Seal integrity inspection of medical device packages
Key challenge in pharmaceutical packages: 100% seal integrity
Total seal integrity of delivered pharmaceutical packages is of crucial importance because harmful contaminants may enter a package through seal defects.
Existing standardized test methods such as dye penetration and bubble tests are destructive to the packaging. Traditional machine vision systems are unable to detect seal imperfections in any reliable way.
The goal is to find a non-destructive and reliable test method that allows for the automatic on-line testing of all the packages produced.
Automated non-destructive on-line solution by LCI-technology
Line Confocal Imaging technology (LCI) has the unique ability to accurately measure the distance to each material surface in a transparent target: A flawless heat seal is detected as one surface, but an air gap in the seal layer causes the seal to be detected as two surfaces.
Both 2D and 3D images of all the surface layers and possible seal defects are recorded simultaneously by just one LCI scan with a micrometer Z resolution. The signal processing needed to generate this 2D and 3D image information is taken care by in-built signal processing power in FocalSpec LCI measurement heads, which greatly reduces burden on other system components and makes the integration work significantly faster and simpler.
The 2D and 3D seal layer images can then be easily processed by a standard computer system allowing for the fast, reliable and automated detection of seal defects invisible to naked eye and traditional machine vision systems.
Detected defect types include: incomplete seals, inclusions, wrinkles, channel defects, misaligned seal, delaminations, pinholes, particles in seal area.
Seal integrity inspection measurement principle
The LCI sensor contains an embedded fast signal processing unit that detects and calculates the surface profiles found in the single tomographic cross section image. The calculation reduces the amount of data so that the measured points can be transferred though Ethernet connection for further processing.
The embedded electronics calculate the 3D profiles of all the surface layers found in the tomographic image. The height information of each point measured is processed in calibrated micrometers. Furthermore, the intensity of every detected surface point is calculated with high resolution (> 12 bits). For example, a single measurement that is completed with an exposure time of 5-50 µs, can contain up to three surface profiles for three transparent layers (The surface layers being the top of the film, the bottom of the film and the top of the Tyvek surface). Each profile is at its maximum 2048 bits wide (in another words the width is 11.2mm when the pixel resolution is 5.5µm) and the 3D- or Z-resolution for each point is 1 µm or better. In addition, the intensity information is provided at the same time for each of these 3 x 2048 points. The measurement is then repeated 500 times/s at specified intervals providing over 3million 3D measurement points. The maximum height (Z-range) of the tomographic profile is 2.8 mm.
The imaging frequency may be increased up to 2500 Hz if the Z- range requirements are reduced to 0.07mm due to accurate sample positioning.
Seal integrity inspection is then performed by utilizing both the 3D and the intensity measurements. The imaging width for the FocalSpec Line Confocal Sensor LCI1200 is 11.26 mm, and for the Line Confocal Sensor LCI1600 it is 16.4 mm. Please note that the LCI1600’s Z-range is 45 % higher than LCI1200’s however, the LCI1600 has a smaller tolerance to surface angles at 13.5 degrees compared to 20 degrees with the LCI1200.