Stats

  • Replies 18
  • Subscribers 163
  • Views 7539
  • Members are here 0
More Content

Display Your Know How: Footprints

PCBTech

Which footprint option is best, A or B?

 

 

Let’s say your PI specialist advises that this part requires maximum power transfer according to the component rating… Which library footprint do you choose?

Simply answer by letter or include any reason to support your answer. Alternatives and opinions are welcome!

Parents
  • Byron365

    Every Contract Manufacturer (CM) I have ever worked with wants option B. I believe this was originally born out of the fact that squeegee blades on solder paste screening equipment wasn't always a steel blade. It was sometimes a flexible blade and it would deform down into the larger stencil opening of option A and scoop some of the paste back out of the aperture, leaving you with less paste on the pad then intended. Since most squeegee blades tend to be steel now, I'm not sure that this is much of a concern.

    The current reason to use option B in my opinion is to control the amount of paste deposited so you keep all the paste migrating to the intended pad. Option A has the risk of applying too much paste and having solder balls form and going elsewhere on the design during reflow. Our entire library is done based on option B and trying to maintain a minimum of 60% pad coverage which I believe is an IPC requirement. CM's still prefer option B as well.

Reply
  • Byron365

    Every Contract Manufacturer (CM) I have ever worked with wants option B. I believe this was originally born out of the fact that squeegee blades on solder paste screening equipment wasn't always a steel blade. It was sometimes a flexible blade and it would deform down into the larger stencil opening of option A and scoop some of the paste back out of the aperture, leaving you with less paste on the pad then intended. Since most squeegee blades tend to be steel now, I'm not sure that this is much of a concern.

    The current reason to use option B in my opinion is to control the amount of paste deposited so you keep all the paste migrating to the intended pad. Option A has the risk of applying too much paste and having solder balls form and going elsewhere on the design during reflow. Our entire library is done based on option B and trying to maintain a minimum of 60% pad coverage which I believe is an IPC requirement. CM's still prefer option B as well.

Children
No Data
Cadence Guidelines

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.