Benefits of using patch elements
First, let's look at the benefits of the patch element.The patch element has many advantages over the lead element.The first aspect: small size, light weight, easy to save and mail.For example, the commonly used patch resistance 0805 package or 0603 package is much smaller than the direct plug resistance we used before.A few dozen directly inserted resistors can fill a bag but enough to hold thousands or even tens of thousands if you replace them with patch resistors.Of course, this is without considering the maximum current it can withstand.The second aspect: the laminated element is easier to weld and disassemble than the directly inserted element.The patch element need not pass through the hole, use less tin.The most difficult thing and the most painful thing about the direct plug element is to disassemble it. All my friends have experienced this. On two or more layers of PCB board, even if there are only two pipe legs, it is not easy to disassemble the circuit board and it is easy to damage the circuit board.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.The third aspect: the patch element also has a very important advantage, which is to improve the stability and reliability of the circuit, and to improve the production success rate.
This is because the patch element is small in size and does not require perforation, thus reducing stray electric and magnetic fields, which are particularly important in high frequency analog circuits and high speed digital circuits.The review states that I am "responsible" to say that once you have adapted and accepted the patch elements, you may not want to use them again unless you have to.
Manual welding procedure of patch element
After understanding the patch welding tool, the welding procedure is now explained in detail.
1. Clean and fix PCB (printed circuit board)
Before welding, the PCB to be welded shall be inspected to ensure its clean.The oily fingerprints and oxides on the surface are removed without affecting the tinning.When welding PCB by hand, if the conditions permit, it can be fixed with the welding platform and so on to facilitate welding. In general, it is good to fix the PCB by hand.
2. Fixed patch elements
The fixation of the patch element is very important.According to the number of pins of the patch element, its fixation method can be broadly divided into two types - single pin fixation method and multi-pin fixation method.For the small number of pins (usually 2-5) patch elements such as resistors, capacitors, diodes, transistors and so on, the single-pin fixation method is generally adopted.That is, the first on the plate on one of its pads tin.
Then hold the device in the installation position with tweezers in the left hand and gently touch the circuit board. Hold the soldering iron in the right hand near the tin plated soldering plate and weld the pin well.After a soldering plate is welded, the element will not move, and the tweezers can be loosened.However, for laminated chip with multiple pins and multi-surface distribution, it is difficult to fix the chip with single pin. At this time, it is necessary to fix the multi-pin.After a pin is welded and fixed, the pin opposite the pin is welded and fixed, so that the whole chip is fixed.It is important to note that there are many pins and dense patch chips, and accurate alignment of the pins to the welded disc is especially important, which should be carefully checked and checked, because the welding quality is determined by this premise.
3. Weld the remaining pins
After the element is fixed, the remaining pins should be welded.For the elements with few pipe legs, you can take soldering tin in your left hand and soldering iron in your right hand.For chips with many and dense pins, in addition to spot welding, drag welding can be adopted, that is, one side of the pipe foot full of tin and then use soldering iron to melt the soldering tin to the rest of the pipe foot on that side to wipe off, the melted soldering tin can flow, so sometimes the plate can be tilted appropriately, so as to remove the surplus soldering tin.It is worth noting that both spot welding and drag welding can easily cause the adjacent pin to be short-circuited by tin.You don't have to worry about that, because you can get it, what you need to care about is that all the pins are well connected to the pad, there's no soldering.
Remove excess soldering tin
Refer to the short circuit of the pin caused by welding in step 3. Now let's talk about how to dispose of the excess solder.Generally speaking, you can take the above mentioned soldering tape to absorb the extra soldering tin.The method of using the soldering belt is very simple. Add a certain amount of flux (such as rosin) to the soldering belt, and then stick close to the soldering plate. Put the clean soldering iron head on the soldering belt.Should pay attention to is the end of the tin, absorption should be welding head and absorb in the tin tin take out of bonding pad at the same time, this time if the suction tin with glue on the pad, don't pull tin with absorption, but to absorb with add flux or to heat with welding head suction tin belt to make it smoothly and then gently pull out of bonding pad and to prevent the hot components around.If there is no special tin - absorbing tape on the market, you can use fine copper wire in the wire to make your own tin - absorbing tape.The homemade method is as follows: after peeling off the wire, expose the fine copper wire inside it, then melt some rosin on the copper wire with soldering iron.Effect after removing excess solder.In addition, if you are not satisfied with the welding results, you can repeatedly use the soldering tape to remove the soldering tin and weld the components again.
5. Clean the welding place
After soldering and removing the excess soldering tin, the chip is basically soldered.However, due to the use of rosin soldering and tin - absorbing tape, there are some rosin around the chip pin on the board.And it may make the inspection inconvenient.It is necessary to clean up the residue.Commonly used cleaning methods can be board water, in this case, alcohol, cleaning tools can be used cotton swab, tweezers can be used to hold toilet paper and so on.When cleaning and erasing, it should be noted that the alcohol should be moderate, and the concentration of the alcohol should be high, so as to dissolve the residues such as rosin quickly.Secondly, the wiping force should be well controlled, not too large, so as to avoid abrasion resistance welding layer and to hurt the chip pipe foot.Finish cleaning effect.At this point you can use a soldering iron or a hot air gun to properly heat the rubbing position of the alcohol to allow the residual alcohol to evaporate quickly.At this point, the welding of the chip is over.
To sum up, the welding patch element is generally fixed - welded - cleaned such a process.The fixation of components is the precondition for good or bad welding. Patience is necessary to ensure the alignment of each pin and its corresponding welding disc accurately.When soldering multi-pin chip, do not worry about the short circuit of the pin by soldering tin, you can use the soldering tape for soldering or only use soldering iron to use the factors of soldering tin after melting to remove the surplus soldering tin.Of course, the mastery of these skills is a matter of practice.Due to the limitation of space, only one kind of multi-pin chip is demonstrated in this paper. For many other types of multi-pin chip, the corresponding welding methods are basically the same under different conditions, such as the density of pin, mechanical strength and quantity, but the details are slightly different.Therefore, to become a master of welding laminated components, more practice is needed to improve proficiency.If the conditions permit, such as old circuit boards and old chips can be used more skillfully.