Author Topic: Via in pad and voids - doing it the Jack Sparrow way  (Read 104 times)

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Offline eTobeyTopic starter

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Via in pad and voids - doing it the Jack Sparrow way
« on: Yesterday at 09:17:27 pm »
Some of you may remember the scene of "Pirates of the Caribbean - At World's End" where they turned the ship uside down. When thinking about reflowing of  parts that have vias in the pads, i thought maybe this could work there too!

As a lot of gases coming out of the solder paste when reflowing and creating bubbles, i thought wouldnt they just vent out of the vias if you flip over the board when reflowing? But would the parts (not considering heavy parts) stay on the board then? What do you think.

This channel has some interesting videos:



 

Online Whales

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Re: Via in pad and voids - doing it the Jack Sparrow way
« Reply #1 on: Yesterday at 09:49:48 pm »
Testing this would be interesting (you'd glue the parts down like they do for 2-sided SMD reflow), but I forsee a lot of annoying variables:

 - Bubbles are large and seldom, which is the opposite of what you want for consistency.
 - Pad size & via size & component thermal mass
 - Solder alloy consistency and flux chemistry across the entire bubbling range of temperatures and time

Online T3sl4co1l

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Re: Via in pad and voids - doing it the Jack Sparrow way
« Reply #2 on: Today at 05:01:19 am »
Gas is trapped when it has nowhere to go, i.e., one-side-tented vias.  You tent both sides, it's fine, it has somewhere to go.  That's why you use untented, or fully tented (preferably plugged and capped) vias, for via-in-pad.

Buoyancy probably doesn't make much difference, as surface tension dominates on these scales.  Maybe it would help some, maybe it would reduce but not eliminate the rate of voiding, for example.  Dunno, would have to see it tested.  Meanwhile, parts simply bubbling/popping off the inverted board (or get shaken off during handling), is probably the elephant in the room.

Tim
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