The Silkscreen is shown in white, and the Fab is shown in blue.
Once populated, the Silkscreen of the symbols will be hidden under the physical part. This was done to provide an easy way to both visually identify the type of part to populate, and to indicate an unpopulated part. The side Silkscreen shows where a perfectly centered and aligned part should be located.
This is very similar to what happens when hand soldering 1206 parts:
Each axis is off by only two(2) degrees, or less. It is surprising to me how much the visual reference on the Silkscreen helps me to achieve better placement when hand soldering.
The pedantic on this forum may wonder why the capacitor Fab layer is not a closed box like the resistor is. Unlike this quicky example, I like to include the value of the part on the Fab layer also. The number of characters required for typical resistors fits inside the box; capacitor values with the same sized text do not fit in the same sized box.
I was wondering, and kind of concerned about something else. Do you have any fab errors (tombstoning, etc) with your pads? I’d just be concerned with the additional thickness of the silkscreen on top of the mask acting like a seesaw fulcrum during reflow. But I don’t have any empirical evidence, just a gut feeling.
If the extra thickness of the silkscreen doesn’t cause any fab issues then I think this is a brilliant technique.
As you wrote pads i will answer the pads part of the question.
Yes these 1206 footprints look like the do not really have enough heel fillet but this could also be because the footprint is not meant for generic 1206 components but for a specific component with much lower dimensional tolerances.
Having too little heel fillet can indeed increase the probability for reflow problems in general.
The same is true for silk under the part. When we discussed not allowing silk under smd parts we found a lot of research in this area and all of it seemed to indicate that silk under parts is a problem especially for smaller parts.
But i would assume that a manufacturing process that benefits from having symbols hidden under parts will not be precise enough to really be hit by this problem. I doubt that anyone hand populating their part will have a well tuned reflow oven. A further variable will be paste application that i doubt will be done by machine in such a process which will introduce another variance.
Meaning my conclusion is: If you hand solder (even with the help of an oven) your board then there are other variables that have more influence on yield than silk under your part or slightly wrong footprints.
It was unfortunate the Piotr didn’t tell the size of his components. I wouldn’t try this with 0402 which we use. Even the component outlines made with silk may go under the component because of wrong silk offset. In my experience the location of the silk items have the largest tolerances in manufacturing. It may easily be e.g. 0.5mm off. This, of course, with a cheap price.
Instead of capacitor and resistor symbols I have put the value field on the silkscreen under the SMD components. I’t’s easy to remember that 100n is a capacitor and 1k2 a resistor. This way you do not only know which resistors and capacitors to place on the board.
Another little thing that helps is to put all polarised capacitors in the same orientation.
This can be a bit of a nuisance during layout, but it pays for itself during hand assembly and inspection.
