Components stand After reflow.Luo

What you describe is called Tombstoning and is caused by different cooling rates 
between the two ends of the component. i.e. 8mil track on one side and solid plane on 
the other side.

The plane acts as a heatsink and pulls the component vertical before the other side 
can cool.

to remedy match track thickness on both sides.

Ian Capps
  ----- Original Message ----- 
  From: Luo ; Yu-Ming (ùɯ IAC-N) 
  To: Protel EDA Forum 
  Sent: Monday, March 03, 2003 12:35 PM
  Subject: [PEDA] Components stand After reflow.


  Dear All, 

  I always set the polygon connect to pads directly, and it always work fine. But now, 
we found there are components stand after reflow, some  contain pads connect to 
polygon, some not. I wonder if this is caused by the polygon connet style or any other 
reason. So my question is:

  1, what are the key points to cause components stand after reflow? 
  2, When will components-stand always occur during reflow process? Preheat or cool. 
  3, How to slove this problem? 

  I am looking forward to your constructive suggestions, any input would be great 
appreciated! 

  Best Regards, 
  Luo. 


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