Overview
IEC 62899-302-2:2018 - "Printed electronics - Part 302-2: Equipment - Inkjet - Imaging-based measurement of droplet volume" defines a method for determining inkjet droplet volume from high-speed images using drop-in-flight measurement systems. The standard focuses on imaging-based measurement (e.g., shadowgraph) and provides guidance on measurement limits, calibration, and uncertainty. It excludes interference-fringe techniques such as holography or phase doppler anemometry, and while it covers drop-on-demand systems, it may not be applicable to continuous inkjet or liquid dispensing systems.
Key Topics and Requirements
- Scope and applicability
- Applies to imaging-based measurement of droplet volume from images obtained by drop-in-flight systems.
- Does not apply to interference-fringe imaging methods (holography, phase doppler anemometry).
- Measurement fundamentals
- Use of high-speed flash imaging to avoid motion blur and produce accurate droplet images.
- Preferential analysis of spherical droplets after shape equalization (merged sub-drops and damped oscillations).
- Consideration of native drop vs. merged droplet volumes for greyscale jetting.
- Imaging and optics
- Recommendations for high magnification (typically ≥10X) and telecentric optics to maintain image linearity and depth of focus.
- Need for sub-microsecond flash illumination; typical droplet speeds cited (5–10 m/s).
- Image processing and calibration
- Greyscale-to-binary conversion, pixel resolution, and sub-pixel fitting algorithms for diameter/area extraction.
- Linear optical calibration (µm/pixel) and optional absolute calibration via traceable methods (e.g., weighed drops).
- Uncertainty and limits
- Discussion of measurement uncertainties, effects of refraction/diffraction, background intensity, focus, and shape non-idealities.
- Guidance on avoiding conditions that produce inaccurate results (e.g., non-spherical droplets, highly particulate or shear-thinning fluids).
- Document notes
- No normative references listed; Annex A provides informative considerations and formulae.
Applications and Users
- Who uses it
- Engineers and technicians in printed electronics, inkjet equipment manufacturers, metrology labs, and R&D teams developing ink formulations and print-heads.
- Practical uses
- Quality control of inkjet dispensing and print-head performance.
- Development and validation of greyscale inkjet imaging and dosing for printed electronics.
- Calibration and verification of drop-analysis systems used in production and research.
Related Standards
- Part of the IEC 62899 series on Printed Electronics - users should consult other parts of IEC 62899 for complementary guidance and check the IEC webstore for the latest editions and related documents.
Open preview (PDF)Printed electronics - Part 302-2: Equipment - Inkjet - Imaging-based measurement of droplet volume
