11. Open Via In and Near Pad
Vias in or near BGA pads will cause loss of
solder balls resulting in a failed assembly
First of all: No.
BGA
12. Open Via In and Near Pad
Vias in or near BGA pads will cause loss of
solder balls resulting in a failed assembly
2nd of all: No.
BGA
13. Open Via In and Near Pad
Vias in or near BGA pads will cause loss of
solder balls resulting in a failed assembly
3rd of all: No
BGA
14. Open Via In and Near Pad
Just No
BGA
We salvaged this one, but don’t count on it
15. Open Via In and Near Pad
Filled and plated over at the board house
Copper plugs
Conductive epoxy
Thermal epoxy
The ONLY viable solution for BGA via
in pad is to have the vias filled and
plated over at the PCB fab house
16. Open Via In and Near Pad
QFN, DFN, QFP may require vias in the center
pad for thermal transfer or for grounding.
Open vias are not acceptable.
QFN and DFN
17. Open Via In and Near Pad
QFN, DFN, QFP may require vias in the center
pad for thermal transfer or for grounding.
Open vias are not acceptable.
QFN and DFN
18. Open Via In and Near Pad
More options with QFN/DFN than
with BGAs. Fill, plate or cap
QFN and DFN
19. Open Via In and Near Pad
This may not be acceptable with immersion silver
surface finish due to corrosion. Check with fab house
QFN and DFN
22. Open Via In and Near Pad
Passives & others
Insufficient solder on
pad and solder on
back side of PCB
23. Open Via In and Near Pad
Small components are subject to a number of
problems that don’t affect larger parts
Passives & others
24. Open Via In and Near Pad
Basically, just don’t do it.
It can lead to too many
reliability problems.
Passives & others
Insufficient solder on
pad and solder on
back side of PCB
IPC-A-610 Class Zero
27. QFN Stencil Layer
QFN/DFN solder paste stencil opening is
sensitive to a number of factors.
QFN Float
28. QFN Stencil Layer
QFN/DFN solder paste stencil opening is
sensitive to a number of factors.
QFN Float prevented
29. QFN Stencil Layer
QFN/DFN solder paste stencil opening is
sensitive to a number of factors.
QFN Voids
30. QFN Stencil Layer
QFN/DFN solder paste stencil opening is
sensitive to a number of factors.
QFN Voids avoided
31. QFN Stencil Layer
Segment the stencil so solder doesn’t
cover the capped vias.
QFN and DFN
Capped vias will
be in between the
stencil openings
Space for six vias
32. QFN Stencil Layer
Segment the stencil so solder doesn’t
cover the capped vias.
QFN and DFN
How not to do it
46. Thermal Issues
Thermal mass of large
component can cause
uneven paste melt
Mask too thick
can cause part to
ride up and not
solder well
Tombstoning
47. Thermal Issues
Thermal mass of
larger copper area
(even internal layer)
on one side can cause
uneven paste melt
Tombstoning