Multilayer substrate and manufacturing method of multilayer substrate

Abstract

To provide a laminated substrate capable of ensuring a long-term reliability by preventing stress from being applied to a conductive paste for electrical connection when the laminated substrate is manufactured by laminating a plurality of multilayer substrates.SOLUTION: In a laminated substrate 100 formed by laminating a plurality of multilayer substrates 10, in each multilayer substrate 10, a through hole 30 penetrating through each multilayer substrate 10 and having an inner wall surface plated and filled with a resin 32 therein, and bonding lands 34 electrically connected to the through hole 30 are formed on an upper surface and a lower surface of the through hole 30. An insulating adhesive layer 40 and a conductive paste via 50 for electrically connecting the bonding lands 34 of the opposed multilayer substrates to each other by a conductive paste filled in a through hole 46 formed in the insulating adhesive layer 40 are provided between the multilayer substrates 10, and the conductive paste via 50 is provided at a position different from the position where the through hole 30 is formed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a laminated substrate and a method for manufacturing the laminated substrate.

Background Art

[0002] Conventionally, circuit boards such as printed wiring boards have been widely used in general to compactly incorporate electronic components into electronic devices. On the other hand, with the demands for miniaturization, high performance, and low cost of electronic devices, miniaturization, multilayer formation, and high-density mounting of electronic circuits on circuit boards have advanced rapidly, and studies on multilayer substrates with a multilayer structure of printed wiring boards have become active.

[0003] When forming through-holes in a multilayer substrate, the drill diameter for drilling through-holes must be increased as the number of layers increases and the board thickness increases. Then, since it cannot cope with fine pitch, it has been considered to prepare a multilayer substrate in which through-holes are formed with a drill of the thinnest possible diameter in a state where the number of layers is not too large, and stack a plurality of these multilayer substrates to finally obtain a multilayer laminated substrate.

[0004] For example, Patent Document 1 discloses a laminated substrate in which an adhesive layer is laminated on the upper surface of one multilayer substrate, through-holes are drilled in this adhesive layer, the through-holes are filled with a conductive paste, and the other multilayer substrate is laminated on the adhesive layer and the conductive paste. Each multilayer substrate is interlayer-connected by through-holes whose inner walls are plated, and bonding lands formed by metal layers are formed on the upper and lower surfaces of these through-holes. The above-described conductive paste electrically connects these bonding lands.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] In the aforementioned Patent Document 1, a configuration is disclosed in which bonding lands of through-holes that penetrate each multilayer substrate and connect the layers are electrically connected by conductive paste.

[0007] However, the through-holes formed in each multilayer substrate are filled with resin to bond the layers that make up the multilayer substrate. Therefore, if conductive paste is placed directly above the through-holes, when the multilayer substrates are joined together by thermocompression bonding, the thermal expansion of the resin will put stress on the conductive paste, which may impair the long-term reliability of the conductive paste.

[0008] Therefore, the present invention has been made to solve the above problems, and its objective is to provide a laminated substrate and a method for manufacturing a laminated substrate that can ensure long-term reliability by preventing stress on the conductive paste used to electrically connect multiple multilayer substrates when manufacturing a laminated substrate by stacking multiple multilayer substrates. [Means for solving the problem]

[0009] The laminated substrate according to the present invention is a laminated substrate formed by stacking a plurality of multilayer substrates, wherein each multilayer substrate has a through-hole that penetrates the multilayer substrate, has a plated inner wall surface and is filled with resin, and has bonding lands on the upper and lower surfaces of the through-hole that are electrically connected to the through-hole, and between each multilayer substrate there is an insulating adhesive layer and conductive paste vias which electrically connect the bonding lands of opposing multilayer substrates by conductive paste filled in through-holes formed in the insulating adhesive layer, wherein the conductive paste vias are provided at positions different from the positions where the through-holes are formed, and the bonding lands are Multiple conductive paste viasThe bonding land is formed to a size that allows for the placement of the conductive paste vias, and is characterized in that the bonding land is formed in a roughly rectangular shape with respect to the through-hole such that the conductive paste vias are provided at four locations around the through-hole. By adopting this configuration, even if the resin inside the through-hole undergoes thermal expansion, the conductive paste via is located in a different position from the through-hole. Therefore, it is not subjected to stress due to thermal expansion, and long-term reliability can be maintained.

[0015] The present invention relates to a method for manufacturing a laminated substrate, which involves stacking multiple multilayer substrates, each having through-holes with plated inner walls and resin-filled interiors, and bonding lands electrically connected to the through-holes on the upper and lower surfaces of the through-holes, and comprising the steps of: stacking an insulating adhesive layer on the upper surface of one multilayer substrate; forming through-holes that penetrate the insulating adhesive layer at positions different from those where the through-holes are formed, so as to electrically connect the bonding lands of one multilayer substrate and another multilayer substrate facing the first multilayer substrate; filling the through-holes with conductive paste to form conductive paste vias; and thermocompressing the multiple multilayer substrates to cure the insulating adhesive layer and the conductive paste and integrate the multiple multilayer substrates. The process includes, prior to the step of laminating an insulating adhesive layer on the upper surface of the first multilayer substrate, filling the recesses between the bonding lands and other metal layers or other bonding lands on the upper surface of the first multilayer substrate and the lower surface of the other multilayer substrate with insulating resin, and polishing the surface to flatten it so that there are no irregularities on the surface facing the other multilayer substrate. It is characterized by containing. According to this method, even if the resin inside the through-hole expands due to thermal expansion, the conductive paste vias are located in a different position from the through-hole. Therefore, a laminated substrate can be obtained that maintains long-term reliability without being subjected to stress due to thermal expansion. Furthermore, it is possible to maintain the flatness of the laminated substrate and prevent the occurrence of abnormal resistance values ​​by making the electrical connection layer using conductive paste vias uniform across the entire substrate. [Effects of the Invention]

[0017] According to the present invention, when manufacturing a laminated substrate by stacking multiple multilayer substrates, long-term reliability can be ensured by preventing stress on the conductive paste used to electrically connect them. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic cross-sectional view showing an example of a multilayer substrate. [Figure 2] This is a schematic plan view of a bonding land, showing an example where multiple conductive paste vias are placed in a single through-hole. [Figure 3] This is a schematic plan view of a bonding land, showing an example where one conductive paste via is placed for each through-hole. [Figure 4] This is a schematic cross-sectional view (part 1) showing an example of a method for manufacturing a multilayer substrate in this embodiment. [Figure 5] This is a schematic cross-sectional view (part 2) showing an example of a method for manufacturing a multilayer substrate in this embodiment. [Figure 6] This is a schematic cross-sectional view (part 3) showing an example of a method for manufacturing a multilayer substrate in this embodiment. [Figure 7] This is a schematic cross-sectional view (part 4) showing an example of a method for manufacturing a multilayer substrate in this embodiment. [Figure 8] This is a schematic cross-sectional view (part 5) showing an example of a method for manufacturing a multilayer substrate in this embodiment. [Modes for carrying out the invention]

[0019] (Laminated substrate) Embodiments of the present invention will be described below with reference to the drawings. Figure 1 shows a schematic cross-sectional view of a laminated substrate. In this embodiment, for convenience, the terms "top surface" or "bottom surface" may be used based on the vertical direction in the drawings, but the top and bottom surfaces of the laminated substrate 100 or multilayer substrate 10 may not necessarily correspond to the actual vertical orientation. Furthermore, the term "side surface" may be used in reference to the laminated substrate 100 or multilayer substrate 10, and this refers to the side surface relative to the top and bottom surfaces described above.

[0020] The stacked substrate 100 shown in FIG. 1 is, as an example, formed by stacking two multilayer substrates 10 in the vertical direction and electrically connecting them to each other. However, it is not limited to the stacking of two multilayer substrates 10 and can be applied to the stacking of two or more multilayer substrates 10. In addition, the stacked substrate 100 shown in FIG. 1 is described by taking the case where both are MLB (multi-layer printed wiring boards) as an example.

[0021] Each multilayer substrate 10 has an insulating layer 20 made of a plurality of insulating substrates and a metal layer (not shown) formed on the upper or lower surface of each insulating layer 20, and through holes 30 penetrating in the vertical direction are formed.

[0022] The insulating layer 20 is not particularly limited as long as it is an insulating layer used in a multilayer substrate and can be appropriately selected according to the purpose. As an example, an inorganic base material such as an inorganic woven fabric or non-woven fabric using glass cloth, etc., or a base material hardened by an organic base material such as an organic woven fabric or non-woven fabric can be adopted.

[0023] More specifically, as an example, the insulating layer 20 can adopt a glass epoxy base material (a glass woven fabric base material impregnated with an epoxy resin, a glass non-woven fabric base material impregnated with an epoxy resin), a glass woven fabric base material impregnated with a bismaleimide triazine resin, an aramid non-woven fabric base material impregnated with an epoxy resin, a glass woven fabric base material impregnated with a modified polyphenylene ether resin, etc.

[0024] The through hole 30 has a plating layer 35 formed by plating the inner wall with a metal such as copper, and a resin 32 is filled in the hollow portion further inside the plating layer 35. The resin 32 is filled to bond the layers constituting each multilayer substrate so that they do not separate.

[0025] On the upper and lower surfaces of each multilayer substrate 10, bonding lands 34 are formed, blocking the through-holes 30, for electrically connecting to through-holes 30 of other multilayer substrates 10 and semiconductor elements (not shown). The bonding lands 34 are electrically connected to the plating layer 35 of the through-holes 30 and can be formed from a metal such as copper.

[0026] An adhesive layer 40 is interposed between the multilayer substrates 10. A thermosetting resin can be used as the adhesive layer 40, and one example is a glass epoxy prepreg.

[0027] In Figure 1, the bonding land 34 on the upper surface of the lower multilayer substrate 10 and the bonding land 34 on the lower surface of the upper multilayer substrate 10 are electrically connected by vias. These vias are conductive paste vias 50 made of conductive paste. The conductive paste can contain a conductive filler and a binder resin.

[0028] The conductive paste vias 50 are located at positions different from the through-holes 30, that is, at positions away from directly above and below the through-holes 30. In other words, although the through-holes 30 of the two multilayer substrates 10 are arranged in a straight line in the vertical direction, the conductive paste vias 50 are located at positions away from this straight line.

[0029] In other words, if conductive paste vias 50 are provided directly above and below through-holes 30, the resin 32 inside the through-holes 30 may expand due to thermal compression during the bonding of multilayer substrates 10, which can cause stress on the conductive paste vias 50 and potentially impair the long-term reliability of the conductive paste vias 50. Therefore, by positioning the conductive paste vias 50 away from directly above and below the through-hole 30, the conductive paste vias 50 are not subjected to stress due to the thermal expansion of the resin 32 inside the through-hole 30, thereby ensuring long-term reliability.

[0030] Although Figure 1 shows a configuration in which multiple conductive paste vias 50 are provided for a single through-hole 30, the number of conductive paste vias 50 for a single through-hole 30 is not limited to any one number; one or more conductive paste vias 50 can be provided for a single through-hole 30.

[0031] Furthermore, the placement of the conductive paste via 50 must be at a distance from the resin 32 such that it is not affected by the thermal expansion of the resin 32 within the through-hole 30, and this distance is set appropriately based on the type of resin 32 and the diameter of the through-hole 30.

[0032] Furthermore, insulating resin 42 is placed between the bonding land 34 on the upper surface of the lower multilayer substrate 10 and the adjacent metal layer 38 (or a bonding land 34 in an adjacent position), and between the bonding land 34 on the lower surface of the upper multilayer substrate 10 and the adjacent metal layer 38 (or a bonding land 34 in an adjacent position), in order to flatten the surface of the multilayer substrate 10.

[0033] In other words, since the multilayer substrate 10 has metal layers 38 including bonding lands 34 protruding from the surface of the insulating layer 20 on its upper and lower surfaces, the surface of the upper multilayer substrate 10 placed on the lower side and the surface of the lower multilayer substrate 10 placed on the upper side can be made flat by filling the step difference.

[0034] Figures 2 and 3 show schematic plan views of the joint land area. In the example shown in Figure 2, a bonding land 34 is used that is large enough to accommodate multiple conductive paste vias 50 for a single through-hole 30. Specifically, the planar shape of the bonding land 34 is roughly rectangular. The through-hole 30 is positioned approximately in the center of this rectangular shape, and conductive paste vias 50 are positioned at four locations around the through-hole 30 (corresponding to the corners of the rectangle). In Figure 2, the through-hole 30 is shown with a dashed line.

[0035] For example, if the diameter of the through-hole 30 is 250 μm and the diameter of the conductive paste via 50 is 180 μm, and the length of one side of the bonding land 34 is 720 μm, then four conductive paste vias 50 can be placed within one bonding land 34 in positions that do not overlap with the through-hole 30.

[0036] In Figure 2, four conductive paste vias 50 are placed for the bonding land 34 of one through-hole 30. However, the number of conductive paste vias 50 is not limited to four; two or three conductive paste vias 50 may also be placed. Furthermore, when multiple conductive paste vias 50 are placed on a bonding land 34 of a single through-hole 30, the planar shape of the bonding land 34 is not limited to a roughly rectangular shape.

[0037] As shown in Figure 2, one example of a case where multiple conductive paste vias 50 are placed on a single through-hole 30 bonding land 34 is when a relatively large current flows, such as in the case of a power supply through-hole 30. By providing multiple conductive paste vias 50 on a through-hole 30 through which a large current flows, the resistance value is reduced, and the amount of heat generated can be kept from increasing. In this way, by keeping the amount of heat generated from increasing, the risk of melting at the stacking points of the multilayer substrates 10 can be eliminated.

[0038] Figure 3 shows an example in which one conductive paste via 50 is placed for a bonding land 34 of one through-hole 30. In this case, the bonding land 34 has a planar shape in which a large circle and a small circle partially overlap, resembling a gourd or a Daruma doll. Specifically, it has a shape in which a first circular portion 34a surrounding the through-hole 30 and a second circular portion 34b surrounding the conductive paste via 50 are connected.

[0039] For example, if the diameter of the through-hole 30 is 250 μm and the diameter of the conductive paste via 50 is 180 μm, the diameter of the first circular portion 34a can be set to 500 μm and the diameter of the second circular portion 34b can be set to 340 μm.

[0040] As shown in Figure 3, one case in which one conductive paste via 50 is placed for a bonding land 34 of a single through-hole 30 is the case of a through-hole 30 where noise countermeasures such as signal lines are necessary. In this case, as shown in Figure 2, if the area of ​​the bonding land 34 becomes large, the effect of noise may increase, so it is necessary to make the area of ​​the bonding land 34 as small as possible. Therefore, by making the bonding land 34a for the through-hole 30 and the bonding land 34b for the conductive paste via 50 circular in shape so that their respective areas are as small as possible, and by partially overlapping these two bonding lands 34a and bonding land 34b, the stub can be eliminated and the influence of noise can be reduced.

[0041] Furthermore, when one conductive paste via 50 is placed for each bonding land 34 of a single through-hole 30, the shape of the bonding land 34 is not limited to the shape shown in Figure 3, and may be an approximately elliptical or oval shape that connects the position where the through-hole 30 is placed and the position where the conductive paste via 50 is placed (not shown).

[0042] (Method of manufacturing a laminated substrate) Next, the manufacturing method of the multilayer substrate will be explained with reference to Figure 4. Note that the multilayer substrate 10 in Figure 4 is the same as that shown in Figure 1, and its structure is denoted by the same reference numerals as in Figure 1, so its explanation is omitted. First, when stacking the multilayer substrates 10, insulating resin 42 is filled into the recesses between the bonding lands 34 and the metal layer 38 (or other adjacent bonding lands 34) in order to make the surface facing the other multilayer substrate 10 flat. Then, the insulating resin 42 is polished to flatten the surface facing the other multilayer substrate 10 so that there are no irregularities. This maintains the flatness of the stacked substrate 100 and makes the electrical connection layer by conductive paste vias 50 uniform throughout the substrate, preventing the occurrence of abnormal resistance values.

[0043] Next, as shown in Figure 5, an adhesive layer 40 is laminated on the surface facing the other multilayer substrates 10 to be laminated. As mentioned above, a thermosetting resin can be used as the adhesive layer 40, and as an example, a glass epoxy prepreg can be used. Furthermore, a resin film 44 is laminated on the upper surface of the adhesive layer 40 to protect the surface of the adhesive layer 40. The adhesive layer 40 and the resin film 44 may be in the form of a pre-integrated sheet.

[0044] Next, as shown in Figure 6, through holes 46 are formed in the adhesive layer 40 and the resin film 44. The through-hole 46 is a closed-bottomed through-hole 46 that penetrates the adhesive layer 40 and the resin film 44, with the bonding land 34 as its bottom. The through-hole 46 can be made, for example, by laser processing. Examples of laser processing methods include CO2 lasers and YAG lasers, but are not limited to these, and can be appropriately selected depending on the purpose.

[0045] In this case, as shown in Figure 1, multiple conductive paste vias 50 are placed on the bonding land 34 of a single through-hole 30. Therefore, multiple through-holes 46 are drilled at a location different from where the through-hole 30 is formed, and at a location away from directly above the through-hole 30.

[0046] Next, as shown in Figure 7, conductive paste is filled into the through hole 46, and then the resin film 44 is peeled off. As a result, conductive paste vias 50 are formed, and by peeling off the resin film 44, the conductive paste protrudes above the adhesive layer 40 by the thickness of the resin film 44. Because the conductive paste protrudes from the adhesive layer 40, the conductive paste can be reliably bonded to the bonding lands 34 of other multilayer substrates 10.

[0047] Next, as shown in Figure 8, another multilayer substrate 10 is laminated onto the multilayer substrate 10 on which the adhesive layer 40 and conductive paste vias 50 are formed. Here, the lower surface of the other multilayer substrate 10 is flattened so that there are no irregularities, by filling the recesses between the bonding lands 34 and the metal layer 38 (or other adjacent bonding lands 34) with insulating resin 42. Then, the multilayer substrates 10 are heat-pressed together. By heat-pressing, the adhesive layer 40 and the conductive paste vias 50 harden, and a laminated substrate 100 is formed by stacking multiple multilayer substrates 10.

[0048] (Other embodiments of multilayer substrates) The specific types of the multilayer substrates 10 and the substrates of the multilayer substrates 10 that make up the laminated substrate 100 are as shown in Figure 1. Both may be MLBs (multilayer printed circuit boards), or the lower multilayer substrate 10 may be an MLB (multilayer printed circuit board) and the upper multilayer substrate 10 may be a PKG (semiconductor package substrate). Alternatively, the lower multilayer substrate 10 may be an MLB (multilayer printed circuit board) and the upper multilayer substrate 10 may be a CL (coreless semiconductor package substrate). Furthermore, a configuration in which a multilayer substrate 10 that is a CL (coreless semiconductor package substrate) is laminated on both the upper and lower surfaces of the lower multilayer substrate 10 that is an MLB (multilayer printed circuit board) is also possible.

[0049] The laminated substrate 100 in this embodiment can be used as a motherboard (support substrate) and also as an interposer (relay substrate). In particular, it can be used as a motherboard or interposer for server systems and high-speed communication systems, and can also be used as a circuit board that constitutes semiconductor elements. Furthermore, it can be applied to inspection equipment and probe cards used for determining the quality of semiconductors. [Explanation of symbols]

[0050] 10 Multilayer board 20 Insulating layer 30 through-holes 32 resin 34 Joining Land 34a First circular section 34b Second circular section 35 Plating layer 38 Metal layer 40 Adhesive layer 40 Insulating adhesive layer 42 Insulating resin 44 Resin film 46 Through hole 50 conductive paste vias 100 Multilayer Substrates

Claims

1. A laminated substrate formed by stacking multiple multilayer substrates, Each multilayer substrate has a through-hole that penetrates the substrate, has a plated inner wall surface, and is filled with resin, and bonding lands are formed on the upper and lower surfaces of the through-hole that are electrically connected to the through-hole. Between each multilayer substrate, Insulating adhesive layer, Conductive paste vias are provided, which electrically connect each of the bonding lands of opposing multilayer substrates by filling through holes formed in the insulating adhesive layer with conductive paste. The conductive paste via is provided at a position different from the position where the through-hole is formed. The bonding land is formed to a size that allows for the arrangement of a plurality of the conductive paste vias. The laminated substrate is characterized in that the bonding land is formed in a roughly rectangular shape with respect to the through-hole such that the conductive paste vias are provided at four locations around the through-hole.

2. A method for manufacturing a laminated substrate by stacking multiple multilayer substrates, each having a through-hole with a plated inner wall surface and filled with resin inside, and bonding lands on the upper and lower surfaces of the through-holes that are electrically connected to the through-holes, A step of laminating an insulating adhesive layer onto the upper surface of a multilayer substrate, A step of forming through holes that penetrate the insulating adhesive layer at a position different from the position where the through-holes are formed, so that the bonding lands of one multilayer substrate and another multilayer substrate facing the first multilayer substrate can be electrically connected to each other. The steps include filling the through-hole with conductive paste to form a conductive paste via, The process includes a step of thermally pressing multiple multilayer substrates together to cure the insulating adhesive layer and the conductive paste, thereby integrating the multiple multilayer substrates, Before the step of laminating an insulating adhesive layer onto the upper surface of the first multilayer substrate, A method for manufacturing a laminated substrate, comprising the steps of filling the recesses between the bonding lands and other metal layers or other bonding lands on the upper surface of one multilayer substrate and the lower surface of the other multilayer substrate with insulating resin, and polishing the surface to flatten it so that there are no irregularities on the surface facing the other multilayer substrate.

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