I've been whipping out PCB's like they were going out of fashion in the last few months, in large because I find I really enjoy the puzzle of laying out a design in the smallest area. The recent burst of productivity however is completely down to OSH Park. The high quality PCB production and quick sub-2 week turn around from this service means I can solve my jigsaw and have it in my hands within a few weeks - jet fuel for a hackers fire.
THE SILK SCREEN CONUNDRUM
Things don't always go well when I make PCBs ;0) Here is a quick shot of the gerbers for a simple DC regulator I bashed out in a few hours. Nice and symmetrical, but can you spot the mistake?
Its a classic - the grey box here is on the silk screen layer (bPlace to be precise in Eagle). My original reason for putting this rectangle on here was so I could mark on the board the output voltage of the board (which depends on the values of R1 + R2 so I can make specific versions of it) - seemed like a great idea at the time.
Why is this an issue? Well, the silk screen layer is the top most layer on a PCB. Underneath this is the solder mask and then the actual copper you want to connect your components to. Putting a large rectangle of silk screen on your PCB pretty much implies that you don't intend to put any components in that area!
In the name of making something prettier, I had inadvertently put a layer of silk screen over the pads that the regulator needed to be soldered onto...
TO KEEPOUT OR NOT TO KEEPOUT?
Now, its not quite the stupid mistake that it looks on first glance. I had put rectangles in the keepout plane (layer 40) around the pads for the components, assuming that this also applied to the solder mask when the gerbers were generated (the pic below has keepout layer enabled for reference). In the Eagle however its hard to see the keepout areas clearly and so when I viewed the PCB images on the OSH Park website, they looked nearly identical and I pressed the order button and went to bed.
A good example of what happens when solder mask goes all over your pads can be found here. You can scrape it off, but its hard to do and keep your pads fully intact.
The first set of boards with the silk screen issue had magical perfect rectangles cut out of the silk screen printing for the pads to shine through!!! Yay! So much better than my large keepout rectangle that stretched over all the pads.
Needless to say my happiness with the OSH Park PCB service just went up another 4 notches! I'd probably not rely on whatever tool set is being used to create the PCB panels to fix up my stupid mistakes in the future (i.e. cut out holes from the silkscreen), but for now I'm super pleased with the results.
Assembled board shot below - the write-up of this can wait for another day however :D
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THE SILK SCREEN CONUNDRUM
Things don't always go well when I make PCBs ;0) Here is a quick shot of the gerbers for a simple DC regulator I bashed out in a few hours. Nice and symmetrical, but can you spot the mistake?
Its a classic - the grey box here is on the silk screen layer (bPlace to be precise in Eagle). My original reason for putting this rectangle on here was so I could mark on the board the output voltage of the board (which depends on the values of R1 + R2 so I can make specific versions of it) - seemed like a great idea at the time.
Why is this an issue? Well, the silk screen layer is the top most layer on a PCB. Underneath this is the solder mask and then the actual copper you want to connect your components to. Putting a large rectangle of silk screen on your PCB pretty much implies that you don't intend to put any components in that area!
In the name of making something prettier, I had inadvertently put a layer of silk screen over the pads that the regulator needed to be soldered onto...
TO KEEPOUT OR NOT TO KEEPOUT?
Now, its not quite the stupid mistake that it looks on first glance. I had put rectangles in the keepout plane (layer 40) around the pads for the components, assuming that this also applied to the solder mask when the gerbers were generated (the pic below has keepout layer enabled for reference). In the Eagle however its hard to see the keepout areas clearly and so when I viewed the PCB images on the OSH Park website, they looked nearly identical and I pressed the order button and went to bed.
A good example of what happens when solder mask goes all over your pads can be found here. You can scrape it off, but its hard to do and keep your pads fully intact.
THE OSH PARK MIRACLE
A day later or so, the image displayed on OSH Park's website for my PCB finally rang an alarm bell as I was driving to work and I realized that the keepout layer was not in-fact doing anything and I'd made a dud PCB order. I whipped off the silkscreen and resubmitted again during lunch - a 2$ mistake and another thing to add to the checklist for sure but not the end of the day.
The boards turned up 10 days later, packages in the mail 2 days in a row. Below are 2 board revisions - top pic is front of the board (identical for both revisions), the middle is the rear with the silkscreen issue and bottom is the second batch where I'd removed it.
Needless to say my happiness with the OSH Park PCB service just went up another 4 notches! I'd probably not rely on whatever tool set is being used to create the PCB panels to fix up my stupid mistakes in the future (i.e. cut out holes from the silkscreen), but for now I'm super pleased with the results.
Assembled board shot below - the write-up of this can wait for another day however :D
