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May 2018

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Subject:
From:
Wayne Showers <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wayne Showers <[log in to unmask]>
Date:
Thu, 10 May 2018 17:08:41 -0500
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This may seem like a silly question, but this question comes to mind:
1) Is there solder mask between the 0201 pads (under the component "belly")?  If so remove it.
This will allow an ever so slight change to the z-height which should help.  Try pulling the Z-height up as the "belly" may have already created the rocking chair causing the lift especially if you have boards with soldermask between the pads.
Now for some solutions:
1) If you are using convection reflow, the sub zone (inside the shield) has a slightly different profile than the overall PCB, this  profile is working against you.  You may need to shorten or lengthen your profile slightly to accommodate.
2) Try to increase you solder paste, not reduce it.  The more you starve the connections, the more likely they are to lift.  1:1 with rounded corners is just about the best.  However, some applications, I have had better results with micro home plate as the solder melts at the point first which creates a great deal of surface tension while the bulk of the solder melts in to form the joint
3) 0201 does not allow for SMT epoxy very well, but if you use a 30 gage dispensing tip, it will leave just about the perfect dot size.
4) Barium Titanate displays some Ferro-Electrical including Ferro-Magnetic properties so that the bigger item to degauss may really be the shield itself.
5) Last but not, least, try increasing you blade pressure to ensure you get a good pack on each aperture and to even out the volume-density of the deposits.  If you are too light on you blade, you may be getting inconsistent solder deposits which melt out at different rates.
6) Well I thought that was going to be the last, but here is one more, if you are using Ramp-Soak-Spike, re-profile using a Ramp to Peak profile, this will also help with the under the shield variations in temperature.

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