Solder bridging is a common occurrence or mistake (defect) that can occur during the Surface Mount Technology (SMT) assembly process. It generally occurs when there is accidental connection of solder that is formed between two pads, pins or even traces that typically form a conductive path. Solder bridges occur more often these days as printed circuit boards have grown smaller over time.
Below are some reasons why you might be getting soldering bridges and some tips on how to fix them.
Here are a few pictures of soldering connecting or in most cases misconnecting two or more adjacent pads that come into contact to form a conductive path.
Causes of solder bridging
There are a number of factors that can possibly contribute to solder bridging including:
Incorrect solder paste viscosity
Solder paste with the wrong viscosity can be more prone to bridging.
Incorrect reflow profile
If the reflow profile is not correct, it can cause the solder to flow excessively, increasing the chances of bridging.
If the pads are contaminated with dirt, oil, or other substances, it can prevent the solder from adhering properly, which can lead to bridging.
Too much solder paste
If too much solder paste is applied to the pads, it can increase the chances of bridging.
If the components are misaligned during placement, it can create gaps between the pads and the components which can then be filled with solder and will then create bridges.
Some helpful example of how to fix some issues in solder bridging:
If you are having problems with solder bridging, there are a number of things you can try to troubleshoot the issue:
Inspect the solder paste
Make sure that the solder paste is being applied correctly and that the amount of paste is not excessive.
Inspect the component placement
Ensure that all of the components are properly aligned and seated.
Check the solder paste viscosity
It is important that the solder paste you are using has the correct viscosity for your application.
Check the reflow profile
Make sure that the reflow profile is correct for the solder paste you are using and the components you are assembling.
Clean the pads
It can help if the pads are clean and free of any contaminants.
How can you prevent solder bridging?
There are a number of things you can do to prevent solder bridging:
Use the correct amount of solder paste
Use a stencil to apply the solder paste to the pads. This will help to ensure that the correct amount of paste is applied and that the paste is evenly distributed.
Accurately place the components
Use a pick-and-place machine to place the components on the PCB. This will help to ensure that the components are properly aligned and seated.
Use the correct solder paste viscosity
Select a solder paste with the correct viscosity for your application. A higher viscosity solder paste will be less prone to bridging.
Make sure to use a correct reflow profile
Use a reflow profile that is optimized for the solder paste you are using and the components you are assembling.
Clean the pads
Make sure that the pads are clean and free of any contaminants before assembling the PCB.
Here are some additional tips for other more specific solder bridging issues:
Bridging between adjacent pads
This can be caused by a number of factors, including too much solder paste, misaligned components, or incorrect reflow profile. Try reducing the amount of solder paste, ensuring that the components are properly aligned, and adjusting the reflow profile.
Bridging between pins on a component
This is often caused by too much solder paste or incorrect reflow profile. Try reducing the amount of solder paste and adjusting the reflow profile.
Bridging between traces on a PCB
This can be caused by a number of factors including misaligned components, incorrect reflow profile, or contaminated pads. Try ensuring that the components are properly aligned, adjusting the reflow profile and cleaning the pads.
We hope this helps resolve your bridging issues. If you have any questions about bridging or anything else, please contact our technical support team. They are always happy to help!
Photo credit: Alpha Technical Solutions