Detailed welding procedure of patch element

- Jun 13, 2018 -

For the patch element, many people may still feel "fear", especially some beginners, it is not as easy to grasp as the traditional lead element. This may be related to the fact that most of the electronic production materials in our country are still dominated by lead elements, but this is an illusion. Here we begin by talking about the advantages of laminated elements, the tools needed for manual welding, and basic welding methods.

Benefits of patch elements

The patch element has many advantages over the lead element. Small size and light weight needless to say, from the perspective of production and maintenance, the patch element is easier to weld than the lead element, easy to disassemble, easy to save and mail. Do friends all know that fuses the removal of components is more troublesome, especially on two or more layers of PCB, even if it is only two pins, tear open come down to is easy to damage the circuit board, not to mention the pins. It is much easier to disassemble the patch element. Not only are two pins easy to disassemble, but even one or two hundred pins can be removed several times without damaging the circuit board. As for easy storage, please see the picture below. Tens of thousands of parts can be put in a clamp. It is very convenient to take and put them. SMT components of another benefit is easy to replace, because many of the resistor, capacitor and inductor are the same package size, the same position can be according to the need to mount resistor, or inductance, increase the flexibility of circuit design and debugging. Another important benefit of the patch element is that it improves the stability and reliability of the circuit and improves the success rate of the fabrication. This is because the patch element has no lead, which reduces stray electric and magnetic fields, especially in high frequency analog circuits and high speed digital circuits. It can be said that once you adapt and accept the patch element, you may not want to use the lead element any more than you have to.

Tools for welding laminated elements

For electronic production, the most important concern is the welding and disassembly of the patch element. In order to effectively and freely perform the welding and disassembly of patch elements, the key is to have appropriate tools. Fortunately, these tools are not hard to find or expensive for hobbyists. Here are some of the most basic tools.

Tweezers electronic production have tweezers, but here is the tip that one, and must be stainless steel, this is because the other may be a magnetic, and patch element is light, if you have any magnetic tweezers are sucked on it doesn't, a pain in the neck.

Everyone has soldering iron, here is also to compare the sharp one (the radius of the tip is less than 1mm), the soldering iron head of course to live a long life. The soldering iron had better prepare two, disassemble the part is to use, although I often use only one, also can deal with the past, but the unskilled friend strongly suggest or prepare two.

The hot air gun is used to remove multi-pin patch elements and can also be used for welding. Buy a dedicated more expensive, may be one, two hundred yuan of above, have a kind of plastics with heat gun (below left), only five, sixty dollars, a lot of sell electronics stores have to sell, is operable. I've measured the temperature at which it blows hot air, 400 to 500 degrees, enough to melt solder.

Fine solder wire should be 0.3mm - 0.5mm, thick wire (0.8mm above) cannot be used, because it is not easy to control the amount of tin.  

When the adjacent legs of IC are short-circuited by tin, the traditional tin absorber is not useful, just use the braid to absorb it.

The magnifying glass should have a seat and the one with a circular lamp tube, and the hand-held one cannot be replaced, because sometimes it needs to be operated with both hands under the magnifying glass. The magnifying power of magnifying glass is more than 5 times, best can be 10 times, but 10 times is not easy to find, and the field of view will be smaller, the field of view will be larger and more expensive. This type of magnifying glass price is less than 100 yuan of the impression, if can find proper magnifying glass, also can make a circular tube is very cheap, I just made a, specific methods introduced article.

With the above tools, it is not difficult to weld and disassemble the patch elements. For only 2, 4 foot components, such as resistor, capacitor, diode, triode, first on one PCB solder tin plating point, then left hand with forceps clamping element on the installation position and hold onto the circuit board, the right hand with the soldering iron will have the pin on the tin solder welding is good. The element can no longer move after welding one foot. The left tweezers can be loosened and the remaining feet can be welded with tin wire instead. It is also easy to disassemble such components by heating both ends of the element with two soldering irons (one on the left and the other on the right) and removing the element when the tin is melted.

More but for the pin spacing wide SMT components (such as many SO packaging of IC, the number of feet, between 6 to 20 feet spacing at around 1.27 mm) is also used a similar approach, first on a solder tin, with forceps clamping components and then left one foot welding is good, the rest of the foot with a tin wire welding. This kind of component disassemble is better with hot air gun commonly, one hand hot air gun will blow soldering tin to melt, the other hand USES forceps and other clamps to take off the element when soldering tin melts.

For components with high pin density (such as 0.5mm spacing), the welding procedure is similar, that is, one foot is welded first and the remaining feet are welded with tin wire. However, the alignment of pins and pads is key for such elements due to the number and density of pins. After a welding plate tin (usually on the Angle of welding plate, tin plated only rarely), use tweezers or hand components and welding plate alignment, be careful to make all the pins of the edge alignment (here the most important thing is patience!) Then press the element on the PCB plate with a little force on the left hand (or through tweezers), and use the right hand soldering iron to weld the pin corresponding to the tin pan. After the welding, the left hand can be loosened, but do not shake the circuit board vigorously, but gently rotate it, the rest of the Angle on the pins first welding. When all four corners are welded together, the element will not move at all, and then the rest of the pins can be easily welded one by one. When welding, you can first apply some rosin water, so that the iron head with a small amount of tin, welding a pin at a time. If you accidentally short-circuit the two adjacent feet, don't worry. After all welding, you can use the braid to absorb the tin. Of course, the mastery of these skills is to be practiced, if there are old circuit boards old IC may be used for practice.

The removal of high density of the pin component mainly use hot air gun, a hand using appropriate tools (such as tweezers) clamp element, another hand back and forth with a heat gun to blow all the pins, etc are melting lift components. If the component is removed, try not to face the center of the component when blowing, and the time should be as short as possible. Clean the welding plate with soldering iron after removing the element. If you are not sure about your welding is, also can get help, cell phones are everywhere now, and most of them have a hot air soldering station, and maintenance of the master will have certain experience, ask them to help (or pay a little money) solved your problem.

Speed in xian jia electronics co., LTD. Is located in the world-famous world one of the four civilized ancient capital of xian, depends on the key scientific research institutions of China in the Midwest talent pool advantage, wish for all kinds of national defense science and technology enterprises and the circuit boards of high-tech industry enterprises to provide professional production and processing, welding and finished product assembly debugging services. It is one of the few enterprises in the central and western regions that have passed military certification.

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