LED Chip defect and PCB color difference inspection

LED Chip defect and PCB color difference inspection

The LED light was widely used in daily life, it has high brightness, high luminous efficiency, saving energy, life-span longer and safety etc. LED bead is the most important part in the core element, it’s hard to find the NG product when they packaging, such as black spots, wool, bubbles and etc. All of industrial factory are use eye to inspect in 30 years before this way of inspect can made errors inspected, because your eye fell fatigue
As far as the machine vision application, visual detection in LED chip defect detection has been used more and more in the industry, let us share specific case with you.

Inspection requirement
1.    The surface of the LED bead is scratched
2.    Black spots, wool, and metal debris on the surface and the bottom, uneven sealing glue, error of glue surround, glue overflow.
3.    LED bead floor cavity on the bottom, subside wire, broken wire
4.    Chromatic aberration of the board
5.    All kinds of NG appearance

Analysis of sample
Work piece
Work piece

1.    According to the maximum bead 50*50 mm field of view and the size of the workpiece is not consistent
2.    The led bead color is not consistent, need to be compatible
3.    Use a RGB camera
4.    Classification of Defects:
a:Defect on the surface-- Black spots, wool, metal debris, uneven sealing glue, mistake of surrounding glue and glue overflow, bubble and metal wire cocked up.
b:Scratch defect on the surface—Scratches on the surface, presses down , dirty parts, etc
c:Defect of the circuit board-- floor cavity on the bottom, subside wire, broken wire
d:Defect of chromatic aberration: Become yellow on the surface of the board
 Design of project      
Defect on the surface:  
Light source selection: Use three-color combination ring light source blue, ring shadowless light

300x200Black spots on the surface
300x200Black spots on the bottom
300x200Wool on the surface
300x200Wool on the bottom
300x200Metal wire is cocked up
300x200Mistake of surrounding glue
300x200Glue overflow
300x200Uneven sealing glue
300x200Missed part of glue

Scratch on the surface
Choose the light source: use coaxial light


Scratch on the surface

Note: Through high angle vertical irradiation to inspection glue on the surface of the LED bead, highlight the scratch

Defect of the circuit board
Light source selection: Use a blue ring light

300x200Floor cavity on the bottom
300x200Subside wire

broken wire

NOTE: Blue color LED bead chip is more sensitive to this product, can clearly show the line part, is good to the inspection of the line part.

Defect of chromatic aberration
Light source selection: Use the square shadowless light


Compare the chromatic aberration

Note: Square shadowless light source is high uniformity, it can highlight the chromatic aberration

 LOTS (Lighting & Tech Specialist) will identify Market Trends, focus on visual light research and development, is committed to promoting the application of machine vision technology in all different kind of industry, to help China AI manufacturing move further, for the majority of machine vision client to provide advanced visual products and one-stop product solutions.