PCB Fault Detection

[linu95k]

Hi I am fairly new to NI vision, I have the following task:

I am using a Basler acA1920-25uc area camera to inspect a PCB for component presence, solder points, short circuit errors, broken copper paths of PCB.

I am however having trouble matching components. The components are not detected due to stable lighting conditions. Also components like Relays cast a shadow on other components. 

Reflective components like LEDs are also a problem.

Geometric Matching isn't sufficient for the Application since components like Resistors, Capacitors and certains ICs may have the same shape yet different values.

I tried using colour and shape matching however I am not getting the desired results.

I also need to take care of orientation specific components like diodes.

How can I check for floating components like Electrolytic capacitors and Transistors.

I also want to read the text on the components.

Can anyone help me with some examples or resources for the given application?

[1100fps]

Lighting is Key.  Contact CCS  CCS America  and / or Advanced Illumination (https://www.advancedillumination.com/)   Describe your board, or send them a snapshot with measurements, and they will recommend a lighting solution.  

The acA1920-25uc camera is a fine device, but will only give you optimal performance when used with a lens designed to work with 2.2 micron pixels.  I would suggest testing the camera with a resolution chart to assure you are getting maximum performance.. Basler will be happy to help you choose the optimal lens.

It's possible that your board is sufficiently large that a 2 megapixel camera won't meet your inspection needs.. The resolution test should help with that.

But.. Start with the lighting..  Good luck!

Robert

[linu95k]

Thank you for your response Robert.

I am using a 1920x1080 resolution and a 1:14 8mm lens. 

Currently I am conducting tests with a 8-channel relay module just to study and understand the techniques. The board that I am supposed to inspect hasn't arrived yet.

Please find the attached images for reference.  

[linu95k]

You can refer to the following link:

https://www.tamron.biz/en/data/fa/fa_mg/m118fm08.html

for the details of the lens.

[1100fps]

It looks like the lens is adequate for this board image you sent.  I tend to avoid lenses that are designed for CCTV, they are typically lower quality than lenses designed for machine vision, and less expensive.  If they do the job, then there is no reason to upgrade.

In some cases, it's worth going to the expense to add a telecentric lens, which gives a true undistorted top down view of the your subject.. They are very expensive, and the lens diameter has to be as big as your part, so sometimes It's not possible.

The picture of the relay board  has mediocre contrast, but adequate resolution, to identify the Resistor Values, and placement, veryify the presents of the other components and possibly verify the part number of the relays.  Getting the part number of the driver IC will be tough because of low contrast and resolution.

It's worth noting that A color camera will have roughly 1/3 the resolution of a monochrome camera, because of the presents of the Bayer Filter that is used to encode the color values.

I would also suggest you try to make your way to the Automate Show in Detroit in June, where there will be a whole series of classes that cover the aspects of machine vision in depth.. (I may or may not be teaching this year).

Certified Vision Professional (CVP) - Basic Certification (automate.org)

One of these days I hope to get back to NI Week (or whatever they call it now), and put on a class in basic optics.

Cheers

Robert