Hand soldering tips for surface mount components
Nowadays, more and more boards use surface mount components, which can reduce the area of ​​the board compared with the conventional package, and are easy to process in large quantities and have high wiring density. The lead inductance of the chip resistor and capacitor is greatly reduced, and has great advantages in high frequency circuits. The inconvenience of surface mount components is that it is not convenient for manual soldering. To this end, this article takes the common PQFP package chip as an example to introduce the basic soldering method of surface mount components.
First, the required tools and materials welding tools need to have a 25W copper head small soldering iron, conditionally adjustable temperature and ESD protection soldering station, pay attention to the tip of the soldering iron should be fine, the width of the top can not be greater than 1mm. A pointed tweezers can be used to move and fix the chip and check the circuit. Also prepare fine wire and flux, isopropyl alcohol, etc. The purpose of using flux is mainly to increase the fluidity of the solder so that the solder can be pulled by the soldering iron and smoothly wrapped around the pins and pads by the effect of surface tension. Remove the flux from the plate with alcohol after soldering.
Second, the welding method 1. Before soldering, apply flux to the solder pad and treat it with a soldering iron to prevent the solder pad from being tinned or oxidized, resulting in poor soldering. The chip generally does not need to be processed.
2. Carefully place the PQFP chip on the PCB with tweezers, taking care not to damage the pins. Align it with the pad to ensure that the chip is placed in the correct orientation.
Adjust the temperature of the soldering iron to more than 300 degrees Celsius, apply a small amount of solder to the tip of the soldering iron, use the tool to press down on the chip in the aligned position, and add a small amount of solder to the pins at the opposite corners. Press and hold the chip and solder the pins at the two diagonal positions to fix the chip and not move. Re-check the position of the chip after soldering the diagonal. Adjust or remove and realign the position on the PCB if necessary.
3. When soldering all the pins, solder should be applied to the tip of the soldering iron and all pins should be soldered to keep the pins wet. Touch the end of each pin of the chip with a soldering iron tip until you see solder flowing into the pins. Keep the tip of the soldering iron in parallel with the soldered lead during soldering to prevent overlap due to excessive soldering.
4. After soldering all the leads, wet all pins with solder to clean the solder. Remove excess solder where needed to eliminate any shorts and overlaps. Finally, use tweezers to check for solder joints. After the inspection is completed, remove the flux from the board and dip the hard brush with alcohol and carefully wipe it along the lead until the flux disappears.
The chip RC component is relatively easy to solder. You can place tin on a solder joint first, then put it on one end of the component, clamp the component with a tweezers, and then solder it to see if it is correct. If you put it right, you will solder another one. To master the welding skills requires a lot of practice.
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