As we know ,circuit welding is an essential skill for hardware engineers. Circuit welding involves correctly soldering various electronic components to the right positions on the PCB according to the circuit markings. The welding mainly uses the tin soldering technology, using tin alloy materials as the solder. At a certain temperature, the solder is melted onto the pins of the components and the pin positions on the PCB. After cooling, a soldered bonding layer is formed, and the components are fixed to the right positions on the PCB.
With the increasing integration of chips, the packages are getting smaller and smaller, and the pin spacing is also getting smaller and smaller. So a good welding tool in hand can make the welding work much easier.
Next, let's take a look at the various tools usually used by the industrial control engineers and compare them with the tools in your hands:
T12 Soldering Station
This is the most frequent used tool. When choosing a soldering station, please choose a soldering station with fast heating and temperature recovery. The T12 soldering station is really a good choice. It is also equipped with many soldering iron tips. The commonly used ones are pointed tips, knife tips, horseshoe tips, etc. Replace different soldering iron tips according to the type of welding components.
Hot Air Gun
It is a necessary tool for desoldering surface mount components. The one in the picture is the Quick 850A+. The maximum air volume is 24L/min, and the temperature is continuously adjustable from 150°C to 500°C in 8 levels.
Heating Soldering Station
It is mainly used for welding preheating, weldingaluminum substrate , reflow soldering, etc. The following CNC heating platform has an effective heating area of 15cm×15cm, and the temperature is adjustable from room temperature to 450°C at a constant temperature, and the use experience is also very good. There is the MHP30 mini heating platform. Some people may be confused here. there has been a CNC heating platform alrady , why is there a mini heating platform? Of course, different station has its different use. The MHP30 mini heating platform has an effective heating area of 3cm×3cm and a maximum heating temperature of 350°C. The power supply adopts the PD protocol for fast charging, and the maximum power is 60W. It is mainly used for some small PCB patch welding and desoldering of the PCB. It only heats the part of the PCB that needs to be desoldered, preventing other parts from being repeatedly heated. This mini heating platform is not only an excellent tool but also a work of art.
Other Welding Tools
High-temperature sponge, tweezers, solder wick, solder sucker, electronic magnifier, circuit board holder, flux, and of course,solder is the most important . Among them, the flux can increase the solderability of the components and the welding surface. There are also many types, and you can choose according to your welding tasks. The commonly used one is rosin. The commonly used solders include solder wire, solder paste, solder balls, and solder bars. Among them, solder wire and solder paste are used most commonly. How to choose solder wire mainly depends on the wire diameter, tin content and melting point. Generally, the three wire diameters of 0.5mm, 0.5mm and 0.8mm are mainly used. The antioxidant of lead-free tin is good, and its melting point is also very high.
The following are the skills and precautions shared in the circuit welding practice:
Connector
Set the temperature of the soldering station to 370°C, insert the component into the corresponding PCB hole, make the component pins as perpendicular to the PCB pads as possible, and the soldering iron tip forms a 45-degree angle with the PCB. The soldering iron tip touch the component pins and the pads for preheating. Then, start feeding the solder wire. When the solder wire melts, you should master the feeding speed. When the entire pad is filled with solder, stop and remove the solder wire. Finally, use diagonal pliers to cut off the redundant pins.
Surface Mount Component Welding
The welding of SOP8 and SOP16 is relatively simple. Align the chip with the PCB pads, fix one pin first, and after confirming that the other pins are also aligned with the right pads, weld the remaining pins in turn. Drag soldering can also be suggested. For the packaging welding of LQFP48, it is inefficient to weld the pins one by one. You can first align the chip with the PCB pins, fix one pin first, and then fix the pin at the diagonal. After the fixation is completed, apply an appropriate amount of flux to the surrounding pins. Then, use a knife tip soldering iron tip to perform drag soldering. After the drag soldering is completed, use an electronic magnifier to check the welding quality and confirm that there is no pin short circuit. If an electric soldering iron is used to weld QFN-24, it is more complex. Welding such chips requires the use of a hot air gun or a heating platform. In the picture, the MHP30 mini heating platform is used. Because no stencil is made, the solder paste can only be manually smeared evenly. After the smearing is completed, align the chip with the PCB pads, set the temperature of the heating platform to 190°C, align the position of the PCB that needs to be welded with the heating platform, and start heating. It can be seen that the solder paste gradually begins to melt, and the process is very decompressing. After all the solder paste is melted, slowly remove the PCB and wait for natural cooling. After the cooling is completed down, use an electronic magnifier to check the welding quality. If there is redundant solder short circuit, use an electric soldering iron to remove the redundant solder and confirm again that there is no pin short circuit, and the welding is completed.
Special PCB Welding
For the students who is learning welding , the welding skills of the universal board are very important in the competition. The quality of welding may affect the progress of the competition and even the function. You can watch the video above for the welding of the universal board. Finally, let's talk about the special PCB welding. This is about the aluminum substrate. The aluminum substrate is a metal-based copper clad laminate with good heat dissipation function. Generally, a single-sided board is composed of three layers, namely the circuit layer (copper foil), the insulating layer and the metal base layer, and is commonly found in LED lighting products. Due to the excellent heat conduction ability of the aluminum substrate, it is difficult to use an electric soldering iron for welding. Usually, manual welding of the aluminum substrate requires the use of a hot bed to assist the electric soldering iron welding or directly use the heating table for manual reflow soldering, and the welding temperature should not be too high, and the welding time should be within 20 seconds.
Well, it often happens that the mind understands how to do but the hands can not do anything. Therefore, I hope everyone can seize every opportunity to practice more in daily study, practice makes perfect, and become a real "welding master" as soon as possible.
