A method for non-destructive prediction of the adhesive strength of components of a printed board assembly

Abstract

This application discloses a method for non-destructively predicting the bonding reinforcement strength of printed circuit board (PCB) components, comprising: measuring a first dyne value of different PCB surfaces; measuring a first bonding strength between the PCB and epoxy adhesive, and establishing a first mapping relationship; measuring a second dyne value of different component enclosures; measuring a second bonding strength between the component enclosure and epoxy adhesive, and establishing a second mapping relationship; measuring the dyne values ​​of the PCB surface to be bonded and the component enclosure surface, and comparing them with the first mapping relationship and the second mapping relationship respectively; selecting the lowest bonding strength value as the predicted epoxy reinforcement strength, and performing component reinforcement based on the predicted epoxy reinforcement strength. This method can measure the surface condition of the reinforcement area before adhesive application, effectively determining whether the PCB surface and component surface meet the reinforcement requirements, and achieving prediction of the reinforcement strength after epoxy reinforcement.

Description

Technical Field

[0001] This application relates to the field of integrated circuit technology, and in particular to a method for non-destructive prediction of the bonding strength of printed circuit board components. Background Technology

[0002] In printed circuit board (PCB) assemblies, various components are electrically interconnected with the PCB via solder joints, enabling the connection between internal and external circuits. Simultaneously, as bridges for these electrical connections, solder joints also serve as crucial mechanical supports and absorbers of external impacts. Therefore, solder joints play a critical role in PCB assemblies. Statistics show that most PCB assembly failures are caused by solder joints. Solder joint failure generally refers to the cracking and eventual failure of electronic components and assemblies at stress concentration points due to external environmental factors such as thermal cycling, vibration, and impact under service conditions. Therefore, improving solder joint lifespan is a key factor affecting the overall lifespan of PCB assemblies. Currently, a common industry practice is to use epoxy adhesives to reinforce the component packages and the PCB, thereby improving the vibration resistance of the solder joints and alleviating stress concentration. However, the effectiveness of adhesive reinforcement and whether it can meet the requirements can only be roughly estimated based on past experience or evaluated based on the results of a large number of reliability tests. On the one hand, the results of estimation based on experience have large deviations and cannot be accurately evaluated for different printed circuit board components. On the other hand, reliability tests have long time cycles and are destructive tests, resulting in high economic costs.

[0003] Therefore, in the field of epoxy bonding reinforcement of printed circuit board components, there is currently a lack of a method that can quickly assess the epoxy reinforcement strength of printed circuit board components in different states. Summary of the Invention

[0004] This application provides a method for non-destructive prediction of the bonding reinforcement strength of printed circuit board components. It can measure the surface condition of the reinforcement area before adhesive application, effectively determine whether the surface of the printed circuit board and the surface of the components meet the reinforcement requirements, and predict the reinforcement strength after epoxy reinforcement.

[0005] This application provides a method for non-destructively predicting the bonding strength of printed circuit board assembly components, including:

[0006] Determine the first dyne value on the surface of different printed circuit boards;

[0007] The first bond strength between the printed circuit board and the epoxy adhesive is measured, and a first mapping relationship between the dyne value of different printed circuit board surfaces and the first bond strength is established based on the first bond strength.

[0008] Determine the second dyne value of different component packaging shells;

[0009] The second adhesive strength between the encapsulation shell of the bonded component and the epoxy adhesive is measured, so as to establish a second mapping relationship between the second dyne value of different encapsulation shells of the bonded component and the second adhesive strength based on the second adhesive strength;

[0010] The dynn values ​​of the printed circuit board surface and the component package shell surface to be bonded are measured and compared with the first mapping relationship and the second mapping relationship, respectively.

[0011] The lowest bond strength is selected as the predicted epoxy reinforcement strength, and component reinforcement is performed based on the predicted epoxy reinforcement strength.

[0012] Optionally, measuring the dyne values ​​of different printed circuit board surfaces includes:

[0013] Using a dyne pen perpendicular to the surface of the printed circuit board, draw a first line of a specified length;

[0014] After a first preset time, the dyne value of the surface of the printed circuit board under test is determined based on the shrinkage of the first line.

[0015] Optionally, determining the second dyne value for different component package housings includes:

[0016] Using a dyne pen at a preset angle to the casing of the component being tested, draw a second line of a specified length and width.

[0017] After a second preset time, the dyne value of the surface of the printed circuit board under test is determined based on the shrinkage of the second line.

[0018] Optionally, the preset angle is 30°-45°.

[0019] Optionally, determining the second bond strength between the component package housing and the epoxy adhesive includes:

[0020] Solder the components that have completed the determination of the second dyne value to the printed circuit board or a pre-set fixing device;

[0021] Select a flexible adhesive material of a specified specification as an adhesive sample, apply epoxy adhesive of a specified thickness to each adhesive sample, and then bond the component housing.

[0022] Cure the epoxy adhesive and let it stand;

[0023] Using a tensile testing instrument, the printed circuit board or pre-set fixing device is stretched and bonded at a set rate, and the force-displacement curve during the stretching process is recorded.

[0024] The bonding strength between the component package shell and the epoxy adhesive is calculated based on the obtained force-displacement curve.

[0025] Optionally, select a flexible adhesive material of a specified specification that meets the following requirements:

[0026] When the width of the component package is ≥25mm, the sample width is 25mm;

[0027] When the component package shell is <25mm, the sample should be kept to have the same width as the component package shell.

[0028] The sample length shall not be less than 350 mm.

[0029] Optionally, the determination of dyne values ​​on the surface of the printed circuit board to be bonded and the surface of the component package housing includes:

[0030] Using a dyne pen, draw dots of a specified size at the corners of components on the printed circuit board;

[0031] After a third preset time, the dyne value of the surface of the printed circuit board under test is determined based on the shrinkage of the dots.

[0032] The method in this application embodiment can measure the surface condition of the reinforcement area before adhesive application, effectively determine whether the surface of the printed circuit board and the surface of the device meet the reinforcement requirements, and predict the reinforcement strength after epoxy reinforcement.

[0033] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0034] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0035] Figure 1 This is a basic flowchart of the method for non-destructive prediction of the bonding reinforcement strength of printed circuit board components according to this application. Detailed Implementation

[0036] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0037] For epoxy adhesive reinforcement of components in printed circuit board assemblies, there are currently no universal testing methods or means to determine whether the surface condition of the printed circuit board and the component meets the dispensing conditions, and whether the reinforcement strength after curing meets the usage requirements. Most tests rely on first-piece destructive peel tests or subsequent reliability tests to determine whether the epoxy adhesive reinforcement strength meets the requirements. However, there is no suitable pre-testing method for each product, which poses a risk of early failure during the later service life of the product. On the one hand, destructive testing or reliability testing has the disadvantages of high economic and time costs; on the other hand, the lack of pre-testing means poses a significant reliability risk during use.

[0038] Based on this, this application provides a method for non-destructive prediction of the bonding reinforcement strength of printed circuit board components, including the following steps:

[0039] In step S101, the first dyne value of different printed circuit board surfaces is determined. A dyne pen is a tool for testing the wetting tension of a material surface, commonly used in the printing industry for testing the surface tension of thin films. However, the surface composition of printed circuit boards is complex, containing various materials such as epoxy solder resist materials, screen printing ink materials, and copper foil. Furthermore, after the printed circuit board is assembled, the space for bonding is small, and there are trace amounts of flux residue and other mixtures. Considering these factors, there is currently a lack of accurate surface tension testing methods in the field of printed circuit board assemblies. In some embodiments, determining the dyne value of different printed circuit board surfaces includes:

[0040] Using a dyne pen perpendicular to the surface of the printed circuit board, draw a first line of a specified length;

[0041] After a first preset time, the dyne value of the surface of the printed circuit board under test is determined based on the shrinkage of the first line.

[0042] This application embodiment addresses the special conditions of printed circuit board (PCB) surfaces. To accurately measure the surface tension of the areas to be bonded, a dyne pen is held perpendicular to the PCB surface, and appropriate pressure is applied to draw a straight line with a length of 5mm-10mm. After 2-3 seconds, the ink distribution of the dyne pen is observed. If the line is evenly distributed and does not produce any beads, the dyne value of the measured surface is higher than or equal to the dyne pen's index. A dyne pen with a higher dyne value is used for repeated measurement until the ink on the drawn line on the PCB surface shows signs of shrinkage. The dyne value of the dyne pen used at this point is the dyne value of the PCB surface. By measuring the surface dyne values ​​of different PCBs using dyne pens with different indices, a first dyne value database for different PCB surfaces is established.

[0043] In step S102, the first bond strength between the printed circuit board and the epoxy adhesive is measured to establish a first mapping relationship between the dyne value of different printed circuit board surfaces and the first bond strength based on the first bond strength. Specifically, the printed circuit board whose dyne value has been measured in step S101 can be used as the rigid bond, and a peel strength test specimen can be prepared using an aluminum sheet with a thickness of about 0.1 mm as the flexible adhesive material for peel testing. This establishes a comparison table of the first mapping relationship between the dyne value of different printed circuit board surfaces and the first bond strength.

[0044] In step S103, the second dyne value of the packaging shell of different adhered components is measured.

[0045] The dyne value of the bonded components is determined using a dyne pen. Unlike thin film materials, the encapsulation shells of the bonded components are mostly epoxy-encapsulated tubing with a frosted surface, resulting in a much lower ink spreading rate for the dyne pen compared to thin film materials. To accurately measure the dyne value of the component encapsulation shells, in some embodiments of this application, the determination of a second dyne value for different bonded component encapsulation shells includes:

[0046] Using a dyne pen at a preset angle to the casing of the component being tested, for example, the preset angle can be 30°-45°, draw a second line of a specified length and width. Specifically, the second line can be a line with a length of 5mm-10mm and a straight line width of not less than 3mm.

[0047] After a second preset time, the dyne value of the printed circuit board surface is determined based on the shrinkage of the second line. For example, the ink distribution of the dyne pen can be observed after 10 seconds. If the straight line is evenly distributed or spreads to the periphery, the dyne value of the surface being tested is higher than or equal to the index of the dyne pen. Replace with a dyne pen with a higher dyne value and measure again until the ink on the straight line drawn on the component package shows signs of shrinkage. The dyne value of the dyne pen used at this point is the dyne value of the printed circuit board surface.

[0048] In step S104, the second bonding strength between the encapsulation shell of the bonded component and the epoxy adhesive is measured, so as to establish a second mapping relationship between the second dyne value of different encapsulation shells of the bonded component and the second bonding strength based on the second bonding strength.

[0049] In some embodiments, determining the second bond strength between the component encapsulation housing and the epoxy adhesive includes:

[0050] The components for which the second dyne value has been determined are soldered to the printed circuit board or a pre-set fixing device. Specifically, the components are required to ensure that there is no relative displacement between them and the test device during the subsequent peel test, and that the surfaces to be bonded are completely exposed without affecting the bonding. The length of the printed circuit board or fixing device is not less than 180 mm.

[0051] Select a flexible adhesive material of a specified specification as the bonding sample. Apply epoxy adhesive of a specified thickness to each bonding sample and bond it to the component housing. Optionally, the selected flexible adhesive material can be a thin aluminum sheet with a thickness of approximately 0.1 mm, meeting the following requirements: when the width of the component housing is ≥25 mm, the sample width is 25 mm; when the width of the component housing is <25 mm, the sample maintains the same width as the component housing; the sample length is not less than 350 mm. The specific process of applying epoxy adhesive of a specified thickness to each bonding sample can include: uniformly applying adhesive across the entire width of each bonding sample, with the application length being the length of the component housing. Alternatively, a template of a certain thickness or other adhesive application device can be used to ensure that the adhesive thickness is between 0.08 mm and 0.12 mm, thereby ensuring test accuracy.

[0052] Cur the epoxy adhesive and let it stand, for example, for 1 hour.

[0053] Using a tensile testing machine, the bonded printed circuit board or pre-set fixing device is stretched at a set rate, and the force-displacement curve during the stretching process is recorded. Specifically, the sample is mounted on the tensile testing machine, with the unbonded end of the flexible adhesive sheet bent 180°. The rigid bonded printed circuit board or fixing device is clamped in the fixed clamp, and the flexible sample is clamped in the other clamp, ensuring accurate positioning of the sample between the clamps and guaranteeing that the applied tensile force is evenly distributed across the sample width. The sample is stretched at a constant rate of 100±10 mm / min, and the force-displacement curve during the stretching process is recorded. Stretching continues until the sample is completely peeled off.

[0054] The bonding strength between the component package shell and the epoxy adhesive is calculated based on the obtained force-displacement curve.

[0055] To calculate the bond strength between a component's enclosure and epoxy adhesive, the average peel force F can be calculated first. The peel length used to calculate the peel force does not include the initial and final 10% peel length. This can be tested using the software included in a tensile testing device, or the average peel force F can be calculated using the lateral area method.

[0056] The bond strength between the component package shell and the epoxy adhesive is calculated as σ² = F / B, where σ² is the 180° peel strength (kN / m), F is the average peel force (kN), and B is the sample width (mm). Using at least five samples of each type and calculating the average value improves testing accuracy. Based on this, a second mapping table is established between the dyne values ​​of different component package shells and the second bond strength.

[0057] The order of steps S101-S104 in this application is not limited and can be changed. The specific steps can be set according to actual needs.

[0058] In step S105, the dynn values ​​of the surface of the printed circuit board to be bonded and the surface of the component package shell are measured and compared with the first mapping relationship and the second mapping relationship, respectively.

[0059] In step S106, the lowest bonding strength is selected as the predicted epoxy reinforcement strength, and component reinforcement is performed based on the predicted epoxy reinforcement strength.

[0060] The method in this application embodiment can measure the surface condition of the reinforcement area before adhesive application, effectively determine whether the surface of the printed circuit board and the surface of the device meet the reinforcement requirements, and predict the reinforcement strength after epoxy reinforcement.

[0061] In some embodiments, measuring the dyne values ​​of the surface of the printed circuit board to be bonded and the surface of the component package housing includes:

[0062] Using a dyne pen, draw dots of a specified size, such as no smaller than 3mm, at the corners of components on the printed circuit board, such as the four corners.

[0063] After a third preset time period, the dyne value of the tested printed circuit board surface is determined based on the shrinkage of the dots. For example, the dyne value can be determined by observing whether the dot imprint shrinks after 2-3 seconds, and the minimum dyne value at the four corners can be taken as the dyne value of the printed circuit board surface. The dyne value of the component package shell surface is tested according to the aforementioned method. After testing, a comparison is made, specifically by comparing the measured values ​​with the first mapping relationship table and the second mapping relationship table. The lowest adhesive strength value is the predicted epoxy reinforcement strength, and its location is the predicted failure location. In the actual dispensing reinforcement process, the minimum dyne value of the printed circuit board surface and the component package shell surface to be reinforced can be determined according to the product reliability requirements. Before epoxy dispensing, the surface tension is measured using a dyne pen, and samples with surface tension that do not meet the requirements are removed, or surface treatment methods are used to improve the surface tension of the bonding area to avoid early failure during service.

[0064] The method described in this application enables the testing and evaluation of the printed circuit board (PCB) surface and component package surface using a dyne pen (surface tension tester) to determine whether the PCB surface meets the dispensing requirements. Based on the PCB surface tension test results and component package surface tension test results, combined with the intrinsic strength of the epoxy adhesive, the method predicts the epoxy reinforcement strength and failure mode. This method allows for non-destructive prediction and assessment of whether the PCB and component surfaces meet the dispensing conditions, avoiding rework due to substandard reinforcement quality.

[0065] Before applying the adhesive, the surface tension of the reinforced surface can be measured using a dyne pen, which can predict the reinforcement strength after epoxy reinforcement. This allows for a non-destructive assessment of whether the reinforcement method can meet the product reliability requirements, thus avoiding significant losses due to failure during service.

[0066] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0067] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0068] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0069] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims. All of these forms are within the protection scope of this application.

Claims

1. A method for non-destructively predicting the bonding strength of components in a printed circuit board assembly, characterized in that, include: Determine the first dyne value on the surface of different printed circuit boards; The first bond strength between the printed circuit board and the epoxy adhesive is measured, and a first mapping relationship between the dyne value of different printed circuit board surfaces and the first bond strength is established based on the first bond strength. Determine the second dyne value of different component packaging shells; The second adhesive strength between the encapsulation shell of the bonded component and the epoxy adhesive is measured, so as to establish a second mapping relationship between the second dyne value of different encapsulation shells of the bonded component and the second adhesive strength based on the second adhesive strength; The dynn values ​​of the printed circuit board surface and the component package shell surface to be bonded are measured and compared with the first mapping relationship and the second mapping relationship, respectively. The lowest bond strength is selected as the predicted epoxy reinforcement strength, and component reinforcement is performed based on the predicted epoxy reinforcement strength.

2. The method for non-destructive prediction of the bonding reinforcement strength of printed circuit board components as described in claim 1, characterized in that, The determination of dyne values ​​for different printed circuit board surfaces includes: Using a dyne pen perpendicular to the surface of the printed circuit board, draw a first line of a specified length; After a first preset time, the dyne value of the surface of the printed circuit board under test is determined based on the shrinkage of the first line.

3. The method for non-destructive prediction of the bonding reinforcement strength of printed circuit board components as described in claim 1, characterized in that, The determination of the second dyne value of different component package shells includes: Using a dyne pen at a preset angle to the casing of the component being tested, draw a second line of a specified length and width. After a second preset time, the dyne value of the surface of the printed circuit board under test is determined based on the shrinkage of the second line.

4. The method for non-destructive prediction of the bonding reinforcement strength of printed circuit board components as described in claim 3, characterized in that, The preset angle is 30°-45°.

5. The method for non-destructive prediction of the bonding reinforcement strength of printed circuit board components as described in claim 3, characterized in that, The determination of the secondary bond strength between the component package and the epoxy adhesive includes: Solder the components that have completed the determination of the second dyne value to the printed circuit board or a pre-set fixing device; Select a flexible adhesive material of a specified specification as an adhesive sample, apply epoxy adhesive of a specified thickness to each adhesive sample, and then bond the component housing. Cure the epoxy adhesive and let it stand; Using a tensile testing instrument, the printed circuit board or pre-set fixing device is stretched and bonded at a set rate, and the force-displacement curve during the stretching process is recorded. The bonding strength between the component package shell and the epoxy adhesive is calculated based on the obtained force-displacement curve.

6. The method for non-destructive prediction of the bonding reinforcement strength of printed circuit board components as described in claim 4, characterized in that, Select a flexible adhesive material of the specified specifications that meets the following requirements: When the width of the component package is ≥25mm, the sample width is 25mm; When the component package shell is <25mm, the sample should be kept to have the same width as the component package shell. The sample length shall not be less than 350 mm.

7. The method for non-destructive prediction of the bonding reinforcement strength of printed circuit board components as described in claim 1, characterized in that, The determination of dyne values ​​on the surface of the printed circuit board to be bonded and the surface of the component package housing includes: Using a dyne pen, draw dots of a specified size at the corners of components on the printed circuit board; After a third preset time, the dyne value of the surface of the printed circuit board under test is determined based on the shrinkage of the dots.

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