JP5066143B2 - Whisker evaluation method and test apparatus for whisker evaluation - Google Patents

Description

  The present invention relates to a whisker evaluation method and a whisker evaluation test apparatus, and more specifically, to a whisker evaluation method and a whisker evaluation test apparatus capable of effectively reducing an evaluation time for an evaluation target in which a semiconductor package is mounted on a substrate. Is.

  With recent lead-free semiconductor mounting substrates, it is known that whiskers, which are bowl-shaped crystals, are generated on leads plated with, for example, tin (Sn) or tin alloy. As methods for evaluating whiskers, various methods such as a room temperature standing test in which a sample is left in a room temperature environment and a test performed in a high temperature and high humidity environment have been proposed.

  Among these tests, the room temperature standing test can be tested under conditions close to the actual use environment, but has a problem that it takes a very long time to evaluate.

  In addition, tests performed under a high temperature and high humidity environment are roughly classified to be performed under conditions adjusted to less than 100 ° C. and those performed under conditions adjusted to 100 ° C. or higher.

  The former high-temperature and high-humidity test is performed by adjusting the inside of the test tank to a condition of less than 100 ° C. such as an atmosphere having a temperature of 60 ° C. and a humidity of 85% or an atmosphere having a temperature of 85 ° C. and a humidity of 85%. When the test conditions are a temperature of 60 ° C. and a humidity of 85%, the water vapor partial pressure with respect to the total pressure in the test tank is about 17 kPa. When the test conditions are a temperature of 85 ° C. and a humidity of 85%, the water vapor partial pressure with respect to the total pressure in the test tank is about 49 kPa. The pressure obtained by subtracting the water vapor partial pressure from the total pressure is the air partial pressure in the test chamber. That is, a certain amount of air exists in the test tank under the test conditions of less than 100 ° C.

  On the other hand, the latter high-temperature and high-humidity test is performed by adjusting the inside of the test tank to conditions of 100 ° C. or higher, such as an atmosphere of 110 ° C. and humidity 85%, and an atmosphere of temperature 120 ° C. and humidity 85%. . In this way, in the process of adjusting the inside of the test chamber to a high temperature and high humidity environment of 100 ° C. or higher, almost all of the air present in the test chamber is replaced with water vapor, so that only water vapor is present in the test chamber. . Therefore, in this high temperature and high humidity test, the evaluation is performed in an environment where the air partial pressure in the test tank is almost zero and there is almost no air.

  Tests conducted in a high-temperature and high-humidity environment as described above can accelerate the generation of whiskers due to oxidation / corrosion compared to the room temperature standing test, but the evaluation time is not necessarily limited to any method. At present, it cannot be said that the time can be sufficiently shortened.

  By the way, in Patent Document 1, when an evaluation object is heated in an environment where air exists in a test tank, an oxide film or a hydroxide film is formed on the surface of the tin plating film, and thus whisker growth is suppressed. Is disclosed. That is, when the evaluation object is heated in the presence of air, the oxide film grows thick on the surface of the tin plating film, so that the whisker cannot grow through the oxide film on the surface. Therefore, in patent document 1, the production | generation of the oxide film or the hydroxide film which suppresses the growth of a whisker on the surface of a tin plating film is suppressed by heating evaluation object in inert atmosphere. As a result, it is said that the evaluation method of Patent Document 1 can accelerate the generation and growth of whiskers.

  Moreover, patent document 2 is disclosing the content that generation | occurrence | production of a whisker is suppressed by making the inside of a test tank high temperature and high humidity. Note that in Patent Document 2, compressive stress is continuously applied to the plating film under an environment of about room temperature instead of the conventional method of setting to a high temperature and high humidity environment.

JP-A-2005-330577 JP 2005-101117 A

  However, there are many points where whisker generation mechanisms have not been elucidated at present, and in fact, whisker generation locations and conditions are often different from those disclosed in Patent Documents 1 and 2. Moreover, in the conventional evaluation method, whisker is evaluated for each member such as plating, solder, component, lead, etc., and evaluation in an actual usage form in which a semiconductor package is mounted on a substrate is not sufficiently performed. . Therefore, the conventional test conditions are not necessarily consistent with the whisker generation mechanism, and there is still much room for improvement particularly in the evaluation in the actual usage form in which the semiconductor package is mounted on the substrate.

  Therefore, the present invention has been made in view of the above points, and an object of the present invention is to provide a whisker evaluation method and a whisker evaluation test apparatus that can shorten the evaluation time of an evaluation target.

  In the process of investigating the mechanism of whisker generation and growth, the present inventors have made the effect of whisker generation and growth by allowing oxygen to exist in a high-temperature and high-humidity environment of 100 ° C. or higher, in which almost no air exists. The present invention has been completed.

  That is, the whisker evaluation method of the present invention adjusts the sample to be evaluated in a test tank to a predetermined amount of oxygen, a set temperature of 100 ° C. or higher, and a predetermined set humidity. And an environment maintaining step of maintaining whisker in the sample by maintaining the inside of the test chamber at the predetermined oxygen amount, the set temperature and the set humidity for a predetermined time.

  In this method, not only the inside of the test tank is adjusted to a high-temperature and high-humidity environment of 100 ° C. or higher, which is the boiling point of water, or a temperature in the vicinity thereof, but the sample is tested under test conditions in which a predetermined amount of oxygen is present in the test tank. Perform the test. According to this method, it is possible to effectively accelerate the generation and growth of whiskers in the sample and shorten the evaluation time.

  In this method, the evaluation time can be effectively shortened particularly in a sample in which a semiconductor package is mounted on a substrate. The reason is presumed as follows. However, the reason shown below presumes the mechanism of whisker generation and growth, and the mechanism is not limited to the following reason.

That is, generally, a semiconductor package has a plurality of leads, and these leads are soldered to a substrate and fixed. The lead is tin-plated on the surface, but the lead base material (for example, copper) is exposed at the tip of the lead having a cut surface. Further, although the base end side of the lead is covered with a resin encapsulating the semiconductor, a part of the resin covering the base end side of the lead may be peeled off to expose the lead base material. Therefore, the base material of the lead and the plating are adjacent to each other on the cut surface of the distal end portion and the base end side where the resin is peeled off, and are exposed to the air. When the test in the method of the present invention using the sample in such a state, that is, the test condition of high temperature and high humidity in the presence of oxygen, the following phenomenon occurs, and the generation and growth of whiskers are promoted. It is thought. That is, since the sample is placed in a high humidity environment, a moisture layer is formed on the surface of the base material and the plating at the tip end portion or the base end side of the lead, and at a high temperature of 100 ° C. or higher. In an environment where oxygen is present, galvanic corrosion occurs at the leading end and proximal end of the lead, and lead plating and solder oxidation are promoted. For example, when the plating is tin plating, Sn becomes SnO ₂ . Since the volume of the oxidized portion increases, an internal stress is generated in the plating layer or the solder layer. It is presumed that the generation and growth of whiskers are promoted due to this internal stress.

  From the above, in the present invention, a sample having a portion in which a lead-free plating layer is formed on the surface of a metal base material and a part of the metal base material exposed from the plating layer is an evaluation target. When used, the evaluation time can be shortened particularly effectively.

  Specifically, the internal environment adjustment step includes adjusting the inside of the test tank to a predetermined initial temperature and a predetermined initial water vapor partial pressure with the exhaust valve of the test tank being opened. An oxygen amount adjusting step for adjusting the inside to a predetermined initial air partial pressure, and a temperature for adjusting the inside of the test tank to the set temperature and the set humidity with the exhaust valve closed after the oxygen amount adjusting step. And a humidity adjusting step.

  In this method, by adjusting the initial temperature and the initial water vapor partial pressure with the exhaust valve of the test tank being opened, the value obtained by subtracting the initial water vapor partial pressure from the total pressure is inevitably the initial air component. Pressure. In this method, since the air partial pressure can be adjusted as described above, for example, a gas introducing means for introducing oxygen into the test tank is unnecessary, and the apparatus can be simplified.

  Further, in the tank environment adjustment step, with the exhaust valve of the test tank being opened, the oxygen concentration detection means provided in the test tank is used to detect the oxygen concentration in the test tank, An oxygen amount adjusting step of introducing oxygen or a gas containing oxygen into the test tank until the predetermined oxygen amount is reached by a provided gas introducing means, and the exhaust valve is closed after the oxygen amount adjusting step The temperature and humidity adjustment step of adjusting the inside of the test tank to the set temperature and the set humidity may be provided.

  In this method, oxygen or a gas containing oxygen is introduced into the test tank by the gas introduction means, so that the oxygen concentration in the test tank can be adjusted to an arbitrary concentration. For example, when an oxygen tank or the like is used as the gas introduction means, the oxygen concentration in the test tank can be further increased as compared with the case where air is supplied by a gas introduction means such as a compressor.

  In addition, the method further includes a vacuum step of evacuating the test chamber while the exhaust valve of the test chamber is closed, and after the vacuum step, the internal environment adjustment step and the environment are performed with the exhaust valve closed. You may make it perform a maintenance process.

  In this method, after the inside of the test tank is evacuated to remove air, the amount of oxygen is adjusted in the tank environment adjustment step, so that the oxygen concentration in the test tank can be accurately adjusted.

  Further, in the tank environment adjustment step, oxygen or oxygen-containing gas is continuously or intermittently introduced into the test tank by the gas introduction means provided in the test tank with the exhaust valve of the test tank being opened. The oxygen amount adjusting step for adjusting the inside of the test tank to a predetermined initial oxygen partial pressure, and after the oxygen amount adjusting step, with the exhaust valve being opened and the gas introduction A temperature / humidity adjusting step for adjusting the inside of the test tank to the set temperature and the set humidity in a state where oxygen or a gas containing oxygen is continuously or intermittently introduced by means, and maintaining the environment The process is performed by continuously or intermittently introducing oxygen or a gas containing oxygen into the test tank by the gas introduction means with the exhaust valve of the test tank being opened. Adjust to the predetermined oxygen amount It may be so that.

  In this method, the temperature / humidity adjusting step and the environment maintaining step are executed in a state where oxygen or a gas containing oxygen is continuously or intermittently introduced by the gas introduction means. That is, since oxygen is continuously supplied into the test tank continuously or intermittently during the test, the oxygen concentration can be prevented from fluctuating during the test.

  Further, the tank environment adjustment step includes a temperature and humidity adjustment step of adjusting the temperature and humidity in the test tank to the set temperature and the set humidity, respectively, with the exhaust valve of the test tank being opened, and the temperature After the humidity adjustment step, with the exhaust valve closed, the amount of oxygen to introduce oxygen or a gas containing oxygen into the test chamber until the predetermined oxygen amount is reached by the gas introduction means provided in the test chamber An adjustment step.

  The set temperature is preferably 105 ° C. or higher and 140 ° C. or lower. By setting the set temperature to 105 ° C. or higher, whisker generation and growth can be further promoted. The set temperature is preferably 140 ° C. or less from the viewpoint of heat resistance of the printed circuit board.

  In addition, when the set humidity is 75% or more of the relative humidity, or when the oxygen partial pressure in the test tank in the environmental maintenance step is 10 kPa or more, the generation and growth of whiskers can be further promoted. .

  The test apparatus for whisker evaluation of the present invention includes a test tank in which a sample to be evaluated can be placed, temperature adjusting means capable of adjusting the inside of the test tank to a set temperature of 100 ° C. or more, and the inside of the test tank. Humidity adjustment means that can be adjusted to a predetermined set humidity, an exhaust valve that can communicate between the inside and outside of the test tank, and control means are provided. The control means controls the temperature adjusting means and the humidity adjusting means so that the inside of the test tank has the set temperature, the set humidity, and a predetermined oxygen amount, and the test is performed so that whiskers are generated in the sample. Control is performed to maintain the inside of the tank at the set temperature, the set humidity, and the predetermined oxygen amount for a predetermined time.

  In this configuration, the inside of the test chamber is adjusted to the set temperature, the set humidity and the predetermined oxygen amount, and can be maintained in this state for a predetermined time, thereby effectively accelerating the generation and growth of whiskers in the sample. Thus, the evaluation time can be shortened.

  In addition, the whisker evaluation test apparatus may further include a gas introduction means capable of introducing oxygen or a gas containing oxygen into the test tank. In this case, the control means includes the test tank in the test tank. The gas introducing means is controlled so as to obtain a predetermined oxygen amount.

  In this configuration, since the gas introduction means is controlled by the control means and the inside of the test tank is adjusted to a predetermined oxygen amount, the inside of the test tank can be accurately and quickly adjusted to the predetermined oxygen amount. Further, for example, when a gas having a higher oxygen concentration than air is introduced into the test tank by the gas introduction means, the oxygen concentration in the test tank can be set higher than that of air.

  Further, the gas introduction means can pump oxygen or a gas containing oxygen into the test tank, and the control means opens the exhaust valve and the gas introduction means in a state where the exhaust valve is opened. Control for adjusting the inside of the test tank to the predetermined amount of oxygen may be performed by adjusting at least one of the pressures during pressure feeding.

  In this configuration, with the exhaust valve opened, oxygen is supplied into the test tank by the gas introduction means, and the amount of oxygen is adjusted by at least one of the opening degree of the exhaust valve and the pressure at the time of pumping by the gas introduction means. Is possible. Therefore, in this configuration, since oxygen is continuously or intermittently supplied into the test tank during the test, it is possible to suppress fluctuations in the oxygen concentration during the test.

  The whisker evaluation test apparatus may further include a vacuum pump capable of discharging the gas in the test tank.

  In this configuration, the oxygen amount can be adjusted after the test chamber is evacuated and the air is removed by the vacuum pump, so that the oxygen concentration in the test chamber can be adjusted with high accuracy.

  The whisker evaluation test apparatus is introduced by the oxygen concentration detection means for detecting the oxygen concentration in the test tank, the pressure detection means for detecting the pressure in the test tank, and the gas introduction means in the test tank. And further comprising at least one flow rate detection means for detecting the flow rate of the gas to be performed, wherein the control means performs control to adjust the inside of the test tank to the predetermined oxygen amount based on a detection result by the detection means It is possible to accurately adjust the oxygen amount in the test tank.

  As described above, according to the present invention, the evaluation time of the evaluation object can be shortened.

It is sectional drawing which shows the structure of the pressure cooker test apparatus used for the whisker evaluation method which concerns on 1st Embodiment of this invention. (A) is a top view which shows a semiconductor package, (b) is sectional drawing which looked at the state which mounted the semiconductor package in the board | substrate from the side surface. FIGS. 2A and 2B are schematic views in which a cross section of a tip portion of the lead in FIG. 2B is enlarged, in which FIG. 2A shows a state before the test, and FIG. 2B shows a state after the test. It is a flowchart which shows the flow of control in the whisker evaluation method of 1st Embodiment. It is a flowchart which shows the flow of control in the whisker evaluation method of 2nd Embodiment of this invention. It is a graph which shows transition of physical quantities, such as temperature of each process in the whisker evaluation method of 2nd Embodiment, humidity, and a pressure. It is a flowchart which shows the flow of control in the whisker evaluation method of 3rd Embodiment of this invention. It is a graph which shows transition of physical quantities, such as temperature of each process in the whisker evaluation method of 3rd Embodiment, humidity, and a pressure. It is a flowchart which shows the flow of control in the whisker evaluation method of 4th Embodiment of this invention. It is a graph which shows transition of physical quantities, such as temperature of each process in the whisker evaluation method of 4th Embodiment, humidity, and a pressure. It is a flowchart which shows the flow of control in the whisker evaluation method of 5th Embodiment of this invention. It is a graph which shows transition of physical quantities, such as temperature of each process in the whisker evaluation method of 5th Embodiment, humidity, and pressure.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Test equipment>
First, the pressure cooker test apparatus (highly accelerated life test apparatus) 1 used for the whisker evaluation method will be described. As shown in FIG. 1, the test apparatus 1 includes a pressure vessel 2 as a test tank whose one end is opened, and a door 3 that can close the open side of the pressure vessel 2. A predetermined amount of humidified water (humidification water) 4 is stored in the lower part of the pressure vessel 2. An inner cylinder 5 is installed inside the pressure vessel 2. The inner cylinder 5 is open on the same side as the open side of the pressure vessel 2, and the inside of the inner cylinder 5 is a test area 6. A sample shelf 7 is installed in the test area 6 so that the sample 8 can be placed on the sample shelf 7. A blower port 9 is formed in the center of the closed end of the inner cylinder 5, and the blower port 9 is covered with a protective mesh 10.

  The pressure vessel 2 is provided with an exhaust valve 100 that can be opened and closed. When the exhaust valve 100 is in an open state, the inside and the outside of the pressure vessel 2 are in communication with each other, and when the exhaust valve 100 is in a closed state, the pressure vessel 2 is in a sealed state. As the exhaust valve 100, for example, an electromagnetic valve that only opens and closes, a motor valve whose opening degree can be adjusted, and the like can be used.

  A fan shaft 11 is rotatably supported on the pressure vessel 2, and a blower fan 12 is fixed to the tip of the fan shaft 11. A drive motor 13 is installed outside the pressure vessel 2, and an output shaft 14 of the drive motor 13 is connected to the fan shaft 11 via a magnetic coupling 15. Thereby, by rotating the drive motor 13, the blower fan 12 is rotated, and the gas in the pressure vessel 2 can be circulated as indicated by the white arrow in the figure.

  The test apparatus 1 includes a temperature adjusting unit and a humidity adjusting unit in the pressure vessel 2. The temperature adjusting means includes a heater 16 and an internal temperature sensor 17. The humidity adjusting means includes a humidified water 4, a humidified water heater 18, and a humidified water temperature sensor 19.

  The heater 16 is provided around the fan shaft 11. The gas in the pressure vessel 2 can be heated by the heater 16. The internal temperature sensor 17 is provided in the internal space of the inner cylinder 5. The internal temperature sensor 17 can detect the temperature in the pressure vessel 2 (temperature of the test area 6).

  The humidifying water heater 18 is provided in the lower part of the internal space of the pressure vessel 2. The humidifying water heater 18 is immersed in the humidifying water 4 and can heat the humidifying water 4. Similarly, the humidified water temperature sensor 19 is immersed in the humidified water 4. The humidified water temperature sensor 19 can detect the temperature of the humidified water 4.

  The pressure vessel 2 is provided with a wick temperature sensor 20. The sphere at the tip of the wick temperature sensor 20 is covered with a wick 21 formed of gauze, for example. The lower end of the wick 21 is immersed in the humidified water 4 and is configured to suck up the humidified water 4 by capillary action.

  The pressure vessel 2 is provided with a gas inlet 41. The distal end side of the gas introduction pipe 43 is inserted into the gas introduction port 41. The rear end side of the gas introduction pipe 43 is connected to the gas introduction means 45.

  As the gas introduction means 45, for example, an oxygen tank (cylinder) can be used. Moreover, you may use an oxygen tank and a nitrogen tank together. Further, as the gas introduction means 45, a compressor capable of pressurizing air can be used in addition to the oxygen tank described above. The amount of oxygen or oxygen-containing gas introduced into the pressure vessel 2 from the gas introduction means 45 is, for example, an unillustrated oxygen concentration sensor (oxygen concentration detection means) or pressure sensor (pressure detection) provided in the pressure vessel 2. Adjustment) based on detection data such as a gas flow meter (flow rate detection means). Thereby, the oxygen concentration (or air concentration) in the pressure vessel 2 can be arbitrarily adjusted.

  The test apparatus 1 includes a microcomputer-type control unit 31, and the control unit 31 includes a CPU (not shown) as a calculation unit, a ROM, a RAM, and the like as storage units. The ROM stores a program for operating the hardware.

<Whisker evaluation method>
Hereinafter, a whisker evaluation method according to an embodiment of the present invention will be described.

  First, samples used for whisker evaluation will be described. FIG. 2A is a plan view showing the semiconductor package 51, and FIG. 2B is a side view showing a state in which the semiconductor package 51 is mounted on the substrate 54. FIG. 3A is a schematic diagram enlarging the cross section of the tip portion T of the lead 53 of FIG.

  As shown in FIG. 2A, the semiconductor package 51 has a package part 52 and a plurality of leads 53 extending from the peripheral part of the package part 52. As shown in FIG. 2B, each lead 53 of the semiconductor package 51 is connected to an electrode 55 provided on the surface of the substrate 54 by a solder 56. The mounting substrate shown in FIG. 2B is used as a sample 8 for each test described later.

  As shown in FIG. 3A, the lead 53 is obtained by applying tin plating 53b to the surface of a copper base material 53a. At the end T of the lead 53, the copper base material 53a is exposed. When an evaluation method described later is applied to the sample 8 having such an end T, the generation and growth of whiskers can be promoted.

That is, when the sample 8 is placed in a high-temperature and high-humidity environment in which oxygen exists as will be described later, the surface of the base material 53a, the tin plating 53b, and the solder 56 at the lead end portion T as shown in FIG. A moisture layer 57 is formed. Moreover, since it is in an environment where oxygen is present at a high temperature of 100 ° C. or higher, galvanic corrosion occurs at the lead end T, and the tin plating 53b and the solder 56 at the lead end T are oxidized to form oxides 53c and 56a. It is formed. For example, when the plating is tin plating, the oxide 53c has SnO ₂ as a main component. For example, when the solder contains Sn, such as Sn-3Ag-0.5Cu, SnO ₂ or the like is formed as the oxide 56a. Since the oxidized portions 53c and 56a increase in volume, internal stress is generated in the plating layer and the solder layer. Further, when the plating is tin plating, an intermetallic compound grows between the base material 53a and the plating 53b in a high temperature environment, thereby generating internal stress. It is presumed that the generation and growth of whiskers 61 are promoted due to these internal stresses.

[First Embodiment]
Next, the whisker evaluation method according to the first embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing the flow of control in the whisker evaluation method of the first embodiment. As shown in FIG. 4, in the first embodiment, control is executed in the order of the oxygen amount adjustment process, the temperature / humidity adjustment process, the environment maintenance process, the temperature drop process, and the storage process. In the present embodiment, the apparatus 1 includes an unillustrated oxygen concentration sensor provided in the pressure vessel 2 and an unillustrated pressure sensor.

  First, the operator places the sample 8 shown in FIG. 2B on the sample shelf 7 inside the pressure vessel 2, and then closes the open side of the pressure vessel 2 with the door 3. A predetermined amount of humidified water 4 is stored in the lower part of the pressure vessel 2.

  As shown in FIG. 4, in step S1, the control unit 31 opens the exhaust valve 100 of the apparatus 1 and proceeds to step S2. In step S <b> 2, the operator sets test conditions using an input button of an operation panel (not shown) of the apparatus 1. Parameters input as test conditions are set values such as a set temperature T, a set relative humidity H, and a set oxygen partial pressure AO. Each set value that has been set is stored in the storage means of the control unit 31. In the first embodiment, a case where the set temperature T is set to 110 ° C., the set relative humidity H is set to 85% RH, and the set oxygen partial pressure AO is set to 26.8 kPa will be described as an example.

  Next, the operator presses a start button (not shown) provided in the device 1 to start the operation of the device 1. When the operation of the apparatus 1 is started, as shown in step S3, the control unit 31 uses the sensors provided in the pressure vessel 2 to detect the current state in the pressure vessel 2, that is, the current temperature, the current humidity, Measure current pressure, current oxygen concentration, etc. Each of these current values is used for control of subsequent processes such as an oxygen amount adjusting process and a temperature / humidity adjusting process described later.

  Next, the control part 31 performs the oxygen amount adjustment process of step S4 to S6. In this oxygen amount adjustment step, the control unit 31 first calculates an oxygen concentration target value in the pressure vessel 2 necessary for adjusting the oxygen partial pressure in the pressure vessel 2 to the set oxygen partial pressure AO in step S4. Then, the process proceeds to step S5.

  In step S5, the control unit 31 introduces oxygen or a gas containing oxygen from the gas introduction means 45 into the pressure vessel 2, and in step S6, the oxygen concentration in the pressure vessel 2 reaches the oxygen concentration target value and is stabilized. Determine whether or not. The oxygen concentration in the pressure vessel 2 is detected by the oxygen concentration sensor.

  As the gas introduction means 45, for example, an oxygen tank can be used. In the case of using an oxygen tank, it is preferable that oxygen and nitrogen are mixed and supplied into the pressure vessel 2 using a nitrogen tank from the viewpoint of safety. Further, air may be introduced into the pressure vessel 2 by using a compressor as the gas introduction means 45. When using an oxygen tank as in the former, the oxygen concentration in the gas to be introduced can be arbitrarily adjusted by changing the supply ratio of oxygen and nitrogen, so compared to the case where air is introduced by a compressor, The oxygen concentration in the pressure vessel 2 can be set high.

  When the oxygen concentration in the pressure vessel 2 reaches the target value and stabilizes, the control unit 31 proceeds to step S7, stops supplying oxygen or air, closes the exhaust valve 100 of the apparatus 1, and proceeds to step S8. At this time, if it is necessary to further increase the oxygen partial pressure, oxygen or air may be further introduced into the pressure vessel 2 after the exhaust valve 100 is closed.

  Next, the control part 31 performs the temperature / humidity adjustment process of step S8, S9. That is, as shown in step S8, the control unit 31 controls the temperature and relative humidity in the pressure vessel 2 to be adjusted to the set temperature T (110 ° C.) and the set relative humidity H (85% RH), respectively.

  Then, in step S9, the control unit 31 determines whether the temperature and relative humidity in the pressure vessel 2 reach the set values (set temperature T, set relative humidity H) and are stable, and the temperature and humidity are determined. If it is determined that the set value is stable, the process proceeds to step S10.

Here, in the test apparatus 1 of the present embodiment, the humidity in a test environment of 100 ° C. or higher is obtained as follows. That is, the relative humidity when the temperature T2 at which the water vapor pressure is the saturated water vapor pressure in the pressure vessel 2 is raised to a higher temperature T1 and the temperature in the pressure vessel 2 is sufficiently increased is expressed by the following formula ( 1).
(Relative humidity) = ((saturated water vapor pressure at T2) / (saturated water vapor pressure at T1)) × 100 (1)
Specifically, for example, the temperature detected by the internal temperature sensor 17 is T1, the temperature detected by the humidified water temperature sensor 19 or the wick temperature sensor 20 is T2, and the values of T1 and T2 are substituted into the above equation (1). Thus, the relative humidity can be obtained.

  Next, the control part 31 performs the environment maintenance process of step S10, S11. In this environmental maintenance step, the temperature and humidity in the pressure vessel 2 are held at the set temperature T and the set relative humidity H for a predetermined time. That is, the control unit 31 starts measuring a timer (not shown) in step S10 and proceeds to step S11.

  In step S11, the control unit 31 determines whether or not the measurement time of the timer has reached a predetermined time set in advance, and repeats this determination until the measurement value of the timer reaches the predetermined time. Until the measured value of the timer reaches a predetermined time, the temperature and humidity are maintained at the set temperature T and the set relative humidity H in the pressure vessel 2. When the measurement time of the timer reaches a predetermined time, the control unit 31 ends the environment maintaining process and proceeds to the temperature lowering process of steps S12 to S15.

  In this temperature lowering step, the temperature and humidity in the pressure vessel 2 are lowered with a predetermined gradient until reaching the preset storage temperature and storage humidity. The exhaust valve 100 of the device 1 is opened when the pressure in the pressure vessel 2 reaches a predetermined set value (for example, 111.3 kPa in the present embodiment) (steps S13 and S14). When the temperature and humidity in the pressure vessel 2 further drop and reach the storage temperature and storage humidity (step S15), the control unit 31 executes a storage step for maintaining the pressure container 2 at the storage temperature and storage humidity (step S15). Step S16).

  In this preservation | save process, until the sample 8 is taken out from the pressure vessel 2, the environment in the pressure vessel 2 is maintained at storage temperature and storage humidity. In the case where the sample 8 is taken out immediately after the test is completed, the storage step can be omitted.

  In the embodiment, the case where the set temperature T is set to 110 ° C. has been described as an example, but the present invention is not limited to this. The set temperature T is preferably 105 ° C. or higher and 140 ° C. or lower. By setting the set temperature to 105 ° C. or higher, whisker generation and growth can be further promoted. The set temperature is preferably 140 ° C. or less from the viewpoint of heat resistance of the printed circuit board.

  Moreover, in the said embodiment, although the case where the set humidity H was 85% of relative humidity was mentioned as an example, it is not limited to this. The lower limit is preferably a relative humidity of 75% or more and an upper limit of 100% or less, and the lower limit is a relative humidity of 85% or more and an upper limit of 100% in terms of enhancing the effect of promoting whisker generation and growth. The following is more preferable.

  Furthermore, in the said embodiment, although the case where the preset oxygen partial pressure AO in the pressure vessel 2 was 26.8 kPa was mentioned as an example, it is not limited to this. The set oxygen partial pressure AO is preferably 10 kPa or more, and more preferably 26 kPa or more, from the viewpoint of enhancing the effect of promoting whisker generation and growth. For the same reason, the air partial pressure in the pressure vessel 2 is preferably 50 kPa or more, and more preferably 128 kPa or more so that the oxygen partial pressure falls within the above range.

[Second Embodiment]
FIG. 5 is a flowchart showing the flow of control in the whisker evaluation method of the second embodiment of the present invention, and FIG. 6 shows physical quantities such as temperature, humidity, pressure, etc. in each step in the whisker evaluation method of the second embodiment. It is a graph which shows transition. In the second embodiment, the oxygen amount adjusting step is different from that of the first embodiment. In addition, the detailed description about the same process as 1st Embodiment is abbreviate | omitted here.

  As shown in FIGS. 5 and 6, in the second embodiment, the control is executed in the order of the oxygen amount adjustment process, the temperature and humidity adjustment process, the environment maintenance process, the temperature drop process, and the storage process.

  First, similarly to the first embodiment, the operator places the sample 8 on the sample shelf 7 inside the pressure vessel 2, and then closes the open side of the pressure vessel 2 with the door 3.

  As shown in FIG. 5, in step S21, the control unit 31 opens the exhaust valve 100 of the apparatus 1 and proceeds to step S22. In step S <b> 22, the operator sets test conditions using an input button on an operation panel (not shown) of the apparatus 1. Parameters input as test conditions are set values such as a set temperature T, a set relative humidity H, a set air partial pressure A, and the like. Each set value that has been set is stored in the storage means of the control unit 31. In the second embodiment, a case where the set temperature T is set to 110 ° C., the set relative humidity H is set to 85% RH, and the set air partial pressure A is set to 128.2 kPa will be described as an example.

  In the second embodiment, the oxygen concentration is adjusted without using the gas introduction means 45 as in the first embodiment. That is, in the second embodiment, the air partial pressure (oxygen concentration) in the test tank is indirectly adjusted by adjusting other conditions than the air partial pressure A. Therefore, in the second embodiment, in addition to the setting of the test conditions described above, the initial conditions for adjusting the air partial pressure are also set. The parameters input as the initial conditions are set values such as the initial temperature T0 and the initial relative humidity H0. Each set value that has been set is stored in the storage means of the control unit 31. In the second embodiment, a case where the initial temperature T0 is set to 30 ° C. and the initial relative humidity H0 is set to 85% RH will be described as an example.

  Next, the operator presses a start button (not shown) provided in the device 1 to start the operation of the device 1. When the operation of the apparatus 1 is started, the control unit 31 sets the temperature and humidity in the pressure vessel 2 to the initial temperature T0 (30 ° C.) and the initial relative humidity H0 (85% RH), respectively, as shown in step S23. adjust. The temperature and relative humidity in the pressure vessel 2 are measured by the internal temperature sensor 17 and the wick temperature sensor 20.

  Since the exhaust valve 100 of the pressure vessel 2 is opened, when the pressure vessel 2 is adjusted to the initial temperature T0 and the initial relative humidity H0, the total pressure and the water vapor partial pressure in the pressure vessel 2 are determined. Thereby, the air partial pressure is inevitably adjusted to a predetermined value. When the initial temperature T0 is adjusted to 30 ° C. and the initial relative humidity H0 is adjusted to 85% RH as in the case of the second embodiment, the water vapor partial pressure is 3.6 kPa. Therefore, the initial air partial pressure at this time is a value obtained by subtracting 3.6 kPa from the total pressure. The total pressure in the pressure vessel 2 may be measured by a pressure sensor (not shown) or may be regarded as 1 atm (101.3 kPa) of atmospheric pressure. In FIG. 6, the case where the total pressure is assumed to be 101.3 kPa and the air partial pressure in the pressure vessel 2 is calculated is described as an example, and the initial air partial pressure in this case is 97.7 kPa.

  In step S24, the controller 31 determines whether or not the temperature and humidity in the pressure vessel 2 have reached the initial temperature T0 and the initial relative humidity H0. When the temperature and humidity reach the initial temperature T0 and the initial relative humidity H0, the control unit 31 proceeds to step S25, closes the exhaust valve 100 of the apparatus 1, and then proceeds to step S26.

  In addition, about temperature / humidity adjustment process, environmental maintenance process, temperature fall process, and step S26-S34 of a preservation | save process, since it is the same as that of step S8-S16 of 1st Embodiment, description is abbreviate | omitted.

[Third Embodiment]
FIG. 7 is a flowchart showing the flow of control in the whisker evaluation method of the third embodiment of the present invention, and FIG. 8 shows physical quantities such as temperature, humidity, and pressure in each step in the whisker evaluation method of the third embodiment. It is a graph which shows transition. The third embodiment is different from the first embodiment in that a vacuum process is included. In addition, the detailed description about the same process as 1st Embodiment is abbreviate | omitted here.

  As shown in FIGS. 7 and 8, in the third embodiment, control is executed in the order of a vacuum process, an oxygen amount adjustment process, a temperature and humidity adjustment process, an environment maintenance process, a temperature drop process, and a storage process.

  First, similarly to the first embodiment, the operator places the sample 8 on the sample shelf 7 inside the pressure vessel 2, and then closes the open side of the pressure vessel 2 with the door 3.

  As shown in FIG. 7, in step S <b> 41, the operator sets test conditions using an input button on an operation panel (not shown) of the apparatus 1. Parameters input as test conditions are set values such as a set temperature T, a set relative humidity H, a set air partial pressure A, and the like. Each set value that has been set is stored in the storage means of the control unit 31. In the third embodiment, a case where the set temperature T is set to 110 ° C., the set relative humidity H is set to 85% RH, and the set air partial pressure A is set to 128.2 kPa will be described as an example.

  Next, the operator presses a start button (not shown) provided in the device 1 to start the operation of the device 1. When the operation of the device 1 is started, the control unit 31 closes the exhaust valve 100 in step S42 and proceeds to step S43. In step S43, the inside of the pressure vessel 2 is evacuated by a vacuum pump (not shown) connected to the pressure vessel 2. The exhaust valve 100 may be closed before inputting the set value.

  When the evacuation is completed, the control unit 31 introduces air into the pressure vessel 2 by the gas introduction means 45 such as a compressor in Step S44. At this time, the temperature in the pressure vessel 2 is adjusted to 30 ° C., for example. Since the set temperature T is 110 ° C. and the set air partial pressure A is 128.2 kPa, the amount of air to be introduced into the pressure vessel 2 at 30 ° C. is a volume at which the total pressure (air pressure) is 101.4 kPa. . The amount of air introduced may be detected by, for example, a pressure sensor that can be installed in the pressure vessel 2, or may be detected by a flow meter that can be installed in a pipe into which air is introduced.

  In step S45, the control unit 31 determines whether or not the amount of air (air partial pressure or air volume) in the pressure vessel 2 has reached a target value. If the target value has been reached, the control unit 31 proceeds to step S46. .

  Next, the control part 31 performs the temperature / humidity adjustment process of step S46, S47. That is, as shown in step S46, the control unit 31 controls the temperature and relative humidity in the pressure vessel 2 to be adjusted to the set temperature T (110 ° C.) and the set relative humidity H (85% RH), respectively.

  Then, the control unit 31 determines whether or not the temperature and relative humidity in the pressure vessel 2 reach the above set values and is stable in step S47, and if the temperature and humidity are determined to be stable at the set values, step Proceed to S48.

  In addition, since it is the same as that of step S10-S16 of 1st Embodiment about step S48-S54 of an environmental maintenance process, a temperature fall process, and a preservation | save process, description is abbreviate | omitted.

[Fourth Embodiment]
FIG. 9 is a flowchart showing a flow of control in the whisker evaluation method of the fourth embodiment of the present invention. FIG. 10 shows physical quantities such as temperature, humidity, and pressure in each step in the whisker evaluation method of the fourth embodiment. It is a graph which shows transition. The fourth embodiment is different from the first embodiment in that the temperature / humidity adjustment step and the environment maintenance step are performed while oxygen or oxygen-containing gas is continuously or intermittently introduced into the pressure vessel 2. Yes. In addition, the detailed description about the same process as 1st Embodiment is abbreviate | omitted here.

  First, after placing the sample 8 on the sample shelf 7 inside the pressure vessel 2, the operator closes the open side of the pressure vessel 2 with the door 3.

  As shown in FIG. 9, in step S61, the control unit 31 opens the exhaust valve 100 of the apparatus 1 and proceeds to step S62. In step S <b> 62, the operator sets test conditions using an input button on an operation panel (not shown) of the apparatus 1. Parameters input as test conditions are set values such as a set temperature T, a set relative humidity H, and a set total pressure B, for example. Each set value that has been set is stored in the storage means of the control unit 31. In the fourth embodiment, a case where the set temperature T is set to 110 ° C., the set relative humidity H is set to 85% RH, and the set total pressure B is set to 500 kPa will be described as an example.

  Next, the operator presses a start button (not shown) provided in the device 1 to start the operation of the device 1. When the operation of the apparatus 1 is started, the control unit 31 performs control so as to discharge air from the exhaust valve 100 while supplying air into the pressure vessel 2 by the gas introduction means 45 in step S63. As the gas introducing means 45, for example, a device capable of pumping air such as a compressor or a gas cylinder can be used. In step S63, the amount of air supplied into the pressure vessel 2 is adjusted to be larger than the amount of air discharged from the exhaust valve 100. This adjustment is performed by at least one of the opening degree of the exhaust valve 100 and the pressure at the time of pumping by the gas introduction means 45. In step S63, the temperature in the pressure vessel 2 is maintained at approximately 30 ° C. as shown in FIG.

  Next, the controller 31 determines whether or not the total pressure in the pressure vessel 2 has reached the set total pressure B in step S64. When the total pressure reaches the set total pressure B, the control unit 31 proceeds to step S65. On the other hand, when the total pressure does not reach the set total pressure B, the control unit 31 performs control to continue the operation of step S63.

  Next, the control unit 31 sets the temperature and humidity in the pressure vessel 2 to the set temperature T (110 ° C.) and the set while maintaining the total pressure at the set total pressure B (500 kPa) in the temperature / humidity adjustment step of step S65. Control to adjust relative humidity H (85% RH) is performed. In this control, since the total pressure is constant, as shown in FIG. 10, the air partial pressure decreases as the water vapor partial pressure increases. In the case of the fourth embodiment, when the temperature and humidity in the pressure vessel 2 reach 110 ° C. of the set temperature T and 85% RH of the set relative humidity H, as shown in FIG. 373.5 kPa and water vapor partial pressure 126.5 kPa.

  In step S66, the controller 31 determines whether or not the temperature and relative humidity in the pressure vessel 2 have reached the above set values and stabilized, and if it is determined that the temperature and humidity are stable at the set values, the control unit 31 proceeds to step S67. move on.

  Next, the control part 31 performs the environment maintenance process of step S67, S68. In this environmental maintenance process, the temperature, humidity, and total pressure in the pressure vessel 2 are held at the set temperature T, the set relative humidity H, and the set total pressure B for a predetermined time. That is, the control unit 31 starts measuring a timer (not shown) in step S67 and proceeds to step S68.

  When the measurement time of the timer reaches a predetermined time, the control unit 31 ends the environment maintaining process and proceeds to a temperature lowering process in step S69.

  In the temperature drop process of steps S69 to S70, the temperature and humidity are lowered with a predetermined gradient until the temperature in the pressure vessel 2 reaches a preset storage temperature. In the fourth embodiment, the operation is performed so as to maintain the total pressure at the set total pressure B even during the temperature lowering process, but the present invention is not limited to this. For example, the temperature may be controlled to decrease and the total pressure to decrease.

  When the temperature in the pressure vessel 2 reaches the storage temperature (step S70), the control unit 31 executes a storage process for maintaining the pressure vessel 2 at the storage temperature (step S71).

[Fifth Embodiment]
FIG. 11 is a flowchart showing the flow of control in the whisker evaluation method of the fifth embodiment of the present invention, and FIG. 12 shows physical quantities such as temperature, humidity, and pressure in each step in the whisker evaluation method of the fifth embodiment. It is a graph which shows transition. The fifth embodiment is different from the first embodiment in that the temperature and humidity adjustment step is executed before the oxygen amount adjustment step. In addition, the detailed description about the same process as 1st Embodiment is abbreviate | omitted here.

  As shown in FIGS. 11 and 12, in the fifth embodiment, control is executed in the order of a temperature / humidity adjustment step, an oxygen amount adjustment step, an environment maintenance step, a temperature drop step, and a storage step.

  First, similarly to the first embodiment, the operator places the sample 8 on the sample shelf 7 inside the pressure vessel 2, and then closes the open side of the pressure vessel 2 with the door 3.

  As shown in FIG. 11, in step S81, the control unit 31 opens the exhaust valve 100 of the apparatus 1 and proceeds to step S82. In step S <b> 82, the operator sets test conditions using an input button on an operation panel (not shown) of the apparatus 1. Parameters input as test conditions are set values such as a set temperature T, a set relative humidity H, a set air partial pressure A, and the like. Each set value that has been set is stored in the storage means of the control unit 31. In the fifth embodiment, a case where the set temperature T is set to 110 ° C., the set relative humidity H is set to 85% RH, and the set air partial pressure A is set to 128.2 kPa will be described as an example.

  Next, the operator presses a start button (not shown) provided in the device 1 to start the operation of the device 1. When the operation of the apparatus 1 is started, the control unit 31 sets the temperature and humidity in the pressure vessel 2 to the set temperature T (110 ° C.) and the set relative humidity H (85% RH), respectively, as shown in step S83. adjust. As shown in FIG. 12, when the set temperature T is 110 ° C. and the set relative humidity H is adjusted to 85% RH, the water vapor partial pressure is 121.8 kPa, and the air partial pressure is almost zero.

  In step S <b> 84, the control unit 31 determines whether the temperature and humidity in the pressure vessel 2 have reached the set temperature T and the set relative humidity H. When each set value is reached, the control unit 31 proceeds to step S85, closes the exhaust valve 100 of the apparatus 1, and proceeds to step S86.

  Next, the control part 31 performs the oxygen amount adjustment process of step S86. In step S86, the control unit 31 introduces (pressure-feeds) a gas such as oxygen or air into the pressure vessel 2 by the gas introduction means 45 such as a compressor or a gas cylinder. The introduction of gas is continued until the air partial pressure in the pressure vessel 2 reaches the set air partial pressure A (128.2 kPa).

  Then, the control unit 31 determines whether or not the air partial pressure in the pressure vessel 2 has reached the set air partial pressure A and is stable in step S87, and proceeds to step S88 if it is determined that the set value is stable.

  In addition, since it is the same as that of step S10-S16 of 1st Embodiment about step S88-S94 of an environmental maintenance process, a temperature fall process, and a preservation | save process, description is abbreviate | omitted.

[Other Embodiments]
Note that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the spirit of the present invention. For example, in each of the above-described embodiments, the case where a sample in which a semiconductor package is mounted on a substrate is described as an example. However, the present invention is not limited to this. The present invention can also be applied to other evaluation objects in which whiskers may occur.

  In the above-described embodiment, the case where copper is used as the lead base material and tin is used as the plating material has been described as an example. However, the present invention is not limited to this. In the present invention, the base material and the plating material may be other combinations.

  The oxygen amount adjustment in the oxygen amount adjustment step may be performed based on the flow rate or pressure of a gas containing oxygen such as oxygen or air, may be performed based on the oxygen concentration, You may perform based on an air partial pressure.

  Further, the gas introduced in the oxygen amount adjusting step may be only oxygen, air, or a gas obtained by mixing oxygen and another gas.

  Further, the storage process and the vacuum process may be omitted. Further, the exhaust valve may be opened after the set value is input.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example.

  Whisker evaluation was performed using a semiconductor mounting substrate having a configuration similar to that shown in FIGS. 2A and 2B as a sample. Details of the samples used for the evaluation are shown in Table 1.

  In this example, as shown in Tables 2 to 4, the occurrence of whiskers was compared under 13 types of test conditions. Among them, test No. in Table 4 Reference numeral 10 denotes a whisker evaluation method according to an embodiment of the present invention.

  Test No. in Table 2 1 is the result when left at room temperature. 2 to 4 are the results when the thermal cycle test was performed. For example, test no. 2 shows the results of evaluation under the condition that the temperature in the test tank is repeatedly changed between 0 ° C. and 60 ° C. as shown in Table 3, and each temperature is maintained for 15 minutes. Test No. 3 and 4 are the results of repeatedly changing between the two temperatures shown in Table 3 in the same manner.

  Test No. in Table 4 In 5-9, the numerical value on the left side of the test condition column is the set temperature in the test tank, and the numerical value on the right side is the set humidity (relative humidity) in the test tank. Of these, test no. In 5 to 7 and 9, since the air partial pressure in the test tank is not adjusted, air having an air partial pressure corresponding to a value obtained by subtracting the water vapor partial pressure from the total pressure exists in the test tank. In addition, Test No. In No. 8, since the operation for removing the air in the test tank was performed when setting the test conditions in the test tank, the air partial pressure in the test tank was 0 kPa.

  Test No. in Table 4 11 to 13 are the results of evaluation by a highly accelerated life test (HAST). In each test, the numerical value on the left side of the test condition column is the set temperature in the test tank, and the numerical value on the right side is the set humidity (relative humidity) in the test tank. In each of these tests, the air partial pressure is 0 kPa because it is in a temperature environment of 100 ° C. or higher.

  The evaluation results of each test are shown in Tables 2-4. Note that a microscope, a scanning electron microscope (SEM), and an electron beam microanalyzer (EMPA) were used for observation of each sample.

  First, as shown in Table 2, test No. In 1, the whisker has not occurred even when the test period is 8 months. Next, as shown in Table 3, the thermal cycle test No. No whisker is generated at the time of 3000 cycles for 2-4.

  In addition, as shown in Table 4, the test No. Among test cases No. 5 to 13, the earliest occurrence of whiskers is test no. 10. Test No. In No. 10, a whisker of 30 μm was confirmed after 200 hours from the start of the test. From this, test No. which is one embodiment of the present invention is described. It can be said that the ten evaluation methods can generate and grow whiskers in a shorter time than other conventional evaluation methods. In addition, Test No. In 10 samples, whiskers occurred near the edge (corner) of the lead tip.

  Note that “foreign matter generation” in Table 4 indicates that spinous foreign matters different from whiskers were generated. When this spinous foreign material was analyzed, Cu, Br, and the like were detected. From this, it is presumed that the spinous foreign body is a salt formed by Cu and flux, which is a lead base material, and is not a single crystal whisker.

1 Pressure cooker test device 2 Pressure vessel (test tank)
4 Humidification water 6 Test area 8 Sample 16 Heater 17 Internal temperature sensor 18 Humidification water heater 19 Humidification water temperature sensor 20 Wick temperature sensor 21 Wick 31 Control unit 41 Gas introduction port 43 Gas introduction pipe 45 Gas introduction means 51 Semiconductor package 53 Lead 53a Base material 53b Tin plating 54 Substrate 57 Moisture layer 61 Whisker

Claims (15)

Placing the sample to be evaluated in the test chamber;
In-tank environment adjustment step of adjusting the inside of the test tank to a predetermined oxygen amount, a set temperature of 100 ° C. or higher, and a predetermined set humidity,
A whisker evaluation method comprising: maintaining the inside of the test tank at the predetermined oxygen amount, the set temperature, and the set humidity for a predetermined time to generate a whisker on the sample.   The whisker evaluation method according to claim 1, wherein the sample has a portion where a lead-free plating layer is formed on a surface of a metal base material, and a part of the metal base material is exposed from the plating layer. . The tank environment adjustment step
An oxygen amount for adjusting the inside of the test tank to a predetermined initial air partial pressure by adjusting the inside of the test tank to a predetermined initial temperature and a predetermined initial water vapor partial pressure with the exhaust valve of the test tank being opened. Adjustment process;
The temperature / humidity adjusting step of adjusting the inside of the test tank to the set temperature and the set humidity with the exhaust valve closed after the oxygen amount adjusting step, according to claim 1 or 2. The whisker evaluation method described. The tank environment adjustment step
While the exhaust valve of the test tank is opened, the predetermined concentration is detected by the gas introduction means provided in the test tank while the oxygen concentration detection means provided in the test tank is used to detect the oxygen concentration in the test tank. An oxygen amount adjusting step of introducing oxygen or a gas containing oxygen into the test chamber until the oxygen amount is reached;
The temperature / humidity adjusting step of adjusting the inside of the test tank to the set temperature and the set humidity with the exhaust valve closed after the oxygen amount adjusting step, according to claim 1 or 2. The whisker evaluation method described. A vacuum step of evacuating the test chamber with the exhaust valve of the test chamber closed;
The whisker evaluation method according to claim 1 or 2, wherein after the vacuum step, the in-vessel environment adjustment step and the environment maintenance step are executed in a state where the exhaust valve is closed. The in-vessel environment adjustment step is to continuously or intermittently introduce oxygen or oxygen-containing gas into the test tank by the gas introduction means provided in the test tank with the exhaust valve of the test tank being opened. An oxygen amount adjusting step for adjusting the inside of the test tank to a predetermined initial oxygen partial pressure,
After the oxygen amount adjusting step, the inside of the test tank is in a state in which the exhaust valve is kept open and oxygen or a gas containing oxygen is continuously or intermittently introduced by the gas introduction means. A temperature and humidity adjustment step for adjusting the set temperature and the set humidity,
The environmental maintenance step is performed by continuously or intermittently introducing oxygen or a gas containing oxygen into the test tank by the gas introduction means with the exhaust valve of the test tank being opened. The whisker evaluation method according to claim 1 or 2, wherein the inside of the tank is adjusted to the predetermined oxygen amount. The environmental adjustment step in the tank is a temperature and humidity adjustment step of adjusting the temperature and humidity in the test tank to the set temperature and the set humidity, respectively, with the exhaust valve of the test tank opened.
After the temperature and humidity adjustment step, oxygen or a gas containing oxygen is introduced into the test tank until the predetermined oxygen amount is reached by the gas introduction means provided in the test tank with the exhaust valve closed. The whisker evaluation method according to claim 1, further comprising an oxygen amount adjusting step.   The whisker evaluation method according to claim 1, wherein the temperature is 105 ° C. or higher and 140 ° C. or lower.   The whisker evaluation method according to claim 1, wherein the set humidity is 75% or more relative humidity.   The whisker evaluation method in any one of Claims 1-9 whose oxygen partial pressure in the said test tank in the said environmental maintenance process is 10 kPa or more. A test chamber in which a sample to be evaluated can be placed;
Temperature adjusting means capable of adjusting the inside of the test tank to a set temperature of 100 ° C. or higher;
Humidity adjusting means capable of adjusting the inside of the test tank to a predetermined set humidity;
An exhaust valve capable of communicating between the inside and outside of the test tank;
The temperature adjusting means and the humidity adjusting means are controlled so that the inside of the test tank has the set temperature, the set humidity, and a predetermined oxygen amount, and the inside of the test tank is set so that whiskers are generated in the sample. A whisker evaluation test apparatus comprising: control means for performing control to maintain the temperature, the set humidity, and the predetermined oxygen amount for a predetermined time. A gas introduction means capable of introducing oxygen or a gas containing oxygen into the test tank;
The whisker evaluation test apparatus according to claim 11, wherein the control unit controls the gas introduction unit so that the inside of the test tank has the predetermined oxygen amount. The gas introducing means is capable of pumping oxygen or a gas containing oxygen into the test chamber,
The control means adjusts the inside of the test tank to the predetermined oxygen amount by adjusting at least one of the opening degree of the exhaust valve and the pressure at the time of pumping by the gas introduction means with the exhaust valve opened. The test apparatus for whisker evaluation according to claim 12, wherein control is performed.   The whisker evaluation test apparatus according to claim 12, further comprising a vacuum pump capable of discharging the gas in the test tank. Oxygen concentration detection means for detecting the oxygen concentration in the test tank, pressure detection means for detecting the pressure in the test tank, and flow rate detection for detecting the flow rate of gas introduced into the test tank by the gas introduction means Further comprising at least one of means,
The whisker evaluation test apparatus according to claim 11, wherein the control unit performs control to adjust the inside of the test tank to the predetermined oxygen amount based on a detection result by the detection unit.

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