4 ms·

??? IME soldermask is pulled back from the pad generally unless you're doing soldermask defined pads for things like BGA. Plus, the fab generally modifies the p

??? IME soldermask is pulled back from the pad generally unless you're doing soldermask defined pads for things like BGA. Plus, the fab generally modifies the pullback themselves. My soldermask layer is pretty much just 1:1 with the pad outline, if I want a particular pullback I would specify that in the fab drawing. I can't see how soldermask color would affect placement either, especially not if you place fiducials (or if the fab places them for you!)

katmannthree 4y ago
Pigments can affect the properties and behavior of resins, if you're working with a sloppy fab I could see that causing issues (even if only not accounting for different curing times). For actual production design like the OOP is talking about, you would likely go with whichever option is cheapest overall (which in my experience has universally been the standard green).
- kurthr 4y ago
  Exactly, if you're hand soldering through hole components, it's not a big deal. However, blue/black/white solder mask pigments were noticeably (>2mil) smaller in tests than the standard green for a high volume manufacturer. Most of the time a partially mangled pad reflow wouldn't be a problem, but when you're automatically stuffing the boards, you won't know and could have latent failures (temperature/time) after production test. This is especially the case for aQFNs and BGA ICs. Fiducials are automatically placed in top copper, but we also noticed larger misalignments of paste and smaller 01005 passive components (pre-reflow) on non-standard colors. Again, unlikely to cause large yield problems unless you've got a lot of components, but why risk it. We did still use red for test PCBs so that they wouldn't be shipped to customers. If we were making gaming video cards colors would have been more of a priority.

4 ms·

??? IME soldermask is pulled back from the pad generally unless you're doing soldermask defined pads for things like BGA. Plus, the fab generally modifies the p

by 0_____0 4y ago

katmannthree 4y ago
Pigments can affect the properties and behavior of resins, if you're working with a sloppy fab I could see that causing issues (even if only not accounting for different curing times). For actual production design like the OOP is talking about, you would likely go with whichever option is cheapest overall (which in my experience has universally been the standard green).
- kurthr 4y ago
  Exactly, if you're hand soldering through hole components, it's not a big deal. However, blue/black/white solder mask pigments were noticeably (>2mil) smaller in tests than the standard green for a high volume manufacturer. Most of the time a partially mangled pad reflow wouldn't be a problem, but when you're automatically stuffing the boards, you won't know and could have latent failures (temperature/time) after production test. This is especially the case for aQFNs and BGA ICs. Fiducials are automatically placed in top copper, but we also noticed larger misalignments of paste and smaller 01005 passive components (pre-reflow) on non-standard colors. Again, unlikely to cause large yield problems unless you've got a lot of components, but why risk it. We did still use red for test PCBs so that they wouldn't be shipped to customers. If we were making gaming video cards colors would have been more of a priority.