Test jig and test method

Some materials desired to acquire mechanical characteristics and fatigue characteristics are difficult to make in a large-size bulk material for a test piece. The invention provides a test jig which includes a primary jig which fixes both sides of a test piece, which is a test object, an upper jig which includes a load portion to load a weight on two places of an upper surface and two places of a lower surface of the primary jig, and a lower jig which includes a load portion to load a weight on two places of the upper surface and two places of the lower surface of the primary jig. The upper surface and the lower surface of the primary jig disposed on both sides of the test piece are on almost the same flat surface.

TECHNICAL FIELD

The present invention relates to a mechanical test jig and a test method for a bonding structure and a bulk material.

BACKGROUND ART

In recent years, the use of machine parts and electric parts is expanding, and various materials are developed for these various uses. To secure reliability of a product when each material is used for various products, it is necessary to grasp the mechanical characteristics and fatigue characteristics of the material. It is generally known that a test piece of a bulk material is prepared and tested as a method for obtaining the mechanical characteristics and the fatigue characteristics of the material. In addition, a method for preparing and testing a bonding test piece for grasping the mechanical characteristics and the fatigue characteristics of the bonding material is also known.

PTL 1 discloses a means “there are provided fixing support parts2and3supporting corresponding positions of one side1aand another side1bof a test piece1with an interval L therebetween, two first load points4aand4bloaded within the interval L of the fixing support parts2and3while being separated from the one side1aof the test piece1, and two second load points5aand5bloaded within the interval L of the fixing support parts2and3while being separated from the other side1bof the test piece1. The test piece1is loaded at different positions of the first load points4aand4band the second load points5aand5b” in order to solve “a true fatigue strength of a test piece is measured when completely reversed four-point bending test is performed”.

PTL 2 discloses a means “a bonding surface of a bonded material5(measuring target) is set to a pentagon or a triangle, and the measuring target5is bonded with a high-strengthened jig6using an adhesive7, and a four-point bending measurement is performed by a strength test” in order to solve “providing a method for measuring a bonding strength with ease and accuracy when various types of materials, specially brittle materials such as glass and ceramic are bonded”.

In PTL 3, there is described “a test device has been used to induce a two-dimensional deformation such as a four-point bending and a three-point bending in a fatigue test caused by a mechanical load in the related art”. These test methods are test methods only for the bending in one direction. Therefore, the bending deformation can be generated in the cross section of the test piece perpendicular to a support side, but the bending deformation hardly occurs in the depth direction. However, the deformation may occur three-dimensionally in many cases when a semiconductor device is thermally loaded. Comparing a stress distribution of the test piece in the case of the three-point bending or the four-point bending test of the related art and a stress distribution of the semiconductor device at the time of thermal load, these distributions of solder bonding stress of the corners are not necessarily matched, for example. As a means for the problem, there is disclosed “a mechanical loading test method for a semiconductor device in which a semiconductor device (including a circuit board)3or a semiconductor simulating member is bent in plural directions by the mechanical load in a mechanical load bending tester which is configured by a loading portion (deformation causing portion)10and a test piece supporting portion9so as to induce a three-dimensional deformation”.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

Some materials desired to acquire mechanical characteristics and fatigue characteristics are difficult to make in a large-size bulk material for a test piece. In addition, in the case of the bonding material, there is a material having different characteristics in the bonding state and a bulk material or a material existing only as a thin bonding layer. Further, in a case where a material having a characteristic that deformation proceeds remarkably in one direction, such as a ratchet deformation and a creep deformation is evaluated, the test piece is deformed in one direction during the test, and thus an appropriate characteristic may be not acquired in a test method where the material is loaded in one direction. An object of the invention is to realize a test which acquires a mechanical characteristic and a fatigue characteristic of various bulk materials and bonding materials.

Solution to Problem

In order to solve the above problem, the invention provides a test jig which includes a primary jig which fixes both sides of a test piece, which is a test object, an upper jig which includes a load portion to load a weight on two places of an upper surface and two places of a lower surface of the primary jig, and a lower jig which includes a load portion to load a weight on two places of the upper surface and two places of the lower surface of the primary jig. The upper surface and the lower surface of the primary jig disposed on both sides of the test piece are on almost the same plane.

Advantageous Effects of Invention

According to the invention, if even a material difficult to be made in a large test piece can be made in a fine test piece, the dimension of the material is suitable to the four-point bending test by fixing both sides to a primary jig. In addition, even in a case where a bonding material having different characteristics in the bonding state and the bulk material, and a bonding material only existing as a thin bonding layer are evaluated, the material evaluation of the bonding state is possible if a fine test piece containing the bonding layer can be created. Further, the upper and lower surfaces of the primary jigs on both sides are on almost the same plane, so that the completely reversed four-point bending test can be performed using the upper and lower jigs. Even in a case where a material having a characteristic that deformation proceeds remarkably in one direction, such as a ratchet deformation and a creep deformation is evaluated, the completely reversed four-point bending load is applied to the test object, so that it is possible to prevent deformation of the test object in one direction during the test.

With these effects, a test for acquiring the mechanical characteristic and the fatigue characteristic can be realized with respect to the bulk material and the bonding material having various characteristics.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments will be described using the drawings.

First Embodiment

A first embodiment of the invention will be described usingFIGS. 1 to 13.

FIG. 1is a diagram and a cross-sectional view of a test jig according to a first embodiment of the invention.

A primary jig3is disposed in both sides of a test piece4(test object), and the primary jig3and the test piece4integrated are set in an upper jig1and a lower jig2. In this embodiment, the description will be given about a test method for testing a mechanical characteristic and a fatigue characteristic of the test piece4using the test jig which is configured by the upper jig1, the lower jig2, and the positioning jig3, and a test jig which is used in the method.

The upper jig1will be described in detail usingFIG. 2. In the upper jig1, four-point bending load portions11on a cylinder are provided at four places in total (11ato11d), and the four-point bending load portions11are supported by four-point bending load portion supporting bodies16(16ato16d), respectively. The four-point bending load portions11aand11bbecome two inner loading portions when the test object is deformed to be convex downward in a completely reversed four-point bending test. The four-point bending load portions11cand11dare two inner loading portions when the test object is deformed to be convex upward in the completely reversed four-point bending test. The four-point bending load portion supporting bodies16aand16bwhich support the four-point bending load portions11aand11bare fixed to one supporting body fixing member17aby a four-point bending load portion span adjusting bolt13, and fixed to an upper jig frame18by a four-point bending load portion vertical adjusting bolt12. Similarly, the four-point bending load portion supporting bodies16cand16dwhich support the four-point bending load portions11cand11dare fixed to one supporting body fixing member17cby the four-point bending load portion span adjusting bolt13, and fixed to the upper jig frame18by the four-point bending load portion vertical adjusting bolt12. The four-point bending load portion vertical adjusting bolt12and the four-point bending load portion span adjusting bolt13are respectively configured to be adjusted in position. The vertical distances of the four-point bending load portions11aand11band the four-point bending load portions11cand11dcan be adjusted by adjusting the four-point bending load portion vertical adjusting bolt12. In addition, the inner span at the time of four-point bending can be adjusted by adjusting the four-point bending load portion span adjusting bolt13. With the functions of adjusting the vertical distances and the span, the jig can handle various types of test conditions. A test device mounting hole15is provided in the upper portion of the upper jig frame18. When performing the test, the upper jig1is connected to a test device using the test device mounting hole15.

Details of the lower jig2will be described in detail usingFIG. 3. In the lower jig2, four-point bending load portions21on a cylinder are provided at four places in total (21ato21d), and the four-point bending load portions21are supported by four-point bending load portion supporting bodies (26ato26d), respectively. The four-point bending load portions21aand21bbecome two outer loading portions when the test object is deformed to be convex upward in a completely reversed four-point bending test. The four-point bending load portions21cand21dare two outer loading portions when the test object is deformed to be convex downward in the completely reversed four-point bending test. The four-point bending load portion21is supported by the four-point bending load portion supporting body26. The four-point bending load portion supporting body26is fixed to a supporting body fixing member27by a four-point bending load portion span adjusting bolt23, and fixed to an upper jig frame28by a four-point bending load portion vertical adjusting bolt22. The four-point bending load portion vertical adjusting bolt22and the four-point bending load portion span adjusting bolt23are respectively configured to be adjusted in position. The vertical distances of the four-point bending load portions21aand21band the four-point bending load portions21cand21dcan be adjusted by adjusting the four-point bending load portion vertical adjusting bolt22. In addition, the outer span at the time of four-point bending can be adjusted by adjusting the four-point bending load portion span adjusting bolt23. With the functions of adjusting the vertical distances and the span, the jig can handle various types of test conditions. A test device mounting hole25is provided in the lower portion of a lower jig frame28. When the test is performed, the lower jig1is connected to an actuator of the test device using the test device mounting hole25.

Details of the test piece4will be described in detail usingFIG. 4. In this embodiment, a mechanical characteristic and a fatigue characteristic of the bonding layer42are evaluated using a bonding test piece in which bonded portions41aand41bare bonded by a bonding layer42. In this embodiment, a solder material containing nickel of a 5×5×30 mm square column is used for the bonded portions41aand41b, and a solder material of a 5×5×0.1 mm square column containing tin as a main component is used for the bonding layer42to be evaluated. The solder material of the bonding layer42is interposed between the bonded portions41aand41bin a sheet shape. The solder material is heated more than a melting point of the solder material. The nickel of the bonded portion41and the solder material react to each other and bonded to create the test piece4. At this time, the bonding layer42is disposed in a surface orthogonal to a longitudinal direction of the test piece4.

In a case where the mechanical characteristic of the bonding layer42is evaluated by the four-point bending test, a bending moment is generated not only in the bonding layer42but also in the bonded portion41. If not only an elastically-deformed linear region but also a plastically-deformed non-linear region of the mechanical characteristic of the bonding layer42are evaluated, when both the bonding layer42and the bonded portion41show a non-linear behavior according to the bending moment, both the bonding layer42and the bonded portion41need to be separated, and thus it is difficult to make an evaluation with accuracy. Therefore, it is desirable that there is no non-linear behavior of the bonded portion41, or the non-linear behavior is sufficiently small compared to the non-linear behavior of the bonding layer42. Therefore, it is desirable that the material of the bonded portion41has a yield stress larger than the material of the bonding layer42. Even in a case where a fatigue test is performed, if the evaluation is performed in a non-linear deformation range such as a low cycle fatigue strength, it is desirable that there is no non-linear behavior of the bonded portion41, or the non-linear behavior is sufficiently small compared to the non-linear behavior of the bonding layer42. Therefore, even in this case, it is desirable that the material of the bonded portion41has a yield stress larger than the material of the bonding layer42. In this embodiment, the bonding layer42to be evaluated is a solder material containing tin as a main component, and thus nickel having a large yield stress compared to the solder material is used for the bonded portion41. Other materials such as metal having a large yield stress may be used for the bonded portion41. However, there is a need to secure the strength of the bounding interface to the bonding layer42. Therefore, in a case where metal is used for the bonded portion41, the surface is desirably coated with nickel.

When the bonding layer42is evaluated by the four-point test, the bending moment is loaded evenly to the bulk portion of the bonding layer42and to the bonding interface between the bonding layer42and the bonded portion41. Therefore, in the fatigue test, the cross surface with the shortest lifespan in the bulk portion of the bonding layer42and the bonding interface between the bonding layer42and the bonded portion is broken, so that the weakest portion of the entire bonding portion can be evaluated.

A procedure of fixing the test piece4to the primary jig3will be described usingFIG. 5. The test piece4is disposed in grooves of lower sides31aand31bof the primary jig3. At this time, the bonding layer42to be evaluated is disposed to be exposed between the lower sides31aand31bof the primary jig3. Next, lower sides32aand32bof the primary jig3are disposed on the lower sides31aand31bof the primary jig3, and both sides of the test piece4are interposed with the upper and lower surfaces of the primary jig3. Finally, the upper and lower surfaces of the primary jig3are fastened by the fastening bolt33to fix the primary jig3and the test piece4. At this time, a spot-faced hole34for bolt is provided in an upper side32of the primary jig3. The upper portion of the fastening bolt33is not exposed from the upper surface of the upper side32of the primary jig after fastening the fastening bolt33. Therefore, as illustrated inFIG. 6, there is no projection in the upper and lower surfaces of the primary jig3on both sides of the test piece4after fixing the test piece4. The upper and lower surfaces become almost flush with each other. When the test is performed, the test piece4is caused to be bent by loading a weight on four points of the upper and lower surfaces of the primary jig3.

In the four-point bending test, a bending moment M generated in the inside span of the test object is expressed by Expression (1).
M=F(L1−L2)/4  (1)

Herein, F represents a total load to be applied, L1 represents an outside span, and L2 represents an inside span.

In a case where the test object is small, a difference between L1 and L2 is not increased. Therefore, there is a need to increase a load F to generate a required moment. However, if F is increased, a contact stress of a supporting place is increased. There is a concern that the test piece is broken at the contact portion. If a curvature of the supporting member is increased, the contact stress is decreased. In that case, however, the span is changed according to the bending deformation of the test object. With this regard, in the invention, the dimension of the test object can be made suitably using the primary jig even in a case where the dimension of the test piece is small. Therefore, the four-point bending test can be performed suitably.

The dimension of the primary jig3is larger in both a thickness and a width compared to the test piece4. A flexural rigidity is proportional to the width, and to a cube of the thickness. Therefore, the primary jig3has a flexural rigidity sufficiently large compared to the test piece4. Therefore, in a case where a bending load is applied to this structure, most deformation is caused by the test piece4, and the material characteristic of the test piece4can be acquired with accuracy.

FIG. 7illustrates a state where the upper jig1and the lower jig2of the test jig according to the first embodiment of the invention are provided in a tester. The upper surface of the upper jig1is connected and fixed to the tester5, and the lower surface of the lower jig2is connected to the actuator of the tester5. When the actuator of the tester5operates up and down, a vertical positional relation of the upper jig1and the lower jig2is changed, and the bending test is enabled.

InFIG. 8, an example of the positional relation between the upper jig1and the lower jig2in a state where the upper jig1and the lower jig2illustrated inFIG. 7are disposed in the tester is illustrated in a cross-sectional view. The four-point bending load portions11aand11bof the upper jig and the four-point bending load portions21aand21bof the lower jig become almost flush with each other. In addition, the four-point bending load portions11cand11dof the upper jig and the four-point bending load portions21cand21dof the lower jig become almost flush with each other.

When the test is performed, first the primary jig3fixed with the test piece4as illustrated inFIG. 9is disposed to the upper jig1and the lower jig2of the positional relation illustrated inFIG. 8. Since there is no projection such as a bolt in the upper and lower surfaces of the primary jig3, a feature that the primary jig3can be inserted from the side surface of the upper jig1or the lower jig2, which is also the feature of the test jig of the invention. With the feature that the primary jig3can be inserted or extracted through the side surface of the upper jig1or the lower jig2, the primary jig can be taken out to replace the test piece without disassembling the upper jig and the lower jig. Therefore, when the test of a plurality of test pieces is performed, there is no need to disassemble the upper jig1and the lower jig2every time when the test is performed. Therefore, an interval between tests can be shortened.

If the primary jig3is provided, the lower surface of the primary jig3is supported by four places of the four-point bending load portions11c,11d,21c, and21d. On the other hand, a gap is provided without bringing the upper surface of the upper jig into contact with the four-point bending load portions11a,11b,21a, and21b. Next, as illustrated inFIG. 10, it is possible to prevent the primary jig3from moving in the horizontal direction by disposing a pressing member6on both side surfaces of the lower jig2.FIG. 11illustrates an enlarged surrounding view the primary jig3. A fine gap8is provided in the vertical direction, and a fine gap9is provided in the horizontal direction. Therefore, it is possible to prevent restriction other than the four-point load while preventing the positional deviation between the test piece4and the primary jig3at the time of bending test.

FIG. 12schematically illustrates the bending load during the test. A state before the test is illustrated inFIG. 12(a). In this state, the weight of the test piece4and the primary jig3is supported only by four places of the four-point bending load portions11c,11d,21c, and21d, and bending load is not generated in the test object.FIG. 12(b)illustrates a state where the upper jig1is moved up by the actuator of the tester5. At this time, the four-point bending load portions11ato11dof the upper jig1move up. Therefore, a four-point bending deformation occurs in which an upward weight is generated in the four-point bending load portions11cand11dof the upper jig1, a downward weight is generated in the four-point bending load portions21aand21bof the lower jig2, and the test object interposed by these portions is deformed to be convex upward.FIG. 12(c)illustrates a state where the upper jig1is moved in the lower direction by the actuator of the tester5. At this time, the four-point bending load portions11ato11dof the upper jig1move down. Therefore, a four-point bending deformation occurs in which a downward weight is generated in the four-point bending load portions11aand11bof the upper jig1, an upward weight is generated in the four-point bending load portions21cand21dof the lower jig2, and the test object interposed by these portions is deformed to be convex downward. Therefore, the states ofFIGS. 12(b) and 12(c)can be repeated by repeatedly moving the lower jig2up and down by the tester so as to realize the completely reversed four-point bending test.

Further, in a case where the vertical gap8illustrated inFIG. 11is not provided, the four-point bending load is not applied onto the test object as illustrated inFIG. 12(b)even if the lower jig2is moved up. A shearing load is applied to a region surrounded by the four-point bending load portions21a,21c,11c, and11aand a region surrounded by the four-point bending load portions11b,11d,21d, and21b, that is, a shearing test. Therefore, it is important to provide the gap8.

In the test using the test jig according to the first embodiment of the invention, the values of the weight and the displacement detected by the tester5can be acquired. The amount of the bending moment loaded on the test piece4and the displacement can be obtained from the values. Further, as illustrated inFIG. 13, a strain gauge is provided in the bonded portion41of the test piece4to measure strain. Therefore, it is possible to acquire data excluding an influence such as a backlash caused by the inside of the tester5and the jig, and the amount of the bending moment loaded on the test piece4can be measured with higher accuracy. At this time, it is effective to provide the strain gauge on the upper surface, the lower surface, or both upper and lower surfaces of the bonded portion41where the strain is maximized by the bending deformation in order to grasp the bending deformation of the bonded portion41with high accuracy. When the strain gauge is provided in the upper and lower surfaces of the bonded portion41, it is considered that a deviation in strain distribution is caused by a rigidity difference with respect to the bonded portion41at a position near the primary jig3and the bonding layer42. Therefore, the strain gauge is desirably installed at almost the center between the end of the bonding layer42and the end of the primary jig3. In addition, a strain gauge line71to acquire a signal from a strain gauge7is led to a side near the bonding layer42, so that it is possible to prevent the strain gauge line71from interfering when the test piece4is fixed to the primary jig3. If the strain of the bonded portion41can be acquired, the bending moment loaded on the test piece4can be obtained, and the strain generated in the bonding layer (evaluation target) can be calculated. Further, in a case where the thickness of the bonding layer42is large, the strain of the bonding layer42can be directly acquired by directly providing the strain gauge in the bonding layer42.

FIG. 14illustrates an example of a temporal variation of the strain of a bonded body which is acquired in the test using the test jig according to the first embodiment of the invention. The graph shows a temporal variation of strain acquired by the strain gauge provided in the upper and lower surfaces of the bonded body in a test where the upwardly convex deformation illustrated in (a) in the drawing, (b) no load, (c) the downwardly convex deformation, and (b) no load are repeatedly performed. The test is performed on a condition of 1 Hz. When a positive strain is generated in the upper surface of the bonded body, a negative strain is generated almost symmetrically in the lower surface. When a negative strain is generated in the upper surface of the bonded body, a positive strain is generated almost symmetrically in the lower surface. From this temporal variation, it is confirmed that the bonded body is repeatedly deformed to both up and down sides by the completely reversed four-point bending load. In addition, when the positive/negative strains of the upper and lower surfaces are reversed, there is a time when the strains of the upper and lower surfaces become 0. This time is an idle running time which is generated when the vertical gap8is provided. In this way, the idle running time and the bending strain repeating in a vertically symmetric manner are features of the test result using the test jig according to the first embodiment of the invention.

In the test using the test jig according to the first embodiment of the invention, an even bending moment can be loaded on the test piece4. Therefore, if the bending strain generated in the bonded body41is the same, the same bending moment can be loaded on the bonding layer42regardless of the thickness of the bonding layer42.FIG. 15illustrates a strain distribution which is generated in the bonding layer42when 0.001 strain is generated in the surface of the bonded body using a finite element analysis method. The longitudinal elastic moduli of the bonded material and the bonding layer are set to 200 and 20 GPa, respectively. The strain of the bonding layer42is evaluated at the center in the thickness direction as illustrated in the drawing. As a result of evaluation on conditions of three different orders of the bonding layer having the thickness of 0.01, 0.1, and 1 mm, it is confirmed that the strain of the bonding layer42does not depend on the thickness of the bonding layer. Currently, various types of bonding materials are developed, and the bonding thicknesses are also varied. The test of the invention can be performed on any bonding thickness in a unified manner. Further, even a test piece of unknown bonding thickness can be evaluated.

Second Embodiment

FIG. 16illustrates a primary jig10of the test jig according to a second embodiment of the invention and a procedure of fixing the test piece4with the primary jig10. This embodiment is different from the first embodiment in that a lower side101of the primary jig10is larger than an upper side102, and the test piece4is fixed by part of the lower side101and the upper side102while plane dimensions of the lower side31and the upper side32of the primary jig3are almost the same, and the test piece4is fixed by overlapping these upper and lower sides in the first embodiment. In this embodiment, the thickness of the primary jig10is determined by the thickness of the lower side101. The thickness caused by the bolt fastening when the test piece4is fixed does not change. Therefore, even in a case where the test piece4is replaced, the thickness of the primary jig10is constant, the vertical gap8when being assembled to the upper jig1and the lower jig2becomes constant, and the test can be performed with more stability. However, the dimension of the primary jig becomes large compared to the first embodiment. In accordance with these features, embodiments can be differently used depending on the test piece, the test condition, etc.

Third Embodiment

FIG. 17illustrates the shape of the test piece according to a third embodiment of the invention. This embodiment is different from the first embodiment in that the test piece4is not provided with the bonding layer but configured by two members161and162while the test piece4is configured by the bonded portion41and the bonding layer42in the first embodiment. This embodiment can be utilized in a case where a bonding interface is cut from a bonding portion where a foreign material is bonded without the bonding material by a bonding method such as a solid diffusion bonding or from a large-scale bonding portion, and evaluated. As described usingFIG. 15, the evaluation can be made without depending on the thickness of the bonding layer in the test of the invention. Even in a case where there is no bonding layer as in this embodiment, the bonding interface is loaded with a well-known bending moment, so that the evaluation can be made in an unified manner similarly to a case where the bonding layer is provided.

Fourth Embodiment

FIG. 18illustrates the shape of the test piece according to a fourth embodiment of the invention. This embodiment is different from the first embodiment in that a bonded portion17of the test piece4serves also the function of the primary jig3while the dimension of the test object is expanded by fixing the test piece4and the primary jig3to enable the four-point bending test in the first embodiment. This embodiment can be utilized in a case where a material of a large dimension is used in the bonded portion17through the bonding method for the bonding layer42. In this embodiment, the test piece serves also as the primary jig3, so that there is no need to separately prepare the primary jig3. On the other hand, the dimension of the test piece becomes large. In accordance with these features, embodiments can be differently used.

Fifth Embodiment

FIG. 19illustrates the shape of the test piece according to a fifth embodiment of the invention.

This embodiment is different from the first embodiment in that the evaluation of a bulk material is a target while the evaluation containing a bonding portion is a target in the first embodiment. Therefore, a test piece18does not have a bonding layer and a bonding portion. Even in the case of this test piece, similarly to the first embodiment, the test can be performed similarly to the other embodiments by fixing the test piece18to the primary jig3. In a case where a bulk material is evaluated, it is effective that the dimension of the center of the test piece18is set to be smaller than that of the fixing portion in order to prevent the fixing portion between the test piece18and the primary jig3from being broken, so that the flexural rigidity is lowered. At this time, if the thickness is set to small, the flexural rigidity becomes effective at the third power. If the width is set to small, the flexural rigidity is effectively linear. The shape of the test piece may be selected according to the shape of the test piece which can be prepared, the purpose of the test, etc.

Further, even in the first to fourth embodiments, in a case where the strength of the bonding layer42and the bonding interface and the strength of the bonded portion41is small, it is effective that the cross-sectional dimension of the bonding portion is small similarly to this embodiment.

Hitherto, the invention has been specifically described on the basis of the embodiments. However, the invention is not limited to the above embodiments, and various changes can be made in a scope nor departing from the spirit.

REFERENCE SIGNS LIST