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  5. New Establishment of the JIS on the Consecutive Measurement of Cure Shrinkage for Curable Resins (Adhesives)

New Establishment of the JIS on the Consecutive Measurement of Cure Shrinkage for Curable Resins (Adhesives)

Promoting the development of adhesives that encourages further technical advancement of precision electronic equipment

March 18, 2019

In order to promote the technical advancement of the latest electronic equipment including smartphones, it is necessary to improve the functions as well as to reduce the size and weight of resin members that are used as components, and curable resins (adhesives) used for assembling them require high dimensional stability. Therefore, as a method to assess the dimensional stability of curable resins, a method that allows for consecutively measuring the cure shrinkage of curable resin is newly established as JIS K 6941 (Consecutive measurement of the cure shrinkage of ultraviolet curable resin and thermoset resin), which is in application on “Standards Development Program to Create New Market.” While products had been made under the judgement that the dispersion of production is inevitable because there was no method to consecutively measure the curing of resins, the establishment of this JIS allows further improvement of product quality with improved precision of production, and a certain level of quality will be guaranteed. Utilizing this measurement method on the production of cellphones, personal computers, auto parts, etc., is expected to contribute to the further technical advancement of precision electronic equipment.

1. Purpose of the establishment

It is important to improve the functions of resin members used in the latest electronic equipment including smartphones and to reduce their size and weight. Accordingly, adhesives (curable resins) to assemble them are also required to fulfil higher dimensional precision than ever before (which means to reduce the cure shrinkage). For example, the camera lens of a smartphone is affixed by just a tiny drop of ultraviolet curable resin. If this is affixed only slightly away from the correct position, it will slightly change the position of the lens, which will result in distortion of images, and the user will not be able to take good pictures. It is necessary to confirm the steps of the process of resin shrinkage up to the final curing. The shrinkage process changes along with the curing method, so it is necessary to find conditions that ensure good, stable curing. However, the measurement precision of the existing measurement methods of shrinkage (specific gravity method, etc.) is low, requiring larger samples than the actual state of use, and it takes a long time for measurement. There used to be no method throughout the world to consecutively observe the shrinkage during the process of curing. However, the new JIS method allows measurement with a rather small quantity similar to the amount actually used in the product, and also to measure the shrinkage of the resin consecutively.

Adopting this JIS test method for resin members enables manufactures and other stakeholders engaging in the electronic equipment industry to easily and quickly measure the changes of curable resins with high precision, and it is expected to contribute to the further technical advancement of electronic equipment.

Consecutive measurement device for measuring the shrinkage of thermoset resin

2. Key points of the newly established JIS

This JIS sets forth the method to identify the cure shrinkage by consecutively measuring the curing process of ultraviolet curable resin and thermoset resin.

The characteristics of this measurement method are as follows.

a) Shortening of measurement time

In this measurement, the measurement before and after the curing of a single sample is implemented as a single process, which significantly shortens the time required for the measurement. Therefore, the analysis of difference by materials preparation at the stage of development or selection among many types of materials can be implemented efficiently.

b) Allowing for measurement with a small sample

The conventional JIS K7112 (Measurement of the density and specific gravity of non-foamed plastics) requires samples as large as about a few centimeters square. However, with the method provided here, measurement is possible with samples of less than one hundredth a part of the aforementioned method. It becomes possible to measure expensive materials and small amounts of samples at the development stage more easily.

c) Allowing for measurement under arbitrary curing conditions (ultraviolet irradiation and/or heating)

While measurement was limited to before and after curing in the previous method, real-time measurement during the curing becomes possible with this method. Because measurement is possible under arbitrary curing conditions that used to not be included in the previous specification, including ultraviolet irradiation, it facilitates simulation in the production process.

d) Allowing for the measurement of the consecutive curing process of shrinkage

Because not only the cure shrinkage before and after the curing but also the behavior during the reaction can be measured, it allows for measurement including the impact of heat expansion by reaction heat and heating/cooling or reaction speed under arbitrary curing conditions. At the same time, it also becomes possible to presume the load on or the behavior of peripheral members under the actual conditions of use. It also allows to observe the behavior of materials that change from moment to moment through the real-time measurement of changes in the volume before, during and after the curing.

3. Expected effects

Adopting the test method stipulated by this JIS in the manufacturing process of cellphones, personal computers, auto parts, etc. is expected to contribute to further technical advancement of precision electronic equipment. Furthermore, it will result in the creation of new technology, including the development of high-performance curable resins and low-price and high-performance cure shrinkage measurement devices, etc.

Division in Charge

International Standardization Division, Industrial Science and Technology Policy and Environment Bureau