I recently generated Gerbers for a design with some rounded rectangle pads. I usually use 1:1 pad to mask and let the fab optimize the mask. They flagged a DFM error because there is a flashed round pad inside the rounded rectangle which I think is drawn as a copper polygon on top of it. Their tool picked up the inside pad and made a circular mask opening instead of just enlarging the existing mask. I think I can fix it by making the pads regular rectangles but I wanted to see if anyone else had this issue with a fab house and how they handled it.
Hm it seems kicad does indeed add a circle inside a roundrect pad when exporting gerbers. This shoudl however not matter to be honest. Not sure why it does for your manufacturers software. Is it possibly that they do not support rounded rectangle pads? (Gerber itself has no rounded rectangle code so the pad is build up from a polygon. Maybe your manufacturers software is too old to support polygons as pads.)
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I think the only reason it was flagged was because the soldermask is the same size and when the fab house receives the Gerbers it sees that the soldermask violates its clearance rules and then oversizes it for their process. The software is looking for the pad (I assume) and so it finds the round circle and not the rounded rectangle. The interesting thing is if the flashed circle is inside a rounded rectangle pad of the of the same diameter (rectangle width / height = circle diameter), then the fab house software picks it up.
I suspect I could just fix it by specifying a soldermask oversize specifically on those pads and then the fab house would just leave them alone in the first place. I was really just more curious why this was happening.
Well set the clearance to the required level then. Not just for the rounded rectangle pads but for the full board. (Or do you really want the manufacturer to modify your files without you being in control?)
If the rounded rectangle features in copper layers are flashed then there should not be any issues. Globally increasing should increase both these features. Yes, there will be an issue with the rounded rectangle feature if they are not in flash mode in the copper layer.
Hello people,
I have a problem with my board. I want to get my board fabricated but when I uploaded my sketch on www.aisler.net, a pad (not really, it is a region where there is no solder mask and the copper is exposed) appears in the board viewer and in the stencil viewer. The pad is not present in the sketch. I viewed the board in different gerber viewers of different PCB manufacturers but the pad is still there. I have attached a few pictures.
Did you upload the Fritzing sketch to Aisler or did you export the Gerber files and then upload a zip of them? If you uploaded the sketch could you try exporting the gerbers and zipping them and uploading them to Aisler to see if it is a problem on there end when they try and convert it from a sketch. If it still appears could you upload your custom part here so we can have a look at the part to see if there is something in the custom part that is causing the problem.
I uploaded the sketch to Aisler. I uploaded the .rar gerber files to www.jlcpcb.com and on www.pcbway.com with the same problem. I did not create any custom parts. I just created some pads and placed them in a way so that I can solder a 5050 led on them.
Believe me, I have checked my sketch a lot off times. With all kinds of gerber viewers, I see the pad. No, It does not affect the circuit, but this pad might be a problem while soldering using solder paste and hot air gun.
Oh, I believe it.
I mean you can check, your circuit diagram in PCB design software, is there a separate pad that does not have a connection?
If it is not, I really do not understand where it will go wrong
Full CAD files are the best choice when working your project in the Unisoft software. However when full CAD files are not available and there is no other choice but to use Gerber file data then this gerber file data can usually be process relatively quickly with the Unisoft software. The Unisoft software has a feature that takes the Flashed Gerber Pad pins and converts them to real components and pins, for example U14 pins 1,2,3, etc.
However a small percentage of the time these gerber files may have additional issues where some or all of the component pins in the Gerber files are not Flashed Pads. Sometimes this is the case in older legacy design PC Boards where the CAD designer who designed the PCB assembly ( PCBA ) may have not created a typical model for the components and the component pins for those components will be displayed as line draws instead of pad flashes. This can also be the case in newer design PCB's but not as often. The Unisoft software can convert these line draws into pad flashes and below is some information on that process.
In the gerber data file when the situation is that the pins a the copper pads are not Flash Pads as they should be but instead are just a single short line or a number of lines forming a rectangular shape pads representing the component pins, then the Unisoft software can usually remedy this situation by converting these pads from lines to solid pads/flash pads using the SHORT DRAW to FLASH conversion feature.
Normally the reason for an incorrect pad/pin condition is the CAD System / CAD Designer did not model those components in the CAD system as is the normal process. So because of this those components on the PCB assembly ( PCBA ) don't have Flashed Pads instead they have silkscreen Short Draws to represent the component pins. Another words the pins are for the most part no different than any other silkscreen on the board for example silkscreen that indicates lettering or board outline or any other figure.
Usually all components shapes are modeled in the CAD system and therefore when generated on the PCB assembly ( PCBA ) the pins on the components are the correctly Flashed Pins. However if components are not modeled as normal this maybe because they are either older legacy PCB assembly ( PCBA ) designs or from less sophisticated CAD systems or sometimes novice CAD designers.
When you view most Gerber files the component pins will be displayed as pad flashes which usually look like a solid square or rectangle, as in the figure below, and these are normally how they should be displayed.
If on looking at the Gerber files it may look like some or all of the components are not pad flashes but that they were simply drawn basically with line draws (example circled in yellow below). Note that these line draws can also be seen as short straight lines.
To utilize this Gerber data properly these pins need to be converted to Pad Flashes. So to get around this problem basically you can use the Unisoft short draw feature on that particular layer only and it will turn the short draws into pad flashes (circled in yellow below).
The result is it ends up creating pad flashes in those areas so you can then MAKE those pad flashes into components and pins using the Unisoft software. At that point the Unisoft software can calculate the X/Y center for those components then you can use that data to program your assembly or AOI machines. Also the displayed components can be used to create process assembly documentation, etc.
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This text (or any other features you draw on that layer) will later be subtracted from the copper layer, so the end result will have better resolution than silkscreen. The silkscreen design rules don't apply here.
Plot copper layers and the text layers you want to subtract from those copper layers (here: F.Cu and User.1; the latter is not visible in the screenshot above). Check the raw output with a gerber viewer:
Not directly Arduino related, but probably there are some folks around that know the answer to my problem.
I'm trying to put a QFN-36 package in a library. The centerpad needs to be connected to the ground layer, so I'd like to put a via in the middle of it, so that I can connect it to a groundplane at the other side of the board.
-Place a center pad on the top layer.
-Click the 'info' button, then the center pad and uncheck the 'cream' and 'stop' layer.
-(as suggested as per the link above): draw two rectangles manually over the center pad, one on the 'tstop' and one on the 'tcream' layer.
-Manually put a via over it.
Its been my experience that this isn't the greatest of practices. While it is acceptable if necessary, it is usually better to instead place the via right next to the pad, and connect it with a very short lead. Ideally, the lead will be slightly less wide than the pad as well if possible. This allows for slower heat transfer into the ground plane, making soldering easier. Also, I think I've seen that some board companies don't allow or charge extra for via-in-pad. If you are absolutely out of board space, then it is okay, but its not recommended. Keep in mind you can extend the via to be under the chip itself as well, so if it is in the way, you can move it around.
via in pad has never caused me problems with 2-layer board with several
vendors, but its risky practice with small components as the surface tension
effects can cause tombstoning if the pads aren't symmetrical. For production
you would best avoid it unless you'd tested the reliability of reflow soldering for
the board in a prototype run.
Thanks for the answers and my apologies for the late reply.
The chip I'm trying to design a good footprint to is the VUB300 which comes in a QFN36 package.
I've attached the recommended footprint according to the datasheet. 152ee80cbc
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