Infrared Imaging Method

A. Introduction 

Non-destructiveTo detect defects in hermetic packages by computer evaluation of infrared (IR) ages with previously defined patterns of acceptance.> 50 μm channel, > 100 μm pinholesOn-line, > 5 s> $50,000

B. Operation 

Infrared light may be absorbed, transmitted, and emitted by a package or a seal. Differences between these parameters provide a means for visual interpretation when sensed automatically and enhanced for visibility.

Infrared imaging (IRI) thermography is an inspection technology that can be implemented on-line in industrial quality control systems to enhance efficiency in removing defective packages. According to the industry, the IRI technique makes a merit of non-destructively scanning and thermally imaging surfaces of various materials.

  • Sample packages
  • Infrared camera
  1. Seal packages by using heat sealers.
  2. Take thermal images after heat sealing by using an IR camera at heat-sealing temperatures in the range of 60 to 140oC. Thermal information in the 3 to 5 μm infrared band will be measured and recorded.
  3. Analyze images at IR Iron, Midgreen, or Midgrey image palette modes.
  • Infrared images of packages with different standard defects are shown in Figures 1 and 2. Each image was taken at an interval of 1/30s and a shutter speed of 2 μs. In general, all defects were easily identified and further characterized by the infrared imaging (IRI) technique. Limit of detections (LODs) of the IRI technique for microchannels in foil-laminate packages and plastic packages were 180 μm and 40 μm, respectively. The LODs for pinholes in in foil-laminate packages and plastic packages were 100 μm and 160 μm, respectively.
  • Linear regression analysis of seal quality data in Figure 3 indicated that average initial surface temperatures of heat-sealed area obtained from infrared images were significantly correlated with seal strength.

C. Application 

PACKAGE TYPES AND DEFECTS

  PACKAGE TYPE
DEFECTS Flexible Pouch Semi-rigid and Rigid plastic container Plastic Can (Double-seam Metal End) Paperboard
Abrasion
Corner Dent      
Crushed  
Cut (Fracture)
Delamination  
Double Seam Defects*      
Flexcracks    
Foreign Matter Inclusion    
Gels    
Hotfold      
Label Foldover      
Leaker      
Leaker (Channel)  
Leaker (Corner)      
Leaker (Notch)      
Leaker (Perforation)      
Leaker (Pulltab)      
Leaker (Seal)      
Loose Flap or Ear      
Malformed    
Puncture (Pinhole)
Seal Defects (Blister)      
Seal Defects (Blocked)      
Seal Defects (Burnt)      
Seal Defects (Compressed)      
Seal Defects (Contaminated)    
Seal Defects (Convolution/Embossing)      
Seal Defects (Creep)      
Seal Defects (Crooked)      
Seal Defects (Incomplete)      
Seal Defects (Misaligned/Deformed)    
Seal Defects (Nonbonding/Weak)      
Seal Defects (Plastic Lumps)      
Seal Defects (Seal-width Variation)      
Seal Defects (Stringy)      
Seal Defects (Uneven Impression)      
Seal Defects (Uneven Juncture)      
Seal Defects (Wrinkle)    
Swell (Swollen Package)
Waffling      

The application is limited by the need for statistical chracterization of all defects and subsequent computerizations.

D. Source 

FLIR Systems (http://www.flir.com/US/)Song, Y., Setikaite, I., and Sadler, G. 2006. Evaluation of seal quality and imperfections in flexible pouches by infrared imaging thermograph. IFT, Orlando, FL.