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  • Author Author: fmilburn
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Microscopes and Solder Masks

fmilburn

Now that the TI-RSLK robot RoadTest is finished I have turned my attention back to a problem spotted in the last round of PCBs ordered for the AIS alarm project.  But first, I have a new toy.

image

I have been looking for the right used Nikon microscope in budget but finally could not stand it any longer and bought this Chinese model after my friend bought one.  I am amazed at how much better this is than peering through a magnifying glass or loupe.  At low magnification stereoscopic details pops and there is good depth of field.  I bought a version that takes a C-mount camera but don't have a camera yet.  Good value for the money I think but this was a "want" rather than "need" purchase.

 

I went back and put some of my old PCB designs under the microscope and discovered several had a problem I reported in a previous blog - that is, the solder mask did not extend between the pins of smaller SMD packages.  This of course makes solder bridging and the resultant need for rework more likely.

 

I have had the problem occur for two reasons:

  1. The PCB manufactures had a minimum guaranteed spacing specification between the pad and the solder mask.  Check the specification especially with low cost prototyping services.
  2. I use KiCad and the default pad mask clearance is pretty high - so high that there is no mask between some SMD pins.  For KiCad the fix is to go into Dimensions -> Pad Mask Clearance while in pcbnew and change the default to the desired value.  OSHPark has a discussion on the topic and recommends 2 mil (0.05 mm) clearance for 2 layer boards.

 

The MSP430FR2xxx protoboard I put together a while back had the second problem and I did not realize it until I looked under the microscope.  They were made by OSH Park and it is hard to see the problem with the naked eye on that purple background.  Pesky default values....  I have reordered the board with the fix since they are inexpensive and I have another project in mind for that particular microcontroller.

Parents

  • Nice microscope. I've got the same one. I got mine with a camera included but it captures a much smaller area than you can see through the eyepiece. I intended to sort out something better but haven't managed to yet. Tried a DSLR C mount adapter without success.

  • in reply to Fred27

      wrote:

     

    Nice microscope. I've got the same one. I got mine with a camera included but it captures a much smaller area than you can see through the eyepiece. I intended to sort out something better but haven't managed to yet. Tried a DSLR C mount adapter without success.

    Hi David,

    Thanks for the comment.  I was planning to try a C mount adapter for my DSLR.   Can you describe more  the issues you had with it? 

  • in reply to fmilburn

    As far as I remember it was impossible to get the focus even close to being right. It got thrown in a box and I've not tried anything else as it wasn't really a priority. It was a cheap one from eBay so other adapters may be better.

     

     

    For anyone getting one of these I can recommend also getting a 2x barlow lens. When I got mine the two pack of barlow lenses was a good deal. The 0.5x is ideal for soldering and general electronic work, but the 2x is even better if the kids want to be grossed out by a spider, etc. You might as well get more use out of it!

  • in reply to Fred27

    Mine came with a 2x as well as the 0.5x.  I tried the 2x for the first time last night and as you say it will be great for the kids and may come in handy for some electronic stuff.  The distance to the stage really shrinks and it is no longer possible to easily work under it.  The depth of field is also greatly diminished of course.  Fun stuff....

  • in reply to Fred27

    The first accessory that I bought for my microscope was a barlow lens (0.5x).  It cost almost as much as my microscope, but it was really worth it.  The increase in working distance was so necessary, as it made it less cramped working under the scope.  The second accessory (built not bought) was a light ring.  Again, what a difference!  The bright and direct light is so useful as in makes everything pop and reduces shadows.

     

    But, I guess these are things that you get when you buy a new Chinese scope.

    Enjoy!

    Gene

  • in reply to Fred27

    It would be interesting to know if you manage to get it working at some point. Adding a DSLR body with a C-mount adapter is one option I was considering because a second hand body from eBay plus the adapter is way cheaper than it appears equivalently specced C-mount cameras cost (Here is an Amscope one on Amazon: https://www.amazon.co.uk/AmScope-USB3-0-C-mount-Microscope-Calibration/dp/B072833HKR/ref=sr_1_fkmr0_1?ie=UTF8&qid=153177…  which maybe you can get cheaper elsewhere but it's probably in the ballpark). Amscope do sell adapters specific to their equipment so maybe this has a specific length which enables it to work. I know they are also 2x lenses so maybe that's a factor if the cheap ones aren't actually lenses just adapters.

     

    Here is the Amscope video on using a DSLR with their microscopes using their adapter: https://www.youtube.com/watch?v=pzpHh1PQAEM

     

    Best Regards,

     

    Rachael

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  • in reply to rachaelp

    I have a T mount that I use on my telescope that fits Nikon cameras.  It doesn't fit the microscope but I found a way to hold it in place.  Among the many issues with this approach is it lacks the wide angle optics to get the full microscope barrel in view.  This photo was taken with a full frame Nikon DSLR.  I had to crank the ISO up to 6400 to get decent shutter speed and did not get the exposure correct but it gives the idea of what is possible with this approach:

    image

    For comparison I took a quick photo with a 105 mm macro Nikkor (that lens alone is more expensive than the microscope with all accessories) on the same camera body.  It will focus down to 1:1 magnification but I was not that close and I have cropped it severely to show roughly the same area.  This was in indirect sunlight, the photo above was lighted with the microscopes LED illumination.

    image

    Neither looks as good as the microscope viewed with the eye.  Since the camera has a HDMI port I could connect it directly to a monitor.  I think my friend's camera is the newest AmScope USB-2 and I hope to get a look at it.  But right now I am leaning towards the AmScope C-Mount Nikon adapter which costs about $100.

     

    PS:  The photos above are not an apples to apples comparison.  It just shows some of the issues with trying to hack a camera onto the 3rd port of the microscope without using proper optics.