IEC 62899-402-3 pdf – Printed electronics – Part 402-3: Printability – Measurement of qualities – Voids in printed pattern using a two-dimensional optical image
1 Scope
This part of lEC 62899 specifies the optical measurement method for acquiring two-dimensionalimages of voids and obtaining the void-related attributes in the dried or cured printed patterns
which are part of the electronic products in the field of printed electronics. The measurablevoids using this document are limited to those that are distinguishable by the optical imagemeasurement.
NOTE In this document,void means an imperfection of pattern observed from a two-dimensional(2D) top-view.
2Normative references
The following documents are referred to in the text in such a way that some or all of their contentconstitutes requirements of this document.For dated references, only the edition cited applies.
For undated references,the latestedition of the referenced document(including anyamendments) applies.
ISO 291，Plastics – Standard atmospheres for conditioning and testing
3 Terms，definitions and abbreviated terms
For the purposes of this document, the following terms and definitions apply.
lSo and lEC maintain terminological databases for use in standardization at the followingaddresses:
. Iso Online browsing platform: available at https:/www.iso.orglobp.IEC Electropedia: available at http://www.electropedia.orgl
3.1
region of interestRol
area, inside defined boundaries, to be analysed
3.2
background area
part of the area in the ROl that contains the background, excluding the patterned part
3.3
pattern area
part of the area in the ROl that contains the patterned part,and which may include voids,excluding the background
3.4
void
absence of ink in an area that should be inked
3.5
ratio of void
ratio of the total void area to the area of the pattern
3.6
void threshold
B ref
brightness level of the pattern which separates voids and non-voids
3.7
void threshold index
Z
weight factor that determines the value of the void threshold
3.8
Bback
brightness level of the background
3.9
Bpattern
brightness level of the pattern
4Atmospheric conditions for evaluation and conditioning
The standard atmosphere for evaluation (test and measurement) and storage of the specimen
shall be a temperature of (23±2) C and relative humidity of (50±10) %,conforming tostandard atmosphere class 2 specified in lSO 291.For a plastic test piece which is a substrate
with printed patterns，the standard atmosphere for evaluation(test and measurement) andstorage of the specimen shall be a temperature of (23 ± 1)°C and relative humidity of (50 ±5) %，conforming to standard atmosphere class 1 specified in lSo 291.
Unless otherwise specified, the conditions shall be reported.
lf conditioning is necessary, the same standard atmosphere specified above shall apply.
5 Measuring methods and instruments
5.1 Measuring instrument
The measurement of voids in the pattern shall be carried out with an instrument that can obtainthe image of the pattern.The repeatability and accuracy of the measuring instrument should be
less than 10 % of the tolerance specification of the smallest dimension of the voids that themeasurer wants to measure. In the measurement system,the image of the pattern should beconverted to an image file.The image should include the pixel information without loss due to
compression (e.g. causes of jpeg compression).The pixel dimension or resolution of the image
is determined by agreement between the user and supplier;if not,the pixel dimension of theimage should be less than half of the smallest dimension of the void that the measurer wants
to measure. lf working with the resolution instead of the pixel dimension,this requirementshould be fulfilled accordingly.
5.2Preparation of specimen
The measuring area of the specimen is determined by agreement between the user and supplier.The specimen should be kept flat during the measurement. The specimen to measure voids inthe pattern necessarily contains the background area which does not have the pattern.
5.3 Measuring method
The printed pattern has the form of a line or solid area and can have voids. For the measurementof voids in the pattern, the boundary between the printed area and the void is recognized and
the number and area of the void are calculated using an appropriate software. The sizeinformation on every measurable void of interest is required.The measurement steps are asfollows:
a) Find a region of interest (ROI)
The ROl shall be set to include a whole pattern or a part of the pattern to be measureddepending on the size of the pattern. The ROl shall contain both the pattern with voids(measuring area) and the background without the pattern as shown in Figure 1.
b) Define the pattern area
The pattern area shall include only the printed pattern excluding the background areawithout the pattern as shown in Figure 1.
c) Define the background area
The background area in the ROl shall include only the background area excluding theprinted pattern as shown in Figure 1. The brightness of the background area is used todefine the void threshold (refer to Annex A).