How to welding ?
Operating Steps
(1) Prior to welding, apply flux to the welding pad and treat it with a soldering iron to prevent poor tinning or oxidation, which can result in faulty welding. Generally, there is no need to treat the chip.
(2) Gently position the PQFP chip onto the PCB board using tweezers, taking care not to damage the pins. Align it with the corresponding pads, ensuring the chip is placed correctly. Adjust the soldering iron temperature to above 300 degrees Celsius. Apply a small amount of solder to the soldering iron tip and press it onto the aligned position of the chip, adding a small amount of flux to the two diagonal positions of the pins. While keeping pressure on the chip, solder the two diagonal pins to secure the chip in place. Afterward, recheck the chip alignment. If necessary, adjust or remove the chip and realign it on the PCB board.
(3) To solder all pins, heat the tip of the soldering iron and apply flux to each pin to keep them moist. Touch the iron’s tip to the end of each pin until solder flows into the pin. Keep the iron tip parallel to the pin during soldering to prevent excessive solder and lap bonding.
(4) After soldering all the pins, apply flux to clean the solder on the pins. Remove excess solder as needed to avoid short circuits or overlapping. Use tweezers to check for any remaining solder. Once the check is complete, remove the flux from the flexible circuit board. Dip a hard bristle brush in alcohol and carefully wipe along the direction of the pins until the flux is removed.
(5) Soldering surface-mount resistors is relatively easy. Start by applying a small spot of solder to one of the pads, then place the component’s end on it while holding it with tweezers. Solder the end in place and check if it’s properly positioned. If it is, solder the other end.
Notes
In the layout, if the size of the flexible circuit board is too large, it can lead to certain drawbacks. Although it may be easier to control the soldering process, there are several disadvantages to consider. Firstly, longer printed lines result in increased impedance and reduced anti-noise capabilities, which can negatively impact performance. Secondly, larger board sizes contribute to higher production costs.
On the other hand, when the flexible circuit board is subjected to prolonged heating, heat dissipation decreases, making it more challenging to control the soldering process. Additionally, there is an increased risk of adjacent lines interfering with each other, such as electromagnetic interference (EMI) affecting the flexible circuit board.
Therefore, it is crucial to optimize the design of flexible PCB circuit boards by implementing the following measures:
- Minimize the distance between high-frequency components to reduce EMI interference.
- Secure heavy components (weighing more than 20g) with additional support before soldering.
- Arrange components in parallel as much as possible, ensuring an aesthetically pleasing layout that is conducive to mass production. The board should be designed in a 4:3 rectangle shape.
- Avoid abrupt changes in wire width to prevent discontinuity in the wiring.
- Large-area copper foil should be avoided as it has a tendency to expand and detach when exposed to prolonged heating.
