LTCC substrate module

Abstract

An LTCC substrate module (101) comprises an LTCC substrate (1) that is formed by stacking a plurality of ceramic layers (2). The LTCC substrate (1) includes a series via structure (70) that is formed so as to penetrate a first group of ceramic layers in the thickness direction, the first group of ceramic layers being at least some of the plurality of ceramic layers (2) and being arranged in the thickness direction. The series via structure (70) is a series of a plurality of series via constituent elements that respectively correspond to the first group of ceramic layers. The plurality of direct via constituent elements include a first type of constituent element (71) that has a trapezoidal cross-sectional shape as viewed in a cross section cut along any direction parallel to the thickness direction, and a second type of constituent element (72) that has a recess such that the lateral outline of the cross-sectional shape thereof is depressed in a wedge-like manner from one side, as viewed in any cross section cut parallel to the thickness direction.

Description

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[0001] The present invention relates to an LTCC substrate module.

[0002] A configuration in which an LSI is mounted on one surface of a substrate having a plurality of through-holes is described in Japanese Patent No. 5387255 (Patent Document 1). Some vias are formed on the inner peripheral surface of the through-holes by a conductive metal. The vias are disposed on the one surface side of the substrate within the through-holes. In the through-holes, in addition to the vias, a heat dissipation filler is also disposed. The heat dissipation filler is disposed on the other surface side of the substrate within the through-holes. In the through-holes, the heat dissipation filler is in contact with the vias. According to Patent Document 1, with this configuration, it is said that heat generated from the LSI can be efficiently dissipated from both surfaces of the substrate.

[0003] Japanese Patent No. 5387255

[0004] An LTCC (Low Temperature Co-fired Ceramics) substrate formed by stacking a plurality of ceramic layers is known. For electrical connection or for promoting heat dissipation, it is conceivable to provide a series via structure inside the LTCC substrate. In this case, through-holes are formed in each ceramic layer, and conductor vias for one layer are formed so as to fill the through-holes with a conductor. By stacking the ceramic layers in this state, the conductor vias of each layer gather and are continuous in the thickness direction, and a series via structure is formed.

[0005] When a structure similar to the structure described in Patent Document 1 is realized in an LTCC substrate, a problem arises as to how to prevent cracks that may occur in the LTCC substrate due to heat generation of components mounted on the surface of the substrate. Also, variations in impedance due to electrical path differences caused by misalignment of the positions of the respective ceramic layers during lamination should be suppressed as much as possible.

[0006] Further, when filling the through-holes formed in each ceramic layer with a conductive paste to be a conductor via, overfilling may occur, and it may appear as a bulge on the surface of the substrate after lamination.

[0007] Therefore, the present invention aims to provide an LTCC substrate module that can prevent crack generation due to heat generation of components, suppress impedance variations caused by electrical path differences due to misalignment when forming a series via structure by lamination, and suppress bulging due to overfilling of conductive paste.

[0008] To achieve the above objective, an LTCC substrate module according to the present invention comprises an LTCC substrate formed by stacking a plurality of ceramic layers, the LTCC substrate comprises a series via structure formed to penetrate in the thickness direction of a first group of ceramic layers arranged in the thickness direction, the series via structure being a series of a plurality of series via components corresponding to each of the first group of ceramic layers, the plurality of series via components including a first type of component whose cross-sectional shape is trapezoidal when viewed in a cross-section parallel to the thickness direction, and a second type of component having a recess in which the lateral outline of the cross-sectional shape enters in a wedge shape from either side when viewed in a cross-section parallel to the thickness direction.

[0009] According to the present invention, since the LTCC substrate is equipped with a series via structure, heat dissipation is performed smoothly, and as a result, crack generation due to heat generation of components can be prevented. Furthermore, since the series via structure includes a second type component having a wedge-shaped recess that enters from either side, impedance variations caused by electrical path differences due to positional misalignment when forming the series via structure by lamination can be suppressed, and bulging due to overfilling of conductive paste can be suppressed.

[0010] This is a cross-sectional view of the LTCC substrate module in Embodiment 1 of the present invention mounted on a mother board. This is a first enlarged cross-sectional view showing a combination of one Type 2 component included in the LTCC substrate module in Embodiment 1 of the present invention and Type 1 components arranged above and below it. This is a second enlarged cross-sectional view showing a combination of one Type 2 component included in the LTCC substrate module in Embodiment 1 of the present invention and Type 1 components arranged above and below it. This is a perspective view of the Type 2 component included in the LTCC substrate module in Embodiment 1 of the present invention. This is an explanatory diagram using a plan view of the Type 2 component included in the LTCC substrate module in Embodiment 1 of the present invention. This is a third enlarged cross-sectional view showing a combination of one Type 2 component included in the LTCC substrate module in Embodiment 1 of the present invention and Type 1 components arranged above and below it. This is a partially enlarged cross-sectional view of the LTCC substrate module in Embodiment 2 of the present invention. This is a partially enlarged cross-sectional view of a modified example of the LTCC substrate module in Embodiment 2 of the present invention. This is a first explanatory diagram of the manufacturing method of the LTCC substrate module in Embodiment 2 of the present invention. This is a second explanatory diagram of the manufacturing method of the LTCC substrate module in Embodiment 2 of the present invention. This is a third explanatory diagram of the method for manufacturing an LTCC substrate module according to Embodiment 2 of the present invention.

[0011] The dimensional ratios shown in the drawings do not necessarily accurately reflect reality, and may be exaggerated for illustrative purposes. In the following explanation, the concepts of "up" or "down" do not necessarily refer to absolute up or down, but rather to relative up or down within the illustrated orientation.

[0012] (Embodiment 1) An LTCC substrate module in Embodiment 1 according to the present invention will be described with reference to Figures 1 to 6. Figure 1 shows the LTCC substrate module 101 mounted on the mother board 501.

[0013] The LTCC substrate module 101 comprises an LTCC substrate 1 formed by stacking a plurality of ceramic layers 2. The LTCC substrate 1 has a first surface 1a and a second surface 1b facing opposite directions. The LTCC substrate 1 comprises a series via structure 70 formed to penetrate in the thickness direction of a first group of ceramic layers arranged in the thickness direction, which constitute at least a portion of the plurality of ceramic layers 2. The series via structure 70 is a series of a plurality of series via components corresponding to each of the first group of ceramic layers. The plurality of series via components include a first type component 71 whose cross-sectional shape is trapezoidal when cut in any direction parallel to the thickness direction, and a second type component 72 which has a recess in which the lateral outline of the cross-sectional shape enters in a wedge shape from either side when cut in any direction parallel to the thickness direction.

[0014] The LTCC substrate 1 is formed by stacking multiple ceramic layers 2, but the multiple ceramic layers 2 are already integrated, and the boundaries between the ceramic layers 2 may not be visible. In Figure 1, the boundaries between the ceramic layers 2 are not shown. Surface electrodes 11 are provided on the second surface 1b of the LTCC substrate 1. A heat dissipation member 5 is provided on the first surface 1a of the LTCC substrate 1. The heat dissipation member 5 may be a metal film. The heat dissipation member 5 is intended to facilitate the smooth dissipation of heat from the LTCC substrate 1 to the motherboard 501.

[0015] A heat-generating electronic component 3 is mounted on the second surface 1b of the LTCC substrate 1. The electronic component 3 may be, for example, a heterojunction bipolar transistor. The electronic component 3 has a plurality of terminals 31 on the side closest to the LTCC substrate 1. Each of the terminals 31 of the electronic component 3 is electrically connected to the surface electrode 11 of the LTCC substrate 1 via solder 12. The electronic component 3 is covered with a sealing resin 6. The second surface 1b of the LTCC substrate 1 is also covered with a sealing resin. The top and side surfaces of the sealing resin 6 are covered with a shielding film 8. The side surfaces of the LTCC substrate 1 are also covered with a shielding film 8.

[0016] Multiple conductor patterns 7 are arranged inside the LTCC substrate 1. Some of the multiple conductor patterns 7 are electrically connected to a shielding film 8 on the side surface of the LTCC substrate 1. In the example shown in Figure 1, five series via structures are shown inside the LTCC substrate 1, but for illustrative purposes, one representative of them is enclosed in a line as a series via structure 70. The concept of "first group of ceramic layers" refers to at least some of all the ceramic layers 2 that make up the LTCC substrate 1. That is, the first group of ceramic layers may be all or some of all the ceramic layers 2 that make up the LTCC substrate 1. The first group of ceramic layers does not necessarily mean all the ceramic layers 2 that make up the LTCC substrate 1. The number of ceramic layers in the first group may be less than the number of the multiple ceramic layers. However, with respect to one series via structure 70 illustrated in Figure 1, the first group of ceramic layers coincides with all the ceramic layers that make up the LTCC substrate 1. In the example shown in Figure 1, the first group of ceramic layers corresponding to the series via structure 70 refers to all 10 ceramic layers. In the example shown in Figure 1, the series via structure 70 is a series of 10 series via components. Among the 10 series via components are 9 first-type components 71 and 1 second-type component 72.

[0017] When the vertical length of a particular series via structure is shorter, the concept of the "first group of ceramic layers" means a set of ceramic layers 2 that is fewer than the total number of ceramic layers 2 required to constitute the LTCC substrate 1. In the example shown in Figure 1, in the series via structures visible first and second from the left, the first group of ceramic layers is fewer than the total number of ceramic layers 2 required to constitute the LTCC substrate 1. In the series via structure visible first from the left, the first group of ceramic layers refers to the five ceramic layers from the bottom. This series via structure does not include the second type of component 72. Such series via structures may be present in the LTCC substrate module 101.

[0018] In the series via structure shown second from the left, the first group of ceramic layers refers to the eighth ceramic layer from the bottom. This series via structure includes a second type component 72 as the sixth series via component from the bottom.

[0019] The specific numbers shown here, such as the number of ceramic layers, the number of series via structures, and the number of series via components, are merely examples for the sake of explanation, and the actual numbers are not limited to those shown here.

[0020] Multiple metal members 51 are arranged inside the motherboard 501 so as to penetrate the motherboard 501 in the thickness direction. When the LTCC board module 101 is mounted on the motherboard 501, the heat dissipation member 5 provided on the first surface 1a of the LTCC board 1 is electrically connected to the metal members 51 of the motherboard 501. This allows heat to be transferred from the heat dissipation member 5 to the metal members 51.

[0021] To explain in more detail, Figure 2 shows a magnified view of one Type 2 component 72 and the Type 1 components 71 positioned above and below it, taken from the series via structure 70. The thickness dimension of the Type 2 component 72 is smaller than that of the Type 1 component 71. When viewed in cross-section, the Type 1 component 71 is trapezoidal. Generally, the concept of a trapezoid means "a quadrilateral figure in which at least one pair of opposing sides are parallel," so the concept of a trapezoid naturally includes rectangles and squares. Therefore, the cross-sectional shape of the Type 1 component 71 may be rectangular or square. However, in reality, such conductive vias may be deformed to some extent by being pressed during the manufacturing of the LTCC substrate 1, so the shape of the Type 1 component 71 when viewed in cross-section is not necessarily a geometrically accurate trapezoid and may have some distortion.

[0022] In the cross-section shown in Figure 2, the second type component 72 has wedge-shaped recesses 72a that extend from both the left and right sides. In the example shown in Figure 2, the recesses 72a are only shallow, but they may extend more deeply. In the example shown in Figure 2, the angle of the tip of the recess 72a is obtuse, but the angle of the tip of the recess 72a may be acute. When considering the three-dimensional shape of the second type component 72, the recesses 72a do not necessarily exist around the entire circumference of the second type component 72. In Figure 2, the appearance of recesses 72a on both the left and right sides is merely how it appears when viewed in this cross-section. Depending on how the cross-section is cut, it is possible that no recesses 72a appear on either the left or right side, for example, as shown in Figure 3.

[0023] Figure 4 shows a perspective view of the second type component 72. In this figure, the second type component 72 is shown as if it were a frustum of a cone, but in reality, it is not a perfect frustum of a cone, but has a wedge-shaped recess 72a that intrudes from at least one side of the outer surface of the frustum of a cone. The recess 72a is not shown in Figure 4. Figure 5 shows the second type component 72 viewed from above. When viewed from above, the second type component 72 is circular. The circular shape is merely an example, and it may have other shapes. Here, we will continue the explanation assuming it is circular as an example. As shown in Figure 5, there are countless ways to define the cross-section 75. In Figure 5, eight straight lines are drawn as examples of the cross-section 75, but these lines are merely examples, and the way the cross-section 75 is defined is not limited to these. When cut along any of the cross-sections 75, a wedge-shaped recess 72a appears in the lateral outline of the cross-sectional shape, intruding from one side. For example, as shown in Figure 6, the recess 72a may appear on only one of the left or right sides. As shown in Figure 2, recesses 72a may appear on both the left and right sides.

[0024] The first type component 71 has a trapezoidal cross-sectional shape regardless of the direction of cross-section parallel to the thickness direction, whereas the second type component 72 has a recess 72a in which the lateral outline of the cross-sectional shape enters in a wedge shape from one side when cut along any of the cross-sectional directions parallel to the thickness direction.

[0025] In this embodiment, since the LTCC substrate 1 is equipped with a series via structure, heat dissipation is smooth even if heat is generated from the electronic component 3. Therefore, crack generation due to heat generation from the component can be prevented. In this embodiment, the series via structure is a series of multiple series via components, and the multiple series via components include a first type component 71 as well as a second type component 72. The second type component 72 has a wedge-shaped recess 72a on at least one side of its outer circumference, so impedance variations caused by electrical path differences due to misalignment when forming the series via structure by lamination can be suppressed. Furthermore, in this embodiment, excess conductive paste flows into the gaps during lamination and becomes the second type component 72, so bulging due to overfilling of conductive paste can be suppressed.

[0026] As shown in this embodiment, the LTCC substrate 1 has a first surface 1a for connection to the motherboard 501 and a second surface 1b which is the surface opposite to the first surface 1a, and heat-generating electronic components 3 are mounted on the second surface 1b, and it is preferable that the end of the series via structure 70 on the side closer to the second surface 1b is located within the projection area of ​​the electronic components 3 onto the second surface 1b and is electrically connected to the electronic components 3. By adopting this configuration, heat generated from the electronic components 3 can be efficiently transferred to the series via structure 70, and as a result, heat can be dissipated through the metal member 51 provided on the motherboard 501. Note that the heat-generating electronic components 3 refer to electronic components that generate heat during operation.

[0027] (Embodiment 2) An LTCC substrate module in Embodiment 2 based on the present invention will be described with reference to Figures 7 to 8. The configuration of the LTCC substrate module in this embodiment is basically the same as that described in Embodiment 1. In Figure 7, the second type component 72 and its vicinity of the LTCC substrate module are shown in an enlarged view. Here, representative elements are selected from among the multiple ceramic layers 2 that constitute the LTCC substrate 1 and are shown as the first type ceramic layer 21 and the second type ceramic layer 22. In Figure 7, two first type ceramic layers 21 sandwich one second type ceramic layer 22.

[0028] In the LTCC substrate module of this embodiment, the first group of ceramic layers can be classified into a first type ceramic layer 21 to which the first type component 71 belongs, and a second type ceramic layer 22 to which the second type component 72 belongs. When the second type ceramic layer 22 is cut in a cross section parallel to the thickness direction, its thickness decreases as it approaches the series via structure 70.

[0029] In this explanation, we have described a configuration in which the conductive pattern 7 is arranged at the interface between the ceramic layers 2 in the vicinity of the second type component 72. However, the layer at the interface between the ceramic layers 2 may be a constraint layer 9 instead of the conductive pattern 7, as shown in Figure 8.

[0030] The restraining layer 9 may be unsintered. The LTCC substrate 1 is manufactured by laminating and sintering ceramic green sheets as unsintered ceramic layers 2, but the restraining layer 9 is manufactured in the same manner as the unsintered ceramic layers 2. The unsintered restraining layer 9 does not substantially sinter at the temperature at which the unsintered ceramic layers 2 sinter. That is, the sintering temperature of the unsintered restraining layer 9 is higher than the sintering temperature of the unsintered ceramic layers 2. For example, when a low-temperature sintered ceramic material is used as the ceramic material included in the unsintered ceramic layers 2, the ceramic material included in the unsintered ceramic restraining layer can be, for example, alumina, zirconium oxide, aluminum nitride, boron nitride, mullite, magnesium oxide, silicon carbide, etc. Among those listed here, alumina is preferred as the ceramic material included in the unsintered ceramic restraining layer.

[0031] Although the restraining layer 9 is in an unsintered state, the sintering temperature of the unsintered restraining layer 9 is higher than the sintering temperature of the unsintered ceramic layer 2. Therefore, the restraining layer 9 does not sinter even when heated to fire the ceramic layer 2. Consequently, the restraining layer 9 does not shrink during this firing process. This makes it possible to suppress unwanted deformation of the LTCC substrate 1 during firing.

[0032] In this embodiment as well, the same effects as those described in Embodiment 1 can be obtained.

[0033] (Manufacturing Method) An LTCC substrate module including the configuration shown in Figure 7 can be obtained by the method shown in Figures 9 to 11 below. First, multiple ceramic layers are stacked as shown in Figure 9. This figure shows three ceramic layers selected from among the multiple ceramic layers. Specifically, this figure shows one type 2 ceramic layer 22 and two type 1 ceramic layers 21 positioned above and below it.

[0034] Each of these three ceramic layers has through holes 18. The ceramic layers may have a conductive pattern 7 on one side. The through holes 18 may be formed, for example, by laser processing. In the first ceramic layer 21, conductive paste 17 is filled inside the through holes 18. In the second ceramic layer 22, conductive paste 17 is not filled inside the through holes 18. Nothing may be filled inside the through holes 18 of the second ceramic layer 22. In the second ceramic layer 22, the areas where conductive paste 17 is not filled inside the through holes 18 are called gaps 19. In Figure 9, these three ceramic layers are stacked as shown by arrows 91 and 92. Immediately after stacking, as shown in Figure 10, the gaps 19 become closed spaces completely surrounded by other materials. When pressure is applied in the thickness direction, the situation becomes as shown in Figure 11. That is, the conductive paste 17 flows from the lower first ceramic layer 21 towards the gaps 19 above, as shown by arrow 93a. From the upper first ceramic layer 21, the conductive paste 17 flows toward the lower decompression section 19, as indicated by arrow 93b. Inside the second ceramic layer 22, the ceramic material on the sides flows toward the decompression section 19, as indicated by arrows 94a and 94b. As various materials penetrate the decompression section 19, as indicated by arrows 93a, 93b, 94a, and 94b, the structure shown in Figure 7 is obtained. The portion of the second ceramic layer 22 near the decompression section 19 becomes thinner due to the flow indicated by arrows 94a and 94b. As a result, when the second ceramic layer 22 is cut in a cross section parallel to the thickness direction, it has a structure in which the thickness decreases as it approaches the series via structure 70. The conductive paste 17 that flowed in from above and below along arrows 93a and 93b merge at the decompression section 19 to form the second component 72. Because it is formed in this way, the second component 72 has the shape described in Embodiment 1. The second type component 72 has a different shape from the first type component 71.

[0035] Furthermore, multiple embodiments of the above-described embodiments may be used in appropriate combinations. The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, including all modifications within the meaning and scope of the claims.

[0036] 1 LTCC substrate, 1a First surface, 1b Second surface, 2 Ceramic layer, 3 Electronic component, 4 Series via component, 5 Heat dissipation member, 6 Sealing resin, 7 Conductor pattern, 8 Shielding film, 9 Constraint layer, 11 Surface electrode, 12 Solder, 17 Conductive paste, 18 Through hole, 19 Layer cutout, 21 Type 1 ceramic layer, 22 Type 2 ceramic layer, 31 Terminal, 51 Metal component, 70 Series via structure, 71 Type 1 component, 72 Type 2 component, 72a Recess, 75 Cross-section, 91, 92, 93a, 93b, 94a, 94b Arrows, 101 LTCC substrate module, 501 Motherboard.

Claims

1. An LTCC substrate module comprising an LTCC substrate formed by stacking multiple ceramic layers, wherein the LTCC substrate includes a series via structure formed to penetrate in the thickness direction of a first group of ceramic layers arranged in the thickness direction, at least a portion of the multiple ceramic layers, the series via structure being a series of multiple series via components corresponding to each of the first group of ceramic layers, and the multiple series via components including a first type of component whose cross-sectional shape is trapezoidal when viewed in cross-section in any direction parallel to the thickness direction, and a second type of component whose lateral outline of the cross-sectional shape has a recess that enters from either side in a wedge shape when viewed in cross-section in any direction parallel to the thickness direction.

2. The LTCC substrate module according to claim 1, wherein the first group of ceramic layers can be classified into a first type ceramic layer to which the first type component belongs and a second type ceramic layer to which the second type component belongs, and the second type ceramic layer, when viewed in cross-section parallel to the thickness direction, becomes thinner as it approaches the series via structure.

3. The LTCC substrate module according to claim 1 or 2, wherein the LTCC substrate has a first surface for connection to a mother board and a second surface which is the surface opposite to the first surface, and heat-generating electronic components are mounted on the second surface, and the end of the series via structure closest to the second surface is located within the projection area of ​​the electronic components onto the second surface and is electrically connected to the electronic components.

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