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January 9, 2018

Source of Wave Solder Bridging

We are having continual lead bridging problems with our wave soldering system.

How would you rank the following as the most likely and least likely causes, and areas to investigate?
  • Flux quantity
  • Flux type
  • Solder pot contamination
  • Solder pot temperature
  • Component angle through wave
  • Wave solder ramp angle
  • Other

V. L.

Experts Comments

In wave soldering, any termination that will wet to the solder while being submerged has the ability to bridge. It's more a function of the lead size and spacing that causes the actual bridge. The closer they get the more bridging can occur.

Bridging of terminations can occur on any component that is submerged in the solder bath during the wave soldering process. Components with tight spacing are most prone to bridging.

This is especially true of connectors and leads which are not trimmed short enough or are clinched toward each other leaving little room for drainage when emerging from the main wave bath.

Areas to check, by order of importance, when attempting to eliminate this defect are as follows:

  • Component leads that are bent or too closely spaced.
  • Excessive flux application.
  • Inadequate flux coverage or depleted flux activity which remains to promote drainage.
  • Inadequate solder pot temperature (alloy specific).
  • Board immersed too deep in the wave or improper angles.
  • Improper solder pot maintenance (leads picking up dross in the wave).
  • Poor component solderability due to oxidation or difficult to solder component plating alloys.

Karl Seelig

Deck Street Consultants
In his 32 years of industry experience, Mr. Seelig has authored over 30 published articles on topics including lead-free assembly, no-clean technology, and process optimization. Karl holds numerous patents, including four for lead-free solder alloys, and was a key developer of no-clean technology.

After investigating the variables you listed if you are still having bridging problems it would be adventageous to discuss this issue with your wave pallet supplier.

Copper solder thieves are a cost effective solution that will reduce or eliminate the bridging of components during the wave solder process.

If you have any questions or would like further information please feel free to let me know.

Scott F. Cain
Global PCB Sales Manager
InsulFab PCB Tooling
Scott Cain is the Sales Manager for the premier PCB Tooling Solution company in the industry, InsulFab PCB Tooling. Cain has seen every application and has worked with process engineers to create a solution to increase their yield and decrease the human interaction.

Bridging during a wave soldering process can be attributed to a combination of factors. Since consistent and effective thru-hole component wave soldering is best addressed through the introduction of a clean surface area to be soldered with a stable angle of attack with contaminate-free solder at an ideal temperature profile consider the following rank of most likely causes.

  1. Flux Type
  2. Contaminate-free Solder
  3. Solder Pot Temperature
  4. Wave Solder Ramp Angle

APS Novastar offers a Selective Wave Solder Troubleshooting Guide with applicability to general wave soldering applications located at http://www.apsgold.com/learning/selective-soldering-troubleshooting

Tim Kardish
APS Novastar
Tim Kardish is a technology business leader with 26+ years experience in the PCB, SMT and AOI assembly equipment industry. Tim is the CEO and a member of the Board of Directors at APS Novastar, LLC. He is a member of IPC and SMTA.

We really need to know if this is Lead Free or Leaded Wave Soldering as they do process differently.

ONE of the most important factors that manufacturers are getting wrong is the conveyor angle with Lead Free soldering. Please check your angle first as this should be kept exactly the same as Leaded at 7 degrees.

The peel off should be as near to the middle of the wave as well so the solder is peeling off both directions for maximum drainage.

If you could advise if Leaded or Lead Free and if possible some post some pictures of the bridging would be excellent

Greg York
Technical Sales Manager
BLT Circuit Services Ltd
Greg York has over thirty two years of service in Electronics industry. York has installed over 600 Lead Free Lines in Europe with Solder and flux systems as well as Technical Support on SMT lines and trouble shooting.
Wave solder bridging can happen for various reasons. First, the data has to be collected:
  • What type of solder is used?
  • How often do you clean your solder pot (dross)?
  • Is there any contamination in the solder pot?
  • What type of flux do you use?
  • Where do you experience the solder shorts (SMT, TH components)?
  • For TH parts, what are the characteristics: lead length, clinched leads (yes/no) and what angle and direction?
  • Wave height?
  • Do you use the chip wave and the regular wave solder?
  • Conveyor speed!
  • Do you have pre-heaters in the machine? If you do, do you use a thermal profiler to design your temperature settings?
  • Do you do a glass panel check on your machine for flux spray accuracy and solder pot level?
Here is some minor guidance for wave solder shorts troubleshoot:
  • Verify component insertion (TH)
  • Verify flux spray
  • Decrease conveyor speed multiples of 5 cm/minute until the lower limit is reached
  • Increase the pre-heater temperatures in multiples of 10C but not more than 30C
Georgian Simion
Engineering and Operations Management
Independent Consultant
Georgian Simion is an independent consultant with 20+ years in electronics manufacturing engineering and operations.
Contact me at georgiansimion@yahoo.com.
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