Solder flux residue is generally defined as the residual material left on the surface of a circuit board or other workpiece during a soldering operation or electronics manufacturing process due to the use of soldering materials (e.g., solder or solders), through-hole soldering, and by-products generated during the soldering process. These residual components may include solder that has not completely melted, solder debris inside the through-hole, solder residue at the edges of the through-hole, and other possible impurities.
Problems caused by solder flux residue:
Conductive barriers: Solder flux residue has the potential to form unintended conductive bridges that can cause poor electrical connections. This can result in unstable circuit operation, interference with signal transmission, or even electrical system failure.
Unintended short circuits: On circuit boards, solder flux residue can cause unwanted short circuits because the solder itself is electrically conductive. Short circuits can cause equipment failure, damage or overheating, posing a threat to the normal operation of the equipment.
Reduced insulation performance: Failure to remove solder flux residue effectively can weaken the insulation performance of electronic components. This is intolerable in some applications, especially in high frequency circuits.
Signal distortion: In high-frequency or high-precision circuits, solder flux residue can be a cause of signal distortion, which can affect the performance and accuracy of the device.
Weakened Reliability: Solder flux residue may lead to a reduction in the mechanical strength of the solder joints, which in turn reduces the overall reliability of the electronic assembly. This can lead to broken solder joints or other forms of mechanical failure over the life of the device.
Environmental Risks: Some of the solder may contain hazardous substances, such as lead, and these residual solder residues may have an adverse effect on the environment. In some regions, this issue has already attracted the attention of environmental regulations.
Loss of productivity: In the production process, once the problem of solder flux residue is detected, additional cost and time may need to be invested in repairing the problem, which affects productivity and may even lead to production delays.
During the cleaning process of circuit board soldering, two main methods exist to remove solder from the PCB. One method targets the removal of solder from the original circuit board, while the other removes excess dross after the soldering job is complete. When performing these operations, it is recommended to use a tin absorber and follow the specific steps below.
First, the method of removing the original circuit board solder
- Need to first shake off the soldering iron tip attached to the solder, and then again on the soldering point to heat so that it melts, this process can be repeated several times to achieve the cleaning effect.
- Select a small section of multi-stranded wire, and make its surface evenly covered with rosin. Afterwards, use the soldering iron to heat the soldering point to the melting state, and pull out the wire while it is hot to take away the excess solder.
- If the area of solder flux residue is large, consider using a professional hot air gun or tin furnace for heating and removal.
Second, the steps to remove the welding slag after welding
Can use anhydrous ethanol (or concentration of 95% and above) for cleaning. If the stains are heavy, you can use a soft brush dipped in alcohol to scrub.
Next, wipe the surface of the board clean with degreasing cotton.
Removing solder slag with a solder suction device and double sided board may be tedious.In this case,the soldering iron can be heated,and then inserted into the soldering holes with a medical needle and rotated,or a special soft wire can be used,heated until melted and then quickly pulled out.
If there is no tin sucker,you can also slightly shake the board after heating, so that the tin slag naturally fall off. But need to pay attention to safety,avoid shaking too large.At the same time,in the welding process,should be timely from the soldering iron head to remove excess solder.
PCBA board welding processing produces air holes, which is what we often call bubbles. Usually, in the PCBA processing process, reflow soldering and wave soldering will produce air holes.So how to improve the PCBA board welding in the air hole problem?
1.Baking treatment:PCB and components for a long time in a dry environment for baking to prevent moisture.
2.Solder paste management: If the solder paste contains moisture, it is also easy to lead to porosity and solder beads. Therefore, you should use high-quality solder paste, and in strict accordance with operating procedures for the return of temperature and mixing. At the same time, should minimize the exposure time of the paste in the air, and reflow soldering in a timely manner after the printing of the paste.
3.Workshop humidity regulation: Workshop humidity should be regularly monitored and controlled within the range of 40% -60%.
4.Furnace temperature curve optimization: test the furnace temperature at least twice a day and optimize the furnace temperature curve according to the test results. The heating speed should not be too fast to ensure the welding quality.
5.Flux spraying control: In the wave soldering, the amount of flux spraying should be reasonably controlled to avoid spraying too much.
6.Furnace temperature profile re-optimization: the temperature of the preheating zone should meet the requirements, not too low, to ensure that the flux is fully volatile. At the same time, the speed through the furnace should not be too fast to ensure that the welding effect.
There are many factors that may affect the PCBA soldering processing bubbles. They can be analyzed in terms of PCB design, PCB humidity, furnace temperature, flux (spray size), chain speed, tin wave height, and solder composition. After several tests, it is possible to get a better process.
Remove solder from the PCB is an important step in ensuring solder quality and product reliability. By applying effective cleaning techniques and strategies, combined with the optimization of process parameters, we can effectively reduce the occurrence of problems such as solder flux residue and porosity. This not only improves soldering accuracy and stability, but also provides a solid guarantee of high performance performance for electronic products.
