Evaluation method for compatibility of conformal coating material and electronic adhesive in electronic assembly

Abstract

The invention relates to a method for evaluating the compatibility of a conformal coating material and an electronic adhesive in electronic assembly, which comprises the following steps of: coating the conformal coating material to be detected and the electronic adhesive on a printed circuit board, and contacting the conformal coating material with the electronic adhesive to obtain a sample plate to be detected; performing a temperature cycle environment test and a humid and hot environment test on the to-be-tested sample plate to obtain a test sample plate; obtaining the difference between the physicochemical properties of the conformal coating material and the electronic adhesive before and after the test, wherein the physicochemical properties comprise at least one of surface appearance, conductivity, organic matrix material components, thermal decomposition temperature, surface insulativity and appearance of the interface of the conformal coating material and the electronic adhesive; and evaluating the compatibility between the conformal coating material and the electronic adhesive according to the difference of the physicochemical properties. According to the method, the compatibility evaluation dimension and standard of the conformal coating material and the electronic adhesive are defined, and the risks of short circuit, degumming, failure and the like of electronic products are reduced.

Description

Technical Field

[0001] This invention relates to the field of testing and evaluation technology, and in particular to a method for evaluating the compatibility of conformal coating materials and electronic adhesives in electronic assembly. Background Technology

[0002] With the booming development of electronic products in industries such as 5G communication, low-orbit satellites, artificial intelligence, quantum computing, and the Internet of Things, the application of electronic assembly materials is becoming increasingly widespread. Individual electronic products often integrate conformal coating materials, electronic adhesives (such as underfill adhesives, side fill adhesives, potting compounds, fixing adhesives, etc.), and other types of electronic assembly materials.

[0003] Due to the wide variety of electronic assembly materials and the complex reaction mechanisms between fine chemicals, incompatibility in physical and chemical properties between different materials can lead to reliability issues or even complete failure in electronic products. For example, conformal coating materials exhibit solvent evaporation and post-curing characteristics, which may cause "poisoning" of electronic adhesives, inducing compatibility problems. Therefore, scientifically and efficiently evaluating the compatibility between conformal coating materials and electronic adhesives is crucial for ensuring the reliability of electronic products.

[0004] Currently, research on the compatibility of such materials lacks evaluation methods and standards, which cannot provide effective guidance for enterprises to carry out material screening work and makes it difficult to reduce potential product quality hazards caused by compatibility issues. Summary of the Invention

[0005] Therefore, it is necessary to provide a method for evaluating the compatibility of conformal coating materials and electronic adhesives in electronic assembly.

[0006] A method for evaluating the compatibility of conformal coating materials and electronic adhesives in electronic assembly includes the following steps:

[0007] A conformal coating material and an electronic adhesive to be tested are coated on a printed circuit board, wherein the conformal coating material and the electronic adhesive are in contact to obtain a test sample;

[0008] The test sample was subjected to temperature cycling environment test and damp heat environment test to obtain the test sample;

[0009] The differences in the physicochemical properties of the conformal coating material and the electronic adhesive before and after the test are obtained. The physicochemical properties include at least one of the following: surface appearance, electrical conductivity, organic matrix material composition, thermal decomposition temperature, surface insulation, and appearance at the interface between the conformal coating material and the electronic adhesive.

[0010] The compatibility between the conformal coating material and the electronic adhesive is evaluated based on the differences in their physicochemical properties.

[0011] In some embodiments, the printed circuit board is at least one of a comb-shaped electrode plate and a copper-clad laminate.

[0012] In some embodiments, the electronic adhesive is an underfill adhesive, a side fill adhesive, or a fixing adhesive. When coating the conformal coating material to be tested and the electronic adhesive on the printed circuit board, the electronic adhesive is first coated on the electrode area of ​​the comb electrode plate or the copper film of the copper-clad laminate and cured. Then, the conformal coating material is coated on the electronic adhesive and cured.

[0013] In some embodiments, the electronic adhesive is a potting compound. When coating the conformal coating material to be tested and the electronic adhesive on the printed circuit board, the conformal coating material is first coated on the electrode area of ​​the comb electrode plate or the copper film of the copper-clad laminate and cured. Then, the electronic adhesive is coated on the conformal coating material and cured.

[0014] In some embodiments, the temperature cycling test includes:

[0015] The test sample was placed in a high-temperature and low-temperature cyclic environment with a maximum temperature of 80℃~125℃ and a minimum temperature of -55℃~40℃. The temperature change rate was 5℃ / min~20℃ / min. The duration of each highest and lowest temperature was 10min~60min, and the number of cycles was 50~1000.

[0016] In some embodiments, the test conditions for the damp heat environment test include:

[0017] The test sample was placed in an environment with a temperature of 65℃~85℃ and a humidity of 40%RH~95%RH for 2h~2000h.

[0018] In some embodiments, multiple sets of test samples are prepared, and the difference between different sets of test samples is that the thickness of the conformal coating material is different; the influence of the thickness of the conformal coating material on the compatibility is compared and analyzed.

[0019] In some embodiments, the selection of physicochemical property testing items is based on the failure mode of the conformal coating material and the electronic adhesive, and the failure mode includes at least one of distortion failure, discoloration failure, degradation failure, adhesive function failure and insulation function failure.

[0020] When the failure mode includes distortion failure, the inspection items include surface appearance inspection and appearance at the interface between the conformal coating material and the electronic adhesive.

[0021] When the failure mode includes discoloration failure, the inspection items include surface appearance inspection.

[0022] When the failure mode includes degradation failure, the test items include electrical conductivity, organic matrix material composition, and thermal decomposition temperature.

[0023] The failure mode includes failure of the adhesive function, and the inspection items include the appearance at the interface between the conformal coating material and the electronic adhesive.

[0024] The failure mode includes insulation failure, and the inspection items include surface insulation.

[0025] In some embodiments, the surface appearance inspection includes observing changes in color, cracking, softening, and powdering of the conformal coating material and electronic adhesive before and after the test.

[0026] In some embodiments, the inspection of the appearance at the interface between the conformal coating material and the electronic adhesive includes: sealing and slicing the test sample, and observing the interface between the conformal coating material and the electronic adhesive using a scanning electron microscope or a metallographic microscope to observe the presence of cracks, delamination, pores, and bubbles.

[0027] In some embodiments, the testing of the organic matrix material composition includes: performing infrared spectroscopy detection on the organic matrix material composition before and after the test, and analyzing the consistency of the number, position, and intensity of peaks of the organic matrix material composition before and after the test.

[0028] In some embodiments, the detection of the thermal decomposition temperature includes: performing thermogravimetric analysis on the conformal coating material and the electronic adhesive before and after the test, and analyzing the difference in thermal decomposition temperature before and after the test.

[0029] In some embodiments, the conductivity detection includes: peeling the conformal coating material from the electronic adhesive, extracting the surface residue with pure water, testing the conductivity of the extract, and analyzing the difference in conductivity before and after the test.

[0030] In some embodiments, the surface insulation detection includes: during the damp heat environment test, using an online monitoring system to measure the resistance value, with a test interval of 20 min to 30 min, applying a bias voltage of DC 5V to 50V, and a test voltage of DC 50V to 110V; observing the corrosion, dendrites, and discoloration of the electrode layer before and after the test.

[0031] Compared with traditional methods, the above-mentioned method for evaluating the compatibility of conformal coating materials and electronic adhesives in electronic assembly has the following advantages:

[0032] The aforementioned evaluation method addresses the unique challenges of conformal coating materials, such as solvent evaporation and post-curing, providing a comprehensive technical solution encompassing "sample preparation, testing, inspection, and evaluation." By subjecting printed circuit boards coated with the conformal coating material and electronic adhesive to temperature cycling and damp heat environments, the core dimensions and standards for evaluating the compatibility of conformal coating materials and electronic adhesives are clarified. This reduces the risks of short circuits, delamination, and failures in electronic products due to poor compatibility, thereby minimizing product quality risks and rework costs. Attached Figure Description

[0033] Figure 1 (a) shows the appearance of the test sample 2-1 in Example 1 before the damp heat environment test; (b) shows the appearance of the test sample 2-1 in Example 1 before the damp heat environment test; (c) shows the appearance of the test sample 2-2 in Example 1 before the damp heat environment test; (d) shows the appearance of the test sample 2-2 in Example 1 before the damp heat environment test; (e) shows the appearance of the test sample 2-3 in Example 1 before the damp heat environment test; and (f) shows the appearance of the test sample 2-3 in Example 1 before the damp heat environment test.

[0034] Figure 2 (a) shows the appearance of the test sample 2-1 in Example 1 before the temperature cycling test; (b) shows the appearance of the test sample 2-1 in Example 1 before the temperature cycling test; (c) shows the appearance of the test sample 2-2 in Example 1 before the temperature cycling test; (d) shows the appearance of the test sample 2-2 in Example 1 before the temperature cycling test; (e) shows the appearance of the test sample 2-3 in Example 1 before the temperature cycling test; and (f) shows the appearance of the test sample 2-3 in Example 1 before the temperature cycling test.

[0035] Figure 3 (a) shows the infrared spectrum of the electronic adhesive in Example 1 before and after the damp heat test, and (b) shows the infrared spectrum of the electronic adhesive in Example 1 before and after the temperature cycling test.

[0036] Figure 4 (a) is the TG curve of the electronic adhesive on the test sample 2-1 in Example 1 before the damp heat test; (b) is the TG curve of the electronic adhesive on the test sample 2-1 in Example 1 after the damp heat test; and (c) is the TG curve of the electronic adhesive on the test sample 2-1 after the temperature cycling test.

[0037] Figure 5(a) is the resistance-time curve of the electronic adhesive on the test sample 1-1 in Example 1 during the damp heat test, where 1#1-2, 1#3-4, 1#5-6, and 1#7-8 represent the four electrode circuits connected to the test sample 1-1 respectively; (b) is the resistance-time curve of the electronic adhesive on the test sample 1-1 in Example 1 during the temperature cycling test, where 1#1-2, 1#3-4, 1#5-6, and 1#7-8 represent the four electrode circuits connected to the test sample 1-1 respectively;

[0038] Figure 6 (a) is an SEM image of the interface between the electronic adhesive and the conformal coating material of the test sample 2-1 in Example 1 before the test; (b) is an SEM image of the interface between the electronic adhesive and the conformal coating material of the test sample 2-1 in Example 1 after the humid heat environment test; and (c) is an SEM image of the interface between the electronic adhesive and the conformal coating material of the test sample 2-2 in Example 1 after the temperature cycling test. Detailed Implementation

[0039] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein; these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0041] An embodiment of a method for evaluating the compatibility of conformal coating materials and electronic adhesives in electronic assembly includes the following steps:

[0042] Step S1: Coat the conformal coating material and electronic adhesive to be tested onto the printed circuit board, so that the conformal coating material and electronic adhesive come into contact to obtain the test sample.

[0043] Step S2: The sample to be tested is subjected to temperature cycling environment test and damp heat environment test to obtain the test sample.

[0044] Step S3: Obtain the differences in physicochemical properties of the conformal coating material and the electronic adhesive before and after the test. The physicochemical properties include at least one of the following: surface appearance, electrical conductivity, organic matrix material composition, thermal decomposition temperature, surface insulation, and appearance at the interface between the conformal coating material and the electronic adhesive.

[0045] Step S4: Evaluate the compatibility between the conformal coating material and the electronic adhesive based on the differences in physicochemical properties.

[0046] The aforementioned evaluation method addresses the unique challenges of conformal coating materials, such as solvent evaporation and post-curing, providing a comprehensive technical solution encompassing "sample preparation, testing, inspection, and evaluation." By subjecting printed circuit boards coated with the conformal coating material and electronic adhesive to temperature cycling and damp heat environments, the core dimensions and standards for evaluating the compatibility of conformal coating materials and electronic adhesives are clearly defined. This effectively reduces the risks of short circuits, delamination, and failures in electronic products due to poor compatibility, thereby lowering potential product quality risks and rework costs.

[0047] Conformal coatings are protective coatings used on printed circuit boards (PCBs). For example, conformal coatings can prevent external contaminants such as salt spray, moisture, mold, and sulfidation from penetrating electronic components, thus preventing failure of both components and PCBs. Electronic adhesives refer to various adhesive materials used in electronic assembly, including but not limited to underfill adhesives, side fillers, potting compounds, and settling adhesives.

[0048] In some examples, in step S1, the printed circuit board is at least one of a comb-shaped electrode plate and a copper-clad laminate. Surface insulation is preferably tested using the comb-shaped electrode plate, while surface appearance, conductivity, organic substrate material composition, thermal decomposition temperature, and the appearance at the interface between the conformal coating material and the electronic adhesive are preferably tested using the copper-clad laminate.

[0049] In some examples, the comb electrode plate is an FR-4 epoxy glass comb electrode plate, meeting the requirements of the IPC-6012 standard. The line spacing of the comb electrode plate is, for example, but not limited to, 0.318 mm.

[0050] In some examples, the copper-clad laminate is a single-sided copper-clad laminate made of FR-4 epoxy glass. The size of the copper-clad laminate is, for example, 5cm × 5cm, and the size of the copper film on the surface is, for example, 3cm × 3cm, with a copper film thickness of 30μm to 50μm, or the same as the copper layer thickness of the actual electronic device.

[0051] In some examples, the electronic adhesive is an underfill adhesive, a side fill adhesive, or a fixing adhesive. In step S1, the electronic adhesive is first applied to the electrode area of ​​the comb electrode plate or the copper film of the copper-clad laminate and cured. Then, the conformal coating material is applied to the electronic adhesive and cured.

[0052] In some examples, the electronic adhesive is a potting compound. In step S1, the conformal coating material is first applied to the electrode area of ​​the comb electrode plate or the copper film of the copper-clad laminate and cured. Then, the electronic adhesive is applied to the conformal coating material and cured.

[0053] The coating thickness of the electronic adhesive is, for example, 0.2mm to 5mm, specifically 0.2mm, 0.5mm, 1mm, 2mm, 3mm, 4mm, 5mm, etc. The coating thickness of the conformal coating material is, for example, 60μm to 125μm, specifically 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 125μm, etc.

[0054] Temperature cycling testing accelerates the separation of the interface layer between the conformal coating material and the electronic adhesive through the rapid effect of high and low temperature changes, thereby enabling rapid identification of the interface compatibility between the conformal coating material and the electronic adhesive. For example, if the interface separates after the test, the compatibility is poor; otherwise, the compatibility is good. In some examples, in step S2, the temperature cycling environment test includes:

[0055] The test sample was placed in a high-temperature and low-temperature cyclic environment with a maximum temperature of 80℃~125℃ and a minimum temperature of -55℃~0℃. The temperature change rate was 5℃ / min~20℃ / min. The duration of each highest and lowest temperature was 10min~60min, and the number of cycles was 50~1000.

[0056] In some of these examples, the temperature cycling test in step S2 includes:

[0057] The test sample was placed in a high-temperature and low-temperature cyclic environment with a maximum temperature of 125℃ and a minimum temperature of -40℃. The temperature change rate was 11℃ / min. The duration of each highest and lowest temperature was 30 minutes, and the number of cycles was 1000.

[0058] Humidity and heat environment testing accelerates the aging of conformal coating materials and electronic adhesives, as well as the penetration of moisture, through the combined effects of high temperature and water vapor. This allows for rapid identification of the interfacial compatibility between the conformal coating materials and electronic adhesives. For example, if the interface separates after the test, the compatibility is poor; conversely, if it remains intact, the compatibility is good.

[0059] In some of these examples, the test conditions for the damp heat environment test in step S2 include:

[0060] The test sample was placed in an environment with a temperature of 65℃~85℃ and a humidity of 40%RH~95%RH for 2h~2000h.

[0061] In some of these examples, the test conditions for the damp heat environment test in step S2 include:

[0062] Place the test sample in an environment with a temperature of 85°C and a humidity of 85%RH for 596h. Use an online monitoring system to measure its resistance value. The test time interval is 30 minutes, the applied bias voltage is 50V (DC), and the test voltage is 110V (DC).

[0063] In step S3, select the test items according to the failure modes that occur between the conformal coating material and the electronic adhesive. Among them, the failure modes include at least one of distortion failure, discoloration failure, deterioration failure, adhesion function failure, and insulation function failure.

[0064] Distortion failure means that the appearance form of the material loses its structural stability due to excessive deformation.

[0065] Discoloration failure means that the appearance color or transparency of the material changes without macroscopic deformation.

[0066] Deterioration failure means that the macroscopic characteristics of the material, such as powdering, embrittlement, hardening, softening, and consistency change, which can be perceived but are not appearance color changes, occur during long-term storage or service.

[0067] Adhesion function failure means that the adhesive material detaches from the adherend and loses its adhesion function.

[0068] Insulation function failure means that the material loses its insulation ability, resulting in problems such as breakdown, leakage, and short circuit of the device.

[0069] When the failure mode includes distortion failure, the inspection items include surface appearance inspection and the appearance at the interface between the conformal coating material and the electronic adhesive.

[0070] When the failure mode includes discoloration failure, the inspection item includes surface appearance inspection.

[0071] When the failure mode includes deterioration failure, the inspection items include conductivity, organic matrix material composition, and thermal decomposition temperature.

[0072] When the failure mode includes adhesion function failure, the inspection item includes the appearance at the interface between the conformal coating material and the electronic adhesive.

[0073] When the failure mode includes insulation function failure, the inspection item includes surface insulation.

[0074] In step S3, the surface appearance refers to the appearance of the conformal coating material or the electronic adhesive coated on the surface layer of the printed circuit board. The inspection of the surface appearance is carried out by visual inspection or an optical microscope. Observe whether there are color changes, cracking, softening, and powdering in the appearance of the conformal coating material and the electronic adhesive before and after the temperature cycle environmental test and the damp heat environmental test. If there are no color changes, cracking, softening, and powdering, the surface appearance inspection item is qualified. Otherwise, it is unqualified.

[0075] In step S3, the inspection method for the organic matrix material composition includes: performing infrared spectrum detection on the organic matrix material composition before and after the temperature cycle environmental test and the damp heat environmental test. The inspection of the organic matrix material composition is carried out, for example, in accordance with the requirements of GB / T6040. If the number of peaks, positions, and intensities of the organic matrix material composition before and after the test are the same, the inspection items for the organic matrix material composition are qualified. Otherwise, they are unqualified.

[0076] In step S3, the inspection of the thermal decomposition temperature is carried out, for example, in accordance with the requirements of GB / T33047.1. Before and after the temperature cycle environmental test and the damp heat environmental test, if the characteristic temperature change of the thermal decomposition temperature of the conformal coating material and the electronic adhesive is within the range of ±10°C, the inspection item for the thermal decomposition temperature is qualified. Otherwise, it is unqualified.

[0077] In step S3, the test of surface insulation includes: during the damp heat environmental test, using an on-line monitoring system to measure the resistance value, with the test time interval being 20 min to 30 min, the applied bias voltage being direct current 5V to 50V, and the test voltage being direct current 50V to 110V; observing the corrosion, dendrites, and discoloration of the electrode layer (such as a comb-shaped electrode) on the printed circuit board before and after the test. Before and after the temperature cycle environmental test and the damp heat environmental test, if the surface insulation of the conformal coating material and the electronic adhesive is greater than or equal to 100 MΩ, and there is no corrosion, dendrites, or discoloration in the comb-shaped electrode part, the inspection item for surface insulation is qualified. Otherwise, it is unqualified.

[0078] In step S3, the inspection steps for the appearance at the interface between the conformal coating material and the electronic adhesive include: sealing and slicing the test sample, and observing the interface layer between the conformal coating material and the electronic adhesive through a scanning electron microscope or a metallurgical microscope. Before and after the temperature cycle environmental test and the damp heat environmental test, observe whether there are obvious cracks, delamination, holes, bubbles, etc. at the interface between the conformal coating material and the electronic adhesive. If there are no obvious cracks, delamination, holes, bubbles, etc., the inspection item for the appearance at the interface between the conformal coating material and the electronic adhesive is qualified. Otherwise, it is unqualified.

[0079] In step S3, the detection of conductivity includes: peeling the conformal coating material and the electronic adhesive, extracting and cleaning the surface residues with 10 mL of pure water repeatedly 3 times, and performing conductivity inspection on the extracted cleaning solution in accordance with the requirements of GB / T12582. If the conductivity after the environmental test is less than or equal to 2 times the conductivity before the environmental test, the inspection item for conductivity is qualified. Otherwise, it is unqualified.

[0080] In some of these examples, physicochemical properties include surface appearance, electrical conductivity, organic matrix material composition, thermal decomposition temperature, surface insulation, and appearance at the interface between the conformal coating material and the electronic adhesive.

[0081] The aforementioned evaluation method constructs a multi-dimensional collaborative evaluation technology system for the interfacial compatibility of conformal coating materials and electronic adhesives. In addition to surface insulation as a basic compatibility evaluation indicator, it integrates multi-dimensional testing methods such as material consistency analysis, composition analysis, functional analysis, and structural analysis. Through precise matching of data from each testing item with failure modes, it achieves comprehensive localization and in-depth analysis of compatibility issues. In particular, it forms a dedicated evaluation logic for the unique compatibility problems caused by solvent evaporation and post-curing of conformal coating materials.

[0082] Example 1

[0083] The following specific embodiments further illustrate the present invention. These specific embodiments are provided to better understand the present invention, but are not intended to limit the scope of the invention and do not constitute a limitation on its content or protection.

[0084] The method for evaluating the compatibility of conformal coating materials and electronic adhesives in electronic assembly in this embodiment includes the following steps:

[0085] (1) Preparation of the sample to be tested using comb-shaped electrode plates.

[0086] Electronic adhesive (underfill adhesive) was uniformly coated onto the comb-shaped electrode plate, and the coating thickness was controlled to be 0.5 mm using a frame applicator. It was cured at 130℃ for 2 hours. After removal, it was allowed to cool naturally to room temperature, and then placed in a desiccator for 24 hours to allow complete curing. Using an automated spraying device, conformal coating materials of different thicknesses were uniformly sprayed onto the surface of the electronic adhesive to mask the gold finger area, resulting in test sample 1-1 (conformal coating material thickness 60 μm), test sample 1-2 (conformal coating material thickness 100 μm), and test sample 1-3 (conformal coating material thickness 125 μm).

[0087] (2) Preparation of copper-clad laminate test samples.

[0088] Electronic adhesive was uniformly coated onto the copper surface of the copper-clad laminate using a frame coater to control the coating thickness to 0.5 mm. It was cured at 130°C for 2 hours, then allowed to cool naturally to room temperature before being placed in a desiccator for 24 hours for complete curing. Conformal coating materials of different thicknesses were uniformly sprayed onto the surface of the electronic adhesive using an automated spraying device and allowed to fully cure, resulting in test sample 2-1 (conformal coating material thickness 60 μm), test sample 2-2 (conformal coating material thickness 100 μm), and test sample 2-3 (conformal coating material thickness 125 μm).

[0089] (3) The failure modes of compatibility are shown in Table 1.

[0090] Table 1. Inspection Items and Failure Modes

[0091]

[0092] (4) Temperature cycling environment test and damp heat environment test were conducted on the above-mentioned test samples, as follows:

[0093] Samples 1-1, 1-2, and 1-3 were connected to a high-resistance online monitoring system and subjected to a 596-hour damp heat environment test at 85°C and 85%RH, with their resistance values ​​monitored in real time.

[0094] Samples 1-1, 1-2, and 1-3 were connected to a high-resistance online monitoring system and subjected to 1000 temperature cycling tests at a heating / cooling rate of 11℃ / min and a storage time of 30min, between -40℃ and 125℃. Their resistance values ​​were monitored in real time.

[0095] Six test samples 2-1, 2-2, and 2-3 were placed in a humid and hot environment test under the above conditions to detect their organic matrix material composition, thermal decomposition temperature, electrical conductivity, and appearance at the interface between the conformal coating material and the electronic adhesive.

[0096] Six test samples 2-1, 2-2, and 2-3 were placed in the temperature cycling test under the above conditions. After 500 temperature cycles, the composition of the organic matrix material, thermal decomposition temperature, electrical conductivity, and appearance at the interface between the conformal coating material and the electronic adhesive were detected.

[0097] (5) Evaluate the compatibility between conformal coating materials and electronic adhesives based on the test results.

[0098] 1. Surface appearance.

[0099] like Figure 1 As shown, after undergoing the damp heat test, the appearance of the test samples 2-1, 2-2, and 2-3 did not change significantly, but their colors changed slightly.

[0100] like Figure 2 As shown, after undergoing temperature cycling tests, the appearance of test samples 2-1, 2-2, and 2-3 did not change significantly, but their colors changed slightly.

[0101] 2. Testing of the composition of organic matrix materials.

[0102] Infrared spectroscopy analysis was performed on the electronic adhesives before and after the damp heat test. For example... Figure 3 As shown in (a), it can be seen that there was no significant difference in the infrared spectrum of the organic matrix material composition before and after the experiment.

[0103] Infrared spectroscopy analysis was performed on the electronic adhesive before and after temperature cycling tests. For example... Figure 3 As shown in (b), it can be seen that there is no significant difference in the infrared spectrum of the organic matrix material composition before and after the experiment.

[0104] 3. Thermal decomposition temperature test.

[0105] Thermogravimetric analysis (TG) was performed on the electronic adhesive on the test sample 2-1 before and after the damp heat test. Figure 4 (a) is the thermogravimetric analysis diagram before the experiment. Figure 4 Figure (b) shows the thermogravimetric analysis after the damp heat test. It can be seen that the electronic adhesive undergoes a degradation stage. The starting temperature of the degradation stage did not change significantly before and after the damp heat test, and its main structure did not show significant degradation. The difference in thermal decomposition temperature between the electronic adhesive before and after the test did not exceed 10℃, indicating that no compatibility issues occurred.

[0106] Thermogravimetric analysis was performed on the electronic adhesives before and after temperature cycling tests. For example... Figure 4 Image (c) shows the thermogravimetric analysis after the temperature cycling test. It can be seen that the electronic adhesive undergoes a degradation phase. The starting temperature of the degradation phase before and after the temperature cycling test did not change significantly, and its main structure did not show obvious degradation. The difference in thermal decomposition temperature between the electronic adhesive after the test and before the test did not exceed 10℃, indicating that no incompatibility issues occurred.

[0107] 4. Conductivity test.

[0108] After the damp heat test, the electronic adhesive and conformal coating material covering the test samples 2-1, 2-2, and 2-3 were peeled off. The copper-clad laminate surfaces after removing the electronic adhesive and conformal coating material were then extracted and cleaned with 10 mL of pure water, repeated three times. The conductivity of the extract was measured, which reflects the total ion content in the extract. The conductivity results are shown in Table 2. As can be seen from the results in Table 2, the conductivity at the interface did not change significantly after the damp heat test, indicating good compatibility between the two materials.

[0109] Table 2. Conductivity analysis results before and after the damp heat test

[0110]

[0111] After the temperature cycling test, the electronic adhesive and conformal coating material covering the test samples 2-1, 2-2, and 2-3 were peeled off. The copper-clad laminate surfaces after removing the electronic adhesive and conformal coating material were then extracted and cleaned with 10 mL of pure water, repeated three times. The conductivity of the extract was measured, which reflects the total ion content in the extract. The conductivity results are shown in Table 3. As can be seen from the results in Table 3, the conductivity at the interface did not change significantly after the temperature cycling test, indicating good compatibility between the two materials.

[0112] Table 3. Conductivity analysis results before and after temperature cycling test

[0113]

[0114] 5. Surface insulation test.

[0115] like Figure 5 As shown in Figure (a), after undergoing a damp heat environment test, the insulation resistance of the conformal coating materials of different thicknesses on the test sample 1-1 did not decrease. No significant decrease in resistance occurred during the test, and there was no corrosion, dendrite formation, or obvious discoloration on the comb-shaped electrodes, indicating good compatibility between the two materials.

[0116] like Figure 5 As shown in (b), after the temperature cycling test, the insulation resistance of the different thicknesses of the conformal coating material on the test sample 1-1 did not decrease or increase, indicating that the two materials are compatible.

[0117] 6. Visual inspection of the interface between the conformal coating material and the electronic adhesive.

[0118] The test sample 2-1, before and after the damp heat test, was sealed and sectioned. The interface between the electronic adhesive and the conformal coating material was observed using a scanning electron microscope. No obvious cracks, delamination, pores, or bubbles were observed at the interface before and after the test. Figure 6 (a) and (b) are SEM images of the interface between the electronic adhesive and the conformal coating material before and after the humid heat environment test, respectively. Figure 6 As can be seen in (b), the interface between the electronic adhesive and the conformal coating material was good after the damp heat test, with no obvious pores or delamination, indicating that the interface between the two materials was well compatible.

[0119] After undergoing temperature cycling tests, the test sample 2-2 was sealed and sliced. The interface morphology between the electronic adhesive and the conformal coating material was observed using a scanning electron microscope. No obvious cracks, delamination, pores, or bubbles were observed at the interface before and after the test. Figure 6As shown in (c), the interface between the electronic adhesive and the conformal coating material was good after the temperature cycling test, with no obvious pores or delamination, indicating that the interface between the two materials was well compatible.

[0120] In summary, electronic adhesives and conformal coatings exhibit good compatibility under humid and hot conditions and temperature cycling conditions.

[0121] The above evaluation method has the following effects:

[0122] 1. The above evaluation method fills the gap in the technology and standards for compatibility evaluation of conformal coating materials and electronic adhesives. It provides a precise scientific basis for material selection for the unique problems of conformal coating materials such as solvent evaporation and post-curing, effectively reducing the risk of short circuits, delamination and failure of electronic products caused by poor compatibility, and significantly reducing product quality risks and rework costs.

[0123] 2. The above evaluation method adopts multiple types of test plates to match the differentiated evaluation needs, realizes the precise matching of environmental testing and failure mode, integrates multi-dimensional test items and quantitative evaluation standards, and covers the core correlation dimensions of material microstructure and macro properties.

[0124] 3. Compared with existing technologies, the above evaluation method is designed with a thickness gradient variable for conformal coating materials, combined with customized environmental tests and multi-dimensional inspection methods, covering aspects such as material consistency, composition, function, and structural analysis. This not only shortens the time for locating compatibility issues, but also eliminates subjective judgment errors through quantitative indicators. At the same time, it adapts to the evaluation needs of coating materials with different thicknesses, improving the accuracy, efficiency, and applicability of the evaluation.

[0125] 4. The above evaluation method supports narrow line width and pitch test boards and low voltage test conditions, which meets the material compatibility evaluation needs of high-density, narrow-pitch, and low-voltage electronic products in fields such as 5G communication, AI, and quantum computing. It breaks through the limitations of existing technologies, such as large line width and pitch of test boards, single test voltage, and inability to cover coating thickness variables.

[0126] 5. The above evaluation method provides a complete technical solution for the entire process of "sample preparation-testing-inspection-evaluation", clarifies the core dimensions and standards for compatibility evaluation of conformal coating materials and electronic adhesives, guides the transformation of electronic assembly material compatibility evaluation from experience-based to standardized and systematic, and helps upgrade the overall technical level of the electronics industry.

[0127] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0128] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for evaluating the compatibility of conformal coating materials and electronic adhesives in electronic assembly, characterized in that, Includes the following steps: A conformal coating material and an electronic adhesive to be tested are coated on a printed circuit board, wherein the conformal coating material and the electronic adhesive are in contact to obtain a test sample; The test sample was subjected to temperature cycling environment test and damp heat environment test to obtain the test sample; The differences in the physicochemical properties of the conformal coating material and the electronic adhesive before and after the test are obtained. The physicochemical properties include at least one of the following: surface appearance, electrical conductivity, organic matrix material composition, thermal decomposition temperature, surface insulation, and appearance at the interface between the conformal coating material and the electronic adhesive. The compatibility between the conformal coating material and the electronic adhesive is evaluated based on the differences in their physicochemical properties.

2. The method for evaluating the compatibility of conformal coating materials and electronic adhesives in electronic assembly as described in claim 1, characterized in that, The printed circuit board is at least one of a comb-shaped electrode plate and a copper-clad laminate.

3. The method for evaluating the compatibility of conformal coating materials and electronic adhesives in electronic assembly as described in claim 2, characterized in that, The electronic adhesive is an underfill adhesive, a side fill adhesive, or a fixing adhesive. When coating the conformal coating material to be tested and the electronic adhesive on the printed circuit board, the electronic adhesive is first coated on the electrode area of ​​the comb electrode plate or the copper surface of the copper-clad laminate and cured. Then the conformal coating material is coated on the electronic adhesive and cured. Alternatively, the electronic adhesive may be a potting compound. When coating the conformal coating material to be tested and the electronic adhesive onto the printed circuit board, the conformal coating material is first coated onto the electrode area of ​​the comb electrode plate or the copper film of the copper-clad laminate and cured. Then, the electronic adhesive is coated onto the conformal coating material and cured.

4. The method of claim 1, wherein the electronic assembly is an electronic assembly comprising a conformal coating material and an electronic adhesive. The temperature cycling environment test includes: The test sample was placed in a high-temperature and low-temperature cyclic environment with a maximum temperature of 80℃~125℃ and a minimum temperature of -55℃~0℃. The temperature change rate was 5℃ / min~20℃ / min. The duration of each highest and lowest temperature was 10min~60min, and the number of cycles was 50~1000.

5. The method of claim 1, wherein the electronic assembly is an electronic assembly comprising a conformal coating material and an electronic adhesive. The test conditions for the damp heat environment test include: The test sample was placed in an environment with a temperature of 65℃~85℃ and a humidity of 40%RH~95%RH for 2h~2000h.

6. The method of claim 1, wherein the electronic assembly is an electronic assembly comprising a conformal coating material and an electronic adhesive. Multiple sets of test samples were prepared, and the difference between the different sets of test samples was the different thicknesses of the conformal coating material; the influence of the thickness of the conformal coating material on the compatibility was compared and analyzed.

7. The method of claim 1, wherein the electronic assembly is an electronic assembly comprising a conformal coating material and an electronic adhesive. The selection of physicochemical property testing items is based on the failure modes of the conformal coating material and the electronic adhesive. The failure modes include at least one of distortion failure, discoloration failure, degradation failure, adhesive function failure, and insulation function failure. When the failure mode includes distortion failure, the inspection items include surface appearance inspection and appearance at the interface between the conformal coating material and the electronic adhesive. When the failure mode includes discoloration failure, the inspection items include surface appearance inspection. When the failure mode includes degradation failure, the test items include electrical conductivity, organic matrix material composition, and thermal decomposition temperature. The failure mode includes failure of the adhesive function, and the inspection items include the appearance at the interface between the conformal coating material and the electronic adhesive. The failure mode includes insulation failure, and the inspection items include surface insulation.

8. The method for evaluating the compatibility of conformal coating materials with electronic adhesives in electronic assemblies according to any one of claims 1 to 7, wherein The evaluation method for the compatibility of the conformal coating material and the electronic adhesive in the electronic assembly meets at least one of the following characteristics (1) to (2): (1) The surface appearance inspection includes: observing the appearance of the conformal coating material and electronic adhesive before and after the test, and whether there are color changes, cracking, softening and powdering. (2) The appearance inspection of the interface between the conformal coating material and the electronic adhesive includes: sealing and slicing the test sample, and observing the interface between the conformal coating material and the electronic adhesive by scanning electron microscope or metallographic microscope to observe the condition of cracks, delamination, holes and bubbles.

9. The method for evaluating the compatibility of conformal coating materials with electronic adhesives in electronic assemblies according to any one of claims 1 to 7, wherein The evaluation method for the compatibility of the conformal coating material and the electronic adhesive in the electronic assembly meets at least one of the following characteristics (1) to (2): (1) The testing of the organic matrix material composition includes: performing infrared spectroscopy detection on the organic matrix material composition before and after the test, and analyzing the consistency of the number, position and intensity of the organic matrix material composition before and after the test; (2) The detection of the thermal decomposition temperature includes: performing thermogravimetric analysis on the conformal coating material and the electronic adhesive before and after the test, and analyzing the difference in thermal decomposition temperature before and after the test.

10. The method for evaluating the compatibility of a conformal coating material with an electronic adhesive in an electronic assembly according to any one of claims 1 to 7, wherein The evaluation method for the compatibility of the conformal coating material and the electronic adhesive in the electronic assembly meets at least one of the following characteristics (1) to (2): (1) The conductivity detection includes: peeling the conformal coating material from the electronic adhesive, extracting the surface residue with pure water, testing the conductivity of the extract, and analyzing the difference in conductivity before and after the test; (2) The surface insulation test includes: during the damp heat environment test, the resistance value is measured using an online monitoring system, the test time interval is 20min~30min, the bias voltage is DC 5V~50V, and the test voltage is DC 50V~110V; observe the corrosion, dendrites and discoloration of the electrode layer before and after the test.

Images