Electronic component module and method for manufacturing electronic component module

Abstract

An electronic component module formed with the use of a copper particle paste which can ensure that even the inner part of a joint material is sintered, where copper particles are excellent in oxidation resistance, and a joint part is provided with high joint reliability; and a method for manufacturing the module.

Claims

1. An electronic component module comprising: a structure such that an external terminal included in an electronic component is electrically and mechanically connected to an object to be connected, with a joint material interposed therebetween, wherein the joint material is formed by making a copper particle paste sintered, the copper particle paste containing: copper particles having a particle size peak in a range of 0.1 m to 5.0 m in a particle size distribution and an average crystallite diameter before sintering in a range of 30 nm to 100 nm, and including, on particle surfaces, no dispersant that suppresses agglomeration; and an organic compound that achieves a reduction action at a firing temperature for making the copper particles sintered.

2. The electronic component module according to claim 1, wherein the joint material is a copper sintered body with an average crystallite diameter in a range of 60 nm to 150 nm for the sintered copper particles.

3. The electronic component module according to claim 1, wherein the organic compound is an organic compound having a hydroxy group.

4. The electronic component module according to claim 1, wherein the organic compound includes at least one selected from the group consisting of triethanolamine, glycerin, ethylene glycol, triethylene glycol, diethylene glycol, and dipropylene glycol.

5. The electronic component module according to claim 1, wherein the object to be connected is a mounting electrode provided on the circuit board.

6. The electronic component module according to claim 1, wherein the object to be connected is a metallic terminal attached to the external terminal.

7. A method for manufacturing an electronic component module comprising a structure such that an external terminal included in an electronic component is electrically and mechanically connected to an object to be connected, with a joint material interposed therebetween, the method comprising the steps of: locating the electronic component and the object to be joined such that the external terminal of the electronic component is opposed to the object to be connected, with a copper particle paste interposed therebetween, the copper particle paste containing copper particles having a particle size peak in a range of 0.1 m to 5.0 m in a particle size distribution and an average crystallite diameter before sintering in a range of 30 nm to 100 nm, and including, on particle surfaces, no dispersant that suppresses agglomeration, and an organic compound that achieves a reduction action at a firing temperature for making the copper particles sintered; and carrying out a heat treatment to cause the copper particles included in the copper particle paste to be sintered, thereby forming a copper sintered body of 60 nm to 150 nm in average crystallite diameter for the copper particles, and thus joining the external terminal of the electronic component and the object to be connected, with the copper sintered body interposed therebetween.

8. The method for manufacturing an electronic component module according to claim 7, wherein the heat treatment is carried out without applying an outside force, with the electronic component disposed on the object to be joined, such that the external terminal of the electronic component is opposed to the object to be connected, with the copper particle paste interposed therebetween.

9. The method for manufacturing an electronic component module according to claim 7, wherein the heat treatment is carried out in an inert atmosphere.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a diagram schematically illustrating a step of a sintering process for copper particles for use in a copper particle paste.

(2) FIG. 1B is a diagram schematically illustrating another step of the sintering process for copper particles for use in the copper particle paste.

(3) FIG. 1C is a diagram schematically illustrating yet another step of the sintering process for copper particles for use in the copper particle paste.

(4) FIG. 1D is a diagram schematically illustrating yet another step of the sintering process for copper particles for use in the copper particle paste.

(5) FIG. 2 is a diagram illustrating a joint part joined with the use of the copper particle paste.

(6) FIG. 3 is a diagram for explaining a method for measuring the joint strength of joint part joined with the use of the copper particle paste.

(7) FIG. 4A is a micrograph (SEM image) showing the state of copper particles before firing in a copper particle paste using the copper particles of 56.7 nm in average crystallite diameter.

(8) FIG. 4B is a micrograph (SEM image) showing the state of the copper particles after firing in the copper particle paste using the copper particles of 56.7 nm in average crystallite diameter.

(9) FIG. 5A is a micrograph (SEM image) showing the state of copper particles before firing in a copper particle paste using the copper particles of 107.2 nm in average crystallite diameter.

(10) FIG. 5B is a micrograph (SEM image) showing the state of the copper particles after firing in the copper particle paste using the copper particles of 107.2 nm in average crystallite diameter.

(11) FIG. 6A is a diagram for confirming an action of triethanolamine as a reductant, which illustrates an XRD chart in the case of heating a copper (I) oxide powder with the triethanolamine applied for 10 min at 230 C.

(12) FIG. 6B is a diagram for confirming an action of triethanolamine as a reductant, which illustrates an XRD chart in the case of heating a copper (I) oxide powder with the triethanolamine applied for 10 min at 200 C.

(13) FIG. 7 is a diagram illustrating the configuration of an electronic component module according to a First Embodiment of the present disclosure.

(14) FIG. 8 is a diagram illustrating the configuration of an electronic component module according to a Second Embodiment of the present disclosure.

(15) FIG. 9 is a micrograph (SEM image) of a vicinity of the joint part between an electronic component and a circuit board in the electronic component module according to the Second Embodiment of the present disclosure.

(16) FIG. 10 is a diagram illustrating the configuration of an electronic component module according to a Third Embodiment of the present disclosure.

DETAILED DESCRIPTION

(17) Features of the present disclosure will be described in more detail below with reference to embodiments of the present disclosure.

First Embodiment

(18) The electronic component module according to a First Embodiment of the present disclosure is an electronic component module that has a structure such that an external terminal included in an electronic component is electrically and mechanically connected to an object to be connected, with a joint material interposed therebetween, formed by making a copper particle paste sintered.

(19) For preparing the copper particle paste to serve as the junction material, copper particles were prepared first with the particle size peak of the particle size distribution in the range of 0.1 to 5.0 m as copper particles, and with the average crystallite diameter before sintering in the range of 30 to 100 nm.

(20) In addition, liquid triethanolamine at normal temperature was prepared as an organic compound for achieving a reduction action at the firing temperature in sintering for the copper particles.

(21) Then, the copper particles and the triethanolamine were combined in such a proportion of 87:13 in ratio by weight, and subjected to kneading to prepare a copper particle paste.

(22) It is to be noted that the particle size peak of the particle size distribution for the copper particles was obtained by the following method. First, the copper particles were observed with the use of a scanning electron microscope, the horizontal feret's diameter was measured for 200 particles in the field of view. Then, the observed measurement values were converted to spheres to calculate the average volume particle diameter, and from the result, the average particle peak was obtained.

(23) In addition, the average crystallite diameter before sintering was obtained by the following method. First, the copper particles were subjected to an X-ray diffraction measurement, thereby finding three peaks of peaks <111>, <200>, and <311>. Then, crystallite diameters were calculated by a Rietveld method with the use of the three peaks obtained, and the average value for the diameters was regarded as the average crystallite diameter.

(24) <Evaluation of Copper Particle Paste>

(25) (1) Joint Strength

(26) With the use of the copper particle paste prepared in the way described above, oxygen-free copper sample pieces were joined to each other and checked for joint strength by the method described below.

(27) In this regard, as shown in FIG. 2, a first oxygen-free copper sample piece 21 of 5 mm5 mm in planar size and 1 mm in thickness and a second oxygen-free copper sample piece 22 of 3 mm3 mm in planar size and 1 mm in thickness were joined with a copper sintered body 23 obtained by firing the copper particle paste prepared in the way described above.

(28) For joining the first oxygen-free copper sample piece 21 and the second oxygen-free copper sample piece 22 with the use of the copper particle paste, the copper particle paste was applied for 40 m in coating thickness onto the first oxygen-free copper sample piece 21 with the use of a metal mask provided with through holes that cause the copper particle paste to pass therethrough (through holes of 2000 m in diameter and circular in planar shape).

(29) Then, the second oxygen-free copper sample piece 22 was disposed on the copper particle paste applied to the first oxygen-free copper sample piece 21, and subjected to firing under the conditions of firing temperature: 230 C., firing time: 60 min, and firing atmosphere: nitrogen without particularly applying any stress, thereby, as shown in FIG. 2, joining the first oxygen-free copper sample piece 21 and the second oxygen-free copper sample piece 22 with the joint material (the copper sintered body of the copper particle paste sintered) 23 interposed therebetween.

(30) Then, the joint strength between the first oxygen-free copper sample piece 21 and the second oxygen-free copper sample piece 22 was measured. The joint strength was measured by measuring the shear strength with the use of a general bond tester Dage 4000 from Dage.

(31) It is to be noted that for the measurement, as shown in FIG. 3, the lower first oxygen-free copper sample piece 21 was fixed with a fixing jig, and shearing was applied at a shear rate of 50 m/s and a distance of 50 m from the surface of the oxygen-free copper sample piece 21 to a head of the tool with the use of a shearing tool 24 of 4 mm in tool width. Then, the fracture surface was photographed, and the joint area was measured by image processing.

(32) Then, the shear strength value was divided by the joint area to obtain the shear strength (MPa) per unit area.

(33) As a result, it has been confirmed that a high strength of 36 MPa is achieved as the shear strength.

(34) (2) In Regard to Average Crystallite Diameter Before and After Firing

(35) The average crystallite diameter before firing was measured by a method of applying an ink of the copper particle paste onto a glass plate, calculating crystallite diameters by a Rietveld method from the three peaks of peaks <111>, <200>, and <311> obtained by the method described above, that is, the X-ray diffraction measurement, and figuring out the average value for the diameters. The average crystallite diameter after firing was measured by a method of extracting the sintered body subjected to shearing with the use of tweezers, disposing the body on a glass plate, calculating crystallite diameters by a Rietveld method from the three peaks of peaks <111>, <200>, and <311> obtained by the method described above, that is, the X-ray diffraction measurement, and figuring out the average value for the diameters.

(36) More specifically, the copper particle paste was applied by printing for 40 m in coating thickness onto the first non-oxygen copper sample piece 21 with the use of a metal mask provided with through holes of 2000 m (2 mm) in diameter and circular in planar shape, and subjected to firing under the conditions of firing temperature: 230 C., firing time: 60 min, and firing atmosphere: nitrogen, thereby checking the crystallite diameters before and after firing.

(37) As a result, it has been confirmed that the average crystallite diameter of 62 nm at the stage before the firing is increased up to 102 m after the firing.

(38) As just described, when the average crystallite diameter at the stage before the firing is reduced so as to meet the range specified by the requirement of the present disclosure, it becomes possible to prevent agglomeration of the copper particles without using any dispersant, and the mechanism described previously with reference to FIGS. 1A to 1D makes it possible to achieve sintering at lower temperatures. As a result, it becomes possible to form a joint material of a high-density copper sintered body of which voids account for a small proportion, without requiring any firing at high temperatures.

(39) FIGS. 4A and 4B and 5A and 5B show micrographs (SEM images) of copper particles before and after firing copper particle pastes using the copper particles within the range specified by the requirement of the present disclosure and the copper particles outside the range.

(40) It is to be noted that FIG. 4A is a micrograph (SEM image) showing the state of the copper particles before the firing in the copper particle paste using the copper particles of 56.7 nm in average crystallite diameter within the range specified by the requirement of the present disclosure, whereas FIG. 4B is a micrograph (SEM image) showing the state of the copper particles after the firing.

(41) In addition, FIG. 5A is a micrograph (SEM image) showing the state of the copper particles before the firing in the copper particle paste using the copper particles of 107.2 nm in average crystallite diameter outside the range specified by the requirement of the present disclosure, whereas FIG. 5B is a micrograph (SEM image) showing the state of the copper particles after the firing.

(42) As can be seen from FIGS. 5A and 5B, in the case of the copper particle paste using the copper particles 10 of 107.2 nm in average crystallite diameter outside the range specified by the requirement of the present disclosure, the copper particles 10 have been hardly found to undergo neck growth.

(43) In contrast, as can be seen from FIGS. 4A and 4B, in the case of the copper particle paste using the copper particles 10 of 56.7 nm in average crystallite diameter within the range specified by the requirement of the present disclosure, it has been confirmed that the copper particles 10 undergo neck growth, that is, are sintered sufficiently.

(44) (3) Evaluation of Triethanolamine for Reducing Performance

(45) The triethanolamine used in the copper particle paste described above as an organic compound (solvent) that achieves a reduction action at a firing temperature for making the copper particles sintered was checked for reducing performance by the following method.

(46) For confirming the reducing performance of the triethanolamine, an experiment was carried out as described below with the use of a commercially available copper (I) oxide (Cu.sub.2O) powder. First, a copper (I) oxide powder was disposed on a glass substrate, liquid triethanolamine at normal temperature was applied thereto, and after heating for 10 min at a predetermined temperature on a hot plate, a composition analysis was carried out by XRD.

(47) The results in the case of heating for 10 min at 200 C., and in the case of heating for 10 min at 230 C. as a temperature condition near the melting point of Sn commonly used as an electrode material will be described herein with respect to FIGS. 6A and 6B.

(48) It is to be noted that FIG. 6A is a diagram showing an XRD chart in the case of heating the copper (I) oxide powder with the triethanolamine applied for 10 min at 230 C. as a temperature condition near the melting point of Sn commonly used as an electrode material, whereas FIG. 6B is a diagram showing an XRD chart in the case of heating the copper (I) oxide powder with the triethanolamine applied for 10 min at 200 C.

(49) As a result, as shown in FIG. 6B, it has been confirmed that in the case of the heating temperature of 200 C., there is no Cu peak found while the peak of copper (I) oxide (Cu.sub.2O) remains high, thus failing to achieve any reduction action.

(50) On the other hand, it has been confirmed that in the case of the temperature of 230 C. as a temperature condition near the melting point of Sn commonly used as an electrode material, as shown in FIG. 6A, there is a clear Cu peak found while the peak of copper (I) oxide (Cu.sub.2O) is reduced, that is, a reduction action is achieved.

(51) It is to be noted that while the triethanolamine was used as an organic compound that has reducing performance in this embodiment, it has been confirmed that organic compounds having a hydroxy group have reducing performance, such as glycerin, ethylene glycol, triethylene glycol, diethylene glycol, and dipropylene glycol, besides triethanolamine, and it is also possible to use these substances as an organic compound that has reducing performance.

(52) Further, it is also possible to use yet other organic compounds as the organic compound for achieving a reduction action. While it is desirable in the present disclosure to use a liquid organic compound at normal temperature as the organic compound for achieving a reduction action mentioned above, it is also possible to use solid substances at normal temperature in some cases, and in that regard, the substances can be dissolved in other solvents, if necessary, and used.

(53) FIG. 7 is a diagram illustrating an electronic component module according to an embodiment (First Embodiment) of the present disclosure, which has a structure electrically and mechanically connected to objects to be connected, with a joint material interposed therebetween, formed by the sintered copper particle paste prepared in the way described above.

(54) This electronic component module 30 is an electronic component module that has a structure such that as shown in FIG. 7, gold bumps (external terminals) 33 formed on surface electrodes 32 of an IC chip (electronic component according to the present disclosure) 31 are electrically and mechanically connected onto mounting electrodes (objects to be connected) 36 of, for example, copper, formed on a circuit board 35, with a copper sintered body (joint material) 34 interposed therebetween, and such that the IC chip (electronic component) 31 is sealed with a sealing resin 37.

(55) It is to be noted that while FIG. 7 shows the structure of the IC chip 31 mounted on the circuit board 35, other electronic components may be mounted such as a chip capacitor and a chip resistance.

(56) The copper sintered body 34 for the joint material mentioned above is formed by baking the copper particle paste mentioned above, and is a copper sintered body with an average crystallite diameter within the range of 60 to 150 nm after sintering.

(57) Next, a method for manufacturing the electronic component module 30 will be described. For manufacturing the electronic component module, the circuit board 35 is first prepared which includes mounting electrodes (land electrodes) 36 on the surface thereof.

(58) In addition, the IC chip (the electronic component according to the present disclosure) 31 is prepared which has the gold bumps (external terminals) 33 formed on the surface electrodes 32.

(59) Then, the copper particle paste mentioned above is applied onto the mounting electrodes 36 on the circuit board 35, and the IC chip (electronic component) 31 is mounted onto the mounting electrodes 36 on the circuit board 35 in such a manner that the gold bumps (external terminals) 33 on the IC chip (electronic component) 31 are located on the copper particle paste applied onto the mounting electrodes 36 on the circuit board 35. Then, without particularly pressing the IC chip (electronic component) 31 toward the circuit board 35, the copper particles included in the copper particle paste are subjected to sintering by firing at 230 C. in a nitrogen atmosphere (inert atmosphere), thereby connecting the gold bumps (external terminals) 33 to the mounting electrode (objects to be connected) 36 with a copper sintered body (joint material) 34 interposed therebetween.

(60) Then, the IC chip (electronic component) 31 mounted on the circuit board 35 is subjected to sealing with the sealing resin 37. Thus, the electronic component module 30 is obtained which is structured as shown in FIG. 7.

(61) This electronic component module 30 has a structure such that the gold bumps (external terminals) 33 on the IC chip (electronic component) 31 are electrically and mechanically connected to the mounting electrodes (objects to be connected) 36 of the circuit board 35 to be connected, with the copper sintered body (joint material) 34 with an average crystallite diameter in the range of 60 to 150 nm after the firing, which is formed by baking the copper particle paste mentioned above.

(62) Accordingly, a highly reliable electronic component module can be provided where the gold bumps (external terminals) 33 on the IC chip (electronic component) 31 and the mounting electrodes (objects to be connected) 36 are reliably joined with the joint material 34 of the high-density copper sintered body of which voids account for a small proportion.

(63) In addition, according to the method for manufacturing the electronic component module as described above, the heat treatment is carried out with the IC chip (electronic component) 31 and the mounting electrodes (objects to be connected) 36 located such that the gold bumps (external terminals) 33 on the IC chip (electronic component) 31 are opposed to the objects 36 to be connected with the copper particle paste interposed therebetween to serve as the copper sintered body 34 after firing, thereby making it possible to join the gold bumps (external terminals) 33 on the IC chip (electronic component) 31 and the objects 36 to be connected with the joint material (copper sintered body) 34 of the high-density copper sintered body of which voids account for a small proportion.

(64) Accordingly, a highly reliable electronic component module can be manufactured efficiently where the gold bumps (external terminals) 33 on the IC chip (electronic component) 31 and the objects 36 to be connected are joined reliably.

(65) In addition, the heat treatment is carried out without applying any outside force, thus making it possible to reduce damage to the IC chip (electronic component) 31, and making it possible to form minute joint parts.

(66) It is to be noted that while a case where the bumps on the IC chip (electronic component) are composed of gold, whereas the mounting electrodes (land electrodes) are composed of copper has been explained as an example in the First Embodiment, it is possible to use Ag, Cu, Ni, AgPd, and the like as a constituent material for the bumps, and it is possible to use Au, Ag, Ni, AgPd, and the like as a constituent material for the mounting electrodes (land electrodes).

Second Embodiment

(67) FIG. 8 is a diagram illustrating an electronic component module according to an embodiment (Second Embodiment) of the present disclosure.

(68) This electronic component module 40 is an electronic component module that has a structure such that external terminals 42 of copper provided on a multilayer ceramic capacitor 41 are electrically and mechanically connected to mounting electrodes (objects to be connected in the present disclosure) 46 of copper formed on a circuit board (alumina board) 45, with a copper sintered body (joint material) 44 interposed therebetween, as shown in FIG. 8.

(69) In this electronic component module 40, it has been confirmed that the joint strength is 45 MPa between the mounting electrodes (land electrodes) 46 and the external electrodes 42.

(70) This electronic component module 40 is formed by applying a copper particle paste to serve as the copper sintered body 44 after firing onto the mounting electrodes (land electrodes) 46 formed on the surface of the circuit board 45, disposing the multilayer ceramic capacitor 41 with the external terminals 42 formed at both ends such that the mounting electrodes (land electrodes) 46 and the external terminals 42 are opposed with the copper particle paste interposed therebetween, and carrying out firing at 230 C. in a nitrogen atmosphere (inert atmosphere) without particularly applying any outside force, thereby providing the sintered copper particles included in the copper particle paste.

(71) FIG. 9 is a micrograph (SEM image) of a vicinity of the joint part between the multilayer ceramic capacitor 41 and the circuit board 45.

(72) From FIG. 9, it is found that the external terminals 42 of copper on the multilayer ceramic capacitor 41 are joined to the mounting electrodes 46 of copper on the circuit board 45 with the joint material of the copper sintered body 44 interposed therebetween.

(73) From the Second Embodiment herein, it is found that without forming any Sn plated layer, solder plated layer, or the like on the external terminals 42 on the multilayer ceramic capacitor 41, the external terminals 42 of Cu on the multilayer ceramic capacitor 41 and the mounting electrodes 46 of copper on the circuit board 45 are joined directly with the use of the copper particle paste mentioned above, thereby making it possible to achieve highly reliable joints without forming any intermetallic compound.

(74) It is to be noted that the constituent material of the external terminals on the multilayer ceramic capacitor is not limited to copper, but may be formed from gold, silver, silver-palladium, nickel, or the like. In addition, the copper may contain glass.

Third Embodiment

(75) FIG. 10 is a diagram illustrating an electronic component with metallic terminals (a broad-sense electronic component module) according to another embodiment (Third Embodiment) of the present disclosure.

(76) The electronic component (for example, multilayer ceramic capacitor) 50 shown in FIG. 10 is the electronic component 50 with metallic terminals, which is obtained by joining metallic terminals (L-shaped metallic terminals in this example) 53 to external electrodes 52 formed on the surface of an electronic component element 51, with a copper sintered body (joint material) 54 formed by baking the copper particle paste mentioned above.

(77) The electronic component 50 with the metallic terminals according to the Third Embodiment can be prepared easily and reliably, for example, by applying the copper particle paste to the external electrodes 52 formed on the electronic component element 51 or the metallic terminals 53, and applying a heat treatment under a predetermined condition with both the electrodes and terminals joined, thereby providing the sintered copper particles in the copper particle paste.

(78) It is to be noted that the electronic component 50 with the metallic terminals has high reliability, because the external electrodes 52 on the electronic component element 51 and the metallic terminals 53 to be connected are joined reliably with the joint material (copper sintered body) 54 of the high-density copper sintered body of which voids account for a small proportion.

(79) It is to be noted that the metallic terminals are not to be considered limited to the configuration as mentioned above, but may be metallic terminals constituting another part of the electronic component. Also in that case, a similar effect can be achieved. The constituent material of the metallic terminal 53 is not particularly limited, but it is possible to use a material composed of gold, silver, copper, silver-palladium, nickel, or the like.

(80) In addition, the copper particle paste mentioned above is not to be considered limited to the application such as the electronic component modules described in the First and Second Embodiments and the electronic component with the metallic terminals (broad-sense electronic component module) described in the Third Embodiment, but it is also possible to apply the paste to intended uses such as, for example:

(81) (a) a connection material for an integrated component provided within a multilayer ceramic substrate;

(82) (b) a via hole conductor forming material for interlayer connection;

(83) (c) an electrode forming material for forming wirings and electrodes;

(84) (d) a conductive sealing material; and

(85) (e) a connection material for die bonding.

(86) The present disclosure is not to be considered limited to the embodiments described above in yet other respects, but various applications and modifications can be made within the scope of the disclosure.