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particle-iot / core

Hardware design files for the Spark Core, a tiny Wi-Fi development kit.
https://www.spark.io/
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Reduce outgassing #25

Closed zsup closed 10 years ago

zsup commented 11 years ago

Suggestion from Bunnie: we should work with the manufacturer to determine where we might run into outgassing issues and resolve any potential problems.

Not sure if there's anything to do here, but @brandoaire we should just raise it with the manufacturer and see if they have any thoughts.

bunnie commented 11 years ago

As a clarification, the outgassing is due to the flux inside the solder paste volatilizing during reflow. When this happens, the flux can cause the solder paste to become displaced, meaning you now have solder where you thought you didn't.

This is particularly bad under QFNs, because the components represent a wide, flat area; and without vias for the gas to escape or proper stencil design to allow for channels for the gas to get out, pressure can build up and the solder can splatter or the part itself can be shifted to the side due to the pressure build up.

As a result, QFN + untented vias underneath component == short circuits waiting to happen.

Remedies:

andyw-lala commented 11 years ago

The CC3000 will also be a good candidate for this problem, with the 6 large ground pads.

On Fri, Jul 12, 2013 at 12:41 PM, bunnie notifications@github.com wrote:

As a clarification, the outgassing is due to the flux inside the solder paste volatilizing during reflow. When this happens, the flux can cause the solder paste to become displaced, meaning you now have solder where you thought you didn't.

This is particularly bad under QFNs, because the components represent a wide, flat area; and without vias for the gas to escape or proper stencil design to allow for channels for the gas to get out, pressure can build up and the solder can splatter or the part itself can be shifted to the side due to the pressure build up.

As a result, QFN + untented vias underneath component == short circuits waiting to happen.

Remedies:

  • vias inside the ground pads (where solder is supposed to be) can help gas escape
  • tented vias outside the areas where solder paste is supposed to be, in case solderpaste is displaced on top of them
  • stencil design with channels in the paste so there is some room for gas to get out

— Reply to this email directly or view it on GitHubhttps://github.com/sprk/core/issues/25#issuecomment-20891850 .

Andy