Integrated surge protector and glue-filling packaging process thereof

Abstract

The present application relates to a kind of integrated surge protector and its glue filling packaging process, the glue filling packaging process includes the following steps: the side of integrated surge protector semi-finished product with auxiliary circuit element is injected with resin using injection molding, after curing, glue filling packaging is completed;Injection molding is carried out under the injection pressure of gradient increasing.The present application uses multistage pressure resin sectional injection molding process, and the glue filling packaging of integrated surge protector semi-finished product effectively solves the series of problems such as soldering point of colloid thermal stress damage, tin paste migration short circuit, encapsulation internal bubble cavity caused by secondary reflow soldering high temperature of integrated surge protector.

Description

Technical Field

[0001] This invention relates to the field of packaging technology, and in particular to an integrated surge protector and its potting encapsulation process. Background Technology

[0002] Integrated surge protectors (BXDs) are modular surge protection devices that integrate auxiliary circuitry and ceramic gas discharge tubes. They are widely used as core components for surge protection in communication equipment, power supplies, and security monitoring equipment. During assembly, these devices are transferred to downstream product stages for a second reflow soldering process at high temperatures to achieve integrated assembly with the mainboard of the entire system.

[0003] Existing technical solutions generally use epoxy resin potting to complete the overall encapsulation. However, this traditional potting encapsulation process has an inherent defect of poor encapsulation density: when the integrated surge protector is subjected to the high temperature thermal shock of secondary reflow soldering, the fully cured epoxy potting compound undergoes significant thermal expansion due to heat. The resulting thermomechanical stress directly acts on the tiny solder joints of the gas discharge tube (GDT) on the printed circuit board (PCB), which can easily cause defects such as micro-cracks, cold solder joints, and desoldering, greatly reducing the reliability of the device's soldering structure.

[0004] Meanwhile, during the potting process, air is easily trapped at the interface between the auxiliary circuit components and the epoxy resin colloid, resulting in numerous bubbles and voids inside the encapsulation shell. Under the high-temperature environment of secondary reflow soldering, the solder paste at the solder joints of the auxiliary circuit components liquefies again after the temperature exceeds the melting point. Under the continuous pressure of thermal expansion stress in the colloid, the liquefied solder will undergo irregular secondary migration and solder creep along the bubble and void channels inside the colloid. The migrating molten solder can easily bridging the electrodes of adjacent auxiliary circuit components, causing a significant decrease in the inter-electrode insulation resistance of the device. In severe cases, it can directly cause a short circuit, leading to the failure of the surge protector and significantly reducing the overall product yield and long-term stability.

[0005] Therefore, how to provide a new integrated surge protector potting and encapsulation process to solve a series of problems caused by high temperature during secondary reflow soldering, such as thermal stress damage to solder joints, short circuits due to solder paste migration, and internal air bubbles and voids in the package, and improve the device's reflow soldering resistance and long-term protection reliability, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides an integrated surge protector and its potting and encapsulation process. A multi-stage pressure resin segmented injection molding process is used to pot and encapsulate the semi-finished integrated surge protector, effectively solving a series of problems caused by the high temperature of secondary reflow soldering, such as thermal stress damage to solder joints, solder paste migration and short circuits, and internal air bubbles and voids within the encapsulation.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a potting and encapsulation process for an integrated surge protector, the potting and encapsulation process comprising the following steps: injecting resin into the side of the integrated surge protector semi-finished product where auxiliary circuit elements are provided, and then curing it to complete the potting and encapsulation; the injection molding is performed under a gradient increasing injection pressure.

[0008] This invention employs a multi-stage pressure resin segmented injection molding process to encapsulate the integrated surge protector semi-finished product with resin. By adjusting the resin injection pressure, it effectively achieves the functions of venting, wetting, and compensating for curing, thereby effectively eliminating air bubbles and voids inside the encapsulation and ensuring that the resin completely covers the integrated surge protector semi-finished product. This also reduces the residual internal stress of the cured colloid and the thermomechanical stress of reflow soldering.

[0009] Preferably, the integrated surge protector semi-finished product includes a printed circuit board, a gas discharge tube, and auxiliary circuit components; the gas discharge tube is soldered to a first surface of the printed circuit board, and the auxiliary circuit components are soldered to a second surface of the printed circuit board opposite to the first surface.

[0010] Preferably, the welding includes reflow soldering.

[0011] Preferably, the integrated surge protector semi-finished product undergoes preheating treatment before potting and encapsulation.

[0012] Preferably, the preheating temperature is 75-80℃ (e.g., 75℃, 76℃, 77℃, 78℃, 79℃ or 80℃, etc.), and the time is 2-4 min (e.g., 2 min, 2.5 min, 3 min, 3.5 min or 4 min, etc.).

[0013] Preferably, the resin used in the potting and encapsulation process includes epoxy resin.

[0014] Preferably, the coefficient of thermal expansion of the epoxy resin is ≤35×10⁻⁶. -6 / ℃, for example, could be 10×10 -6 / ℃, 15×10 -6 / ℃, 20×10 -6 / ℃, 25×10 -6 / ℃, 30×10 -6 / ℃ or 35×10 -6 / ℃.

[0015] Preferably, the glass transition temperature of the epoxy resin is 110-150℃, for example, it can be 110℃, 120℃, 130℃, 140℃, 150℃, etc.

[0016] The methods for testing the coefficient of thermal expansion and glass transition temperature of the epoxy resin are as follows: The epoxy resin to be tested is added to a pusher-type dilatometer, and the temperature is increased from 70°C to 150°C in 10°C increments. The expansion amount is read and the expansion coefficient is calculated. The temperature at which the expansion coefficient changes abruptly is the glass transition temperature.

[0017] Preferably, the resin is preheated before potting and encapsulation.

[0018] Preferably, the preheating temperature is 75-80℃ (e.g., 75℃, 76℃, 77℃, 78℃, 79℃ or 80℃, etc.), and the time is 0.5-2 min (e.g., 0.5 min, 1 min, 1.5 min or 2 min, etc.).

[0019] Preferably, the integrated surge protector semi-finished product is pre-placed in an injection mold.

[0020] Preferably, the height of the injection mold is 3-5 mm, for example, it can be 3 mm, 3.5 mm, 4 mm, 4.5 mm or 5 mm.

[0021] Preferably, the gradient injection pressure includes resin segmented injection molding under two or more graded pressures, and more preferably resin segmented injection molding under three pressures.

[0022] Preferably, the resin segmented injection molding under the three-stage pressure includes a first injection, a second injection, and a third injection.

[0023] Preferably, the first injection is performed by injecting epoxy resin under a pressure of 150-250 bar (e.g., 150 bar, 160 bar, 180 bar, 200 bar, 220 bar, 240 bar or 250 bar, etc.), and then holding the pressure for 3-8 seconds (e.g., 3 seconds, 4 seconds, 5 seconds, 6 seconds, 7 seconds or 8 seconds, etc.).

[0024] Preferably, the second injection molding involves injecting epoxy resin under a pressure of 500-700 bar (e.g., 500 bar, 550 bar, 600 bar, 650 bar, or 700 bar, etc.), and then holding the pressure for 10-20 seconds (e.g., 10 seconds, 12 seconds, 14 seconds, 16 seconds, 18 seconds, or 20 seconds, etc.).

[0025] Preferably, the third injection molding is performed by injecting epoxy resin under a pressure of 800-1200 bar (e.g., 800 bar, 900 bar, 1000 bar, 1100 bar or 1200 bar, etc.), and then holding the pressure for 5-15 s (e.g., 5 s, 6 s, 8 s, 10 s, 12 s, 14 s or 15 s, etc.).

[0026] Preferably, the ratio of the injection volume of the first injection, the second injection, and the third injection is 1:(2.2-2.8):(1.2-1.8).

[0027] Among them, 2.2-2.8 can be, for example, 2.2, 2.4, 2.5, 2.6 or 2.8; 1.2-1.8 can be, for example, 1.2, 1.4, 1.5, 1.6 or 1.8.

[0028] In this invention, epoxy resin is first injected under a pressure of 150-250 bar, and then held under pressure for 3-8 seconds to fully remove air from the system. Next, epoxy resin is injected under a pressure of 500-700 bar, and then held under pressure for 10-20 seconds to fully fill the mold gaps. Finally, epoxy resin is injected under a pressure of 800-1200 bar, and then held under pressure for 5-15 seconds to compensate for curing.

[0029] Preferably, the curing temperature is 160-200℃ (e.g., 160℃, 170℃, 180℃, 190℃ or 200℃, etc.), and the time is 20-40 s, e.g., 20 s, 25 s, 30 s, 35 s or 40 s, etc.

[0030] Preferably, the curing process further includes a step of static cooling.

[0031] Preferably, the cooling process includes first cooling to 95-105℃ (e.g., 95℃, 96℃, 98℃, 100℃, 102℃, 104℃ or 105℃, etc.) for demolding, and then cooling to 20-30℃ (e.g., 20℃, 22℃, 24℃, 25℃, 26℃, 28℃ or 30℃, etc.).

[0032] In a second aspect, the present invention provides an integrated surge protector, which is prepared by the potting encapsulation process described in the first aspect.

[0033] Compared with the prior art, the present invention has at least the following beneficial effects: This invention employs a multi-stage pressure resin segmented injection molding process to encapsulate integrated surge protector semi-finished products, abandoning the traditional single-pressure, one-time encapsulation method. By controlling the injection pressure in stages, the resin can uniformly and fully fill the tiny gaps in the device, effectively eliminating air bubbles and voids inside the encapsulation. This results in a dense and well-fitting encapsulation structure, buffering high-temperature thermal stress, protecting precision solder joints, and preventing short circuits caused by solder paste migration. This significantly improves the product's packaging yield, high-temperature stability, and electrical reliability, solving the industry's technical problems of unstable packaging and easy failure at high temperatures, and possesses significant industrialization value. Detailed Implementation

[0034] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0035] Example 1 This embodiment provides a potting encapsulation process for an integrated surge protector, which includes the following steps: (1) Preheat the integrated surge protector semi-finished product to 78°C and keep it warm for 3 minutes, then set it aside; Preheat the epoxy resin to 78°C and hold for 1 minute; set aside. (2) Place the preheated integrated surge protector semi-finished product into the injection mold. Use preheated epoxy resin to inject the second plate side of the integrated surge protector semi-finished product. First, perform the first injection at 200 bar pressure, hold the pressure and stand for 5 s. Then, perform the second injection at 600 bar pressure, hold the pressure and stand for 15 s. Then, perform the third injection at 1000 bar pressure, hold the pressure and stand for 10 s after injection. The ratio of the injection volume of the first, second and third injections is 1:2.5:1.5. Inject until the mold is completely filled. After injection, keep it at 180°C for 30 s to cure. After curing, cool the integrated surge protector to 100°C to demold, and then let it stand to cool to 25°C to complete the potting and encapsulation.

[0036] Example 2 This embodiment provides a potting encapsulation process for an integrated surge protector, which includes the following steps: (1) Preheat the integrated surge protector semi-finished product to 75°C and keep it warm for 4 minutes, then set it aside; Preheat the epoxy resin to 75°C and hold for 2 minutes; set aside. (2) Place the preheated integrated surge protector semi-finished product into the injection mold. The preheated epoxy resin is injected into the second plate side of the integrated surge protector semi-finished product. First, the first injection is performed under a pressure of 150 bar, and the pressure is held for 8 s. Then, the second injection is performed under a pressure of 700 bar, and the pressure is held for 20 s. Then, the third injection is performed under a pressure of 800 bar, and the pressure is held for 15 s after injection. The ratio of the injection volume of the first, second and third injections is 1:2.5:1.5. The injection is performed until the mold is completely filled. The mold is kept at 200°C for 30 s for curing. After curing, the integrated surge protector is cooled to 100°C for demolding and then allowed to cool to 25°C to complete the potting and encapsulation.

[0037] Example 3 This embodiment provides a potting encapsulation process for an integrated surge protector, which includes the following steps: (1) Preheat the integrated surge protector semi-finished product to 80°C and keep it warm for 2 minutes, then set it aside; Preheat the epoxy resin to 80℃ and hold for 0.5 min, then set aside. (2) Place the preheated integrated surge protector semi-finished product into the injection mold. The preheated epoxy resin is injected into the second plate side of the integrated surge protector semi-finished product. First, the first injection is performed under a pressure of 250 bar, and the pressure is held for 3 seconds. Then, the second injection is performed under a pressure of 700 bar, and the pressure is held for 10 seconds. Then, the third injection is performed under a pressure of 1200 bar, and the pressure is held for 5 seconds after injection. The ratio of the injection volume of the first, second and third injections is 1:2.5:1.5. The injection is performed until the mold is completely filled. The mold is cured at 160°C for 30 seconds. After curing, the integrated surge protector is cooled to 100°C and demolded. Then, it is allowed to cool to 25°C to complete the potting and encapsulation.

[0038] Example 4 This embodiment provides a potting encapsulation process for an integrated surge protector, which includes the following steps: (1) Preheat the integrated surge protector semi-finished product to 78°C and keep it warm for 3 minutes, then set it aside; Preheat the epoxy resin to 78°C and hold for 1 minute; set aside. (2) Place the preheated integrated surge protector semi-finished product into the injection mold, and inject the preheated epoxy resin into the second plate side of the integrated surge protector semi-finished product. First, perform the first injection under 600 bar pressure, hold the pressure and stand for 20 s, and then perform the second injection under 1000 bar pressure, hold the pressure and stand for 10 s. The ratio of the injection volume of the first injection and the second injection is 3.5:1.5. Inject until the mold is completely filled, and keep it at 180°C for 30 s to cure. After curing, cool the integrated surge protector to 100°C to demold, and then let it stand and cool to 25°C to complete the potting and encapsulation.

[0039] Example 5 This embodiment provides a potting encapsulation process for an integrated surge protector, which includes the following steps: (1) Preheat the integrated surge protector semi-finished product to 78°C and keep it warm for 3 minutes, then set it aside; Preheat the epoxy resin to 78°C and hold for 1 minute; set aside. (2) Place the preheated integrated surge protector semi-finished product into the injection mold, and inject the preheated epoxy resin into the second plate side of the integrated surge protector semi-finished product. First, perform the first injection under 200 bar pressure, hold the pressure and stand for 20 s, and then perform the second injection under 1000 bar pressure, hold the pressure and stand for 10 s. The ratio of the injection volume of the first injection to the second injection is 3.5:1.5. Inject until the mold is completely filled, and keep it at 180°C for 30 s to cure. After curing, cool the integrated surge protector to 100°C to demold, and then let it stand and cool to 25°C to complete the potting and encapsulation.

[0040] Example 6 This embodiment provides a potting encapsulation process for an integrated surge protector, which includes the following steps: (1) Preheat the integrated surge protector semi-finished product to 78°C and keep it warm for 3 minutes, then set it aside; Preheat the epoxy resin to 78°C and hold for 1 minute; set aside. (2) Place the preheated integrated surge protector semi-finished product into the injection mold, and inject the preheated epoxy resin into the second plate side of the integrated surge protector semi-finished product. First, perform the first injection under 200 bar pressure, hold the pressure and stand for 5 s, and then perform the second injection under 600 bar pressure, hold the pressure and stand for 25 s. The ratio of the injection volume of the first injection to the second injection is 1:4. Inject until the mold is completely filled, and keep it at 180°C for 30 s to cure. After curing, cool the integrated surge protector to 100°C to demold, and then let it stand and cool to 25°C to complete the potting and encapsulation.

[0041] Comparative Example 1 This comparative example provides a potting encapsulation process for an integrated surge protector, the potting encapsulation process comprising the following steps: (1) Preheat the integrated surge protector semi-finished product to 78°C and keep it warm for 3 minutes, then set it aside; Preheat the epoxy resin to 78°C and hold for 1 minute; set aside. (2) Place the preheated integrated surge protector semi-finished product into the injection mold, and inject the preheated epoxy resin into the second plate side of the integrated surge protector semi-finished product. Inject at a pressure of 200 bar until the mold is completely filled. Hold the pressure and stand for 30 s. After injection, keep it at 180°C for 30 s to cure. After curing, cool the integrated surge protector to 100°C to demold, and then let it stand and cool to 25°C to complete the potting and encapsulation.

[0042] Comparative Example 2 This comparative example provides a potting encapsulation process for an integrated surge protector, the potting encapsulation process comprising the following steps: (1) Preheat the integrated surge protector semi-finished product to 78°C and keep it warm for 3 minutes, then set it aside; Preheat the epoxy resin to 78°C and hold for 1 minute; set aside. (2) Place the preheated integrated surge protector semi-finished product into the injection mold, and inject the preheated epoxy resin into the second plate side of the integrated surge protector semi-finished product. Inject at a pressure of 600 bar until the mold is completely filled. Hold the pressure and stand for 30 seconds. After injection, keep it at 180°C for 30 seconds to cure. After curing, cool the integrated surge protector to 100°C to demold, and then let it stand and cool to 25°C to complete the potting and encapsulation.

[0043] Comparative Example 3 This comparative example provides a potting encapsulation process for an integrated surge protector, the potting encapsulation process comprising the following steps: (1) Preheat the integrated surge protector semi-finished product to 78°C and keep it warm for 3 minutes, then set it aside; Preheat the epoxy resin to 78°C and hold for 1 minute; set aside. (2) Place the preheated integrated surge protector semi-finished product into the injection mold, and inject the preheated epoxy resin into the second plate side of the integrated surge protector semi-finished product. Inject at a pressure of 1000 bar until the mold is completely filled. Hold the pressure and stand for 30 seconds. After injection, keep it at 180°C for 30 seconds to cure. After curing, cool the integrated surge protector to 100°C to demold, and then let it stand and cool to 25°C to complete the potting and encapsulation.

[0044] Test methods The integrated surge protectors provided in the embodiments and comparative examples were subjected to the following performance tests: (1) Yield (%): 100 sets of integrated surge protectors provided in each embodiment and comparative example were batch-tested for electrical performance (including DC breakdown voltage test and AC breakdown voltage test according to GB / T 18802.11-2020; DC withstand voltage test and AC withstand voltage test according to GB / T 18802.11-2020 dielectric withstand voltage test; insulation resistance test according to GB / T18802.11-2020). If any defect of solder run-through or solder bridging is found after the test, it is judged as defective. (2) Interface bonding force (N): Using a tension gauge, hang the hook on the interface between the printed circuit board and the gas discharge tube and apply an upward pulling force. At the same time, hang the other hook on the gas discharge tube and apply a downward pulling force. Then, hang the second hook on the gas discharge tube and apply a downward pulling force until the printed circuit board and the gas discharge tube are separated. The count of the tension gauge at this time is the interface bonding force.

[0045] The test results are shown in Table 1: Table 1 The test results show that: (1) As can be seen from Examples 1 to 6, the product prepared by the multi-stage pressure resin segmented injection molding process of the present invention has a product yield of over 84%, and the interface bonding force between the printed circuit board and the gas discharge tube all reach 33 N or more, meeting the qualified standard of ≥24 N; while the comparative example using the traditional single constant pressure one-time potting has a product yield of only 52-60%, the highest interface bonding force is only 24 N, most samples are below the qualified threshold, and the product reliability is poor.

[0046] (2) As can be seen from Examples 1 and 3-6, when two-stage gradient injection molding is used, the effects of venting, filling and shrinkage compensation decrease during injection molding, the number of internal micro bubbles and insufficient interface wetting increases, the yield drops to 84-88%, and the interface bonding force drops back to 33-38 N, proving that three-stage gradient segmented injection molding is the optimal process solution.

[0047] (3) As can be seen from Example 1 and Comparative Examples 1-3, Comparative Example 1 only uses 200 bar low-pressure one-time injection molding. The colloid cannot fully wet the tiny interface between the printed circuit board and the gas discharge tube. A large number of air bubbles and voids are trapped inside the cavity. During the second reflow soldering, the solder paste is easy to migrate and short-circuit along the voids. The product yield is only 52%, and the interface bonding force is only 20 N, which is far below the qualified threshold. Comparative Example 2 only uses 600 bar medium-pressure one-time injection molding. The filling capacity is slightly improved, but there is no low-pressure pre-venting and high-pressure compensation process. There is still a small amount of air inclusion defect. The interface bonding force just reaches the critical value of 24 N. The product yield is only 60%. There is still a risk of delamination and solder joint failure under high temperature conditions. Comparative Example 3 only uses 1000 bar high-pressure one-time injection molding. The high-pressure melt is sprayed at high speed to form turbulence and carry air. At the same time, the residual stress of molding is greatly increased. After cooling, the colloid continues to pull the solder joint of the gas discharge tube, resulting in solder dripping and poor component misalignment. The interface bonding force is 23 N, and the product yield is 58%.

[0048] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A potting and encapsulation process for an integrated surge protector, characterized in that, The potting and encapsulation process includes the following steps: resin is used to inject the side of the integrated surge protector semi-finished product with auxiliary circuit components, and then the potting and encapsulation is completed after curing; the injection is carried out under a gradient increasing injection pressure.

2. The potting and encapsulation process according to claim 1, characterized in that, The integrated surge protector semi-finished product includes a printed circuit board, a gas discharge tube, and auxiliary circuit components; the gas discharge tube is soldered to the first surface of the printed circuit board, and the auxiliary circuit components are soldered to the second surface of the printed circuit board opposite to the first surface. Preferably, the welding includes reflow soldering.

3. The potting and encapsulation process according to claim 1 or 2, characterized in that, The integrated surge protector semi-finished product undergoes preheating treatment before potting and encapsulation. Preferably, the preheating treatment is performed at a temperature of 75-80°C for 2-4 minutes.

4. The potting and encapsulation process according to any one of claims 1-3, characterized in that, The resin used in the potting and encapsulation process includes epoxy resin; Preferably, the coefficient of thermal expansion of the epoxy resin is ≤35×10⁻⁶. -6 / ℃; Preferably, the glass transition temperature of the epoxy resin is 110-150°C.

5. The potting and encapsulation process according to any one of claims 1-4, characterized in that, The resin is preheated before encapsulation. Preferably, the preheating treatment is performed at a temperature of 75-80°C for a time of 0.5-2 min.

6. The potting and encapsulation process according to any one of claims 1-5, characterized in that, The integrated surge protector semi-finished product is pre-placed in the injection mold; Preferably, the height of the injection mold is 3-5 mm.

7. The potting and encapsulation process according to any one of claims 1-6, characterized in that, The gradient-increasing injection pressure includes resin segment injection molding under two or more graded pressures, preferably resin segment injection molding under three graded pressures. Preferably, the three-stage resin injection molding under pressure includes first injecting epoxy resin at a pressure of 150-250 bar, holding the pressure for 3-8 seconds after injection, then injecting epoxy resin at a pressure of 500-700 bar, holding the pressure for 10-20 seconds after injection, and then injecting epoxy resin at a pressure of 800-1200 bar, holding the pressure for 5-15 seconds after injection.

8. The potting and encapsulation process according to any one of claims 1-7, characterized in that, The curing temperature is 160-200℃, and the time is 20-40 seconds.

9. The potting and encapsulation process according to any one of claims 1-8, characterized in that, The curing process also includes a static cooling step.

10. An integrated surge protector, characterized in that, The integrated surge protector is prepared by the potting and encapsulation process as described in any one of claims 1-9.

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