【EETALK】Welding competition, come and share your welding training experience~~

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【EETALK】Welding competition, come and share your welding training experience~~ [Copy link]

 

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Engineers working in the electronics industry always need to solder components and boards by themselves. From the first time I picked up a soldering gun, I soldered a bunch of them with shaking hands:

For example, a photo posted by a welding novice in one of our EE technical groups

To the smooth, shiny and tiny welding beads under high efficiency and casualness:

After so many times of practice, the skill is in your hands. So whether you are an experienced master who often solders boards can be seen by looking at the solder joints left.

So, what welding skills can you learn to advance from a novice? And what should you pay attention to?

If you want to do your work well, you must first sharpen your tools. In addition to your own welding skills, good tools can also help. So, what do you recommend for welding guns, flux paste and other items? What kind of welding gun head is more useful, and what kind of flux paste is more useful? Let's share together~~

Finally, let’s start a welding competition~ Friends, come and show off your welding skills! ! ! !

秦天qintian0303

A 936 in hand, a blade, can solve most problems

bitter

The last time I soldered was during a lab class in my sophomore year. After I started working, I always asked a hardware engineer to help me with soldering.

fxyc87

The soldering iron in Figure 2 is too unprofessional, at least the blade is constant temperature.

wangerxian

I think solder paste is very important. Before there was no solder paste, everything was soldered in clumps. Since the advent of solder paste, the soldering becomes more and more beautiful.

zhaoyanhao

wangerxian posted on 2023-7-14 09:07 I think solder paste is very important. Before there was no solder paste, everything was soldered in lumps. Since the advent of solder paste, the more you solder, the more beautiful it becomes~

It is better to use less solder paste, as it always seems to be quite harmful to the body.

wangerxian

zhaoyanhao posted on 2023-7-14 09:22 It is better to use less solder paste, as it always seems to do great harm to the body

Yes, you need to use a fan when using solder paste, otherwise the smell will really affect your body.

maychang

The soldering used in the electronics industry is soft soldering.

Brazing is the opposite of welding.

Fusion welding is the process of melting the workpieces to be welded, and then solidifying them to form a whole. Manual arc welding is a typical fusion welding method.

In brazing, the workpiece does not melt but the solder melts. After the solder melts into liquid state, the solder and the workpiece infiltrate each other, and the solder solidifies to connect the workpieces into one. In the welding of electronic equipment, the copper foil (which may be plated with other metals such as gold and silver) on the circuit board and the pins of the chip do not melt, but the solder melts. After solidification, the workpieces are connected into one, and the chip pins are firmly connected to the copper foil or pads on the circuit board.

maychang

The so-called "wetting" refers to the interaction between liquid and solid surface.

Water can soak clean glass, but not paraffin. Mercury can soak clean copper, silver and other metal surfaces, but not iron. We often see water droplets rolling on the surface of lotus leaves in a nearly spherical shape, which means that water cannot soak the surface of lotus leaves because there is a layer of wax on the surface of lotus leaves.

The molten solder can wet the clean metal surfaces of copper, silver, gold, etc., but it cannot wet the oxidized copper, silver, etc.

"Wetting" was originally taught in high school physics, together with "surface tension". But now it is not taught in high school physics, nor in general university physics. As a result, many people have never known "surface tension" or "wetting".

maychang

We just talked about "wetting", now let's talk about "surface tension".

Liquids always try to shrink their volume to the minimum when they are on a solid surface that cannot be wetted. The water droplets on the surface of a lotus leaf are an example. "Shrinking the volume to the minimum" obviously means that the liquid surface has a tendency to shrink. In other words, the liquid surfaces are "tightened" against each other. The force per unit length of the liquid surfaces pulling against each other is called surface tension.

The surface tension of liquid metal is very large, much greater than that of non-metals such as water, kerosene, alcohol, etc. Therefore, after the solder melts, it always forms small beads on the surface of paper, ceramics, wood, etc.

maychang

However, if the surface of liquid metal is oxidized, the surface tension will be greatly reduced. If you use a soldering iron to melt the solder and keep it for one or two minutes, the solder will oxidize, and the originally very bright solder surface will change from a mirror reflection surface to a diffuse reflection surface (hairy). At the same time, the surface tension will be greatly reduced, and the solder will become flat on the surface of paper, ceramics, wood, etc.

If you add a little flux, such as rosin alcohol solution, solder paste, etc., to the solder surface that is still in a molten state, you will see that the solder surface immediately becomes shiny again, and shrinks from a flat shape to a nearly spherical shape. It can be seen that the flux removes the oxide layer on the solder surface. The solder on the surface of the electric soldering iron tip will also oxidize if it is not used for a few minutes. But as long as the soldering iron tip is immersed in the rosin alcohol solution, the soldering iron tip will immediately become shiny.

maychang

It can be seen that the role of flux is to reduce the oxidized metal surface.

When soldering circuit boards, the commonly used flux is rosin. Rosin dissolved in alcohol is a very easy-to-use flux. The solder wire is a hollow tube with a flux such as rosin added in the middle. When soldering, just heat the workpiece (pads on the circuit board, chip pins, etc.) with a soldering iron, and then touch the workpiece with the solder wire. The flux will melt and flow to the surface of the workpiece to reduce the oxide layer on the surface of metals such as copper and silver. Then the solder wire will melt and flow to the surface of the workpiece and the holes in the pad. Since the molten solder has a strong surface tension, the liquid solder will infiltrate the workpiece, and the surface area will be very small after solidification, so the workpiece will be "wrapped tightly".

maychang

Please note: the solder wire is melted by the workpiece, not by the soldering iron. The workpiece should be heated with the soldering iron first, and then the solder wire should touch the workpiece. The flux in the solder wire will melt first, and then the solder will melt. As long as the solder melts, the welding is completed, and the solder will automatically flow into the hole of the pad and even flow to the component surface of the circuit board.

Many people think that the solder wire is melted by the soldering iron tip, so they touch the solder wire to the soldering iron tip, hoping that the solder wire will melt on the soldering iron tip and then flow to the workpiece. This is wrong. Let me say it again: the solder wire is melted by the workpiece.

maychang

So why does a layer of tin need to be placed on the tip of the soldering iron? Isn't it possible to avoid tinning?

There is a layer of tin on the tip of the soldering iron, and the contact area of the tip when it contacts the workpiece is greatly increased, which can rapidly increase the temperature of the workpiece. If there is no tin on the tip of the soldering iron, the tip and the workpiece are in "point contact", and it takes a long time for the workpiece to rise to the temperature that melts the solder. However, at this time, the flux may have expired, and the oxide layer on the surface of the workpiece cannot be reduced, so it cannot be soldered. The first picture in the first post is a typical example of a failed flux, with the solder surface in pieces, and no surface tension to make the solder surface smooth and flat.

maychang

It has become like the first picture in the first post, what should I do?

Let the solder melt and add a little flux. Of course, there is no way to use the flux in the hollow solder wire at this time, so you can only apply some other things, such as solder paste or homemade rosin alcohol solution.

传媒学子

I remember that what I welded was very ugly, but it didn't stop me from winning the award.. Some people are very good welders, but they can't even get a high-value award. So comrades who are not good at welding should not be discouraged, you may have the potential to be a boss, haha. Of course, students who are good at welding are great and worthy of admiration.

freebsder

I learned welding through Bilibili, but my hands were shaking, so I gave up.

abc9981

Welding is a compulsory course for our electronics majors, and even for engineering majors. Welding is mainly divided into theory and practice.

In theory, welding requires understanding of some tools, such as solder, soldering iron, soldering iron tip, flux, and then the operation theory. For example, the soldering iron should touch the pad and the device pin at the same time, and solder cannot be added directly to the soldering iron (I basically did not follow the requirements). Finally, it is necessary to judge what kind of solder joint is a qualified solder joint. These are all theoretical things. I personally think that it is enough to know some basics. More insights can be gained through practice.

Practice. Excellent welders accumulate their achievements through practice. As the saying goes, practice makes perfect. When you weld more things, your welding skills will naturally improve. However, someone should know it in the early stage, otherwise you will develop some bad habits, which will be difficult to change in the later stage.

xutong

Authentic