JP5045742B2 - Evaluation method for chip parts - Google Patents

Description

  The present invention relates to a quality determination method for chip parts such as a multilayer ceramic capacitor.

  Chip components mounted on a wiring board are subject to various stresses under the actual use environment of the product. Cracks may occur inside the chip component due to the stress applied to the chip component.

  On the other hand, as a method for evaluating the stress resistance of an electronic component, a moisture resistance test is known in which the impedance of a moisture sensitive element disposed in a test tank that is in a high humidity environment is measured over time (see Patent Document 1).

  However, it has been difficult to detect internal cracks that may occur in chip components due to various stresses received in the use environment, simply by performing a moisture resistance test.

Japanese Patent Laid-Open No. 7-35714

  The present invention has been made in view of such a situation, and an object thereof is to provide a chip part quality determination method capable of effectively detecting an internal crack of a chip part that may occur in a use environment. It is.

In order to achieve the above-described object, a chip part quality determination method according to the present invention includes:
Preparing a chip component on which a plurality of terminal electrodes are formed;
Connecting the pad portion of the test substrate provided with wiring and the terminal electrode;
The test substrate on which the chip component is mounted by placing the test substrate in a moisture-proof load testing machine having a pressurizing unit, pressurizing the test substrate with the pressurizing unit from the back surface of the test substrate. Bending the test substrate so that the surface of the substrate protrudes;
A step of performing a humidification test using the moisture resistance load tester in a state where the test substrate is bent, and evaluating the presence or absence of deterioration of electrical characteristics.

  In an actual use environment of a product, a chip component may be used in a state where the substrate is bent. The conventional test method did not assume such a state. In the present invention, a humidification test is performed using a moisture resistance load tester in a state where the test substrate is bent. That is, whether or not the electrical characteristics of the chip component are deteriorated is evaluated in a state where the test substrate is bent and stress is applied to the chip component. Therefore, structural defects due to stress corrosion that may occur in the product in the future can be determined in advance. Therefore, it becomes possible to effectively detect an internal crack of a chip component that may occur in the use environment.

  Preferably, the presence or absence of deterioration of the electrical characteristics is evaluated by measuring electrical resistance characteristics of the chip component.

  If an internal crack is generated in the chip component, moisture easily enters the internal crack, and electrical conduction occurs when a voltage is applied to the chip component in such a state. Therefore, by measuring the electrical resistance characteristics of the chip component, it is possible to determine whether or not the electrical characteristics have deteriorated.

  Preferably, when viewed from the pressurization direction, the moisture resistance load test is performed on the test substrate so that the chip part is smaller than the pressurization part and the pressurization part and the chip part overlap each other. Place in the plane.

  By arranging in this way, stress can be accurately applied to the chip component in accordance with the amount of deflection of the wiring board.

  The test substrate may be arranged in the moisture-resistant load test machine so that the surface of the test substrate to which the chip component is attached faces upward, but the test substrate to which the chip component is attached It is preferable to arrange the test substrate in the moisture-proof load tester so that the surface faces downward.

  The chip component in which the lead portion of the chip component is displaced from the terminal electrode can also be detected by evaluating whether or not the electrical characteristics of the chip component are deteriorated.

  In the chip component manufacturing process, a chip component in which the lead portion is slightly exposed from the terminal electrode may be manufactured due to a stacking error or a printing error. Such a chip component is difficult to detect only by inspection by appearance. In such a chip component, moisture enters the chip component from the portion where the lead portion is exposed on the surface, and is likely to cause stress corrosion cracking. In the present invention, since the presence or absence of deterioration of electrical characteristics is evaluated using the above-described process, chip parts that are likely to be deteriorated in electrical characteristics due to the displacement of the lead portion from the terminal electrode are easily detected with high accuracy. It becomes possible to do.

FIG. 1 is an external view of a chip component mounted on a test substrate. FIG. 2 is an exploded perspective view of the chip component shown in FIG. FIG. 3 is a side view of the chip component showing how the lead portion is displaced from the terminal electrode. 4 is a cross-sectional view taken along the line IV-IV in FIG. FIG. 5 is a side view of the moisture resistance load tester used in the present invention. FIG. 6A is a cross-sectional view of a test substrate on which chip components are arranged, and FIG. 6B is a view taken along the arrow VIB-VIB in FIG.

First, an overall configuration of a multilayer ceramic capacitor having a multi-terminal structure will be described as an example of the chip component 2 determined by the chip component quality determination method according to an embodiment of the present invention. As shown in FIG. 1, the chip component 2 has an element body 12 which is a rectangular parallelepiped sintered body obtained by firing a laminate in which a plurality of dielectric layers 12a (shown in FIG. 2) are laminated. .

  In the chip component 2 shown in FIG. 1, the element body 12 has a width W, a length L, and a height T. The values of the width W, the length L, and the height T are not particularly limited. For example, the width W = 0.7 to 0.9 mm and the length L = 1.5 to 1.7 mm. It is a low-profile chip component having a height T smaller than the length L.

  As shown in FIG. 1, the chip component 2 has a plurality of terminal electrodes 31 to 38 along the X-axis direction (the length L direction of the element body 12). The plurality of terminal electrodes 31 to 38 are end portions of the lead portions 31L to 38L exposed to the first surface 12A and the second surface 12B facing each other along the Y-axis direction (the width W direction of the element body 12) (see FIG. 2). (Shown). The X axis, the Y axis, and the Z axis are perpendicular to each other.

  The material of the plurality of terminal electrodes 31 to 38 is not particularly limited. Usually, copper, copper alloy, nickel, nickel alloy, or the like is used, but silver, silver-palladium alloy, or the like can also be used.

  As shown in FIG. 2, internal electrodes 31C to 38C are formed on each dielectric layer 12a. The internal electrodes 31C to 38C have lead portions 31L to 38L along the Y-axis direction, respectively.

  The material of the dielectric layer 12a is not particularly limited, and is made of a dielectric material such as calcium titanate, strontium titanate and / or barium titanate. The thickness of each dielectric layer 12a in the Z-axis direction is not particularly limited, but is, for example, 1.5 to 2.5 μm.

  In the manufacturing process of the chip component 2 described above, as shown in FIG. 3, the lead portions 31 </ b> L to 38 </ b> L are caused by misalignment of the dielectric layer 12 a, printing misalignment of the internal electrodes 31 </ b> L to 38 </ b> L, or misalignment of the terminal electrodes 31 to 38. May slightly deviate from the terminal electrodes 31 to 38, and chip parts having the lead portions 31L to 38L exposed on the surface may be manufactured.

  In the example shown in FIG. 3, the lead portions 35L to 38L protrude in the X-axis direction from the terminal electrodes 35 to 38 and are exposed on the surface. The amount of protrusion is, for example, about 50 to 100 μm. In FIG. 3, the lead portions 35 </ b> L to 38 </ b> L are illustrated so as to protrude beyond the actual ratio for easy understanding of the problem. Such a chip component 2 has a small size as a whole, and it is difficult to detect the protrusion of the lead portions 35L to 38L by inspection based on the appearance.

  In such a chip component 2, moisture tends to enter the chip component 2 from the portion where the lead portion is exposed on the surface due to various stresses received in the actual product use environment. As a result, when cracks (stress corrosion cracks) 40 that straddle the dielectric layers occur as shown in the IV-IV sectional view of FIG. 1 shown in FIG. It easily intrudes and causes problems such as short circuit defects. In this embodiment, in order to detect such a problem that may occur after shipment from the factory, a moisture resistance load test described below is performed.

Humidity resistance test First, a chip component 2 shown in FIG. 1 is prepared. And the terminal electrodes 31-38 of the chip component 2 are connected to the pad part 14 (shown in FIG. 6A) formed on the surface 4a of the test substrate 4 shown in FIG. It is preferable that the pad portion 14 is disposed at the approximate center in the Y-axis direction of the test substrate 4. This is because the amount of deflection is large at the center of the test substrate 4 in the Y-axis direction. The stress generated in the chip component 2 can be increased by largely bending the test substrate 4 at the position where the chip component 2 is attached.

  As shown in FIG. 6B, the test substrate 4 has test terminals 18A and 18B at positions of a distance L1 from the center of the chip component 2 in the Y-axis direction. A plurality of chip components 2 and test terminals 18A and 18B are arranged along the X-axis direction of the surface 4a of the test substrate 4 respectively. Although it does not specifically limit about the number of arrangement | positioning, It is preferable to arrange | position 5-10 pieces.

  The size of the test substrate 4 is not particularly limited, but the distance L1 described above is preferably 30 times the width W of the chip component 2. Further, the distance L2 between the test terminals in the X-axis direction is preferably 5 times the length L of the chip component 2.

  The test substrate 4 is provided with a wiring 16 for electrically connecting the pad portion 14 and the test terminals 18A and 18B shown in FIG. The pad portion 14 is connected to the terminal electrode groups 31 to 34 and the terminal electrode groups 35 to 38 by soldering or the like. As a result, the chip component 2 is electrically and mechanically connected to the test substrate 4 and is in close contact with the test substrate 4.

  The wiring 16 electrically connects the terminal electrodes 31 to 34 of the chip component 2 and the test terminal 18A, and electrically connects the terminal electrodes 35 to 38 of the chip component 2 and the test terminal 18B. The wiring 16 shown in FIG. 6 is connected to the measuring device 23 as shown in FIG. A measurement result of a test to be described later is displayed on the display device 25.

  Next, as shown in FIG. 5, both ends in the Y-axis direction of the test substrate 4 described above are attached to the support portions 26, 26 of the jig 24 arranged inside the moisture-proof load testing machine 22 having the pressurizing portion 20. It arrange | positions so that the parts 4c and 4c may contact. At this time, it arrange | positions so that the surface 4a of the board | substrate 4 for a test to which the chip component 2 was attached may face downward. Although the downward direction in FIG. 5 and the Z-axis direction coincide with each other in terms of the structure of the jig 24 used in the moisture resistance load test, the surface 4a of the test substrate 4 faces the pressurizing direction described later. In this case, it does not have to coincide with the Z axis.

  Note that the test substrate is placed so that the chip component 2 is smaller than the pressurization unit 20 and the pressurization unit 20 and the chip component 2 overlap each other when viewed from the Z-axis direction shown in FIG. It is preferable to arrange inside the moisture resistance load tester 22.

  Next, a deflection amount condition is input from the input device 21 shown in FIG. 5, and the test substrate 4 is pressed in the Z-axis direction by the pressurizing unit 20 from the back surface 4 b of the test substrate 4. By pressurizing the test substrate 4 with the pressurizing unit 20, the test substrate 4 is bent by a predetermined amount so that the chip component 2 protrudes. The amount of deflection f at the center of the test substrate 4 shown in FIG. 5 is preferably 0.5 to 2.0 mm. In the state where the test substrate 4 is bent as described above, the humidification test is performed using the moisture resistance load tester 22. The time for the humidification test is preferably 10 to 100 hours.

  When the humidity condition is input by the input device 21, the water vapor is sent into the inside of the moisture resistance load tester 22 from a water vapor introduction port (not shown). Humidity is measured in real time by a humidity sensor (not shown) arranged inside the moisture resistant load tester 22, and the humidity inside the moisture resistant load tester 22 is kept constant. The relative humidity inside the moisture resistance load tester 22 is preferably 90 to 100% RH.

  The moisture resistance load tester 22 is provided with a heater and a temperature sensor (not shown), and the temperature inside the moisture resistance load tester 22 is controlled to be constant. The temperature inside the moisture resistance load tester 22 is preferably controlled at a relatively high temperature, and preferably 60 to 150 degrees during the humidification test.

  After a predetermined time of the humidification test has elapsed, a voltage is applied to the test terminals 18A and 18B shown in FIGS. The applied voltage is preferably 0.8 to 2.0 times the rated voltage of the chip component 2. It is preferable that the voltage is relatively higher than the rated voltage of the chip component 2. Then, the voltage and current values between the test terminals 18A and 18B are measured by the measuring device 23, and the electric resistance value between the terminals of the chip component 2 is calculated.

  When the measured electrical resistance value between the terminals of the chip component 2 is less than or equal to a predetermined value, it is considered that the chip component 2 to be measured has caused a short-circuit failure, and the chip component 2 is shown in FIG. It can be determined that such a crack 40 may have occurred.

  That is, if the electrical resistance value displayed on the display device 25 is equal to or less than a predetermined value, it is determined that the lead portions 31L to 38L of the chip component 2 are displaced from the terminal electrodes 31 to 38 as shown in FIG. can do.

  In an actual use environment of a product, a chip component may be used in a state where the substrate is bent. The conventional test method did not assume such a state. In the present embodiment, the humidity test is performed using the moisture resistance load tester 22 in a state where the test substrate 4 is bent. That is, whether or not the electrical characteristics of the chip component are deteriorated is evaluated in a state where the test substrate 4 is bent and stress is applied to the chip component 2. Therefore, structural defects due to stress corrosion that may occur in the product in the future can be determined in advance. Therefore, it becomes possible to effectively detect the internal crack 40 of the chip component 2 that may occur in the use environment.

  If the internal crack 40 is generated in the chip component 2, moisture easily enters the internal crack 40, and electrical conduction occurs when a voltage is applied to the chip component 2 in such a state. Therefore, by measuring the electrical resistance characteristics of the chip component 2, it is possible to determine whether or not the electrical characteristics have deteriorated.

  Further, in the present embodiment, the chip component 2 is smaller than the pressurizing unit 20 as viewed from the Z-axis direction shown in FIG. 5, and the pressurizing unit 20 and the chip component 2 overlap each other. The test substrate is placed inside the moisture resistance load testing machine 22. By arranging in this way, stress can be accurately applied to the chip component 2 in accordance with the amount of deflection of the wiring board 4.

  In the present embodiment, since the presence or absence of deterioration of the electrical characteristics is evaluated using the above-described process, the lead parts 31L to 38L are displaced from the terminal electrodes 31 to 38, and the chip parts are likely to be deteriorated in electrical characteristics. 2 can be easily detected with high accuracy.

  In the above-described embodiment, the resistance value between the terminals is calculated by the measurement device 23 illustrated in FIG. 5, but a parameter other than the resistance value may be measured. Specifically, a current value or the like may be measured.

  In addition, a plurality of chip parts 2 are randomly tested from one lot in a moisture resistance load test, and if the electrical resistance values of all the tested chip parts are below a predetermined value, all chip parts in the same lot are determined to be OK. You may do it. Further, if there is a chip part 2 that has a predetermined number or more and an electrical resistance value of a predetermined value or less, the same lot may be retested.

  In addition, after the above-described test is performed, the test may be performed by using different chip components in the same lot and changing the direction of the chip component 2 mounted on the test substrate shown in FIG. 6B. That is, the test may be performed so that the length L direction of the chip component 2 and the Y-axis direction shown in FIG. In this case, the test order according to the direction of the chip component 2 may be reversed.

Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.
Example 1
As the size of the chip component 2, a chip having a width W = 0.8 mm, a length L = 1.6 mm, and a height T = 0.6 mm was used. The material of the plurality of terminal electrodes 31 to 38 shown in FIG. 1 is a Cu paste baking layer / Ni plating layer / Sn plating layer. The material of the dielectric layer 12a shown in FIG. 2 is mainly composed of barium titanate, and the thickness of each dielectric layer 12a in the Z-axis direction is 2.0 μm.

  Twenty-five chip components 2 described above were randomly selected from the same lot and mounted on the pad portion 14 of the test substrate 4 shown in FIG. 6 by soldering. As the solder, Sn-Ag3-Cu0.5 was used. The test substrate 4 made of FR-4 glass cloth base epoxy resin was used. The size of the test substrate 4 was 40 mm in the X-axis direction, 100 mm in the Y-axis direction, and 1.6 mm in thickness as shown in FIG. The distance L1 = 25 mm and the distance L2 = 5 mm shown in FIG.

  The test substrate 4 was placed on the jig 24 shown in FIG. 5, and the test substrate 4 was pressurized by the pressure unit 20. The pressure was applied so that the deflection amount f = 1 mm shown in FIG.

  In the above state, a humidification test was performed for 80 hours. The conditions of the humidification test were such that the relative humidity in the moisture resistance load tester 22 was 95% RH and the temperature was 121 degrees.

  After 80 hours, a voltage of 3.6 V was applied to the test terminals 18A and 18B shown in FIGS. 5 and 6 to determine whether or not the electrical resistance value of each chip component 2 was 1 MΩ or less. . When the electric resistance value was 1 MΩ or less, the chip component 2 was determined to be defective.

  Of the total 25 chip parts used in the test, the proportion of defective products was determined as the crack occurrence rate. The results are shown in Table 1.

Comparative Example 1
The chip component 2 was humidified in the same manner as in Example 1 except that the test substrate 4 shown in FIG. 6 was not pressurized. The electrical resistance value between the terminals of the chip component 2 was measured in the same manner as in Example 1, and the ratio of defective products out of the total 25 chip components used in the test was determined as the crack occurrence rate.

Comparative Example 2
The chip component 2 was subjected to a humidification test in the same manner as in Example 1 except that the test substrate 4 shown in FIG. 6 was pressurized only for 10 seconds and that the test substrate 4 was not pressurized during the humidification test. The electrical resistance value between the terminals of the chip component 2 was measured in the same manner as in Example 1, and the ratio of defective products out of the total 25 chip components used in the test was determined as the crack occurrence rate.

  From the experimental results shown in Table 1, the crack occurrence rates in Comparative Example 1 and Comparative Example 2 were 0% and 4%, respectively, whereas in Example 1, a high value of 36% was obtained. Therefore, it was found that the internal cracks of the chip part 2 that cannot be detected in the comparative examples 1 and 2 can be effectively detected in the example.

2 ... Chip component 4 ... Test substrate 4a ... Front surface 4b ... Back surface 12 ... Element body 16 ... Wiring 20 ... Pressure part 22 ... Moisture resistance evaluation tester 31-38 ... Terminal electrodes 31L-38L ... Lead part

Claims (3)

Preparing a chip component having a multi-terminal structure in which a plurality of terminal electrodes are formed along the longitudinal direction of the element body ; and
Connecting the pad portion of the test substrate provided with wiring and the terminal electrode;
The test substrate on which the chip component is mounted by placing the test substrate in a moisture-proof load testing machine having a pressurizing unit, pressurizing the test substrate with the pressurizing unit from the back surface of the test substrate. Bending the test substrate so that the surface of the substrate protrudes;
With the test substrate bent, performing a humidification test using the moisture resistance load tester, and evaluating the presence or absence of deterioration of electrical characteristics ,
The test substrate is arranged in the moisture resistant load tester so that the chip part is smaller than the pressurizing part when viewed from the pressurizing direction, and the pressurizing part and the chip part overlap each other. And
A method for determining the quality of a chip component , wherein the chip component in which a lead portion of the chip component is displaced from the terminal electrode is detected by evaluating whether or not the electrical characteristics of the chip component are deteriorated .   2. The chip part quality determination method according to claim 1, wherein presence / absence of deterioration of the electrical characteristics is evaluated by measuring electrical resistance characteristics of the chip parts. 3. Wherein as the surface of the test substrate faces downward, quality determination method of the chip component according to claim 1 or 2, characterized in placing the test substrate to the humidity load test machine.

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