Structure and method for testing bonding strength of potting material and printed board

Abstract

The invention belongs to the technical field of electronic packaging testing, and particularly relates to a potting material and printed board bonding strength testing structure and method.The potting material is poured between two printed boards, the two printed boards and the potting material form a printed board potting piece, after a positioning ring and a potting ring are removed, positioning baffles are fixed to the upper end and the lower end of a clamping handle, and the potting material is fixed to the upper end and the lower end of the clamping handle; the two clamping handles are clamped on the outer sides of the two printed boards through a strong adhesive under the constraint of the two positioning baffles, so that the printed board potting piece and the two clamping handles form a test sample piece; the two positioning baffles are removed, clamping handles at the two ends of the printed board potting piece are pulled outwards through a universal tensile testing machine, tensile force data are recorded till the printed board is separated from the potting material, the tensile force is the maximum when the printed board is separated from the potting material, and the bonding strength is calculated through the tensile force data. The connection mode of the tested piece and the clamping handle through the strong adhesive gets rid of the limitation of the installation space and the structural form, and the application range and the feasibility of interconnection are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic packaging testing, and in particular relates to a bonding strength testing structure and method for a potting material and a printed circuit board. Background Art

[0002] In order to meet the application requirements of electronic equipment to resist high impact, internal potting reinforcement is an effective means. In actual engineering, in addition to the density and hardness of the potting material, attention should also be paid to the bonding strength between the potting material and the electronic components, especially between the printed circuit board and the potting material. Due to insufficient bonding strength, the interface between the potting material and the printed circuit board may fail under impact due to delamination and peeling, resulting in reduced reliability of the equipment. Since the potting material is a polymer composite material and the internal structure of the electronic equipment is complex, it is very difficult to test the bonding strength of the potting material directly based on the object being filled. Therefore, there is still no simple and effective bonding strength test method, resulting in the potting process without relevant data support. The reliability of potting reinforcement is not high, which has become one of the main technical risks of impact protection. Summary of the invention

[0003] The invention provides a structure and method for testing the bonding strength between a potting material and a printed circuit board, so as to solve the technical problem of difficulty in testing the bonding strength of the potting material of a potted object existing in the prior art.

[0004] In order to achieve the above object, the present invention adopts the following technical solution: A bonding strength testing structure between a potting material and a printed circuit board is characterized in that it comprises a potting ring, a positioning ring and a printed circuit board, printed circuit boards are arranged at both ends of the potting ring, two printed circuit boards and the potting ring form a cavity, the positioning ring is spliced ​​on the outside of the potting ring; and clamping handles are also clamped on the outside of the two printed circuit boards.

[0005] The printed circuit board is bonded to the outer surface of the potting ring through silicone rubber.

[0006] The printed circuit board is circular, and its diameter is between the inner and outer diameters of the potting ring.

[0007] The potting ring is composed of two equally divided semicircular rings, which are spliced ​​into a circular ring. An oblique groove is opened on the potting ring, and semicircular holes are left in both semicircular rings. The two semicircular holes form a circular hole to form a potting hole.

[0008] The positioning ring is a circular ring, and a circular hole is opened at the hole position of the positioning ring corresponding to the potting hole of the potting ring for potting and disassembly.

[0009] A threaded hole is provided on the potting ring, and the threaded hole is used to fix the disassembly rod. One end of the disassembly rod is threaded and matches the internal thread of the threaded hole of the potting ring.

[0010] The end face of the clamping handle is cubic or circular.

[0011] The clamping handles are adhesively clamped at both ends of the outer sides of the printed circuit board.

[0012] A method for testing the bonding strength between a potting material and a printed circuit board comprises the following steps: pouring potting material between two printed circuit boards, wherein the two printed circuit boards and the potting material constitute a printed circuit board potting piece; after removing the positioning ring and the potting ring, positioning baffles are fixed at the upper and lower ends of a clamping handle; the two clamping handles are clamped on the outer sides of the two printed circuit boards by a strong adhesive under the constraints of the two positioning baffles, so that the printed circuit board potting piece and the two clamping handles constitute a test sample.

[0013] Remove the two positioning baffles, use a universal tensile testing machine to pull the clamping handles at both ends of the printed circuit board potting outward, and record the tensile data until the printed circuit board and the potting material are separated. The maximum tensile force is when the printed circuit board and the potting material are separated. The bonding strength is calculated by the tensile data. The calculation method is: Bond Strength = , , where F is the maximum tensile force, S is the contact area between the potting material and the printed circuit board, and d is the inner diameter of the potting circle.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a bonding strength test structure between a potting material and a printed circuit board. By fixing the printed circuit board at both ends of a potting ring to form a closed cavity, the actual working environment is simulated to ensure that the potting material is cured under controlled conditions. The bonding strength test results obtained in this way are closer to the actual application scenario, and the accuracy of the test data and the repeatability of the experiment are improved. The splicing design of the positioning ring helps to accurately align and fix the position of the printed circuit board and the potting ring, avoiding deviations caused by manual placement, allowing the potting material to be evenly distributed, ensuring that the test results are not affected by human factors, and improving the standardization of the test. The design of the clamping handle facilitates the handling, installation and disassembly process of the test structure, making it more convenient to transfer samples between different test conditions or laboratories, and also facilitates necessary operations or observations during the potting and curing process, reducing the difficulty of operation and improving work efficiency.

[0015] Furthermore, the splicing and bevel groove design of the potting ring ensures that a stress concentration position is left at the bevel groove mouth. The inner ring is coated with a release agent to reduce the adhesion between the potting material and the potting ring, making it easy to peel off. Combined with the disassembly rod, the tooling can be easily disassembled and reused after potting, realizing a low-cost design of the tooling; at the same time, the disassembly rod can facilitate hand-held operation and torque application.

[0016] Furthermore, the design of a circular printed circuit board with a diameter between the inner diameter and the outer diameter of the potting ring is convenient for gluing the potting ring and disassembling the positioning ring after potting. On the other hand, it increases the difference in contact area between the printed circuit board and the potting material and the clamping handle, that is, increases the bonding area between the printed circuit board and the clamping handle to ensure the bonding force between the two, while reducing the bonding area between the printed circuit board and the potting material to reduce the bonding force between the two, thereby ensuring that the printed circuit board and the potting material interface are separated first during the tensile test, so that the measured data is the bonding strength between the printed circuit board and the potting material. This design method ensures the detachability of the tooling, and at the same time, on the premise of simplifying the connection method between the sample and the clamping handle, it ensures the measurability of the bonding strength between the printed circuit board and the potting material. It comprehensively solves the problems of the interconnection of the potting sample and the clamping handle and the measurability of the potting bonding strength.

[0017] Furthermore, the present invention discloses a method for testing the bonding strength between a potting material and a printed circuit board, which significantly improves the accuracy and reliability of the test results by constructing a special test structure and adopting a standardized operating procedure, such as accurately controlling the filling of the potting material, fixing the position of the printed circuit board and the clamping handle, and performing a tensile test on a universal tensile testing machine, making the test data more convincing.

[0018] Furthermore, the present invention is based on the universal tensile testing machine for testing, and has strong versatility. In addition to the standardized design of the handle of the clamping handle, the end face shape can be freely designed according to the tested structure. In addition to the printed circuit board, it can also test the bonding strength of components, chips and other components with corresponding characteristics, and has strong expansibility. The strong adhesive connection between the tested part and the clamping handle gets rid of the limitations of installation space and structural form, improves the scope of application and feasibility of interconnection, and the method has clear steps and is easy to operate. In particular, with the assistance of the clamping handle and the positioning baffle, the sample preparation and fixing process is simplified, the operation complexity is reduced, and the test efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a front view of the potting tooling structure; Figure 2 It is a side schematic diagram of the potting tooling structure; Figure 3 Prepare a front view diagram for the test specimen; Figure 4 This is a side view of the test sample; Figure 5 Schematic diagram of the loading force change of the universal tensile testing machine.

[0020] Number: 1. Printed circuit board; 2. Threaded hole; 3. Potting ring; 4. Disassembly rod; 5. Positioning ring; 6. Potting hole; 7. Clamping handle; 8. Potting material; 9. Printed circuit board potting parts; 10. Positioning baffle. DETAILED DESCRIPTION

[0021] In order to further understand the content of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the embodiments are only for explaining the present invention and are not intended to limit it.

[0022] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0023] See also Figure 1 and Figure 2 , is a schematic diagram of the potting tooling structure, including a printed circuit board 1, a potting ring 3 is fixed on the outer periphery of the printed circuit board 1, a positioning ring 5 is fixedly attached to the outer side of the potting ring 3, the potting ring 3 is composed of two equally divided semicircles, one end of the two equally divided semicircles is provided with an inclined groove, and the other end is provided with a semicircular hole, and the two equally divided semicircles are also provided with threaded holes 2, and the two threaded holes 2 are respectively located at the two ends of the diameter of the potting ring 3, and the two semicircular holes of the two equally divided semicircles constitute a circular hole, and the positioning ring 5 is also provided with a circular hole formed by the two semicircular holes of the potting ring 3 and a hole corresponding to the threaded block 2, and two disassembly rods 4 are inserted into the two threaded holes 2 of the potting ring 3 through the circular holes of the positioning ring 5.

[0024] See also Figure 3 and Figure 4 , is a schematic diagram of test sample preparation and testing, the potting material 8 is potted in the middle of the two printed circuit boards 1, the potting material 8 and the printed circuit board 1 form a printed circuit board potting part 9, two clamping handles 7 are clamped on the outside of the two printed circuit boards 1, so that the two clamping handles 7 are clamped on both ends of the printed circuit board potting part 9, the two clamping handles 7 and the printed circuit board potting part 9 form a test sample, the upper and lower ends of the two clamping handles 7 are fixed with positioning baffles 10, which constrain the clamping of the clamping handles 7 and the printed circuit board potting part 9, so that the clamping handles 7 and the printed circuit board 1 are tightly fitted and fixed. When testing the bonding strength, the upper and lower positioning baffles 10 are removed, and the two clamping handles 7 are pulled outwards respectively by a universal tensile testing machine. The bonding strength is calculated by monitoring the loading force of the universal tensile testing machine, and the loading force is the tensile force.

[0025] See also Figure 5 The figure is a schematic diagram of the loading force variation of the universal tensile testing machine when the clamping handle 7 is pulled outward. When the time is 8.43S, the loading force reaches the maximum value: 2034N. At this time, both printed circuit boards 1 are separated from the potting material 8, the universal tensile testing machine stops applying force, and the loading force immediately becomes 0.

[0026] This embodiment provides a structure and method for testing the bonding strength between a potting material and a printed circuit board, and the specific implementation steps are as follows: To test the bonding strength between the potting material 8 and the printed circuit board 1, a potting ring 3 is first required. The potting ring 3 is composed of two equally divided semicircular rings. The potting ring 3 is provided with an inclined groove, and a semicircular hole and a threaded hole 2 are left. The two semicircular rings are spliced ​​into a circular ring for use. At this time, the two semicircular holes also form a circular hole, which is the potting hole 6. The threaded block 2 is used for tooling disassembly after potting and curing. A circular printed circuit board 1 is made. The diameter of the circular printed circuit board 1 is between the inner diameter and the outer diameter of the potting ring 3. The demoulding agent is evenly applied to the inner ring of the potting ring 3. After the demoulding agent is cured, the two parts of the potting ring 3 are placed in the positioning ring 5. The potting ring 3 and the positioning ring 5 are spliced ​​into a full circular ring. The positioning ring 5 is also provided with circular holes corresponding to the threaded holes 2 and the potting holes 6 of the potting ring 3. Therefore, when splicing, it should be noted that the circular holes on the positioning ring 5 are consistent with the threaded holes 2 and the potting holes 6 of the potting ring 3. Apply silicone rubber to the inner and outer diameter parts of the printed circuit board 1, that is, the contact parts of the potting ring 3. Do not apply too much silicone rubber and ensure that it is flat. Bond the two printed circuit boards 1 to the two sides of the potting ring 3 respectively, tightly and without any gaps. The two printed circuit boards 1 and the potting ring 3 form a cavity. After the silicone rubber is cured, pass the disassembly rod 4 through the circular hole of the positioning ring 5 and install it on the threaded hole 2 of the potting ring. Fix the disassembly rod 4 at both ends and keep the potting hole 6 at the top. Slowly inject the potting material 8 from the potting hole 6. After potting, When the material 8 is basically flush with the potting hole 6, stop injecting and let it solidify. After the potting material 8 is solidified firmly, first remove the two disassembly rods 4, then take out the positioning ring 5, and reinstall the disassembly rods 4 on the threaded hole 2 of the potting ring 3. Hold the two disassembly rods 4 and apply a torque in the direction away from the notch of the potting ring 3. The two parts of the potting ring 3 will peel off the potting material 8 along the notch direction. Finally, two printed circuit boards 1 with the potting material 8 sandwiched in the middle will remain. The two printed circuit boards 1 and the potting material 8 constitute a printed circuit board potting part 9.

[0027] After the PCB potting part 9 is prepared, the test sample is prepared. Two positioning baffles 10 are prepared. The specifications of the two positioning baffles 10 are required to be the same, and the surface is flat and has a certain weight. The two positioning baffles 10 are placed parallel to each other on a flat surface. The distance between the two baffles is about the width of the end face of the clamping handle 7. The two clamping handles 7 are placed at the two ends of the positioning baffle 10. Take out the PCB potting part 9, and evenly apply a strong adhesive (such as 502 glue) on the outer surface of the PCB 1 on both sides, and then put the PCB potting part 9 back between the two positioning baffles 10, as shown in the figure. Figure 3 Position, under the constraint of the two positioning baffles 10, push the clamping handle 7 towards each other in the horizontal direction at the same time, so that the clamping handle 7 is closely attached to the printed circuit board 1 through a strong adhesive (such as 502 glue), such as Figure 3 As shown by the arrows, until both ends contact the printed circuit board potting part 9 and apply pressure to ensure that the printed circuit board 1 is firmly bonded to the clamping handle 7. At this point, the preparation of the test sample is completed.

[0028] After the preparation is completed, the bonding strength test can be started. The prepared test sample is placed on the universal tensile testing machine, and the two ends of the handle 7 are clamped and the tensile test is performed. Since the bonding strength between the potting material 8 and the printed circuit board 1 is not high, a lower tensile rate is set for stretching, and the tensile force change data is recorded. The relevant test data is as follows: Figure 5 As shown, the tension gradually increases until a sudden change occurs, and the two printed boards 1 are separated from the potting material 8. At this time, the tension data when the printed board 1 is separated from the potting material 8 is recorded. At this time, the loading force of the universal tensile testing machine is the maximum value, that is, the maximum tension: 2834N, and the bonding strength = , where F is the maximum tensile force, S is the contact area between the potting material 8 and the printed circuit board 1, , d is the inner diameter of the potting ring 3; after the printed circuit board 1 is separated from the potting material 8, the universal tensile testing machine stops applying force, and the loading force of the universal tensile testing machine is 0.

[0029] After the test is completed, the test sample is immersed in acetone organic solvent. After a short soaking, the strong adhesive can be ineffective, and the clamping handle 7 can be peeled off from the printed circuit board 1. After cleaning the end surface of the clamping handle 7, the clamping handle can be recovered for reuse. The same method can be used to remove the mold release agent and potting material 8 remaining in the inner ring of the potting ring 3. After cleaning, the potting ring 3 can be reused. In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A bonding strength test structure between a potting material and a printed circuit board, characterized in that: The invention comprises a potting ring (3), a positioning ring (5) and a printed circuit board (1). The printed circuit boards (1) are arranged at both ends of the potting ring (3). The two printed circuit boards (1) and the potting ring (3) form a cavity. The positioning ring (5) is spliced ​​on the outside of the potting ring (3). The outsides of the two printed circuit boards (1) are also clamped with clamping handles (7).

2. The bonding strength test structure between a potting material and a printed circuit board according to claim 1, characterized in that: The printed circuit board (1) is bonded to the outer surface of the potting ring (3) via silicone rubber.

3. The bonding strength test structure between a potting material and a printed circuit board according to claim 1, characterized in that: The printed circuit board (1) is circular, and its diameter is between the inner diameter and the outer diameter of the potting ring.

4. The bonding strength test structure between a potting material and a printed circuit board according to claim 1, characterized in that: The potting ring (3) is composed of two equally divided semicircular rings, which are spliced ​​into a circular ring. An inclined groove is opened on the potting ring (3), and semicircular holes are left in both semicircular rings. The two semicircular holes form a circular hole to form a potting hole (6).

5. The bonding strength test structure between a potting material and a printed circuit board according to claim 4, characterized in that: The positioning ring (5) is a circular ring, and a circular hole is formed in the positioning ring (5) at a position corresponding to the potting hole (6) of the potting ring (3) for potting and disassembly.

6. The bonding strength test structure between a potting material and a printed circuit board according to claim 4, characterized in that: A threaded hole (2) is provided on the potting ring (3), and the threaded hole (2) is used to fix the disassembly rod (4). One end of the disassembly rod (4) is threaded and matches the internal thread of the threaded hole (2) of the potting ring (3).

7. The bonding strength test structure between a potting material and a printed circuit board according to claim 1, characterized in that: The end face of the clamping handle (7) is cubic or circular.

8. The bonding strength test structure between a potting material and a printed circuit board according to claim 7, characterized in that: The clamping handles (7) are adhesively clamped on the outer ends of the printed circuit board (1).

9. A method for testing the bonding strength between a potting material and a printed circuit board, characterized in that: A test structure for the bonding strength between a potting material and a printed circuit board based on any one of claims 1 to 8, wherein the test method comprises: pouring a potting material (8) between two printed circuit boards (1), wherein the two printed circuit boards (1) and the potting material (8) form a printed circuit board potting member (9); after removing the positioning ring (5) and the potting ring (3), fixing positioning baffles (10) at the upper and lower ends of the clamping handle (7); and clamping the two clamping handles (7) on the outer sides of the two printed circuit boards (1) by a strong adhesive under the constraints of the two positioning baffles (10), so that the printed circuit board potting member (9) and the two clamping handles (7) form a test sample.

10. The method for testing the bonding strength between a potting material and a printed circuit board according to claim 9, characterized in that: The two positioning baffles (10) are removed, and the clamping handles (7) at both ends of the printed circuit board potting component (9) are pulled outward using a universal tensile testing machine, and the tensile force data are recorded until the printed circuit board (1) and the potting material (8) are separated. The maximum tensile force is obtained when the printed circuit board (1) and the potting material (8) are separated. The bonding strength is calculated using the tensile force data, and the calculation method is as follows: Bond Strength = , , where F is the maximum tensile force, S is the contact area between the potting material and the printed circuit board, and d is the inner diameter of the potting circle.

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