Types and Causes of Plating Defects and Solutions for Problems in Observation and Evaluation
Plating with high functionality requires high-quality assurance through, for example, appearance inspection. This section introduces typical plating defects that impair quality and functions and explains the symptoms and causes of such defects.
This section also introduces new examples of plating defect inspections and problem solutions using KEYENCE’s latest 4K digital microscope.
- Types and Causes of Plating Defects
- Inspection Examples of Plating Defects Using the 4K Digital Microscope
- Examples of Problems in Plating Inspections Solved with KEYENCE’s 4K Digital Microscope
- A Single Unit Provides More Advanced and Streamlined Inspection and Evaluation for Plating
Types and Causes of Plating Defects
Plating is frequently used to process surfaces of various shapes and materials including metal, plastic, and ceramics. Covering material surfaces with a coating of appropriate thickness can add not only ornamental effects but also various functions such as wear resistance, corrosion resistance, heat resistance, chemical resistance, electric conductivity, lubricating properties, and adhesion properties. At the same time, any plating defects that occur in plating processes can greatly affect the quality and characteristics of materials and products.
The following are three major types of plating defects that occur in metal plating and the symptoms and causes of such defects.
Insufficient adhesion: Peeling, blister
Symptoms that can be seen when the adhesion to a substrate surface is reduced for some reason and thus the plating fails to firmly adhere to the surface. Plating that has firmly adhered to the surface can also blister or peel off when bended in post processing due to differences in flexibility between the substrate and plating.
Defects due to foreign particle adhesion: Rough surface
This symptom can be seen when fine protrusions are generated on plating surfaces in wet plating. This symptom occurs when foreign particles (metal particles) floating in a plating bath are mixed into the plating layer.
Deposit missing: Stain, unevenness, pit, pin hole
Most “uneven brightness” and “staining” on plating surfaces occur when the surfaces are partially fogged or tarnished by various factors such as certain environments. These symptoms are caused by uneven roughness or insufficient degreasing on the material surface or by variations in the plating processes.
(A. plating layer, B. base material)
Both pits and pin holes are concave defects on plated surfaces. They are caused by deposit missing. A pit is a visible (macroscopic) hole that does not penetrate a plating layer, while a pin hole is a micropore that penetrates into a base material or a lower layer. Pin holes can cause secondary failures and defects such as “blistering” and “corrosion” of plating layers.
To accurately determine whether a defect is a pit or a pin hole, the information of the Z direction (layer thickness and hole depth) is required in addition to 2D images.
Inspection Examples of Plating Defects Using the 4K Digital Microscope
Plating, which provides material surfaces with not only ornamental effects but functions as well, greatly affects product functionality, performance, and durability as well as appearance quality. Also, plating in recent years has achieved a higher level of functionality, thus requiring more advanced defect analysis and reliability evaluation.
Plating layers, however, are thin and shiny, and typical defects that occur on such layers are microscopic and three-dimensional. Inspections using measuring instruments or 2D images have various problems when it comes to ensuring reliable plating quality.
KEYENCE’s VHX Series high-definition 4K Digital Microscope uses a high-resolution lens and cutting edge technologies such as a 4K CMOS, enabling accurate observation and analysis of plating layers with clear 4K images.
The VHX Series also supports 2D measurement and 3D shape and profile measurement even on magnified images, thus making it possible to complete the procedures of quality control and assurance in inspections of plating defects easily and quickly with a single unit.
This section introduces the latest inspection examples of plating defects using the VHX Series.
Discolouration and corrosion in plating
Pin hole on plating layers
Peeling of plating
Cracks in plating
Analysis of rough surfaces (adhesion of foreign particles)
Thickness measurement of plating layers (sample embedded in resin)
Examples of Problems in Plating Inspections Solved with KEYENCE’s 4K Digital Microscope
Magnified observation, defect analysis, and measurement on plated surfaces are difficult and have many problems.
This section introduces examples of problems in plating inspections solved with the VHX Series, KEYENCE’s latest 4K Digital Microscope.
Clear imaging of plating surfaces even at high magnification
With the VHX Series 4K Digital Microscope
The high-resolution lens and 4K CMOS provide a deep depth of field even in high-magnification observation. Fully focused clear observation that is not affected by irregularities on plated surfaces is possible even at high magnification.
Fully-focused imaging and effortless zooming
With the VHX Series 4K Digital Microscope
Real-time depth composition enables users to instantly capture fully-focused images of targets that have surface irregularities. This reduces the time required for focusing and makes it possible to observe the entire target, providing more effective analysis and evaluation.
Furthermore, the high-resolution lenses and the motorised revolver mounted on the VHX Series enable seamless zoom between 20x and 6000x without lens replacement.
Focusing with a lens automatically changed according to the magnification enables quick zooming. Efficient data management is also possible because the information of the lens and magnification is recorded with the captured image.
- A. High-resolution lens
- B. Motorised revolver
3D shape and profile measurement possible in magnified observation
With the VHX Series 4K Digital Microscope
The various menus enable 3D shape and profile measurement with simple operations.
With 3D shape and profile measurement, targets can be examined quantitatively to determine whether a defect is a foreign particle, dent, pit, or pinhole. Operations from magnified observation to 2D/3D measurement can be performed effectively with a single VHX Series unit.
Quantitative evaluation with automatic area measurement
With the VHX Series 4K Digital Microscope
The automatic area measurement function easily measures the area, crystal grain size, and number of grains in a specified region. In addition, measurement results can be binary processed, displayed in a list and histogram, and output as a report with simple operations performed on a single unit.
Plated surface appearance evaluation optimised by light switching
With the VHX Series 4K Digital Microscope
The multi-lighting function allows users to capture and select images instantly under various lighting conditions and provides effective analysis and evaluation of plated surfaces that look different depending on the lighting.
In addition, images captured under different lighting conditions can be displayed side by side, a function that enables users to perform smooth analysis and evaluation with comprehensive judgement.
- A. Coaxial illumination
- B. Ring illumination
- C. Coaxial partial illumination
- D. Mixed illumination
A Single Unit Provides More Advanced and Streamlined Inspection and Evaluation for Plating
KEYENCE’s VHX Series high-definition 4K Digital Microscope uses clear 4K images to significantly streamline observation, analysis, and quantitative evaluation of plating defects—which are difficult with conventional microscopes. It also enables previously impossible 2D/3D measurement, binary measurement, and report creation seamlessly in a single unit.
The VHX Series is equipped with many more useful functions in addition to those introduced here.
For details on the VHX Series, click the button shown below to download the catalogue. For inquiries, click the other button shown below to contact KEYENCE.
