Experimental determination method for curing shrinkage rate of adhesive

Abstract

The present application relates to the technical field of detection of the curing shrinkage rates of adhesives, and more specifically relates to an experimental determination method for the curing shrinkage rate of an adhesive. The method comprises the following steps: step 1, preparing a binary warping sample composed of an adhesive and an elastic material; step 2, curing the sample according to standard adhesive curing steps; step 3, placing the cured sample in an environment where the temperature gradually rises, and observing warping changes of the sample; and step 4, when the warping of the sample returns to zero, recording the current temperature of the sample, and calculating the curing shrinkage rate of the adhesive. The method achieves the measurement of the curing shrinkage rate of the adhesive, is simple, and is suitable for the measurement of curing shrinkage rates under the adhesive working conditions of different sizes, different materials, different interface states, etc.

Description

An experimental method for determining the curing shrinkage of an adhesive Technical Field

[0001] The present application relates to the technical field of adhesive curing shrinkage detection, and more specifically, to an experimental determination method for adhesive curing shrinkage. Background Art

[0002] Adhesives are widely used in industries such as electronic packaging, building materials, aerospace, automotive manufacturing, and healthcare. Their primary functions include interfacial bonding, waterproofing, and enhancing reliability. Therefore, the cure shrinkage of adhesives is a key parameter in assessing their reliability.

[0003] Currently, the test methods for adhesive curing shrinkage are mainly obtained through experimental methods such as pycnometers and grating optical fibers. Among them, the pycnometer method requires the adhesive sample to be placed in a liquid environment for curing, and its curing shrinkage is measured by the change in the liquid level during the curing process. The current study reported a curing shrinkage test method based on the pycnometer experiment. In this method, 5ml of high-temperature curing adhesive is poured into a 10ml pycnometer, and then silicone oil is added to make the upper liquid level reach the specified scale line; the pycnometer is placed in an oil bath and heated to the adhesive curing temperature; after curing is completed, the pycnometer is cooled and the upper liquid level scale is read. The difference between the scales before and after curing is considered to be the curing shrinkage of the adhesive. The main disadvantages of this method are low accuracy and the obtained curing shrinkage is the full-process curing shrinkage, rather than the post-gel point curing shrinkage, which is more important in engineering applications.

[0004] The current study proposes a method for measuring adhesive cure shrinkage using a grating fiber. A Fiber Bragg Grating (FBG) sensor is placed in an uncured cylindrical adhesive specimen in a mold and illuminated with a broadband light source. During the thermal curing process, the wavelength of the light reflected by the grating is continuously recorded. The wavelength change of the Bragg grating can then be used to calculate the adhesive's cure shrinkage. While the FBG experiment offers higher accuracy than the pycnometer test, the extremely high cost of manufacturing a FBG sensor limits the method's application.

[0005] The main drawbacks of the pycnometer test method are its low accuracy: (1) Adhesives are generally high-viscosity liquids, making initial volume measurement relatively difficult; (2) Due to the high viscosity of adhesives, bubbles are easily introduced during manual injection, making the measurement error of volume change uncontrollable; (3) The volume change before and after adhesive curing is read visually, which results in large errors. In addition, the curing shrinkage rate obtained by the pycnometer test method is the shrinkage rate before and after curing, rather than the shrinkage rate after the gel point, which is more meaningful for engineering purposes.

[0006] The main drawback of the Bragg grating test method is its high test cost: (1) The optical fiber etched with the grating is a disposable consumable and requires extremely high processing precision, which makes the experimental cost uncontrollable during batch testing and is not suitable for industrial development processes; (2) The light source, modem, and signal processing equipment required in this method are not widely used standard laboratory equipment and need to be purchased separately, which creates obstacles to the wider application of this method in laboratories.

[0007] Summary of the Invention

[0008] The present disclosure provides an experimental measurement method for the curing shrinkage rate of an adhesive, which realizes the measurement of the curing shrinkage rate of an adhesive. The method is simple and can be applied to the measurement of the curing shrinkage rate under adhesive working conditions such as different sizes, different materials, and different interface states.

[0009] In a first aspect, the present disclosure provides a method for experimentally measuring the curing shrinkage of an adhesive, comprising the following steps:

[0010] The first step is to prepare a binary warpage specimen consisting of adhesive and elastic material;

[0011] The second step is to cure the sample according to the standard adhesive curing procedure;

[0012] The third step is to place the cured sample in a gradually increasing temperature environment and observe the warpage change of the sample;

[0013] In the fourth step, when the warpage of the sample returns to zero, the current sample temperature is recorded and the curing shrinkage of the adhesive is calculated.

[0014] Preferably, the specific method of the first step is: use tape to make an adhesive limiting mold, and stick the mold on a base made of elastic material. The base needs to be made of a material with a small thermal expansion coefficient and performance that is not sensitive to temperature.

[0015] Preferably, the first step also includes the following specific method: using alcohol to clean the inner base of the limiting mold, and after the alcohol is completely evaporated, using a plasma cleaning machine to treat the surface of the base so that the surface of the base can be fully wetted by the adhesive.

[0016] Preferably, the second step specifically includes the following method steps:

[0017] (1) injecting the adhesive into the mold, controlling the amount of adhesive so that the adhesive does not overflow from the mold;

[0018] (2) heating the sample to the flow temperature of the adhesive, so that the adhesive flows naturally and fills the mold;

[0019] (3) Curing the adhesive using the adhesive curing parameters.

[0020] Preferably, the sample is gradually heated, and the temperature at which the warpage value of the sample drops to 0 is recorded as T Flat ; The test method for the warpage value of the sample can be accurately selected according to the required experiment. If the accuracy requirement is relatively low, the naked eye observation method is used; if the accuracy requirement is relatively high, a non-contact three-dimensional morphology measuring instrument is used.

[0021] Preferably, the specific method of the fourth step is: calculating the curing shrinkage S of the adhesive, and the calculation formula is as follows:

[0022] Among them, T Cure is the curing temperature of the adhesive, CTE is the coefficient of thermal expansion of the adhesive after curing, and the number of the test specimens can be increased to N to increase the experimental measurement accuracy of the curing shrinkage rate; for the N experimental specimens, the curing shrinkage rates are calculated in sequence using the method, and the average value of the curing shrinkage rates measured for all experimental specimens is used as the final curing shrinkage rate of the adhesive.

[0023] In summary, this application has the following beneficial effects:

[0024] 1. This application achieves the measurement of adhesive curing shrinkage. The method is simple and can be applied to the measurement of curing shrinkage under different bonding conditions such as different sizes, different materials, and different interface states. It can provide key parameters for the study of stress changes during the use of adhesives.

[0025] 2. Compared with the pycnometer test, this method has high precision, good repeatability, and shorter time. Compared with the grating fiber test, this method has low cost, low equipment requirements, and simple sample preparation;

[0026] 3. This application realizes the measurement of adhesive curing shrinkage. The test method is simple and can be applied to the measurement of curing shrinkage of adhesives of different types and sizes. It can be widely used in the study of adhesive curing stress.

[0027] It should be understood that the foregoing general description and the following detailed description are merely exemplary and explanatory and are not intended to limit the scope of protection of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 1. Figure 1 shows the binary warping test specimen structure of the present application: (a) adhesive limiting mold, (b) elastic material base;

[0029] 2. Figure 2 is a comparison of the morphology of the binary warpage specimen after curing and cooling and the specimen after heating;

[0030] 3. Figure 3 is the curve of warpage changing with temperature in this application. DETAILED DESCRIPTION

[0031] The present application is further described in detail below with reference to the examples. It is particularly noted that if no specific conditions are specified in the following examples, the reactions are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0032] Example

[0033] A method for measuring the curing shrinkage of an adhesive, the method comprising the following steps:

[0034] The first step, as shown in Figure 1, is to use a punching machine to make a polyimide tape limit mold with a thickness of 0.3 mm, an inner frame size of 70*10 mm, and an outer frame size of 80*12 mm. The mold is then tightly attached to an 80*30 mm silicon wafer substrate.

[0035] In the second step, alcohol is used to clean the surface of the silicon wafer in the mold, and a plasma cleaning machine is used to treat the surface after the alcohol is completely evaporated.

[0036] In the third step, 300 mg of bottom filling material X is injected into the mold to prepare a binary warpage specimen.

[0037] In the fourth step, the sample is heated to 100° C. to allow the bottom filling material X to flow naturally to fill the bottom of the mold.

[0038] In the fifth step, the sample is cured at 165° C. for two hours to completely cure the underfill material X, and the sample is cooled to room temperature.

[0039] In the sixth step, the sample is placed in a three-dimensional topography measuring instrument and gradually heated until the warping disappears (as shown in FIG2 ), and T is obtained according to the warping temperature curve (as shown in FIG3 ). Flat =197.26℃.

[0040] Step 7: Calculate the curing shrinkage of the bottom filling material X.

[0041] The design of the two-dimensional warpage specimen consists of a rectangular mold made of 0.3-0.6mm thick tape and a base made of 0.3-1mm thick elastic material. The key is to properly control the adhesive dosage and base thickness to ensure that the warpage is large enough to be easily measured, while not too large to damage the base.

[0042] The above description is merely an exemplary embodiment of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present disclosure should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. An experimental measurement method for the curing shrinkage rate of an adhesive, characterized in that, It includes the following steps: In the first step, make a binary warping specimen composed of an adhesive and an elastic material; In the second step, cure the specimen according to the standard steps for adhesive curing; In the third step, place the cured sample in an environment with gradually increasing temperature and observe the warping change of the specimen; In the fourth step, when the warping of the specimen returns to zero, record the current specimen temperature and calculate the curing shrinkage rate of the adhesive.

2. The experimental measurement method for the curing shrinkage rate of an adhesive according to claim 1, wherein The specific method for the first step is as follows: Use tape to make an adhesive limiting mold, and attach the mold to the substrate made of an elastic material. When making the substrate, a material with a small coefficient of thermal expansion and whose properties are not sensitive to temperature should be selected.

3. The experimental measurement method for the curing shrinkage rate of an adhesive according to claim 1, wherein, The first step also includes the following specific method: Clean the inner substrate of the limiting mold with alcohol. After the alcohol has completely evaporated, use a plasma cleaner to treat the surface of the substrate so that the surface of the substrate can be fully wetted by the adhesive.

4. The experimental measurement method for the curing shrinkage rate of an adhesive according to claim 1, wherein The second step specifically includes the following method steps: (1) Inject the adhesive into the mold, and control the amount of the adhesive used so that the adhesive does not overflow from the mold; (2) Heat the specimen to the flow temperature of the adhesive to make the adhesive flow naturally and fill the mold; (3) Cure the adhesive using the curing parameters of the adhesive.

5. The experimental measurement method for the curing shrinkage rate of an adhesive according to claim 1, characterized in that, The specific method for the third step is as follows: Gradually heat the specimen and record the temperature when the warpage value of the specimen drops to 0, which is recorded as T Flat ; The test method for the warpage value of the specimen can be accurately selected according to the required experiment. If the accuracy requirement is relatively low, the naked-eye observation method is used; if the accuracy requirement is relatively high, a non-contact three-dimensional topography measurement instrument is used.

6. The experimental measurement method for the curing shrinkage rate of an adhesive according to claim 1, characterized in that The specific method of the fourth step is as follows: calculate the curing shrinkage rate S of the adhesive, and the calculation formula is as follows: where T Cure is the curing temperature of the adhesive, CTE is the coefficient of thermal expansion after the adhesive is cured, and the number of specimens can be increased to N to improve the experimental measurement accuracy of the curing shrinkage rate; for N experimental specimens, the curing shrinkage rate is calculated successively by the method, and the average value of the curing shrinkage rates measured for all experimental specimens is used as the final curing shrinkage rate of the adhesive.

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