The reflow soldering manufacturer Shenzhen Chengyuan Industry has found the following common problems in reflow soldering for a long time. The following are some common soldering problems, as well as suggestions for maintenance and prevention:
1. The surface of the solder joint appears frosted, crystallized or rough.
Repair: This joint can be repaired by reheating and allowing it to cool undisturbed.
Prevention: Secure solder joints to prevent problems
2. Incomplete melting of the solder, usually characterized by a rough or uneven surface. Solder adhesion is poor in this case, and cracks can grow in the joint over time.
Repair: It can usually be repaired by simply reheating the joint with a hot iron until the solder flows. Excess solder can also usually be drawn out with the tip of the iron.
Prevention: A properly preheated soldering iron with sufficient power will help prevent this.
3. The solder joint is overheated. The solder hasn’t flowed well yet, and the residue from the burnt flux is causing this to happen.
Repair: Overheated solder joints can usually be repaired after cleaning. Remove burnt flux by carefully scraping with the tip of a knife or toothbrush.
Prevention: A clean, properly hot soldering iron, proper preparation and cleaning of joints will help prevent overheated joints.
4. The joints all showed signs of insufficient pad wetting. The solder wets the leads nicely, but it doesn’t form a good bond with the pads. This could be due to a dirty board, or not heating the pads and pins.
Repair: This condition can usually be repaired by placing the tip of a hot iron on the bottom of the joint until the solder flows to cover the pad.
Prevention: Cleaning the board and even heating the pads and pins can prevent this problem.
5. The solder in the joint did not wet the pin at all and only partially wet the pad. In this case, no heat was applied to the pins, and the solder did not have enough time to flow.
Repair: This joint can be repaired by reheating and applying more solder. Make sure the tip of the hot iron touches the pin and pad.
Prevention: Even heating the pins and pads can prevent this problem.
6. (Surface Mount) We have three pins of a surface mount component where the solder does not flow to the pad. This is caused by heating the pin, not the pad.
Repair: Easily repaired by heating the pad with the solder tip, then applying solder until it flows and melts with the solder on the pin.
7. Solder starved solder joints simply don’t have enough solder to solder. This kind of solder joint is prone to problems.
Fix: Reheat the solder joint and add more solder to make a good contact.
8. Too much solder
Fix: You can usually draw out some excess solder with the tip of a hot iron. In extreme cases, a solder sucker or some solder wick is also helpful.
9. If the lead wire is too long, there is a risk of potential short circuit. The two joints on the left are clearly a danger to touch. But the one on the right is also dangerous enough.
Repair: Trim all leads on top of solder joints.
10. The two solder joints on the left melt together, creating a connection between the two.
Fix: Sometimes excess solder can be drawn out by dragging the tip of the hot iron between two solder joints. If there is too much solder, a solder sucker or solder wick can help draw out the excess.
Prevention: Weld bridging usually occurs between joints with excessive welds. Use just the right amount of solder to make a good joint.
11. Pads detached from the board surface. This happens most often when trying to desolder a component from a board, possibly due to adhesive failure.
This is especially common on boards with thin copper layers or no plated through holes.
It might not be pretty, but it can usually be fixed. The easiest fix is to fold the lead over the copper wire that is still connected and solder it as shown on the left. If you have a solder mask on your board, it will need to be carefully scraped to expose the bare copper.
12. Stray solder spatter. These solders are held on the board only by sticky flux residue. If they come loose, they can easily short out the board.
Repair: Remove easily with the tip of a knife or tweezers.
If the above problems occur, don’t panic. Take it easy. Most problems can be fixed with patience. If the solder doesn’t flow the way you want:
(1) Stop and let the solder joint cool down.
(2) Clean and iron your soldering iron.
(3) Clean any burnt flux from the joint.
(4) Then reheat.
Post time: Apr-23-2023