First you will need to determine if this is a design related bridging issue or a process related defect.
For design related defects consider the following. This can include, but is not limited too:
If you have "design related" issues that are the root cause of the defect, your choices are somewhat limited as to what you can do to eliminate them. You can consider some technologies in the market that include de-bridging hot airknives or selective de-bridging tools.
If running with a lead free alloy the window of operation on these tools is reduced, so make sure you visit a supplier and test this first. You can also consider solder thieves, These are open land traces or so called drainage pads that are placed onto the assembly at the trailing edge of a connector.
The design provides a drainage point to pull the solder from the connectors to a open plated land. Note, these work best with connectors parallel to the conveyor rails.
If not a design related issue, here are some choices
- Connector pitch to tight,
- Connector leads too long off bottom of assembly
- Bridge is caused by the use of a selective soldering pallet
- Connector positions in various directions on the assembly.
This is just to name a few.
- Run the connectors parallel to the conveyor direction.
- Use a smooth exit transition from the primary wave with a small amount of back flow.
- Run the immersion depth in the primary wave shallow to the boards bottom surface.
- And of coarse your standard process requirements for the flux manufactures and preheat profile.
John Norton started his soldering career in 1983 for Hollis Engineering. He has also worked with Electrovert as a technical training manager and Vitronics Soltec for the last ten years. He has held various technical development and sales positions.
Try to rotate the direction of the pcb flow by 90 deg, ie, have the connector parallel to the conveyor flow, if possible. If not, try soldering at different conveyor speeds.
Managing Director, Asia Pacific
EH Lim has been in the PCB Assy industry since 1985, starting at Thomson/Singapore for 5 years before moving to Electrovert Asia Pacifc. Lim was Sales Director for Vitronics Soltec prior to joining ECD in 2007 as Managing Director for Asia Pacific.
Have you considered selective soldering? You have a lot more control over the process and it's easier to eliminate bridging.
National Sales and Marketing Manager, North America
Business Development Manager, DAGE | X-Ray component counting
Mr. O'Neil has been in the electronics manufacturing industry for over 20 years.
You can put the silk screen in between the PTH. So, as solder resist, it can prevent the bridging formed. Secondly, the pin over the board should be from 0.8 to 1 mm.
A pictorial of your issues would have helped us to response more accurately. Anyway, below are few actions & hope you find a solution out of it.
- Provide thieve pads to arrest solder short
- Insure the component pitch is maintained as per standard, avoid less then 2mm connector pitch.
- You can provide silk screen between the PTH
- Change the direction of travel through wave solder. Also note, the preferred direction of PCBA would be to align most difficult component in wave conveyor direction to reduce solder shorts.
Have 18 years of experience in electronic Industrialization. Specialties in PCB Design & manufacturing process, PCBA Process Development and Continuous Improvement.