This standard provides for the methods to evaluate the endurance of semiconductor devices when used in high temperature and high humidity ambient. As well known, high temperature humidity is not our ambient environment, then, a environmental test chamber is needed for create specific environment.
At the beginning, this test was designed by assuming the evaluation of the endurance of semiconductor devices contained mainly in resin sealed packages, against the corrosion phenomenon of metallic wiring on the chip.
Recently, however, this test is being used to accelerate the leak phenomenon due to infiltration of moisture through the passivation film and as a part of various kinds of series tests, but care must be taken because accelerability data are not necessarily well known, and it may bring about failure modes that do not occur in the field.
Care must be taken because failure modes consisting of short-circuit (leak) between external leads by plating metal, that do not occur in the field, may occur under condition C (temperature 85℃, humidity 85%), and Unsaturated Pressurized Vapor Test.
Equipment to be used in this test should be provided with a chamber capable to keep the test temperature and humidity specified for long time, a power supply, and whenever required a timer to turn the power supply ON and OFF during the specified time, when required.
The chamber should be made of material that does not react under high humidity conditions. Moreover, water condensed on the ceiling of the chamber should not drop on the specimen.
Water to be used in the tests should be distilled water or deionized water, with pH from 6.0 to 7.2,and resistivity of 500 Ohm-m or more at 23 C.
When the specimen is a plastic-molded SMD, carry out the moisture soaking and soldering heat stress treatment specified in test method 104 (moisture soaking and soldering heat stress series tests)before executing this test.
Carry out the initial measurements in conformity with the items and conditions specified in the relevant specifications.
Apply the specified voltage on the specimen in the test chamber kept at high temperature and high humidity conditions. When required turn the power ON and OFF cyclically. When putting the specimen in and out of the chamber, make sure that water drops are not stuck to the specimen and do not dip it in water.
Remarks: When the SMD is to be mounted on a jig for evaluation, the relevant conditions (substrate material, size of the land, soldering method. flux cleaning. etc.) should be specified in the relevant specifications.
The test circuit should be in conformity with the relevant specifications.
Apply voltage continuously in conformity with the conditions specified in the relevant specifications. Apply the voltage intermittently when the power dissipation is large, however, and turn the power supply ON and OFF in conformity with the time specified in the relevant specifications.
The applied voltage should be in conformity with the stipulations of the relevant specifications, and it is desirable to restrict the internal heat generation so as to minimize power dissipation.
The relative humidity of the chip surface in the package decreases due to heat generation of the chip when the device has large power dissipation, and corrosion becomes less probable. In this case, it is recommendable to turn the power ON and OFF in order to attain more effective results related to corrosion. In general, continuous power application is desirable when the power dissipation is smaller than 100mW, and intermittent power application consisting of 1-hour ON and 3-hour OFF is recommended when the power dissipation exceeds 100mW.
The tolerance of the applied voltage should be within 5% of the preset value.
Select the temperature and humidity conditions out of those ones of Table 1, and apply the Conditions C unless otherwise specified. Under condition D, E, and F (Unsaturated Pressurized Vapor Test), the temperature and the humidity from the start to the end of the test should be controlled in conformity with the profile of Figure 1, unless otherwise specified.
The relative humidity in the chamber during the heating and humidification phase as well as in the cooling and dehumidification phase should be kept from 50% to 85%.
Test duration should be refered to Table 1, except when otherwise specified. Under condition D, E, and F (Unsaturated Pressurized Vapor Test), the time count should be started when the vapor pressure and temperature reach stable state as shown in Figure 1.
After finishing the tests, leave the specimen standing under normal conditions, from 2 hours to 24 hours.
Under condition D, E, and F (Unsaturated Pressurized Vapor Test), special care should be taken when handling the specimen after finishing the test,because failure modes differnt from those ones of the tests may occur due to condensation, sudden changes in the temperature and pressure, and other relevant factors. After finishing the test, remove the specimen from the chamber after confirming that the interior of the chamber has returned approximately to the normal condition in conformity with the specified temperature and humidity profile, and then leave the specimen in room temperature.
Carry out the end-point measurements in conformity with the items and conditions specified in the relevant specifications. These measurements should be carried out within 48 hours under normal conditions after the completion of the tests, except when other specified.
Remarks: In case of expending more completion time of the measurements than 48 hours, the specimen should be storaged in suitable storage conditions such as no influence of test results.
EIAJ ED-4701 has five parts which is 100-500. Every parts has many methods. This article talks about EIAJ ED-470/100 test method 102 Temperature Humidity Bias which is mainly about temperature and humidity.
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