joint due to the limited strength of lead-tin material, it is difficult to ensure that the solder joints enough strength, and Figure I (b) of the connector design is a great improvement. Figure 2 shows the printed circuit board through-hole mounting component leads and hole size is different when the impact on the quality of soldering.
II. Manual soldering points
The following points are derived from the soldering mechanism and practical experience has proved to be universally applicable.
1. Mastery of the heating time
Tin soldering can be used at different heating speeds, such as the poor shape of the iron head, with a small iron soldering large soldering we have to extend the time in order to meet the requirements of the tin temperature. In most cases, extended heating time is harmful to electronics assembly because
(1) the bonding layer of the solder joints exceeds the proper thickness due to prolonged heating, causing deterioration of the solder joints.
(2) Printed boards, plastics and other materials will be deformed and deteriorated by too much heat.
(3) Components heat performance changes or even failure.
(4) The surface of the solder joints due to flux evaporation, loss of protection and oxidation.
Conclusion: In order to ensure that the premise of the solder wetting solder the shorter the better.
2. Maintain the appropriate temperature
If in order to shorten the heating time and the use of high-temperature soldering iron soldering school soldering point, it will bring about the other side of the problem: solder wire in the flux does not have enough time
in the soldering surface of the roaming and premature volatilization and failure; the solder melting speed is too fast to affect the play of the role of the flux; due to the temperature is too high, although the heating time is also short, resulting in the phenomenon of overheating.
Conclusion
Conclusion: Keep the soldering iron tip in a reasonable temperature range. General experience is that the soldering iron head temperature is higher than the solder melting temperature of 50 ℃ is more appropriate.
The ideal state is a lower temperature to shorten the heating time, although this is contradictory, but in practice we can get a satisfactory solution through the operation of the maneuver.
3. The soldering iron tip on the soldering point of force is harmful
Soldering iron tip to the heat transfer to the soldering point mainly by increasing the contact area, the soldering iron on the soldering point of force on the heating is futile. Many cases will cause damage to the soldered parts, such as potentiometers, switches, connectors are often fixed in the plastic components of the soldering point, the result of the force is easy to cause the failure of the original.
Three. Tin soldering operation essentials
1. soldering surface treatment
Manual soldering iron welding encountered in the soldering is a variety of electronic parts and wires, unless in the scale of production conditions, the use of "insurance period" within the electronic components, generally encountered in the soldering often need to carry out the surface cleanup work to remove the soldering surface of rust, oil and grease on the surface. Surface rust, oil, dust and other impurities that affect the quality of welding. Manual operation of the commonly used mechanical scraping and alcohol, acetone scrubbing and other simple and easy methods.
2. Pre-soldering
Pre-soldering is to be soldered component leads or conductive soldering parts pre-wetted with solder, generally also known as tin, tin, tin-lined and so on. Called pre-soldering is accurate, because the process of its mechanism is the whole process of tin soldering - solder to wet the surface of the soldered parts, by the diffusion of the metal to form a bonding layer after the surface of the soldered parts and make the solder "plated" on a layer of solder.
Pre-soldering is not an indispensable operation of tin soldering, but the manual soldering iron welding, especially maintenance, debugging, research and development work can almost be said to be essential.
3. Do not use too much flux
The right amount of flux is indispensable, but do not think that the more the better. Excessive rosin not only caused by the workload around the solder joints need to be cleaned after welding, and extend the heating time (rosin melting, volatilization needs and take away the heat), reducing efficiency; and when the heating time is not enough time and easy to clip to the solder in the formation of "slag" defects; the welding of switching components, excessive flux is easy to flow into the contacts, thus causing poor contact. This will result in poor contact.
The appropriate amount of solder should be the amount of rosin that can only wet the solder joints that will be formed, do not let the rosin flow through the printed circuit board to the component surface or socket holes (such as IC sockets). For soldering wires with rosin core, there is basically no need to reapply solder flux.
4. Keep the soldering iron head clean
Because the soldering iron head when soldering is in a high temperature state for a long time, and contact with flux and other heat-decomposed substances, its surface is easy to oxidize and the formation of a layer of black impurities, these impurities are almost the formation of insulation, so that the head of the iron to lose the role of heating. Therefore, it is necessary to rub the impurities on the soldering iron stand at any time. With a wet cloth or wet sponge at any time to wipe the iron head, is also a common method.
5. Heating to rely on the soldering bridge
Non-assembly line operation, the shape of a welded soldering point to make a variety of different, we can not constantly change the iron head. To improve the efficiency of the iron tip heating, the need to form a heat transfer solder bridge. The so-called solder bridge, is to rely on the soldering iron to retain a small amount of solder as a bridge for heat transfer between the soldering iron head and the soldered parts when heated.
Obviously due to the thermal conductivity of the liquid metal is much higher than the air, so that the weldment is quickly heated to the soldering temperature, such as Figure IV. It should be noted that as a bridge of solder tin retention must not be too much.
6. The amount of solder to be appropriate
Excessive solder not only unnecessarily consume the more expensive tin, but also increase the soldering time, and correspondingly reduce the speed of work. More seriously, in high-density circuits, excessive tin can easily cause an undetectable short circuit.
But too little solder can not form a strong bond, reducing the strength of the solder joints, especially when welding wires on the board, the lack of solder often results in the wire off.
7. solder to solid
Don't move or vibrate the solder before the solidification of the solder, especially the use of tweezers to hold the solder must wait for the solidification of the solder and then remove the tweezers. This is because the solder solidification process is the crystallization process, according to the crystallization theory, during the crystallization of external forces (welding pieces moving) will change the crystallization conditions, resulting in coarse crystals, resulting in the so-called "cold welding". The appearance of the phenomenon is the surface of the luster of the dregs; solder joints within the structure of the loose, easy to have air gaps and cracks, resulting in a reduction in the strength of the solder joints, poor electrical conductivity. Therefore, before the solidification of the solder must be to keep the weldment stationary, the actual operation can be used in a variety of suitable methods to fix the weldment, or the use of reliable clamping measures.
8. Iron withdrawal has to pay attention to
Soldering iron handling in a timely manner, and withdrawal of the angle and direction of the formation of the solder joints have a certain relationship.
Withdrawal of the soldering iron gently rotated, can keep the solder joints appropriate solder, which needs to be experienced in the actual operation.
Solder
① Flux
Flux can be generally divided into inorganic flux, organic flux and resin flux, can dissolve the oxides on the surface of the metal, and in the soldering and heating the surface of the metal surrounded by the metal, so that it is isolated from the air, to prevent oxidation of the metal when heated; can reduce the surface tension of the molten solder, which is conducive to the soldering of the wetting.
② Solder Resist
Restriction of solder only in the need for soldering joints, the printed circuit board does not need to be welded to the board partially covered, to protect the panel so that it is welded by the thermal shock is small, not easy to blistering, but also play a role in preventing bridging, pulling the tip of the short-circuit, false soldering and other situations.
The use of flux, must be welded according to the size of the area and the surface of the state of the appropriate amount of application, the dosage is too small to affect the quality of welding, the dosage is too much, the flux residue will corrode the components or make the circuit board insulation performance deterioration.
The basic requirements of the welding point
1, the welding point should have sufficient mechanical strength to ensure that the welded parts in the vibration or impact will not fall off, loose. Can not use too much solder buildup, which is likely to cause false soldering, solder joints and solder joints short circuit.
2, reliable welding, good conductivity, must prevent soldering. Virtual welding refers to the solder and the surface of the welded part does not form an alloy structure. Simply attached to the surface of the welded metal.
3, the surface of the solder joints should be smooth, clean, the surface of the solder joints should have a good luster, there should be no burrs, voids, no dirt, especially the harmful residues of the flux, to choose the right solder and flux.
Basic operation of manual soldering
" Soldering preparation
Prepare the soldering iron and tweezers, scissors, diagonal pliers, sharp-nosed pliers, solder, solder, flux and other tools, soldering iron and soldering enameled, the left hand holds the solder, the right hand holds the soldering iron, to maintain the state of soldering at any time.
" Use the soldering iron to heat the soldering parts.
" Feed the solder, melt the right amount of solder.
" Remove the solder.
" Quickly remove the soldering iron when the flow of solder covers the solder joint.
Master the temperature and time of soldering. When soldering, there should be enough heat and temperature. If the temperature is too low, the solder mobility is poor, it is easy to solidify, the formation of false soldering; if the temperature is too high, will make the solder flow, the solder joints are not easy to store the tin, the flux decomposition speed accelerated, so that the metal surface to accelerate the oxidation and lead to the pad on the printed circuit board to fall off. Especially in the use of natural rosin as a flux, tin soldering temperature is too high, it is easy to oxidize the skin and produce carbonization, resulting in false soldering.
Aluminum tin soldering method
Aluminum is extremely easy to oxidize, the surface is usually covered with a layer of aluminum oxide film, even if the welding is, scrape off the film, but due to the high temperature of the soldering iron when soldering, so that the welding surface and quickly generate a layer of oxide film, so that scrape out the new surface of the air does not come into contact with the air, then the tin can be made to adhere to the aluminum. The following two methods of tin soldering aluminum parts.
1, first aluminum welding surface with sandpaper light, put some rosin and iron powder. With a power of more than 60W soldering iron, dipped in a sufficient amount of solder, placed on the welding surface rubbing hard. Due to the role of iron powder, the oxidation layer grinding off, tin is attached to the aluminum surface. While the tin is not solidified, use a cloth to wipe away the iron powder on the soldering surface and iron, you can weld according to the ordinary method.
2, in the aluminum wire or aluminum plate to be soldered on the welding surface, coated with a layer of mercury nitrate solution. As a result of chemical action, the aluminum surface to generate a layer of aluminum amalgam, rinse with water can be welded. Just soldered on the tin is welded on the aluminum amalgam, welding strength is not high. Therefore, when welding with 100W soldering iron, soldering iron head more in the welding surface to stay, so that the mercury in the aluminum diffusion, tin can be firmly welded with the aluminum substrate to strengthen the welding strength.
Solder
Solder
Solder
Solder with a lower melting point. Mainly refers to the solder made of tin-based alloys. Melt method ingot, pressure processing into material. Types of solder:
1. Leaded solder: tin (melting point 232 degrees) and lead (melting point 327 degrees) alloy. One of the solder composed of 63% tin and 37% lead is known as *** crystal solder, the melting point of this solder is 183 degrees.
2. Lead-free solder: in order to adapt to the EU environmental requirements put forward by the ROHS standard. Solder is made of tin-copper alloy. The lead content is 1000PPM or less!
Solder can be divided into different ways of use:
1. Wire: the wire solder used in standard soldering operations is called rosin into the solder or wire solder. A flux is added to the solder as shown in Figure ⊙. This flux is composed of rosin and a small amount of active agent.
2. Stick: Solder is melted-molded-finished; it is formed into a rectangular shape of about one kilogram.
Potless solder melting temperature range:
Sn-Cu series Sn-0.75Cu 227℃
Sn-Ag series Sn-3.5Ag 221℃
Sn -Ag-Cu Series Sn-3.5Ag-0.75Cu
Sn-3.0Ag-0.7Cu
Sn -3.0Ag-0.5Cu 217℃～219℃
217℃～219℃
217℃～219℃
Lead-free solder and its problems
①Poor ability to get on the tin
Lead-free solder's solder diffusion is poor, and the diffusion area is
②High melting point
The melting point of lead-free solder is about 34~44 degrees higher than that of general Sn-Pb*** crystal solder, so that the temperature setting of the soldering iron tip should be relatively high.
Solder Melting Point (℃) Soldering Operation Temperature (℃)
(Solder Melting Point +50℃) Soldering Iron Tip Temperature (℃)
(Soldering Operation Temperature +100℃)
Sn-Pb*** Crystals 183 233 333
Sn-0.75Cu 227 277 377
3 ③The soldering iron tip's Shorter life cycle
④Oxidation of soldering iron tip
When using lead-free solder, the surface of the soldering iron tip may be blackened and lose its ability to hold solder, causing the soldering operation to stop.
◆When the temperature of the soldering iron tip is set at 400 degrees
◆When the soldering iron is left energized for a long period of time without soldering operation.
◆It is not cleaned.
When the soldering iron tip is not cleaned, oxidation is more likely to occur.
5. Lead-free soldering points of attention when using
①Temperature management of the iron head is very important
Temperature-regulated soldering iron, according to the use of the solder, choose the most appropriate temperature setting of the iron head is very important.
Before working, it is important to measure the temperature of the soldering iron tip with a tip thermometer.
② Use and manufacturers (such as white tools) supporting the authentic iron head
Counterfeit iron head, aperture (into the heating core) has a large and small, casing the thickness of the differences between these are caused by the performance of the soldering iron can not be played, and sometimes cause the cause of the soldering iron failure.
③ use of heat recovery and other thermal properties of the soldering iron
In the use of lead-free solder for soldering operations, due to the heat resistance of the parts, safety considerations, the soldering iron head setting temperature is generally hoped to be below 350 degrees -370 degrees.
Theory of soldering
Soldering iron
Soldering iron is divided into two types of external heat and internal heat, external heat is generally higher power.
Endothermic soldering iron is smaller and cheaper. General electronic production are used 20W-30W endothermic soldering iron. Of course, there is a 50W externally heated soldering iron can be prepared. Endothermic soldering iron heating efficiency is higher, and replace the iron head is also more convenient.
The soldering iron is used for soldering, and is usually made into "solder wire" for ease of use, which generally contains rosin for fluxing. Soldering wire is synthesized using about 60% tin and 40% lead, and has a low melting point. (Bitbaby has a good habit of washing her hands every time she's done, and while lead is not a good thing, rosin is quite pleasant to smell.)
Rosin is a flux that helps with soldering, and I'm sure people who play the erhu have it, and I've heard that you can buy it at the drugstore. Rosin can be used directly, can also be configured into a rosin solution, that is, the rosin crushed, put into a vial, and then add alcohol to stir. Note that the alcohol is volatile, remember to tighten the cap after use. You can put a small piece of cotton in the bottle, and use tweezers to clip it out and apply it to the printing plate or components when you use it.
Note that there is a solder paste on the market (known as soldering oil), which is a corrosive thing, is used in industry, is not suitable for electronic production use. There are also commercially available rosin, and not the rosin solution we use here. Soldering iron is pinched in the hand, use must pay attention to safety. Newly purchased soldering iron should first use the multimeter resistance file to check the resistance value between the plug and the metal shell, the multimeter pointer should not move. Otherwise it should be checked thoroughly.
Recently produced endothermic soldering iron, manufacturers in order to save costs, the power cord are not used rubber wire, but directly with plastic wires, more unsafe. It is strongly recommended to switch to rubberized floral wire, because it is not as easy to be burned and broken as plastic wires to short-circuit or electric shock!
New soldering iron before use dipped in tin, turn on the power and wait a while the color of the iron head will change, proving that the iron is hot, and then use the solder wire placed on the tip of the soldering iron plated with tin, so that the iron is not easy to be oxidized. In use, should make the soldering iron head to keep clean, and ensure that the tip of the soldering iron always have solder.
When using the soldering iron, the temperature of the iron is too low to melt the solder, or so that the soldering point is not completely melted and the formation of unattractive, unreliable look. Too high a temperature will make the iron "burn" (despite the high temperature, but can not be dipped in tin). In addition to control the soldering time, the soldering iron stays too short a time, the solder is not easy to melt completely, the formation of "false soldering", and soldering time is too long and easy to damage the components, or make the printed circuit board copper foil warping. Every one or two seconds to weld a good spot, if not completed, rather wait a while and then weld again.
Practice the following points over and over again and you will soon become an expert. Step 4 is decisive for the quality of the solder joints.
1. Place the tip of the soldering iron at the pads and component pins to warm up the solder joint.
2. When the solder joint reaches the proper temperature, promptly place the rosin solder wire on the solder joint to melt.
3. Solder melting, the soldering iron should be slightly moved according to the shape of the soldering point, so that the solder evenly covered with soldering points, and penetrate into the gaps in the welded surface. After melting the right amount of solder wire, you should quickly remove the solder wire.
4. Take away the soldering iron, when the soldering point on the solder has been nearly full, flux (rosin) has not been completely evaporated, the temperature is appropriate, the solder is the brightest, the most liquid, the soldering iron head along the direction of the component pins to move quickly, quickly leave, quickly bring back a little while leaving the soldering point, in order to ensure that the soldering point is bright, smooth, no burrs. Use offset pliers to cut off the component pins that are too long, so that the component pins are slightly exposed to the solder joints.
5. Weld a few points with a wire rubbing iron head, so that the iron head clean, clean.
If the head of the soldering iron "gray", can not see the light, hot iron can not be dipped into the tin, is burned "dead", this time available to wash dishes with the wire to the head of the soldering iron to wipe clean, and then use the solder wire plated with tin. Really can not be unplugged, to be cooled iron, with a file or sandpaper bright iron head, plug, dip tin.
Soldering iron
Soldering iron is divided into two types of external heat and internal heat.
Endothermic soldering iron is smaller and cheaper. General electronic production are used 20W-30W endothermic soldering iron. Of course, there is a 50W externally heated soldering iron can be prepared. Endothermic soldering iron heating efficiency is higher, and replace the iron head is more convenient.
External heat type, as the name says, "external heat" means "heat outside", because the heating resistance in the outside of the soldering iron and so named. It is suitable for soldering both large components and small components. Since the heating resistor wire is outside the iron head, most of the heat is emitted to the outside space, so the heating efficiency is low and the heating speed is slow. It generally takes 6 to 7 minutes to preheat before welding. Its volume is large, welding small devices appear to be inconvenient. But it has the advantages of longer use of the soldering iron tip and higher power, with 25W, 30W, 50W, 75W, 100W, 150W, 300W and other specifications. High-power soldering irons are usually externally heated.
Soldering iron is used to solder, for ease of use, usually made of "solder wire", solder wire generally contain flux rosin. Solder wire is synthesized using about 60% tin and 40% lead, and has a low melting point.
The rosin is a flux that helps with soldering, and I'm sure people who play erhu have it, and I've heard that you can buy it at the drugstore. Rosin can be used directly, can also be configured into a rosin solution, that is, the rosin crushed, put into a vial, and then add alcohol and stir. Note that the alcohol is volatile, remember to tighten the cap after use. You can put a small piece of cotton in the bottle, and use tweezers to clip it out and apply it to the printing plate or components.
Note that there is a solder paste on the market (known as soldering oil), which is a corrosive thing, is used in industry, not suitable for electronic production use. There are also commercially available rosin, and not the rosin solution we use here.
The soldering iron is pinched in the hand, the use of millions of attention to safety. Newly purchased soldering iron should first use the multimeter resistance file to check the resistance value between the plug and the metal shell, the multimeter pointer should not move. Otherwise it should be checked thoroughly.
Recently produced endothermic soldering iron, manufacturers in order to save costs, the power cord are not used rubber wire, but directly with plastic wires, more unsafe. It is strongly recommended to switch to rubberized floral wire, because it is not as easy to be burned and broken as plastic wires to short-circuit or electric shock.
New soldering iron in the use of a file before filing the tip of the soldering iron, turn on the power and wait a while after the tip of the soldering iron color will change, proving that the iron is hot, and then use the solder wire placed on the tip of the soldering iron plated with tin, so that the soldering iron is not easy to oxidize. In use, should make the soldering iron head to keep clean, and ensure that the tip of the soldering iron always have solder.
When using the soldering iron, the temperature of the iron is too low to melt the solder, or so that the soldering point is not completely melted and become unattractive, unreliable appearance. Too high and will make the iron "burn" (despite the high temperature, but can not be dipped in tin). In addition to control the welding time, the soldering iron stays too short a time, the solder is not easy to completely melt, good contact, the formation of "soldering", and welding time is too long and easy to damage the components, or make the printed circuit board copper foil warping.
Generally one or two seconds to weld a good spot, if not completed, rather wait a while and then weld again. Soldering iron can not be moved when welding, you should first choose the location of the contact soldering point, and then use the soldering iron tip of the tin-lined surface to contact the soldering point.
Mobile phone repair, often to replace the circuit board components, the need to use the soldering iron, and it is also very high requirements. This is because the components of the cell phone using surface mount process, component size is small, integration is very high, the printed circuit is fine, the pad is small. If the soldering iron is not selected properly, in the welding process is easy to cause man-made failures, such as welding, short circuit or even welded circuit boards, so as far as possible to choose some of the high-grade soldering iron, such as thermostatic temperature control anti-static soldering iron. In addition, some large devices such as shield welding, to use high-power soldering iron, so also prepare a common 60W or more thick head soldering iron.