Uncovering method of plastic package body

Abstract

The invention relates to the technical field of semiconductors, in particular to an uncovering method of a plastic package body. Comprising the steps of performing ultrasonic scanning on a plastic package body needing to be uncovered, determining an internal structure and dividing a range needing to be uncovered; preliminarily unsealing the plastic package body by adopting a laser ablation mode, so that a surface bonding wire is exposed out of a chip area of the plastic package body, and a welding spot is exposed out of a thermistor area; dropwise adding an acid solution to an area, which is thinned by laser ablation, of the primarily unsealed plastic package body, corroding for a certain time, and then pouring out a waste solution; when excessive reaction waste liquid is accumulated in the internal area, the device is washed clean with water and blow-dried, and whether the range needing to be uncovered is completely exposed or not is observed. And if the epoxy material is still partially covered, continuing the above steps until the internal environment is completely exposed. The unsealing method of the electronic device more suitable for the dense plastic packaging material is provided, laser ablation and acid liquor corrosion are combined, the unsealing efficiency is higher, the area is controllable, and the success rate is high.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductors, and in particular to a method for opening a plastic package. Background Art

[0002] Plastic encapsulated devices have many advantages such as low cost, light weight, small size, high integration, excellent physical and electrical properties, and easy procurement. Their application fields are becoming more and more extensive. At present, more than 97% of integrated circuits on the market are in plastic packaging. Therefore, research on its reliability experiments and failure analysis has also been developed. Among them, in the requirements of failure analysis, opening the cover of plastic encapsulated devices is an extremely critical analysis method, which affects the subsequent research on chip surface, copper-clad ceramic (DBC), bonding strength, shear strength, etc.

[0003] At present, among the methods for unsealing plastic-sealed components, an automatic unsealing device can meet the usual unsealing needs. However, the automatic unsealing device requires a suitable mask gasket, lacks control over the sprayed acid mist during the process, and is limited by the external shape and height of the component. Therefore, the unsealing area cannot be well grasped, and the corrosion direction during the process cannot be controlled, resulting in low efficiency and success rate of unsealing plastic-sealed components.

[0004] Since the current application process needs to meet higher use conditions and more demanding use environments, a type of injection molding material has been developed that modifies the epoxy functional group and adds various additives during the production process to enable the device to obtain higher thermodynamic and physical properties. However, this type of plastic-encapsulated device poses a great challenge to the artificial acid opening process. The traditional chemical process of opening the cover using mixed acid for corrosion has the disadvantages of long cycle and low efficiency in the application of this type of device, which seriously affects the product development cycle and its failure analysis process. Summary of the invention

[0005] The purpose of the present invention is to provide a method for opening a plastic-sealed body to solve the above technical problems;

[0006] The technical problem solved by the present invention can be achieved by adopting the following technical solutions:

[0007] A method for opening a plastic-sealed body, comprising:

[0008] Step S1, performing ultrasonic scanning on the plastic package body to be opened, determining the internal structure and dividing the range to be opened;

[0009] Step S2, preliminarily unsealing the plastic package body by laser ablation, so that the surface bonding wires are exposed in the chip area of ​​the plastic package body, and the solder joints are exposed in the thermistor area;

[0010] Step S3, adding acid solution dropwise to the area of ​​the initially opened plastic package body thinned by laser ablation, and pouring out the waste liquid after etching for a certain period of time;

[0011] Step S4, detecting whether the residual amount of waste liquid in the initially opened plastic-sealed body exceeds a preset amount, if not, returning to step S3 and continuing to drip the acid solution; if exceeding, cleaning and drying the plastic-sealed body, and observing whether the internal environment of the plastic-sealed body is completely exposed, if not completely exposed, returning to step S3 and continuing to drip the acid solution; if completely exposed, the opening of the cover is completed, and the opened plastic-sealed body is obtained.

[0012] Preferably, in step S1, an ultrasonic scanning device is used to perform ultrasonic scanning on the plastic package body, the resolution of the ultrasonic scanning device is below 0.1 mm and has an adjustable scanning frequency, and the scanning frequency of the ultrasonic scanning device is 10 MHz to 50 MHz.

[0013] Preferably, in step S1, when performing ultrasonic scanning, the plastic package is placed on a fixed fixture, and the scanning process includes a preliminary scan for obtaining the contour of the plastic package and the distribution of internal components and a fine scan for obtaining the detailed positions of the chip and thermistor of the plastic package.

[0014] Preferably, in step S2, a pulse laser is used for laser ablation, the pulse width of the pulse laser is 10ns to 100ns, the repetition frequency is 1kHz to 10kHz, the laser spot of the pulse laser has a switchable diameter, and the diameter range of the laser spot is 0.1mm to 1mm;

[0015] The time for laser ablation of the chip region is 20s to 40s, and the time for laser ablation of the thermistor region is 30s to 50s.

[0016] Preferably, the initial power of the pulse laser is 5W-15W, and an infrared thermometer is also used in step S2 to monitor the temperature change of the laser ablation area, and the power of the pulse laser is adjusted based on the temperature data obtained by the infrared thermometer.

[0017] Preferably, in step S3, before adding the acid solution, the process further includes heating the preliminarily opened plastic-sealed body, and the heating temperature is 100° C. to 140° C.

[0018] Preferably, in step S3, the acid solution is dripped with a glass dropper, and the preliminarily opened plastic-sealed body is evenly shaken while the acid solution is dripped, and the reaction time after the acid solution is dripped is 40s to 60s.

[0019] Preferably, in step S3, the acid solution is heated concentrated sulfuric acid.

[0020] Preferably, in step S4, detecting whether the residual amount of waste liquid in the initially opened plastic package exceeds a preset amount comprises:

[0021] Observe the distribution of the residual waste liquid in the plastic package, and if the level of the residual waste liquid exceeds the preset level or the residual waste liquid begins to spread, determine that the waste liquid in the initially opened plastic package exceeds the preset amount; otherwise, determine that it does not exceed; or;

[0022] Add a certain amount of the acid solution, and if the reaction speed of the acid solution is lower than a preset speed or the flow resistance of the acid solution is higher than a preset resistance, it is determined that the waste liquid in the initially opened plastic package exceeds the preset amount; otherwise, it is determined that it does not exceed; or;

[0023] A sensor is preset in the plastic package to detect the residual amount of waste liquid based on a sampling signal output by the sensor. The sensor is one of a capacitive liquid level sensor, an optical fiber sensor, a pressure sensor, and a microwave liquid level sensor.

[0024] Preferably, it also includes,

[0025] Step S5, rinse with heated fuming nitric acid for several times, clean with cleaning liquid, and blow dry after cleaning.

[0026] Beneficial effects of the present invention: Due to the adoption of the above technical scheme, the present invention provides a method for unsealing electronic devices that is more suitable for dense plastic packaging materials. By combining laser ablation and acid corrosion, the unsealing efficiency is higher, the area is controllable, and the success rate is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the steps of the method for opening the plastic-sealed body of the present invention;

[0028] Figure 2 The figure is a flow chart of a method for opening a plastic-sealed body in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0032] A method for opening a plastic package body, such as Figure 1 , Figure 2 As shown, including,

[0033] Step S1, performing ultrasonic scanning on the plastic package body to be opened, determining the internal structure and dividing the range to be opened;

[0034] Step S2, preliminarily opening the plastic package by laser ablation, so that the surface bonding wires of the chip area of ​​the plastic package are exposed, and the solder joints of the thermistor area are exposed;

[0035] Step S3, adding acid solution dropwise to the area of ​​the initially opened plastic package body that is thinned by laser ablation, and pouring out the waste liquid after etching for a certain period of time;

[0036] Step S4, detect whether the residual amount of waste liquid in the initially opened plastic-sealed body exceeds the preset amount. If not, return to step S3 and continue to add acid. If exceeded, clean and blow dry the plastic-sealed body to observe whether the internal environment of the plastic-sealed body is completely exposed. If not, return to step S3 and continue to add acid. If completely exposed, the opening is completed to obtain the opened plastic-sealed body.

[0037] Specifically, the present invention provides a more convenient, effective and low-cost method for opening a cover to meet the demand for opening a cover for analyzing a plastic-sealed body using a dense plastic-sealing material.

[0038] First, perform ultrasonic scanning on the device that needs to be opened to confirm its internal structure, including the location and size of the negative temperature coefficient thermistor (NTC) and the chip, and divide the range that needs to be opened as accurately as possible to improve the efficiency of subsequent acid opening.

[0039] Before acid opening, the thickness of the epoxy injection molding material needs to be physically thinned. Laser ablation is usually used to open the device to expose the surface bonding aluminum wire in the chip area and the tin-lead solder joint near the NTC.

[0040] Because the component layout in plastic-encapsulated electronic devices is relatively complex, the chip sizes vary, and the depths of each component vary, the laser ablation power and time must be controlled during the laser thinning process to avoid excessive ablation, which will damage the chip surface and affect the judgment of the subsequent failure analysis. However, it is also necessary to avoid being too conservative during the laser thinning process, and the remaining thickness of the injection molding material is too large, which will affect the removal speed of the subsequent acid corrosion process.

[0041] More specifically, after the pre-opening, the device is transferred to the acid-opening laboratory. During the process, concentrated sulfuric acid is used as a corrosion reagent and heated to 100° C. At the same time, the device is heated to 120° C.

[0042] Use a glass dropper to slowly drip concentrated sulfuric acid into the pre-laser thinned area, and shake the injection molded device at the same time to allow the concentrated sulfuric acid and epoxy to fully contact. The corrosion time is 50 seconds, and then pour the waste liquid inside the area into the waste liquid tank, and add concentrated sulfuric acid again for corrosion. When too much reaction waste liquid accumulates in the internal area, rinse the device with water and blow it dry, and observe whether the required opening range is completely exposed. If there is still a part covered with epoxy material, continue the above steps to completely expose the internal environment.

[0043] In a preferred embodiment, in step S1, an ultrasonic scanning device is used to perform ultrasonic scanning on the plastic package. The resolution of the ultrasonic scanning device is below 0.1 mm and has an adjustable scanning frequency. The scanning frequency of the ultrasonic scanning device is 10 MHz to 50 MHz.

[0044] In a preferred embodiment, in step S1, when performing ultrasonic scanning, the plastic package is placed on a fixed fixture, and the scanning process includes a preliminary scan for obtaining the contour of the plastic package and the distribution of internal components and a fine scan for obtaining the detailed position of the chip and thermistor of the plastic package.

[0045] Specifically, the present invention places the plastic package body to be opened on a fixing fixture for fixing, so as to keep the device stable during the scanning process.

[0046] Before scanning, the ultrasonic scanning equipment needs to be calibrated and parameters such as gain and contrast need to be set to obtain clear and accurate images of internal structures.

[0047] First, an overall scan is performed to obtain the general outline of the plastic package and the approximate distribution of the internal components. Then, a local fine scan is performed on the chip and NTC area. By adjusting the scanning angle and focus depth, the size of the chip, including length, width and thickness (accuracy of ±0.05mm) and the position coordinates of the NTC (accuracy of ±0.1mm) are accurately measured.

[0048] Based on the scanning results, a detailed schematic diagram of the internal structure is drawn in the software, and the range that needs to be opened is marked. It should be noted that the opening range should be minimized as much as possible while ensuring that subsequent analysis can be carried out effectively, so as to reduce the workload during the acid opening process and the impact on other parts of the device.

[0049] In a preferred embodiment, in step S2, a pulse laser is used for laser ablation, the pulse width of the pulse laser is 10ns to 100ns, the repetition frequency is 1kHz to 10kHz, the laser spot of the pulse laser has a switchable diameter, and the diameter range of the laser spot is 0.1mm to 1mm;

[0050] The time for laser ablation of the chip area is 20s to 40s, and the time for laser ablation of the thermistor area is 30s to 50s.

[0051] In a preferred embodiment, the starting power of the pulse laser is 5W-15W, and an infrared thermometer is also used in step S2 to monitor the temperature change of the laser ablation area, and the power of the pulse laser is adjusted based on the temperature data obtained by the infrared thermometer.

[0052] Specifically, the present invention uses a pulsed laser with a wavelength of 1064nm, and preliminarily sets the laser ablation power according to the material of the plastic package and the previous experimental data. For general epoxy injection molding materials, the initial power can be set to 8W.

[0053] During the ablation process, an infrared thermometer is used to monitor the temperature change of the laser ablation area in real time (with a measurement accuracy of ±1°C) to adjust the power. If the temperature rises too quickly and exceeds the preset temperature threshold, which is 150°C in this embodiment, the laser power is reduced; if the temperature rises too slowly, the power is increased to improve the ablation efficiency.

[0054] The power amplitude of the present invention is adjusted no more than 1W each time. At the same time, the ablation time is strictly controlled. For the chip area, the time from the start of ablation to the exposure of the surface bonding aluminum wire should be determined according to factors such as chip size and injection molding thickness. The present invention is between 20 and 40 seconds. For the area near the NTC, the time from ablation to the exposure of the tin-lead solder joint is between 30 and 50 seconds.

[0055] During the entire ablation process, a high-resolution microscope (magnification of 50 to 200 times) can be used to observe the opening situation in real time and detect laser ablation.

[0056] In a preferred embodiment, in step S3, before adding the acid solution, the step further includes heating the initially opened plastic package body, and the heating temperature is 100°C to 140°C.

[0057] Specifically, the present invention uses a heating platform to heat the initially opened plastic package body. After the device is placed on the heating platform, the temperature of the initially opened plastic package body is monitored in real time by a temperature sensor, and the center temperature is 120°C.

[0058] At the same time, the concentrated sulfuric acid is heated to 100°C using an oil bath heating device, and the temperature is monitored using a thermometer (with an accuracy of ±0.5°C). During the heating process, the concentrated sulfuric acid is continuously stirred to ensure that it is heated evenly.

[0059] In a preferred embodiment, in step S3, the acid solution is dripped with a glass dropper, and the initially opened plastic-sealed body is evenly shaken while the acid solution is dripped. The reaction time after the acid solution is dripped is 40s to 60s.

[0060] Specifically, the present invention uses a glass dropper with an inner diameter of 1 mm to 3 mm for slowly dropping concentrated sulfuric acid. The dropping speed is controlled at 1-2 drops per second, and the dropping position should accurately fall on the center of the area pre-laser thinned.

[0061] While adding concentrated sulfuric acid, the operator holds the device or uses a clamp to shake it evenly at a frequency of 30 to 60 times per minute. The shaking angle is within the range of ±10° so that the concentrated sulfuric acid can fully contact the epoxy material.

[0062] The corrosion time was set to 50 seconds. In actual operation, the corrosion situation was observed every 10 seconds. The corrosion progress was judged by observing the color change of the corrosion area, the degree of material dissolution, and whether there were new components exposed.

[0063] When the 50-second corrosion time is over, immediately tilt the device and use gravity to pour the waste liquid inside the area into the waste liquid tank. The waste liquid tank should be made of corrosion-resistant materials and equipped with a sealed lid to prevent the waste liquid from volatilizing and polluting the environment. Then start dripping concentrated sulfuric acid for the next round of corrosion, and repeat the above operation until the desired opening effect is achieved.

[0064] When too much reaction waste liquid is found to accumulate in the internal area, such as when obvious liquid accumulation is observed in the corrosion area, or when a significant increase in resistance is felt when shaking the device, remove the device from the heating table and place it on a dedicated flushing rack in the fume hood.

[0065] Use deionized water (resistivity greater than 18MΩ·cm) to rinse the device with a slow and even water flow (flow rate between 100ml / min and 200ml / min) for 30s to 60s. After the waste liquid on the surface and inside of the device is rinsed clean, use dry nitrogen (nitrogen purity greater than 99.99%) to blow dry the device at a flow rate of 5L / min to 10L / min. During the drying process, constantly adjust the position of the nitrogen nozzle to ensure that all parts of the device can be fully dried.

[0066] Then observe again whether the required opening range is completely exposed. If not, continue the concentrated sulfuric acid dripping corrosion operation.

[0067] In a preferred embodiment, in step S3, the acid solution is heated concentrated sulfuric acid.

[0068] In a preferred embodiment, in step S4, detecting whether the residual amount of waste liquid in the initially opened plastic package exceeds a preset amount includes:

[0069] Observe the distribution of residual waste liquid in the plastic package. If the level of the residual waste liquid exceeds the preset level or the residual waste liquid begins to spread, it is determined that the waste liquid in the initially opened plastic package exceeds the preset amount; otherwise, it is determined that it does not exceed the preset amount; or;

[0070] A certain amount of acid is added dropwise. If the reaction speed of the acid is lower than the preset speed or the flow resistance of the acid is higher than the preset resistance, it is determined that the waste liquid in the initially opened plastic package exceeds the preset amount; otherwise, it is determined that it does not exceed the preset amount; or;

[0071] A sensor is preset in the plastic package to detect the residual amount of waste liquid based on a sampling signal output by the sensor. The sensor is one of a capacitive liquid level sensor, an optical fiber sensor, a pressure sensor, and a microwave liquid level sensor.

[0072] Specifically, too much residual waste liquid will hinder the reaction effect of the subsequently added acid solution and the plastic packaging material, so it is necessary to continuously detect the residual amount of the waste liquid, and when too much residual waste liquid is present, it needs to be removed.

[0073] The invention ensures the reaction effect of re-adding acid solution by continuously detecting the waste liquid residue after pouring out the waste liquid each time, avoids the hindrance caused by excessive waste liquid residue, and improves the reaction efficiency.

[0074] Specifically, when the acid liquid is observed to form an obvious liquid layer on the surface of the accumulated liquid, it can be preliminarily determined that the reaction waste liquid begins to increase.

[0075] For example, if there is always a pool of liquid in the corrosion area that cannot dissipate within a period of time after the acid is added, and the newly added acid cannot quickly penetrate into the interior of the plastic packaging body, but stays on the surface of the accumulated liquid, it indicates that too much waste liquid has accumulated.

[0076] Observe the entire surface of the plastic package. If liquid begins to flow or gather in the area where the acid is not added, or if the originally dry area becomes moist, it means that a lot of waste liquid may have accumulated inside and is likely to overflow or spread.

[0077] For example, if liquid seeping out or water beads forming on the sides or bottom of the plastic package, it indicates that there is too much waste liquid inside.

[0078] When shaking the plastic packaging body normally to allow the acid to fully contact the plastic packaging material, if you feel the resistance gradually increasing and it is no longer the smooth shaking at the beginning, it is because the reaction waste liquid accumulated inside has increased, causing the internal space of the plastic packaging body to be filled, thus hindering normal shaking.

[0079] The operator can subjectively judge the change in resistance by shaking the plastic package. If shaking is difficult, it means that too much waste liquid remains.

[0080] More specifically, if the plastic-sealed body is clamped by a fixture and shaken automatically, a torque sensor can be provided on the fixture to detect whether the residual amount of waste liquid in the initially opened plastic-sealed body exceeds a preset amount.

[0081] When the clamp shakes the plastic package, the force applied by the clamp to the plastic package is transmitted through the contact interface. Under normal circumstances, the clamp needs to overcome the inertia of the plastic package itself and the friction of the internal structure to make it shake. The torque at this time is related to the mass distribution of the plastic package, the internal structure state, etc. When reaction waste liquid is generated and accumulated inside, the waste liquid will add additional resistance.

[0082] When the waste liquid flows and shakes inside the plastic package, it will generate viscous resistance and hinder the relative movement between the parts inside the plastic package. The resistance will be transmitted to the fixture through the entire plastic package, so that the fixture needs a larger torque to maintain the same motion state when shaking. Therefore, the change in the fixture torque measured by the torque sensor indirectly reflects the change in resistance caused by the accumulation of waste liquid inside the plastic package.

[0083] After adding the acid solution, if it is observed that the reaction rate between the newly added acid solution and the plastic packaging material becomes significantly slower, and bubbles and other reaction phenomena are no longer generated as quickly as at the beginning, it is determined that too much waste liquid remains, which hinders the sufficient contact between the acid solution and the plastic packaging material.

[0084] The quantitative way to observe the reaction speed is to observe the number or density of bubbles. For example, 10 bubbles can be produced per second at the beginning, but after too much waste liquid remains and acid is added, only 2-3 bubbles can be produced per second, and the intensity of bubble generation is significantly weakened. It is possible that too much waste liquid has affected the reaction.

[0085] Specifically, the principle of the capacitive liquid level sensor is to install a capacitive liquid level sensor probe inside the plastic package near the laser ablation thinning area. The probe consists of two electrodes. When the reaction waste liquid accumulates in the plastic package, the liquid level rises, and the medium between the electrodes changes. Since the dielectric constant of the waste liquid is different from that of air, the capacitance value will change accordingly.

[0086] By measuring the change in capacitance and comparing it with a pre-calibrated capacitance-liquid level height curve, it is determined whether the liquid level of the waste liquid exceeds the liquid level height corresponding to the preset amount, thereby determining whether the amount of residual waste liquid is excessive.

[0087] Before the acid corrosion operation, the capacitive liquid level sensor probe is installed on the plastic package body and connected to the capacitance measurement circuit and the data acquisition unit. The data acquisition unit collects the capacitance value data of the capacitive liquid level sensor in real time.

[0088] According to the pre-calibrated capacitance value-liquid level height relationship curve, the real-time collected capacitance value is converted into the liquid level height. If the liquid level height exceeds the preset waste liquid excessive liquid level threshold, it is determined that the waste liquid in the initially opened plastic package exceeds the preset amount.

[0089] Specifically, the detection principle of the optical fiber sensor is that when light propagates in the optical fiber, it encounters different media, such as air and waste liquid, and reflection and refraction occur at the interface.

[0090] When the liquid level of the waste liquid rises, the intensity of the optical signal received by the optical fiber sensor will change. By pre-establishing a relationship model between the optical signal intensity and the liquid level height, the real-time measured optical signal intensity is used to determine whether the liquid level of the waste liquid exceeds the height corresponding to the preset amount, thereby determining the amount of waste liquid.

[0091] The present invention installs the optical fiber sensor probe at the bottom of the plastic package body near the laser ablation thinning area, connects the optical fiber sensor to the optical signal detection device and the corresponding data processing unit. Before the acid solution is added, the optical signal is calibrated and the initial optical signal intensity is recorded.

[0092] In this embodiment, the intensity of the optical signal output by the optical fiber sensor is monitored in real time. When the intensity of the optical signal changes and exceeds the threshold value of the corresponding waste liquid level determined according to the relationship model, it is determined that the waste liquid in the plastic package exceeds the preset amount.

[0093] The principle of pressure sensor detection is to install a pressure sensor at the bottom of the plastic package or at a location connected to the waste liquid accumulation area. As the reaction waste liquid accumulates in the plastic package, the weight of the waste liquid will exert pressure on the sensor. By measuring the pressure and based on the relationship between the pressure and the liquid level, it is determined whether the waste liquid volume exceeds the preset amount.

[0094] Before performing step S3, the pressure sensor is installed and connected to the pressure measuring instrument. The pressure sensor is calibrated, and the pressure sensor measures the pressure value in real time. According to the pressure-liquid level-waste liquid amount relationship determined in advance through experiments, it is judged that when the pressure value reaches the pressure threshold corresponding to excessive waste liquid, the waste liquid in the initially opened plastic package exceeds the preset amount.

[0095] The principle of microwave liquid level sensor detection is to set up microwave transmitting and receiving devices around the plastic package. When microwaves propagate inside the plastic package, they will be reflected and scattered when encountering waste liquid. The characteristics of the reflected and scattered waves are related to the liquid level of the waste liquid. By analyzing the changes in microwave reflection and scattering signals, a relationship model with the liquid level is established to determine whether the amount of waste liquid exceeds the preset amount.

[0096] After step S2 is completed, adjust the position and parameters of the microwave transmitting and receiving device, and perform a microwave signal reference measurement before the acid solution is added to obtain the microwave signal characteristics when there is no waste liquid. During the acid solution addition process, microwaves are regularly emitted and reflected and scattered signals are received. The signal is processed and analyzed. According to the relationship model between the signal change and the liquid level height, when the signal characteristic change indicates that the liquid level height exceeds the preset waste liquid excess level, it is determined that the waste liquid in the plastic package exceeds the preset amount.

[0097] In a preferred embodiment, it also includes:

[0098] Step S5, rinse with heated fuming nitric acid for several times, clean with cleaning liquid, and blow dry after cleaning.

[0099] Specifically, the unsealed device is rinsed twice with 80°C fuming nitric acid, each time for 20 seconds. The rinsing time needs to be controlled in this process to avoid excessive corrosion of the copper layer and terminals inside the device.

[0100] Finally, the plastic-encapsulated device was cleaned with water and cleaning solution in turn, and then air-dried with nitrogen. The required range was observed under a microscope to lay the foundation for subsequent failure analysis.

[0101] Due to differences in the density and texture of the device injection molding material and the usage of the device, the acid opening speed will also vary. The corrosion time mentioned above is an empirical value. During actual operation, the time to actually expose the internal components and chips should be used as the basis.

[0102] Specifically, the fuming nitric acid is heated to 80°C and heated by a constant temperature water bath device, with a water bath temperature control accuracy of ±0.5°C. A timer is used to accurately control the rinsing time, with each rinse lasting 20 seconds and an error of no more than ±1 second. During the rinsing process, the device is completely immersed in the fuming nitric acid to ensure that all surfaces to be treated are in full contact with the fuming nitric acid.

[0103] To avoid excessive corrosion of the internal copper layer and terminals of the device, the initial state of the internal copper layer and terminals of the device should be evaluated before flushing, and their appearance characteristics, such as color, glossiness, etc., and size information should be recorded.

[0104] During the flushing process, closely observe the changes in the copper layer and the terminals. Stop flushing immediately when you find that the surface of the copper layer begins to change color, such as from the original red to dark red or black, or the terminals show obvious signs of dissolution.

[0105] At the same time, according to different types of plastic packages and device structures, the maximum safe corrosion time range of fuming nitric acid on the copper layer and terminals is determined through preliminary experiments, and this range is strictly adhered to in actual operations.

[0106] After the fuming nitric acid rinse is completed, the device is first rinsed with deionized water for 60 to 120 seconds to rinse away the residual fuming nitric acid and reaction products. Then the device is immersed in a special cleaning solution. The cleaning solution should be selected according to the material of the plastic package and the type of device, and can remove pollutants. The immersion time is 3 to 5 minutes. During this period, the device can be properly shaken to enhance the cleaning effect. After the immersion is completed, the device is rinsed again with deionized water for 30 to 60 seconds.

[0107] Place the cleaned device in an air drying device that uses a nitrogen circulation system with a nitrogen flow rate of 8L / min to 2L / min. During the air drying process, adjust the temperature and humidity in the air drying device to maintain the temperature at 20℃ to 30℃ and the relative humidity at 30%-50% to promote rapid and uniform drying of the device.

[0108] The air-drying time depends on the complexity and structural characteristics of the device, and is generally between 10 and 30 minutes. After the air-drying is completed, a microscope (magnification of 100 to 500 times) is used to comprehensively observe the required range of the device to check for residual impurities, corrosion marks and other abnormal conditions, providing an accurate and reliable basis for subsequent failure analysis.

[0109] In a specific embodiment, the process of the present invention is as follows Figure 2 As shown, firstly, ultrasonic scanning is performed on the device to be opened to confirm its internal structure. Before acid opening, the thickness of the epoxy injection molding material is physically thinned. Laser ablation is usually used to open the device so that the surface bonding aluminum wire is just exposed in the chip area and the tin-lead solder joint is just exposed near the NTC.

[0110] After the pre-opening is completed, the device is transferred to the acid opening laboratory. Concentrated sulfuric acid is used as the corrosion reagent during the process and heated to 100°C. At the same time, the device is heated to 120°C. Use a glass dropper to slowly drip concentrated sulfuric acid into the pre-laser thinned area, and shake the injection molded device at the same time to make the concentrated sulfuric acid and epoxy fully contact. The corrosion time is 50 seconds, and then the waste liquid inside the area is poured into the waste liquid tank, and concentrated sulfuric acid is added again for corrosion. When there is too much reaction waste liquid accumulated in the internal area, rinse the device with water and blow it dry, and observe whether the required opening range is completely exposed. If there is still part of the epoxy material covered, continue the above steps to completely expose the internal environment.

[0111] Next, the unsealed device is rinsed twice with 80°C fuming nitric acid, each time for 20 seconds. The rinsing time needs to be controlled in this process to avoid excessive corrosion of the copper layer and terminals inside the device. Finally, the plastic-sealed device is washed with water and cleaning solution in turn, and then air-dried with nitrogen. The required range is observed under a microscope to lay the foundation for subsequent failure analysis.

[0112] Due to differences in the density and texture of the device injection molding material and the usage of the device, the acid opening speed will also vary. The corrosion time mentioned above is an empirical value. During actual operation, the time to actually expose the internal components and chips should be used as the basis.

[0113] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for opening a plastic-sealed body, characterized in that: include, Step S1, performing ultrasonic scanning on the plastic package body to be opened, determining the internal structure and dividing the range to be opened; Step S2, preliminarily unsealing the plastic package body by laser ablation, so that the surface bonding wires are exposed in the chip area of ​​the plastic package body, and the solder joints are exposed in the thermistor area; Step S3, adding acid solution dropwise to the area of ​​the initially opened plastic package body thinned by laser ablation, and pouring out the waste liquid after etching for a certain period of time; Step S4, detecting whether the residual amount of waste liquid in the initially opened plastic-sealed body exceeds a preset amount, if not, returning to step S3 and continuing to drip the acid solution; if exceeding, cleaning and drying the plastic-sealed body, and observing whether the internal environment of the plastic-sealed body is completely exposed, if not completely exposed, returning to step S3 and continuing to drip the acid solution; if completely exposed, the opening of the cover is completed, and the opened plastic-sealed body is obtained.

2. The method for opening the plastic-sealed body according to claim 1, characterized in that: In step S1, an ultrasonic scanning device is used to perform ultrasonic scanning on the plastic package body. The resolution of the ultrasonic scanning device is below 0.1 mm and has an adjustable scanning frequency. The scanning frequency of the ultrasonic scanning device is 10 MHz to 50 MHz.

3. The method for opening the cover of a plastic-sealed body according to claim 2, characterized in that: In step S1, during ultrasonic scanning, the plastic package is placed on a fixed fixture, and the scanning process includes a preliminary scan for obtaining the contour of the plastic package and the distribution of internal components, and a fine scan for obtaining the detailed positions of the chip and thermistor of the plastic package.

4. The method for opening the cover of a plastic-sealed body according to claim 1, characterized in that: In step S2, a pulse laser is used for laser ablation, wherein the pulse width of the pulse laser is 10 ns to 100 ns, the repetition frequency is 1 kHz to 10 kHz, and the laser spot of the pulse laser has a switchable diameter, and the diameter range of the laser spot is 0.1 mm to 1 mm; The time for laser ablation of the chip region is 20s to 40s, and the time for laser ablation of the thermistor region is 30s to 50s.

5. The method for opening the cover of a plastic-sealed body according to claim 4, characterized in that: The initial power of the pulse laser is 5W-15W. In step S2, an infrared thermometer is also used to monitor the temperature change of the laser ablation area, and the power of the pulse laser is adjusted based on the temperature data obtained by the infrared thermometer.

6. The method for opening the cover of a plastic-sealed body according to claim 1, characterized in that: In step S3, before the acid solution is added, the preliminarily opened plastic-sealed body is heated at a temperature of 100°C to 140°C.

7. The method for opening a plastic-sealed body according to claim 1, characterized in that: In step S3, the acid solution is dripped with a glass dropper, and the preliminarily opened plastic-sealed body is evenly shaken while the acid solution is dripped. The reaction time after the acid solution is dripped is 40s to 60s.

8. The method for opening a plastic-sealed body according to claim 1, characterized in that: In step S3, the acid solution is heated concentrated sulfuric acid.

9. The method for opening a plastic-sealed body according to claim 1, characterized in that: In step S4, the step of detecting whether the residual amount of waste liquid in the initially opened plastic package exceeds a preset amount includes: Observe the distribution of the residual waste liquid in the plastic package, and if the level of the residual waste liquid exceeds the preset level or the residual waste liquid begins to spread, determine that the waste liquid in the initially opened plastic package exceeds the preset amount; otherwise, determine that it does not exceed; or; A certain amount of the acid solution is added dropwise, and if the reaction speed of the acid solution is lower than a preset speed or the flow resistance of the acid solution is higher than a preset resistance, it is determined that the waste liquid in the initially opened plastic package exceeds a preset amount; Otherwise, it is determined that it is not exceeded; or; A sensor is preset in the plastic package to detect the residual amount of waste liquid based on a sampling signal output by the sensor. The sensor is one of a capacitive liquid level sensor, an optical fiber sensor, a pressure sensor, and a microwave liquid level sensor.

10. The method for opening a plastic-sealed body according to claim 1, characterized in that: Also includes, Step S5, rinse with heated fuming nitric acid for several times, clean with cleaning liquid, and blow dry after cleaning.

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