JP4457893B2 - Method for investigating bonding reliability of substrate bonding structure - Google Patents

Description

  The present invention relates to a method for investigating the bonding reliability of a substrate bonding structure in which terminals are bonded to each other via a metal.

  Patent Document 1 describes an evaluation method for a semiconductor device in which an electrode metal plated on a pellet is mounted on a substrate via solder, and then the pellet is crushed and an adhesion state between the electrode metal and the solder is evaluated. Yes. In this semiconductor device evaluation method, the adhesion state related to the mounting of the pellet is evaluated by how much the electrode metal after the pellet is crushed adheres to the solder. As a result, it is possible to immediately cope with the occurrence of defects in the semiconductor device due to poor adhesion of the pellets.

  However, in the evaluation method described in Patent Document 1, since the adhesion state between the electrode metal and the solder is only evaluated, the quality of the joining state using the solder (that is, a void or the like is formed in the solder). Etc.) cannot be evaluated.

  On the other hand, as a method for evaluating the quality of the bonding state using solder, for example, in the case of a laminated body in which corresponding terminals of the substrates on which the terminals are formed are bonded by solder, the substrate surface (the terminals are formed). A method is conceivable in which the solder is cut together with the substrate and the terminals in a direction perpendicular to the surface and evaluated from the cross section. That is, the quality of the solder fillet shape with respect to the terminal and whether or not a void is formed in the solder are inspected and evaluated from the formed cross section.

JP-A-2-246124

  However, in the solder evaluation method described above, since the presence or absence of voids can be inspected from only one cross section, it cannot be detected even if voids are formed in places other than the cross section in the solder. Therefore, it is impossible to accurately evaluate the quality of the joining state using solder. If it is inspected whether a void is formed in the solder from a plurality of cross sections obtained by cutting the solder in the thickness direction at a plurality of locations of the solder, the operation becomes very complicated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for investigating the bonding reliability of a substrate bonding structure capable of investigating the bonding state between terminals in a short time and with high accuracy.

Means for Solving the Problems and Effects of the Invention

  The method of investigating the bonding reliability of a substrate bonding structure according to the present invention includes a substrate bonding structure in which a first terminal formed on a first substrate and a second terminal formed on a second substrate are bonded via a metal. In the bonding reliability investigation method, the metal is heated to a temperature lower than its melting point, a heat peeling step of peeling off the first substrate and the second substrate, and affixed to the first terminal after the heat peeling step An inspection step of inspecting the state of adhesion of the metal to the first terminal.

  According to this, the complicated operation | work which cut | disconnects the laminated body of the 1st board | substrate and 2nd board | substrate with which the 1st terminal and the 2nd terminal were joined through the metal in the direction orthogonal to a board | substrate surface is performed in several places. Therefore, the bonding reliability between the first terminal and the second terminal can be investigated in a short time. In addition, since the adhesion state of the metal to the first terminal can be inspected in a cross-section along the direction orthogonal to the stacking direction of the stacked body, the bonding reliability investigation can be performed with high accuracy. Further, since the magnitude of the force required to peel off the first substrate and the second substrate is reduced, the peeling operation can be easily performed. Furthermore, since the heating temperature is lower than the melting point of the metal, the metal does not melt. Therefore, the shape of the metal does not change before and after heating. Therefore, the accuracy of the bonding reliability investigation is further increased.

  In the present invention, in the inspection step, it is preferable to inspect whether or not the flat area of the top surface of the metal exposed in the heat peeling step is a predetermined area or more. Here, the top surface of the metal refers to the surface most distant from the first terminal in the metal adhering to the first terminal after the heat peeling step. For example, in the case where a part of the metal adheres to the first terminal after the heat peeling step and the rest of the metal adheres to the second terminal, the metal fracture surface becomes the top surface, and the metal In the case where everything is attached to the first terminal, the boundary surface between the metal and the second terminal is the top surface. Thereby, it can be investigated reliably whether the 1st terminal and the 2nd terminal are joined with the intensity more than desired joining intensity.

  In the present invention, it is preferable that the plane area of the first terminal is larger than the plane area of the second terminal. This increases the possibility that at least a part of the top surface of the metal attached to the first terminal is exposed on the surface even when the second terminal is peeled off from the second substrate in the heat peeling step. In the inspection process, the metal can be reliably inspected.

  At this time, the predetermined area may be 30% of a plane area of the second terminal. Thereby, it can be investigated reliably whether the 1st terminal and the 2nd terminal are joined with the intensity beyond the minimum joining strength.

  Moreover, in this invention, it is preferable to test | inspect whether the said metal has protruded from the said 1st terminal in the said test process. Thereby, it can be reliably investigated whether or not the protruding metal may be electrically connected to the adjacent terminal.

  Moreover, in this invention, it is preferable to peel off the said 1st board | substrate and the said 2nd board | substrate so that the said 2nd terminal may not peel from the said 2nd board | substrate in the said heat peeling process. According to this, when the second terminal is peeled off from the second substrate and attached to the first terminal together with the metal during the heat peeling step, it becomes an obstacle to inspecting the state of the metal attached to the first terminal. However, according to the present invention, such a problem can be avoided.

  Moreover, in this invention, it is preferable to use what has melting | fusing point below the heat-resistant temperature of a said 1st board | substrate and a said 2nd board | substrate as said metal. Thereby, since the first substrate and the second substrate are not softened, the work of peeling off the first substrate from the second substrate can be easily performed. Furthermore, it is possible to conduct a joint reliability investigation with higher accuracy.

  Moreover, in this invention, it is preferable that the heating temperature of the said metal in the said heat | fever peeling process exists in the range of (melting | fusing point-20 degreeC of the said metal)-(melting point -10 degreeC of the said metal). As a result, the metal is sufficiently soft as long as the metal is not melted, so that the first substrate can be peeled off from the second substrate with a very small force.

  Moreover, in this invention, the said metal is a tin lead (SnPb) alloy or a tin silver copper (SnAgCu) alloy, and the heating temperature of the said metal in the said heat peeling process is 150 degreeC or more and 173 degrees C or less, or 180 degreeC, respectively. It is preferably 190 ° C. or lower. Thereby, the tin lead alloy and tin silver copper alloy suitable as a metal which joins a 1st terminal and a 2nd terminal can be made soft enough in the range which does not fuse | melt.

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

  FIG. 1 is a partial cross-sectional view showing a joint structure of a flexible substrate and a hard substrate investigated by a method for investigating the joint reliability of a substrate joint structure according to an embodiment of the present invention. FIG. 2A is a plan view of a hard substrate, and FIG. 2B is a plan view of a flexible substrate. As shown in FIG. 1, the substrate bonding structure 1 is configured by bonding a hard substrate (first substrate) 11 and a flexible substrate (second substrate) 31 with a conductive metal 2. The hard substrate 11 is made of a glass epoxy resin having a heat resistance temperature of 250 ° C. or higher (generally, the peak temperature during solder reflow is 245 ° C. for tin-silver-copper alloy solder and 215 ° C. for tin-lead alloy solder). And a plurality of terminals (first terminals) 13 to 15 formed on the substrate 12 and connected to electronic components and wiring (both not shown). The base material 12 has a rectangular planar shape as shown in FIG. In the plurality of terminals 13 to 15, the same type of terminals 13 to 15 are arranged along the longitudinal direction of the base material 12, and form a plurality of terminal rows 23 to 25. Each of the terminals 13 to 15 is made of, for example, an Ag-glass frit type conductive material. The terminal 13 has a rectangular planar shape whose short side direction is parallel to the longitudinal direction of the substrate 12. The terminal 14 has a circular planar shape. The terminal 15 has an elliptical planar shape whose longitudinal direction is parallel to the lateral direction of the substrate 12.

  The flexible substrate 31 includes a base material 32 made of a polyimide resin having a heat resistant temperature of 250 ° C. or more, and a plurality of terminals (second terminals) 33 formed on the base material 32 and connected to a plurality of wirings (not shown). ~ 35. As shown in FIG. 2B, the base material 32 has a rectangular planar shape. In the plurality of terminals 33 to 35, the same type of terminals 33 to 35 are arranged along the longitudinal direction of the base material 32 to form a plurality of terminal rows 43 to 45.

  In FIG. 1, the terminals 33 belonging to the terminal row 43 are arranged at positions facing the terminals 15 belonging to the terminal row 25. The terminals 34 belonging to the terminal row 44 are arranged at positions facing the terminals 14 belonging to the terminal row 24. The terminals 35 belonging to the terminal row 45 are arranged at positions facing the terminals 13 belonging to the terminal row 23. As shown in FIGS. 2A and 2B, each of the terminals 33 to 35 has a shape similar to the planar shape of the corresponding terminals 13 to 15 and is slightly smaller than the flat area of the corresponding terminals 13 to 15. It has an area. And the terminal arrange | positioned in the position which mutually opposes is joined through the metal 2 between.

  In the metal 2 in the present embodiment, tin (Sn) is 96.5%, silver (Ag) is 3.0%, copper (Cu) is 0.5%, and the melting point is 222 ° C. (Sn-3.0Ag-0.5Cu) alloy is used. The metal 2 may be a tin silver copper alloy in which the content of each metal is different from that described above. Further, it may be a tin-lead (SnPb) alloy, and in that case, the ratio of tin and lead may be appropriately determined.

  A bonding process between the hard substrate 11 and the flexible substrate 31 will be described. FIG. 3 shows a joining process of the hard substrate 11 and the flexible substrate 31, and (a) is an explanatory view showing a situation in which the metal 2 is printed on the hard substrate placed on the gantry. ) Is an explanatory view showing a state where the terminals of the hard substrate 11 and the flexible substrate 31 are arranged to face each other, and (c) is an explanatory view showing a state in which the flexible substrate 31 is pressed against the hard substrate 11. It is.

  As shown in FIG. 3A, first, the hard substrate 11 is placed on a gantry 51 having a flat upper surface. Next, the paste-like metal 2 is printed on the upper surfaces of the terminals 13 to 15 of the hard substrate 11 placed on the gantry 51. Then, a flux is applied to the surface of the metal 2. Note that the gantry 51 is equipped with a heater (not shown) inside so that the hard substrate 11 can be heated.

  Next, as illustrated in FIG. 3B, the flexible substrate 31 is held on the lower surface of the holding member 52 so that the terminals 33 to 35 of the flexible substrate 31 face downward. Then, the holding member 52 is aligned so that the terminals 33 to 35 of the flexible substrate 31 are arranged at positions facing the corresponding terminals 13 to 15 of the hard substrate 11. In addition, the holding member 52 is equipped with a heater (not shown) inside, so that the flexible substrate 31 can be heated.

  Next, the gantry 51 is heated to 50 ° C. to 100 ° C. to heat the hard substrate 11, and the holding member 52 is gantry 51 while the flexible substrate 31 is heated by the holding member 52 as shown in FIG. The metal 2 is pressed between the terminals 33 to 35 and the terminals 13 to 15. At this time, the gantry 51 and the holding member 52 are controlled so that the metal 2 is heated and held at a temperature between about 120 ° C. and 150 ° C. for a predetermined time and then heated until reaching the melting point. By such control, the flux is activated and an oxide film is hardly formed on the surface of the metal 2. Thereafter, the metal 2 having reached the melting point is rapidly cooled. In this way, the board | substrate joining structure 1 by which the corresponding terminals of each terminal 13-15 of the hard board | substrate 11 and each terminal 33-35 of the flexible substrate 31 were joined via the metal 2 is comprised.

  A method for investigating the bonding reliability of the substrate bonding structure 1 formed through the bonding process described above will be described. FIG. 4 shows the steps of the method of investigating the bonding reliability of the substrate bonding structure according to one embodiment of the present invention. FIG. 4A is an explanatory view showing a state where the substrates bonded to each other are arranged on the hot plate 61. (B) is explanatory drawing which shows the state by which the flexible substrate was peeled off from the hard substrate, (c) is a top view of the hard substrate by which the flexible substrate was peeled off.

  As shown in FIG. 4A, first, the hard substrate 11 and the flexible substrate 31 bonded together are placed on the hot plate 61. And the hot plate 61 is heated and the metal 2 which joined between each terminal is heated to predetermined temperature.

  Here, the relationship between the temperature of metal 2 and the tensile strength will be described with reference to FIG. FIG. 5 shows the above-described tin-silver-copper (Sn-3.0Ag-0.5Cu) alloy, tin-silver-copper (Sn--) containing 96.3% tin, 3.0% silver and 0.7% copper. 3.0Ag-0.7Cu) alloy, tin silver copper (Sn-3.5Ag-0.75Cu) alloy with 95.75% tin, 3.5% silver and 0.75% copper, and tin 4 shows the relationship between the temperature and tensile strength of four types of alloys of tin-lead (Sn-40.0Pb) with 60.0% lead and 40.0% lead. The three types of tin silver-copper alloys have a melting point of about 222 ° C., and the tin-lead alloy has a melting point of about 183 ° C.

  In FIG. 5, when the temperature of each alloy is room temperature (for example, 20 ° C.), the tensile strength of each alloy is about 55 MPa. In the three types of tin-silver-copper alloys, even when the temperature rises, the tensile strength decreases in the same manner, and the tensile strength becomes approximately 10 MPa when the temperature of each alloy is around 200 ° C. On the other hand, with a tin-lead alloy, the tensile strength is approximately 10 MPa at a temperature near 150 ° C. As a result, each alloy has a tensile strength of 10 MPa or less in the temperature range from −20 ° C. to −10 ° C. from the melting point, and becomes sufficiently soft in the range where each alloy does not melt. Therefore, the hard substrate 11 and the flexible substrate 31 can be peeled off with a very small force.

  Moreover, in each tin silver copper alloy, 180 degreeC or more and 190 degrees C or less are the most suitable temperature range. Within this temperature range, the tensile strength of each alloy is 10 MPa to 13 MPa. In other words, the alloy can be sufficiently soft as long as each alloy does not melt. On the other hand, when the alloy temperature exceeds 190 ° C., the tensile strength of each alloy becomes smaller. However, since both the hard substrate 11 and the flexible substrate 31 are heated to 200 ° C. or more, they are too hot and tweezers etc. It becomes more difficult to peel off both substrates with a human hand. That is, both substrates must be peeled off using a special jig. Further, when the alloy temperature is lower than 180 ° C., the alloy does not become so soft, so that a part of the peeled terminal may remain attached to the metal 3 (described later).

  In the tin-lead alloy, the most suitable temperature range is 150 ° C. or more and 173 ° C. or less. Within this temperature range, the tensile strength of the alloy is 10 MPa or less. That is, it can be sufficiently soft as long as the alloy does not melt. On the other hand, when the alloy temperature exceeds 173 ° C., the possibility that the alloy melts increases, and it becomes difficult to inspect the top surface 3a of the metal 3 as described later. In addition, when the alloy temperature is lower than 150 ° C., the alloy does not become so soft, so that a part of the peeled terminal may remain attached to the metal 3.

  In consideration of the relationship between the temperature and tensile strength of each alloy, in this embodiment, the substrates 11 and 31 in the bonded state are heated while the metal 2 is heated to 185 ° C. (predetermined temperature). Take out from the plate 61, and slowly peel off the flexible substrate 31 from the hard substrate 11 so as to separate the terminals 13 to 15 and the terminals 33 to 35 as shown in FIG. (Heat peeling process). At this time, the metal 2 is separated at a portion having the lowest strength. For example, in the case where a void is formed in the metal 2, the metal 2 is likely to be separated at a cross-sectional portion parallel to the substrate surface reduced by the void. That is, the metal 2 is separated at a portion having the smallest cross-sectional area parallel to the substrate surface.

  In the present embodiment, the metal 2 is separated just at the lower surface level of the terminals 33 to 35 of the flexible substrate 31. That is, the metal 3 which is a part of the metal 2 is attached to the terminals 13 to 15 of the hard substrate 11, and the remaining metal 4 of the metal 2 is attached to the terminals 33 to 35 of the flexible substrate 31. Thus, by peeling both the boards 11 and 31 so that the terminals 33 to 35 are not peeled off from the flexible board 31, the peeled terminals 33 to 35 hinder the inspection of the top surface 3 a of the metal 3 in the inspection process described later. do not become. That is, when the terminals 33 to 35 are peeled off from the flexible substrate 31 and attached to the terminals 13 to 15 together with the metal 3 during the heat peeling step, the state of the metal 3 attached to the terminals 13 to 15 is inspected. However, according to the present embodiment, such a problem can be avoided. In order to peel off both the boards 11 and 31 so that the terminals 33 to 35 are not peeled off from the flexible board 31, it is necessary to appropriately adjust the temperature and the peeling speed of the metal 2 when the boards 11 and 31 are peeled off. For example, when the heating temperature of the metal 2 is in a temperature range of 180 ° C. or higher and 190 ° C. or lower and / or the peeling speed is relatively slow, the terminals 33 to 35 are very difficult to peel from the flexible substrate 31.

  According to the modification, if the metal 2 is made of the above-described tin-lead alloy, the bonded substrates 11 and 31 are taken out from the hot plate 61 with the tin-lead alloy heated to 160 ° C., and tweezers are removed. The flexible substrate 31 is slowly peeled off from the hard substrate 11 so that the terminals 13 to 15 and the terminals 33 to 35 are separated from each other in the same manner as described above (heating and peeling step). At this time, since the heating temperature of the tin-lead alloy is in the temperature range of 150 ° C. or higher and 173 ° C. or lower, the above-described effects can be obtained.

  Next, as shown in FIG.4 (c), the adhesion state of the metal 3 adhering to each terminal 13-15 of the hard board | substrate 11 from which the flexible substrate 31 was peeled off is test | inspected visually (inspection process). Here, the inspection standard regarding the adhesion of the metal 3 will be described below. The inspection standard is described using the metal 3 attached to the terminal 14, but the same applies to the metal 3 attached to the terminals 13 and 15. FIG. 6 is an explanatory view showing an adhesion state of the metal 3 attached to the terminal 14 of the hard substrate 11. In FIG. 6, the outer shape of the terminal 34 is drawn with a two-dot chain line in order to make the adhesion state of the metal 3 easier to understand.

  FIG. 6A shows a case where the plane area of the top surface 3 a of the metal 3 attached to the terminal 14 is 30% or less of the plane area of the terminal 34. FIG. 6B shows a case where the plane area of the top surface 3 a of the metal 3 attached to the terminal 14 is 30% or more and 100% or less of the plane area of the terminal 34. FIG. 6C shows a case where the plane area of the top surface 3 a of the metal 3 attached to the terminal 14 is substantially the same as the plane area of the terminal 34. FIG. 6D shows a case where the plane area of the top surface 3 a of the metal 3 attached to the terminal 14 is larger than the plane area of the terminal 34 and smaller than the plane area of the terminal 14. FIG. 6E shows a case where the flat area of the top surface 3 a of the metal 3 attached to the terminal 14 is larger than the flat area of the terminal 34 and smaller than the flat area of the terminal 14, and the metal 3 protrudes from the terminal 14. Show.

  In the inspection process, first, it is inspected whether or not the plane area of the top surface 3a of the metal 3 has reached a predetermined area (30% of the plane area of the terminal 34). In the case shown in FIG. 6A, the plane area of the top surface 3 a of the metal 3 does not reach 30% of the plane area of the terminal 34. In this way, if the top area 3a of the metal 3 does not reach 30% of the plane area of the terminal 34, the thermal shock test (in this embodiment, the metal is connected between the terminals by the metal 2). In the state where 2 is heated to 40 ° C. and 70 ° C., a test in which stress is repeatedly applied 200 times for 30 minutes, respectively, the possibility of fracture increases. In this case, the main cause is insufficient press and / or a small amount of printing of the metal 2 during the bonding process of the substrates 11 and 31, and therefore, when the new bonding process of the substrates 11 and 31 is performed, The pressing force and / or the printing amount of the metal 2 may be increased. In the case of FIGS. 6B, 6C, 6D, and 6E, the plane area of the top surface 3a of the metal 3 reaches 30% of the plane area of the terminal 34, and Since it is within the plane area, it can be judged that the bonding state is good. In this way, by examining whether or not the plane area of the top surface 3a of the metal 3 has reached a predetermined area, it is investigated whether or not the joint strength between the terminals is joined at a strength equal to or greater than the minimum joint strength. be able to.

  Next, in the case of FIG. 6B to FIG. 6E joined at a strength higher than the minimum joining strength, it is inspected whether or not the metal 3 protrudes from the terminal 14. As shown in FIGS. 6B to 6D, there is no particular problem as long as the metal 3 does not protrude from the terminal 14. However, as shown in FIG. If it protrudes, the metal 2 may come into contact with the other terminals 13 to 15 adjacent to the terminal 14, and an electrical short circuit may occur between the terminals. Thus, by inspecting whether or not the metal 3 sticks out of the terminal 14, it is possible to prevent an electrical short circuit between the terminals. In this case, an excessive pressing force and / or a large amount of printed metal 2 at the time of bonding the substrates 11 and 31 are the main causes. In addition, the pressing force and / or the printing amount of the metal 2 may be reduced.

  In addition, an inspection standard when a part 34a of the terminal 34 is peeled off from the flexible substrate 31 and attached to the metal 3 in the heat peeling step will be described. FIG. 7 is an explanatory diagram showing a state in which a part 34 a of the terminal 34 peeled from the flexible substrate 31 is attached to the metal 3 of the terminal 14 of the hard substrate 11. As shown in FIG. 7, when a part 34 a of the terminal 34 is attached to the metal 3, a part of the top surface 3 a of the metal 3 is covered by the part 34 a. In this case, it is inspected whether or not the flat area of the top surface 3a of the metal 3 excluding the region hidden by the part 34a of the terminal 34 reaches 30% or more of the flat area of the terminal 34. Thereby, as described above, it is possible to investigate whether or not the bonding strength between the terminals is bonded with a strength higher than the minimum bonding strength. The part of the terminal 34 is peeled off from the flexible substrate 31 and attached to the metal 3 because the heating temperature of the metal 2 is low and the adhesion force of the metal 2 is large, and the metal 2 is heated to a certain temperature. Thus, it is desirable to suppress the part 34 a of the terminal 34 from adhering to the metal 3. In addition, since a part 34a of the terminal 34 is attached to the metal 3, it can be considered that a large part of the part 34a is the top surface of the metal 3, so that 50% of the part 34a is taken into consideration. Inspect whether or not the flat area, which is obtained by adding the flat area to the flat area of the portion excluding the region hidden by the part 34a of the terminal 34 on the top surface 3a of the metal 3, reaches 30% or more of the flat area of the terminal 34. May be. Even in this case, the same effect as described above can be obtained.

  As described above, according to the method of investigating the reliability of the substrate bonding structure in the present embodiment, the lamination of the hard substrate 11 and the flexible substrate 31 in which the terminals 13 to 15 and the terminals 33 to 35 are bonded via the metal 2. The bonding reliability between the terminals can be investigated in a short time without performing a complicated operation of cutting the structure in a direction perpendicular to the substrate surface (plane of the substrate on which the terminals are formed) at a plurality of locations. In addition, since the adhesion state of the metal 3 of the terminals 13 to 15 can be inspected in a plane in a cross section parallel to the surface direction of the substrate surface, it is possible to conduct a joint reliability survey with high accuracy. This is because the metal 2 is separated from the portion with the lowest strength in the heat peeling process, and therefore, the top surface 3a of the metal 3 formed at that time is inspected to inspect the portion where the strength of the metal 2 is weak. Because it becomes. Moreover, since the flexible substrate 31 is peeled off in a state where the metal 2 is heated, the magnitude of the force required for the peeling is reduced. As a result, the peeling operation can be easily performed. Furthermore, since the heating temperature of the metal 2 is lower than the melting point, the metal 2 does not melt. Therefore, the shape of the metal does not change before and after heating. Therefore, the accuracy of the bonding reliability investigation is further increased.

  Further, since the terminals 13 to 15 of the hard substrate 11 have a larger plane area than the corresponding terminals 33 to 35 of the flexible substrate 31, the terminals 33 to 35 are peeled off and attached to the metal 3 in the heat peeling step. However, since there is a high possibility that at least a part of the top surface 3a of the metal 3 is exposed, the metal 3 can be reliably inspected in the inspection process.

  Moreover, in the heat peeling process, since the flexible substrate 31 is peeled off from the hard substrate 11 in a state where the metal 2 is heated to 185 ° C., the temperatures of the base materials 12 and 32 of the substrates 11 and 31 are lower than the heat resistant temperature. . Therefore, since each board | substrate 11 and 31 does not soften, the operation | work which peels off the flexible substrate 31 from the hard board | substrate 11 can be performed easily. Therefore, it is possible to further investigate the bonding reliability between the terminals with higher accuracy.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. For example, in the above-described embodiment, the heating temperature of the metal 2 in the heat peeling step is 185 ° C., but the printed circuit board is in a state where the metal 2 is heated to at least the room temperature and below the melting temperature of the metal 2. What is necessary is just to peel 31 from the hard board | substrate 11. Further, in the inspection process, it is not necessary to inspect whether the plane area of the top surface 3a of the metal 3 is equal to or greater than a predetermined area or 30% or more of the plane area of the terminal corresponding to the terminal to which the metal 3 is attached. . Moreover, it is not necessary to inspect whether the metal 3 protrudes from the terminal to which the metal 3 is attached. In the heat peeling step, each substrate may be simply peeled off while the metal 2 is heated. Further, the plane area of the terminals 13 to 15 formed on the hard substrate 11 may be the same as or less than the plane area of the corresponding terminals 33 to 35 formed on the printed board 31. Moreover, you may test | inspect the adhesion state of the metal adhering to the terminals 33-35 after a heat peeling process. Further, the metal 2 may have a melting point equal to or higher than the heat resistance temperature of each of the substrates 11 and 31.

It is a fragmentary sectional view which shows the joining structure of the flexible substrate investigated by the joining reliability investigation method of the board | substrate joining structure by one Embodiment of this invention, and a hard substrate. (A) is a top view of a hard substrate, (b) is a top view of a flexible substrate. FIG. 2 illustrates a bonding process between the hard substrate and the flexible substrate illustrated in FIG. 1, and (a) is an explanatory diagram illustrating a situation in which a metal is printed on a hard substrate placed on a gantry, and (b) is a hard substrate. It is explanatory drawing which shows the condition arrange | positioned so that the terminal of a board | substrate and a flexible substrate may oppose, (c) is explanatory drawing which shows the state by which the flexible substrate was pressed with respect to the hard board | substrate. FIG. 6 shows a process of a method for investigating the bonding reliability of a substrate bonding structure according to an embodiment of the present invention, wherein (a) is an explanatory diagram showing a state in which substrates bonded to each other are arranged on a hot plate; ) Is an explanatory view showing a state where the flexible substrate is peeled off from the hard substrate, and (c) is a plan view of the hard substrate where the flexible substrate is peeled off. It is a figure which shows the relationship between the temperature of metal shown in FIG. 1, and tensile strength. It is explanatory drawing which shows the adhesion state of the metal adhering to the terminal of the hard board | substrate. It is explanatory drawing which shows the condition where a part of terminal corresponding to the said terminal adhered to the metal of the terminal of a hard board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate junction structure 2-4 Metal 3a Top surface 11 Hard substrate (1st board | substrate)
12 Substrate 13-15 Terminal (first terminal)
31 Flexible substrate (second substrate)
32 Substrate 33-35 Terminal (second terminal)

Claims (10)

In the bonding reliability investigation method of the substrate bonding structure in which the first terminal formed on the first substrate and the second terminal formed on the second substrate are bonded through a metal,
A heating and peeling step of peeling the first substrate and the second substrate in a state where the metal is heated to a temperature lower than its melting point;
An inspection step of inspecting a state of adhesion of the metal adhering to the first terminal after the heat peeling step to the first terminal.   2. The bonding reliability of the substrate bonding structure according to claim 1, wherein in the inspection step, it is inspected whether or not a flat area of the top surface of the metal exposed in the heat peeling step is a predetermined area or more. Survey method.   The method for investigating the bonding reliability of a substrate bonding structure according to claim 1, wherein the plane area of the first terminal is larger than the plane area of the second terminal.   The method for investigating the bonding reliability of a substrate bonding structure according to claim 3, wherein the predetermined area is 30% of a flat area of the second terminal.   5. The method for investigating the bonding reliability of a substrate bonding structure according to claim 1, wherein in the inspection step, it is inspected whether or not the metal protrudes from the first terminal.   The said heat peeling process WHEREIN: The said 1st board | substrate and the said 2nd board | substrate are peeled off so that the said 2nd terminal may not peel from the said 2nd board | substrate, The any one of Claims 1-5 characterized by the above-mentioned. Method for investigating the bonding reliability of substrate bonding structures.   The bonding reliability of the substrate bonding structure according to claim 1, wherein the metal has a melting point lower than a heat resistant temperature of the first substrate and the second substrate. Method.   8. The heating temperature of the metal in the heat peeling step is in a range of (melting point of the metal—20 ° C.) to (melting point of the metal—10 ° C.). The method for investigating the bonding reliability of the substrate bonding structure according to the item. The metal is a tin-lead (SnPb) alloy;
The method for investigating the bonding reliability of a substrate bonding structure according to any one of claims 1 to 7, wherein a heating temperature of the metal in the heat peeling step is 150 ° C or higher and 173 ° C or lower. The metal is a tin silver copper (SnAgCu) alloy,
The method for investigating the bonding reliability of a substrate bonding structure according to any one of claims 1 to 7, wherein a heating temperature of the metal in the heat peeling step is 180 ° C or higher and 190 ° C or lower.

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