A reliability evaluation method for plastic packaged devices

Abstract

The present invention provides a reliability assessment method for plastic-encapsulated devices, which belongs to the field of device defect detection technology, and includes the following steps: first, collecting initial device data, then performing ultrasonic scanning on the device, selecting layered devices, sampling the layered devices, and performing sample preparation microscopic inspection on each sampled device to screen out qualified devices, layered devices, and suspicious devices. The suspicious device is baked, and after baking, the device is subjected to water vapor treatment, and after treatment, the device is reflow soldered. After the reflow soldering is completed, an aging test is performed on the device, and after the aging test, the device is visually inspected, and devices with no physical damage to the appearance of the plastic-encapsulated body are screened out. Finally, integrated circuit testing equipment is used to perform a three-temperature test on the performance of the device with no physical damage to the appearance of the plastic-encapsulated body, and the reliability of the device can be determined according to the test results. The present invention can evaluate the reliability of unqualified devices scanned by ultrasonic waves, and support the use of components.

Description

Technical Field

[0001] The invention belongs to the technical field of device defect detection, and in particular relates to a reliability assessment method for a plastic packaged device. Background Art

[0002] Plastic encapsulated devices refer to semiconductor devices encapsulated with resin polymers. Plastic encapsulation technology can effectively protect semiconductor devices. When screening customer devices before use, the ultrasonic scanning project showed a large number of external bonding point delamination and device surface delamination, causing PDA to exceed the standard. Customers cannot complete the whole machine assembly task normally, and the ultrasonic scanning still fails when replacing other batches, which seriously affects the progress of research and production tasks.

[0003] Research has found that there are still semiconductor devices that meet industry standards among the layered devices screened out by ultrasonic scanning. Currently, there is no method to evaluate the reliability of devices that fail ultrasonic scanning. Summary of the invention

[0004] The purpose of the present invention is to provide a reliability evaluation method for a plastic packaged device to solve the problems mentioned in the background technology.

[0005] To achieve the above object, the present invention provides a reliability evaluation method for a plastic packaged device, comprising the following steps:

[0006] S1: Use integrated circuit test equipment to retain the initial data of the device;

[0007] S2: Perform ultrasonic scanning on the device, save the scanned photos, then observe the scanned photos to select the layered devices, and sample the layered devices;

[0008] S3: Perform sample preparation and microscopic inspection on each device selected by sampling, and use metallographic microscope and scanning electron microscope to distinguish the device status: qualified, delaminated or suspicious;

[0009] S4: Bake the suspected device to remove moisture inside the device;

[0010] S5: Place the device with internal water vapor removed into the HAST test chamber to fully inject water vapor into the device;

[0011] S6: placing the device after water vapor injection into a reflow oven for reflow soldering;

[0012] S7: Perform aging test on the device after reflow soldering;

[0013] S8: Perform appearance inspection on the devices after the aging test, and select the devices without physical damage on the appearance of the plastic package according to the appearance of the devices;

[0014] S9: Use integrated circuit testing equipment to perform three-temperature tests on the performance of devices without physical damage, and determine the reliability of the devices based on the test results.

[0015] Furthermore, step S3 specifically includes the following steps:

[0016] S301: preparing a sample of the selected device, placing the device into a mold, curing it with epoxy resin, and grinding and polishing it with a grinder after curing;

[0017] S302: Use a metallographic microscope to observe and take photos at the delamination position at 500X-1000X, and determine whether it is delamination or unclear based on the observed results; for devices with unknown status, perform ion polishing, and observe the delamination points after ion polishing through a scanning electron microscope between 2000X-5000X, retain photos, and determine whether it is qualified or suspicious based on the observation results.

[0018] Furthermore, the aging experiment includes the following steps:

[0019] S701: Wet heat test, put the device after reflow into HAST test box, conditions: 130℃, 85%RH, 96h;

[0020] S702: Ambient temperature cycle test, place the device in a temperature cycle box, temperature: -55℃~125℃, cycle number is 20 times, maintain at each temperature for 30 minutes.

[0021] Furthermore, after step S9 is completed, the device is sampled again for sample preparation microscopic inspection, and the change amount is compared with the initial microscopic inspection result, and the reliability of the device is determined based on the change amount.

[0022] Furthermore, the three-temperature detection includes a low-temperature test, a normal-temperature test and a high-temperature test.

[0023] Furthermore, before the device is ultrasonically scanned, the device to be scanned is baked to remove moisture inside the device.

[0024] The advantages of the present invention are:

[0025] 1. The plastic-encapsulated device reliability assessment method provided by the present invention can assess the reliability of unqualified devices detected by ultrasonic scanning, provide support for the use of components, ensure the normal completion of the whole machine assembly task, and ensure the progress of research and development and production tasks.

[0026] 2. The reliability assessment method of the plastic-encapsulated device provided by the present invention can accelerate the impact of long-term hot and humid environment and temperature changes on the device structure, speed up the aging of the device, and enable the long-term life of the device to be detected in a shorter time.

[0027] 3. The present invention adopts an environmental temperature cycle test method, using the physical layer to observe and confirm the delamination, and the reliability can be preliminarily judged by confirming the size of the delamination.

[0028] The present invention is described in detail below with reference to the embodiments. DETAILED DESCRIPTION

[0029] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose, the specific implementation methods, structural features and effects of the present invention are described in detail below in combination with embodiments.

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. 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.

[0031] In the description of the present invention, it is to be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "aligned", "overlap", "bottom", "inside", "outside" and the like to indicate directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the present invention.

[0032] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features; in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0033] Example 1

[0034] This embodiment provides a reliability assessment method for a plastic packaged device, comprising the following steps:

[0035] S1: Use integrated circuit testing equipment to test the initial performance and parameters of electronic components at room temperature according to the product manual. The samples during the test are fully numbered and the data are fully numbered and retained;

[0036] S2: Place the device in an oven and set the temperature to 85°C for 2 hours to bake the device to remove moisture inside the device and make the stratification obvious and stable. Then use an ultrasonic scanning device to scan the contact surface between the chip and the plastic packaging material on the front of the device, and the contact surface between the frame and the plastic packaging material. Save the photos with all the numbers, and then observe the scanned photos to select the stratified devices, that is, the unqualified devices detected by the ultrasonic scanning, and sample the stratified devices for S3 and S4.

[0037] S3: Perform sample preparation and microscopic inspection on each device selected by sampling, and use metallographic microscope and scanning electron microscope to distinguish the device status: qualified, delaminated or suspicious, which specifically includes the following steps:

[0038] S301: Prepare samples of the selected device, put the device into the mold, cure it with epoxy resin, and grind it with a grinder after curing. The grinding sandpaper should be 80 mesh, 240 mesh, 600 mesh, 1000 mesh, 2500 mesh, and 4000 mesh in sequence. The process should be observed continuously. The device should be cleaned when the sandpaper is replaced. Before approaching the delamination point, it should be replaced with 600 mesh sandpaper, and before reaching the middle position of the delamination, it should be replaced with 2500 mesh sandpaper. Before polishing, it should be replaced with 4000 mesh sandpaper. After the sandpaper is ground to the middle position of the delamination, it should be polished. The polishing liquid (powder) of 1um or less than 1um should be used for polishing. Polishing should be stopped when the bright mirror effect is achieved, and then cleaned;

[0039] S302: Observe and take photos at the delamination position under 500X-1000X with a metallographic microscope, and judge based on the observed results. If delamination can be observed under 500X-1000X, the device state is confirmed to be delamination, and the delamination is unqualified; if no delamination is observed under 500X-1000X, the device state is confirmed to be unknown; for the device with unknown state, ion polishing is performed, and the delamination point after ion polishing is observed under a scanning electron microscope between 2000X-5000X, and photos are retained. According to the observation results, if delamination can be observed at 2000X-5000X, the device state is confirmed to be suspicious, and if no delamination is observed at 2000X-5000X, the device state is confirmed to be qualified;

[0040] S4: Place the suspected device in an oven, set the temperature to 125°C, and bake for 24 hours to remove moisture inside the device and make the device consistent in its initial state, in preparation for subsequent moisture injection and reflow soldering;

[0041] S5: Place the device with internal moisture removed into the HAST test chamber at 110°C, 85% RH, for 48 hours to allow the device to fully absorb moisture and prepare for subsequent reflow soldering.

[0042] S6: Place the device after water vapor injection into a reflow oven for no less than 15 minutes and no more than 4 hours, select temperature conditions according to the type of device used, and let the sample undergo one cycle of reflow soldering. The reflow soldering conditions are shown in Tables 1 and 2;

[0043] Table 1: Reflow conditions for leaded components

[0044]

[0045] Table 2: Reflow conditions for lead-free components

[0046]

[0047]

[0048] S7: Perform an aging test on the device after reflow soldering. The specific steps are as follows:

[0049] S701: Wet heat test: put the device after reflow soldering into HAST test box, the conditions are: 130℃, 85%RH, 96h, so as to accelerate the simulation of the influence of long-term wet heat environment on the device structure. During the process, it can be confirmed whether to power on the device according to the needs of the user;

[0050] S702: Ambient temperature cycle test: put the device into a temperature cycle box, temperature: -55℃~125℃, cycle number is 20 times, keep each temperature for 30 minutes, create a temperature change storage environment, give sufficient attraction to the stratification, so as to cause its sufficient change;

[0051] S8: Perform appearance inspection on the devices after the aging test, and select the secondary qualified devices according to the appearance of the devices; the appearance inspection is to use a 10x magnifying glass (microscope) to inspect the samples that have been through high-temperature storage, wet heat, and reflow soldering. If there is no physical damage to the appearance of the plastic package (such as cracks, bulges, damage, etc.), continue the subsequent experiments. If there is physical damage to the appearance of the plastic package, it is directly judged as unqualified;

[0052] The devices that have completed the appearance inspection are placed in an oven at 85°C for 2 hours to remove moisture inside the device and make the stratification obvious and stable. Then, an ultrasonic scanning device is used to perform an ultrasonic scan on the second qualified device, and the change is compared with the initial ultrasonic scanning result to confirm the impact of aging on the reliability of the device. A change greater than 20% is considered unqualified. The devices that have completed the appearance inspection can also be directly processed to step S9.

[0053] S9: Use integrated circuit testing equipment to perform three-temperature tests on the performance of devices without physical damage. The three-temperature tests include low-temperature test of -55℃, normal temperature test of 15-25℃ and high temperature test of 125℃. Determine the reliability of the device based on the test results and the parameter warranty requirements in the device manual. If there are unqualified samples, they are judged as unqualified. If there are no unqualified samples, they are judged as qualified and can be used.

[0054] Furthermore, after step S9 is completed, the device is sampled again for sample preparation microscopic inspection. The microscopic inspection is the same as the microscopic inspection step mentioned in S3. The change amount of the microscopic inspection result is compared with the initial microscopic inspection result, and the reliability of the device is judged based on the change amount. If the change amount is less than or equal to 1μm, it means that the stratification of the suspicious device does not affect the use, and it is judged to be qualified and can be used. If the change is greater than 1μm, it is judged to be unqualified.

[0055] Finally, a conclusion is drawn based on the results of each step. If all items of the sampled devices are qualified, the conclusion of "recommended for use" is given for the batch of devices. If any of the sampled devices is unqualified, the conclusion of "not recommended for use" is given for the batch of devices.

[0056] In summary, the plastic-encapsulated device reliability assessment method provided by the present invention can assess the reliability of unqualified devices detected by ultrasonic scanning, provide support for the use of components, ensure the normal completion of the whole machine assembly task, and ensure the progress of research and development and production tasks.

[0057] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and the specific implementation of the present invention cannot be considered to be limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A reliability assessment method for a plastic packaged device, characterized in that: The steps include: S1: Use integrated circuit test equipment to retain the initial data of the device; S2: Perform ultrasonic scanning on the device, save the scanned photos, then observe the scanned photos to select the layered devices, and sample the layered devices; S3: Perform sample preparation and microscopic inspection on each device selected by sampling, and use metallographic microscope and scanning electron microscope to distinguish the device status: qualified, delaminated or suspicious; The specific steps include: S301: preparing a sample of the selected device, placing the device into a mold, curing it with epoxy resin, and grinding and polishing it with a grinder after curing; S302: Observe and take photos at the delamination position under 500X-1000X using a metallographic microscope, and judge as delamination or unknown according to the observed results; for the device with unknown status, ion polishing is performed, and the delamination point after ion polishing is observed under 2000X-5000X by a scanning electron microscope, and photos are retained, and judged as qualified or suspicious according to the observation results; S4: Bake the suspected device to remove moisture inside the device; S5: Place the device with internal water vapor removed into the HAST test chamber to fully inject water vapor into the device; S6: placing the device after water vapor injection into a reflow oven for reflow soldering; S7: Perform aging test on the device after reflow soldering; The aging experiment comprises the following steps: S701: Wet heat test, put the device after reflow into HAST test box, conditions: 130℃, 85%RH, 96h; S702: Ambient temperature cycle test: put the device into a temperature cycle box, temperature: -55℃~125℃, cycle number is 20 times, keep each temperature for 30 minutes; S8: Perform appearance inspection on the devices after the aging test, and select the devices without physical damage on the appearance of the plastic package according to the appearance of the devices; S9: Use integrated circuit testing equipment to perform three-temperature tests on the performance of devices without physical damage, and determine the reliability of the devices based on the test results.

2. A plastic package component reliability evaluation method as claimed in claim 1, characterized in that: After step S9 is completed, the device is sampled again for sample preparation microscopic inspection, and the change amount is compared with the initial microscopic inspection result, and the reliability of the device is determined based on the change amount.

3. A plastic package component reliability evaluation method as claimed in claim 1, characterized in that: The three-temperature test includes a low temperature test, a normal temperature test and a high temperature test.

4. A plastic package component reliability evaluation method as claimed in claim 1, characterized in that: Before ultrasonic scanning of the device, the device to be scanned is baked to remove moisture inside the device.

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