Method for manufacturing multilayer substrate

Abstract

Provided is a multilayer substrate manufacturing technique with which it is possible to manufacture a multilayer substrate at low cost. First, a cover plate (2) is overlaid on a base material sheet (1) having the same shape and size. Wiring (11) is provided on one surface of the base sheet (1). A hole (21) is opened in the cover plate (2) at a position where the electronic component is to be mounted on the base material sheet (1). Thereafter, the overlapped base sheet (1) and cover plate (2) are folded such that the holes (21) are exposed to the outside. An electronic component is inserted into the hole (21), and the electronic component is mounted in a state of being electrically connected to the wiring (11) of the base material sheet (1).

Description

Technical Field

[0001] This invention relates to a method for manufacturing multilayer substrates. Background Technology

[0002] Various electronic devices contain components mounted on a substrate with wiring that forms circuits. Furthermore, among these substrates, there exist substrates known as multilayer substrates.

[0003] Multilayer substrates are constructed by stacking multiple substrates. Each substrate is equipped with a plate-like or sheet-like substrate material, and wiring is provided on at least one surface of the substrate material. For multilayer substrates with a structure consisting of multiple substrates, each with wiring, it goes without saying that although their thickness is increased, more circuits and electronic components can be contained in the same area than in a single-layer substrate, achieving high integration, and therefore they are widely used.

[0004] Generally, the circuits in the individual substrates contained in a multilayer substrate need to be interconnected.

[0005] Therefore, in multilayer substrates, vias called through holes are typically provided through each substrate in an overlapping multilayer substrate. Generally, a metal layer plated with a conductive metal is provided on the inner peripheral surface of the through hole, for example, and the wiring in each substrate is made conductive to the metal layer, thereby making the wiring in each substrate in the multilayer substrate interconnected through the metal layer in the through hole. For example, wiring respectively provided on both sides of a substrate is interconnected through the metal layer in the through hole.

[0006] Alternatively, wiring on two or more sides of a substrate can be interconnected using connecting lines outside the conductive substrate, thereby enabling wiring in separate locations to conduct to each other. This technology is also in practical use. Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] As described above, multilayer substrates exist, but there is still room for improvement.

[0009] As mentioned above, conventional multilayer substrates are equipped with through holes and interconnects outside the substrate.

[0010] In the presence of through-holes, it is necessary to perform the process of opening holes on the substrate to form the through-holes, and the process of forming a metal layer on the inner peripheral surface of the through-holes, thereby increasing the manufacturing cost of multilayer substrates.

[0011] Furthermore, as mentioned above, in order for through-holes to communicate with the wiring of each substrate contained in a multilayer substrate, the wiring needs to be correctly positioned relative to the substrate in each substrate, and the relative positions of the stacked substrates need to be correctly positioned when multiple substrates are stacked. It goes without saying that the two correct positioning requirements for the reasons stated above are technically achievable. However, achieving them requires considerable effort and can easily lead to increased costs.

[0012] Furthermore, conventional multilayer substrate manufacturing processes involve separately manufacturing multiple substrates to be stacked, and then overlapping these individually manufactured substrates. Alternatively, in some cases, cover plates and copper foil are stacked on top and bottom of the substrates to form circuits on the upper and lower surfaces of the substrates, and this step is repeated to increase the number of layers. Here, when manufacturing individual substrates, for example, since each substrate typically undergoes a common process such as gold plating to cut circuits from copper foil adhered to the substrate material, it is easy to increase costs due to repeatedly performing the common process on each substrate. The same applies when cover plates and copper foil are stacked on top and bottom of the substrates.

[0013] When interconnects are added outside the substrate, this process increases the manufacturing cost of the multilayer substrate. Furthermore, the same applies to the increased costs caused by repeatedly performing the same process on various substrates.

[0014] The main objective of this invention is to provide a manufacturing technology for multilayer substrates that enables the production of multilayer substrates at low cost.

[0015] Methods for solving problems

[0016] The invention of this application for solving the above-mentioned problems is described below.

[0017] The invention disclosed in this application is a method for manufacturing a multilayer substrate, comprising the following steps: an overlapping step, wherein the cover plate is overlapped onto the surface of the substrate material sheet such that the outline of the substrate material sheet matches the outline of the cover plate; the substrate material sheet is a rectangular sheet made of thermoplastic resin and having insulating properties; conductive wiring is appropriately arranged on the surface of the substrate material sheet; the cover plate is a sheet of substantially the same shape and size as the substrate material sheet; the cover plate has at least one hole at the location where electronic components will be subsequently placed; the cover plate is made of thermoplastic resin and has insulating properties; bending. The process includes a bending process in which the overlapping substrate material sheet and the cover plate are bent and folded such that the hole is exposed to the outside; a fixing process in which the folded substrate material sheet and the cover plate are heated to melt at least a portion of the cover plate, and then cooled and hardened, thereby fixing the adjacent substrate material sheet and the cover plate; and an electronic component mounting process in which the electronic component inserted into the hole is fixed to the substrate material sheet exposed from the hole in such a way that the wiring in the surface of the substrate material sheet exposed from the hole is conductive.

[0018] In this method of manufacturing a multilayer substrate, as described above, the overlapping process, bending process, fixing process, and electronic component mounting process are performed sequentially.

[0019] In the overlapping process, the cover plate is overlapped onto the surface of the base material sheet. The base material sheet is a rectangular sheet with insulating properties made of thermoplastic resin. Wiring is provided on the surface of the base material sheet. The wiring is not provided on the cover plate, but only on the base material sheet. Furthermore, the wiring is only provided on one side of the base material sheet. The side of the base material sheet on which the wiring is provided is the surface. The wiring is conductive and is generally made of a conductive metal. There are no restrictions on the method of providing wiring on the base material sheet; known or widely accepted methods can be used to provide wiring on the surface of the base material sheet. For example, as a technique for placing wiring on a substrate material sheet, the following methods can be used: a subtractive method where copper foil is adhered to the entire surface of the substrate material sheet with an adhesive, and unwanted portions are removed by chemical etching, leaving the wiring portion; and an additive method where wiring is plated (in most cases, electroless plating and electrolytic plating) on ​​the surface of the substrate material sheet. The cover plate is a rectangular sheet that is essentially the same shape and size as the substrate material sheet. The cover plate is made of thermoplastic resin and has insulating properties. At least one hole is provided in the cover plate. The hole in the cover plate is positioned corresponding to the location where electronic components are subsequently placed on the substrate material sheet. The cover plate overlaps the substrate material sheet in a manner that matches its contour.

[0020] In the subsequent bending process, the overlapping substrate material sheet and the cover plate are bent together. The bending occurs at least once, and can be either a convex or concave bend, or a combination of both. After the bending process, the aforementioned holes in the cover plate become exposed. By bending together with the cover plate, regardless of whether the cover plate may enter, at least a portion of the substrate material sheet becomes at least double-layered with the remaining portion of the substrate material sheet. Consequently, the wiring on the surface of the substrate material sheet also becomes at least double-layered.

[0021] In the subsequent fixing process, the adjacent base material sheets and cover plates are fixed in their bent state. During this fixing, the bent base material sheets and cover plates are heated, at least a portion of the cover plates are melted, and then cooled and hardened. Thus, the adjacent base material sheets and cover plates are fixed by using the molten cover plates as an adhesive. The "cooling" described in this application does not necessarily refer to an active cooling process; it also includes placing the heated base material sheets and cover plates in an atmosphere at a temperature lower than the melting point of the thermoplastic resin constituting the cover plates (e.g., room temperature). Furthermore, it is permissible to melt not only the cover plates but also a portion of the base material sheets, followed by cooling and hardening. Additionally, in the fixing process, adjacent cover plates among overlapping base material sheets and cover plates can also be fixed to each other. In summary, by implementing the fixing process, the folded base material sheets and cover plates are integrated, resulting in a state where their relative positional relationship as a whole is substantially fixed.

[0022] Furthermore, an electronic component mounting process is performed, in which electronic components are mounted onto a substrate material sheet. As described above, after the bending process is completed, the holes provided in the cover plate are exposed to the outside. The holes in the cover plate correspond to the positions where electronic components are mounted. The electronic components are inserted through the holes and fixed to the exposed substrate material sheet while maintaining electrical conductivity with the wiring on the surface of the substrate material sheet exposed through the holes. It goes without saying that the wiring provided on the substrate material sheet is designed to form a circuit through combination with at least one predetermined electronic component when it is mounted on the substrate material sheet.

[0023] This is how multilayer substrates are manufactured.

[0024] In addition, the electronic components used in manufacturing multilayer substrates are IC (integrated circuit) chips, BGA (ball grid array), CSP (chip-scale package), resistors, capacitors, etc., which are the same as the electronic components mounted on general substrates.

[0025] The multilayer substrate manufactured using the manufacturing method of this application described above eliminates the need for through holes or external wiring because at least one predetermined electronic component is mounted on the substrate material sheet to form a circuit. This eliminates the need for additional steps in manufacturing these components, thus reducing the cost of manufacturing the multilayer substrate.

[0026] Furthermore, in the above-mentioned method for manufacturing multilayer substrates, multilayer substrates with various structures can be obtained by bending the overlapping substrate material sheets and cover plates in the bending process.

[0027] Furthermore, in the multilayer substrate manufactured using the aforementioned method, the surface of the substrate material sheet is covered by a cover plate, except for the portion with holes. Therefore, since the wiring is protected by the cover plate, the wiring is less prone to breakage.

[0028] As described above, the substrate material sheet and cover plate used in the invention of this application are both made of thermoplastic resin.

[0029] The thermoplastic resins that make up the base material sheet and the cover plate may or may not be the same.

[0030] Thermoplastic resins that can be used to form the base material sheet and cover plate are, for example, liquid crystal polymers (LCPs). Other available materials include polyphenylene sulfide (PPE), polyether ether ketone (PEEK), fluoropolymers (FR), etc., but other thermoplastic resins may also be used.

[0031] Liquid crystal polymers are known as raw materials, and are also known as raw materials with excellent low-loss and high-frequency characteristics, making them suitable for use as substrate materials and cover plates.

[0032] The thickness of the substrate sheet and the cover plate needs to be thin enough to allow for bending when they are overlapped. On the other hand, preferably, the thickness of the cover plate exceeds the thickness of the wiring formed on the substrate sheet. As mentioned earlier, the cover plate protects the wiring after the fixing process; however, if the cover plate is thinner than the wiring, insufficient protection of the wiring may occur, leaving the wiring exposed. Furthermore, even when the wiring can be protected by covering it with a cover plate, the thickness of the wiring may appear as a protrusion on the cover plate, compromising the flatness of the multilayer substrate. In such cases, there is a risk of poor bonding when mounting electronic components onto surfaces with poor flatness. Alternatively, the thickness of the cover plate can also be thinner than the thickness of the substrate sheet. By making the cover plate thinner than the substrate sheet, rigidity during bending is reduced, bending performance is improved, and cost reductions in processing and material costs are also achieved.

[0033] As described above, the substrate material sheet used in the invention of this application is rectangular, and the cover plate is a rectangle with the same shape and size as the substrate material sheet.

[0034] It doesn't matter if the substrate sheet is square. The substrate sheet and cover plate are folded by bending them in an overlapping state, as described above. However, if the substrate sheet and cover plate are square, various folding methods used in origami, a traditional Japanese art form, can be employed. For example, a multilayer substrate of a regular shape, such as a rectangle or triangle, can be obtained in all parts of the thickness direction, with the same number of substrate sheets and cover plates present therein.

[0035] For example, the substrate material sheet and the cover plate after the electronic component mounting process can be shaped as a square or a right-angled isosceles triangle. This regular shape is convenient when assembling multilayer substrates onto the final product. A square can be formed by combining two right-angled isosceles triangle multilayer substrates.

[0036] In the invention of this application, after the electronic component mounting process is completed, all parts of the substrate material sheet and the cover plate, except for the bent parts, are actually parallel, and the bending process can be performed.

[0037] In this way, the substrate sheet and cover plate of the multilayer substrate are actually stacked in parallel, except for the bent portions, forming a plate as a whole. This plate-shaped multilayer substrate has the same shape as most conventional multilayer or single-layer substrates and is expected to have a wide range of applications.

[0038] On the other hand, after the electronic component mounting process is completed, a portion of the substrate material sheet and cover plate may become non-parallel in relation to other parts of the substrate material sheet and cover plate. In this case, the multilayer substrate is not plate-shaped but becomes a three-dimensional shape. Depending on the final product to which the substrate is to be mounted, a multilayer substrate with a three-dimensional shape is considered convenient.

[0039] Using the same manufacturing method, multilayer substrates of various shapes can be obtained, which can be said to be one of the advantages of the manufacturing method of multilayer substrates according to the invention of this application.

[0040] The bending process can also be carried out in such a way that the number of substrate material sheets and cover plates overlapped at a portion other than the portion that was bent after the electronic component installation process was completed is different from the number of substrate material sheets and cover plates overlapped at other portions.

[0041] For example, a plate-shaped multilayer substrate is manufactured using a multilayer substrate manufacturing method. Furthermore, within a certain area of ​​the formed multilayer substrate, four substrate material sheets and four cover plates are overlapped each; in other areas, eight substrate material sheets and eight cover plates are overlapped each. Thus, of course, the thickness of the multilayer substrate increases in the other areas compared to the aforementioned area. Using the same manufacturing method, multilayer substrates with varying thicknesses can be obtained in such portions, which is one of the advantages of the multilayer substrate manufacturing method according to this invention. Since substrates with varying thicknesses can be manufactured, less substrate material is used in the thinner substrate portions, thereby contributing to lower material costs and lower engineering costs.

[0042] As described above, in the fixing process, the overlapping substrate material sheets and cover plates are heated. Alternatively, the overlapping substrate material sheets and cover plates can be heated while being pressurized. This allows for uniform and secure fixing of the substrate material sheets to the cover plates, or cover plates to cover plates.

[0043] The fixing process can be carried out by heating (or heating and pressurizing) the entire substrate material sheet and cover plate after the bending process once, or by heating (or heating and pressurizing) a portion of the substrate material sheet and cover plate after the bending process along with other parts multiple times. When the formed multilayer substrate has a three-dimensional shape, the fixing process is more often carried out in the latter way.

[0044] In the method for manufacturing a multilayer substrate according to the present invention, a wiring process for setting the wiring on the surface of the substrate material sheet may also be performed before the overlapping process. There are no specific limitations on the techniques that can be used to set the wiring on the surface of the substrate material sheet in the wiring process; as already explained, known or publicly known techniques can be used.

[0045] For the wiring, the width at the bent portion of the substrate material sheet can be wider than the width of the portions on both sides in its length direction. In the manufacturing method of the multilayer substrate of this application, the wiring is bent together with the substrate material sheet. Therefore, there is a certain risk of wiring breakage. If the width of the wiring at the bent portion of the substrate material sheet is wider than the width of the portions on both sides in its length direction, it helps to prevent breakage of the wiring bent together with the substrate material sheet.

[0046] When the wiring process is performed before the overlapping process, the wiring can also be made such that the width of the wiring at the part where the base material sheet is bent is wider than the width of the parts on both sides in its length direction. Attached Figure Description

[0047] Figure 1 This is a diagram showing a substrate material sheet used in one embodiment of the invention of this application, viewed from the side.

[0048] Figure 2 This is a diagram showing a substrate material sheet with wiring installed as viewed from the surface.

[0049] Figure 3 It is Figure 2 The image is enlarged near the X mark in the attached figure.

[0050] Figure 4 This is a diagram showing the cover plate as viewed from the side.

[0051] Figure 5 This is a diagram showing the substrate material sheet and cover plate as viewed from the side in one embodiment when the overlapping process is completed.

[0052] Figure 6 This is a diagram illustrating a method of implementing the bending process in one embodiment.

[0053] Figure 7 This is a diagram showing a multilayer substrate completed after the electronic component mounting process in one embodiment.

[0054] Figure 8 (A) to (D) are diagrams showing the implementation method of the bending process in Modified Example 1, and (E) is a side view of the base material sheet and cover plate shown in (D).

[0055] Figure 9 This is a diagram showing the base material sheet and cover plate as observed from the surface in Variation Example 2 when the overlapping process is completed.

[0056] Figure 10 This is a diagram illustrating the implementation method of the bending process in Variation Example 2.

[0057] Figure 11 This is a diagram showing the multilayer substrate completed after the electronic component mounting process in Variation Example 2.

[0058] Figure 12 This is a diagram showing the base material sheet and cover plate as observed from the surface in Variation Example 3 when the overlapping process is completed.

[0059] Figure 13 A diagram illustrating the implementation method of the bending process in Variation Example 3.

[0060] Figure 14 This diagram shows the multilayer substrate completed after the electronic component mounting process in Variation Example 3.

[0061] Figure 15 This is a diagram showing the base material sheet and cover plate as observed from the surface in Variation Example 4 when the overlapping process is completed.

[0062] Figure 16 This is a diagram illustrating the implementation method of the bending process in variation example 4.

[0063] Figure 17 This is a perspective view of the multilayer substrate completed after the electronic component mounting process in Variation Example 4 is finished. Detailed Implementation

[0064] Hereinafter, an embodiment and variations thereof of the present invention will be described with reference to the accompanying drawings.

[0065] In this embodiment, a method for manufacturing a multilayer substrate will be described. The multilayer substrate is manufactured by performing the various steps described below.

[0066] Multilayer substrates are manufactured using substrate material sheets, cover plates, and electronic components as raw materials.

[0067] First, let's explain the substrate material sheet.

[0068] exist Figure 1 The image shows the state of the substrate material sheet 1 as viewed from the surface. The wiring, which will be described later, has not yet been installed on this substrate material sheet 1.

[0069] The substrate material sheet 1 is rectangular. As will be described later, the substrate material sheet 1 can also be square; however, in… Figure 1 The example shown is not a square.

[0070] The substrate material sheet 1 is made of a thermoplastic resin and has insulating properties. Examples of thermoplastic resins constituting the substrate material sheet 1 include liquid crystal polymers (LCP), polyphenylene sulfide (PPE), polyether ether ketone (PEEK), and fluorinated resins (FR). However, it is not limited to these, and in this embodiment, liquid crystal polymers (LCP) are selected as the thermoplastic resin constituting the substrate material sheet 1.

[0071] The thickness of the substrate material sheet 1 can be appropriately selected within a range that allows it to be bent together with the cover plate as described later. Its thickness can be, for example, from 20 μm to 200 μm, preferably from 25 μm to 100 μm.

[0072] In this embodiment, wiring 11 is provided for such a substrate material sheet 1. Figure 2 Additionally, in Figure 2 In the figure, the double-dotted line assigned to reference numeral 12 is a bend line indicating that the substrate material sheet 1 is subsequently bent.

[0073] Wiring 11 is only disposed on the surface of the substrate material sheet 1. The surface on one side of the substrate material sheet 1 where wiring 11 is disposed is the surface of the substrate material sheet 1.

[0074] Wiring 11 is conductive and is generally made of a conductive metal. Although not limited to this, in this embodiment, wiring 11 is made of a conductive metal.

[0075] There are no specific limitations on the techniques used to set the wiring 11 on the substrate material sheet 1, and known or commonly known techniques can be employed. For example, the wiring 11 can be set on the surface of the substrate material sheet 1 by a subtractive or additive method. The subtractive method involves: attaching copper foil to the entire surface of the substrate material sheet with an adhesive; removing unwanted portions (the portions of the copper foil not covered by the mask) by chemical etching while the wiring portion is covered by a mask; and finally, removing the mask to leave the copper foil covered by the mask as the wiring 11 on the surface of the substrate material sheet 1. The additive method involves: setting a mask such that only the portion corresponding to the wiring 11 is exposed on the surface of the substrate material sheet 1; then performing plating (e.g., electroless plating and electrolytic plating); thereby setting a metal plating layer on the portion where the mask is not present; and then removing the mask to obtain the wiring 11 on the substrate material sheet 1. By performing a single process for wiring on the substrate material sheet 1, such as a subtractive or additive method, the wiring 11 can be set simultaneously. Although not limited to this, it is done in this embodiment.

[0076] In addition, Figure 2In the figure, the position enclosed by the dashed line designated as reference numeral 13 is the predetermined position for the subsequent installation of electronic components. The reason for the non-uniformity in the size of the predetermined position Y is that the predetermined position 13 corresponds to the size of the predetermined electronic component to be installed there.

[0077] Furthermore, it is not necessarily necessary for Figure 1 The substrate material sheet 1 shown is provided with wiring 11. For example, the following method can also be used: for a ratio of Figure 1 The matrix material sheet 1 shown is a larger matrix material sheet (e.g., Figure 1 The substrate material sheet 1 shown has a length of 10 times its cross length. 10 × 10 = 100 wirings 11 are then installed on the substrate material sheet 1. Next, the substrate material sheet 1 is cut into 10 pieces in each direction, thus obtaining 100 wirings 11 in one operation. Figure 2 The same substrate material sheet 1 is shown for the wiring 11. This method of manufacturing wiring 11 enables efficient mass production of multilayer substrates. In this case, 10×10=100 wirings for a large sheet of substrate material can be set up at the same time by performing a single wiring process on the large sheet of substrate material, thereby reducing the manufacturing cost of the substrate material sheet 1.

[0078] The wiring 11 may or may not have all sections of the same width. As will be described later, each of the linear wirings 11 that connects the electronic components mounted on the substrate material sheet 1 can be given an appropriate width. For example, the width of at least one of the linear wirings 11 may also be different from the width of the other linear wirings 11.

[0079] Furthermore, the width of a linear wiring 11 does not necessarily need to be constant along its entire length. The linear wiring 11, as from... Figure 2 As can be seen, there are cases where the wire 11 crosses the bend line 12. In this case, it doesn't matter if the width of the wiring 11 at the location where it crosses the bend line 12 is wider than the width of the wiring 11 on both sides along its length. Figure 3 The text shows an example of this situation. Figure 3 yes Figure 2An enlarged view of the portion marked by the dashed line X. Thus, the width of the wiring 11 at the portion crossing the bend line 12 is wider than its width on both sides or front and back in the length direction. While not limited to this, in this embodiment, all wiring 11 crossing the bend line 12 has a width at the portion crossing the bend line 12 that is wider than its width on both sides or front and back in the length direction. In this embodiment, when the wiring 11 is provided on the substrate material sheet 1, the width of the wiring 11 at the portion crossing the bend line 12 is wider than its width on both sides or front and back in the length direction. It goes without saying that... Figure 3 This is an example. In Figure 3 In the case of wiring 11, the width of the portion crossing the bend line 12 increases linearly compared to the sides or front and back in its length direction. However, for example, the width of wiring 11 at the portion crossing the bend line 12 may also increase curvilinearly compared to the sides or front and back, or it may increase in a crank-like manner from a certain position.

[0080] Next, we will explain the cover plate.

[0081] Figure 4 This diagram shows the view of the cover plate 2 from the surface side. The surface side of the cover plate 2, when the cover plate 2 is subsequently overlapped with the substrate material sheet 1, is the side that does not face the substrate material sheet 1.

[0082] The cover plate 2 is a rectangular sheet that is essentially the same shape and size as the substrate material sheet 1. No wiring is provided on the cover plate 2.

[0083] The cover plate 2 is made of thermoplastic resin and has insulating properties. Examples of thermoplastic resins constituting the cover plate 2 include: liquid crystal polymer (LCP), polyphenylene sulfide (PPE), polyether ether ketone (PEEK), and fluorinated resin (FR).

[0084] While not limited to this, in this embodiment, liquid crystal polymer (LCP) is selected as the thermoplastic resin constituting the cover plate 2. Furthermore, the thermoplastic resin constituting the cover plate 2 and the thermoplastic resin constituting the substrate material sheet 1 can be the same or different. Regardless of whether the substrate material sheet 1 and the cover plate 2 are made of the same or different materials, the substrate material sheet 1 and the cover plate 2 can be processed as needed by adjusting the processing conditions such as the heating temperature, heating time, and pressure applied as required in the fixing process described later.

[0085] The thickness of the cover plate 2 can be appropriately selected within a range that allows it to be bent together with the substrate material sheet 1 as described later. Its thickness can be, for example, from 20 μm to 200 μm, preferably from 25 μm to 100 μm.

[0086] The thickness of the substrate material sheet 1 and the cover plate 2 can be the same or different. As already described, the thickness of the substrate material sheet 1 and the cover plate 2 needs to be thin enough to allow for a bending process when they are overlapped.

[0087] On the other hand, preferably, the thickness of the cover plate 2 exceeds the thickness of the wiring 11 shaped like the substrate material sheet 1. This is because if the thickness of the cover plate 2 is thinner than the thickness of the wiring 11, after the fixing process described later, the cover plate 2 may not properly cover the wiring 11. Furthermore, if the cover plate 2 is thinner than the wiring 11, after the fixing process, even if the cover plate 2 covers the wiring 11, the thickness of the wiring 11 will appear as a protrusion on the surface of the cover plate 2 covering the wiring 11 (the surface that does not contact the substrate material sheet 1). If the thickness of the wiring 11 appears as a protrusion on the surface of the cover plate 2, there is a risk of poor bonding or other problems when mounting electronic components to surfaces with poor planarity. However, if the thickness of the cover plate 2 is thicker than the thickness of the wiring 11, such problems are less likely to occur.

[0088] In addition, the thickness of the cover plate 2 can be thinner than the thickness of the base material sheet 1. By making the thickness of the cover plate 2 thinner than the thickness of the base material sheet 1, the rigidity is reduced and the flexibility is improved during the bending process described later. In addition, it helps to reduce processing costs and material costs.

[0089] At least one hole 21 is provided in the cover plate 2. The hole 21 is provided at the position where electronic components are subsequently disposed relative to the substrate material sheet 1, that is, at the position corresponding to the predetermined position 13. The reason for the non-uniform size of the hole 21 is that the hole 21 must conform to the size of the predetermined electronic component to be installed there. Although not limited to this, in this embodiment, the cover plate 2 is provided with seven holes 21.

[0090] in addition, Figure 4 The double-dotted line assigned to reference numeral 22 in the accompanying drawings is the bend line indicating the portion where the cover plate 2 is subsequently bent together with the substrate material sheet 1. Since the overlapping substrate material sheet 1 and cover plate 2 are bent together, the bend line 12 of the substrate material sheet 1 and the bend line 22 of the cover plate 2 are located in corresponding positions.

[0091] After preparing the substrate material sheet 1 and cover plate 2 as described above, the first step is to perform the overlapping process.

[0092] In the overlapping process, the cover plate 2 is overlapped on the surface of the base material sheet 1 in a manner that matches the contours of both. Figure 5Therefore, the holes 21 in the cover plate 2 correspond to predetermined positions 13 on the substrate material sheet 1. Near the periphery of each hole 21, the wiring 11 is exposed.

[0093] Next, the bending process will be carried out.

[0094] In the bending process, the overlapping substrate material sheet 1 and cover plate 2 are bent together. Bending is performed along the bending line 12 of the overlapping substrate material sheet 1 and the bending line 22 of the cover plate 2. At least one bending is performed. The bending may be either a convex bend or a concave bend, or a combination of both. However, after the bending process, the aforementioned hole 21 in the cover plate 2 becomes exposed. "Hole 21 exposed" means that the hole 21 is not covered by the substrate material sheet 1 or the cover plate 2.

[0095] In addition, after the overlapping process and before the bending process, in order to prevent the outlines of the overlapping substrate material sheet 1 and cover plate 2 from deviating during the bending process, a temporary fixing process can be performed to temporarily fix the substrate material sheet 1 and cover plate 2. Although it is not limited to this, it is done in this embodiment. Temporary fixing can be performed by bonding a portion (e.g., the four corners) of the part where the substrate material sheet 1 and cover plate 2 abut together with an adhesive. Of course, there are no limitations on the method of temporary fixing. The pin stacking method used in general multilayer substrate manufacturing methods can be used, in which substrates with holes are stacked and pins pass through the holes provided on each substrate, thereby positioning each substrate. Alternatively, a temporary fixing fixture (clamp, etc.) that clamps the substrate material sheet 1 and cover plate 2 together can be used for temporary fixing.

[0096] While not limited to this, in the bending process of this embodiment, firstly, the overlapping base material sheet 1 and cover plate 2 (which are the result of the overlapping process) are... Figure 5 , Figure 6 (A) The portion above the laterally extending bend lines 12 and 22 is directed towards the portion along the laterally extending bend lines 12 and 22. Figure 6 It folds back in the inward direction. Thus, the substrate material sheet 1 and the cover plate 2 become... Figure 6 The state shown in (B).

[0097] Secondly, it will become Figure 6 (B) The substrate material sheet 1 and cover plate 2 in state Figure 6 (B) The portion to the right of the longitudinally extending bend lines 12 and 22, at the portion along the longitudinally extending bend lines 12 and 22... Figure 6 Fold it back in the inward direction. In this way, the base material sheet 1 and the cover plate 2, which are folded by bending, become... Figure 6The state shown in (C). When from Figure 6 When observing the folded substrate material sheet 1 and cover plate 2 from the inside of (C), they become... Figure 6 The state shown in (D).

[0098] The bending process in this embodiment is now complete. With the bending process finished, hole 21 becomes... Figure 6 (C) shows 4 exposed faces. Figure 6 (D) shows a state where 3 holes are exposed. That is, all 7 holes 21 that originally existed in the cover plate 2 are exposed to the outside after the bending process is completed.

[0099] In addition, in utilizing Figure 6 In the illustrated example, all parts of the substrate material sheet 1 and the cover plate 2, except for the bent portions, are practically parallel. That is, the bent substrate material sheet 1 and the cover plate 2 become parallel to each other. Figure 6 (C) shows the surface to Figure 6 (D) shows the state in which the substrate material sheet 1 and the cover plate 21 are stacked in the order of cover plate 2, substrate material sheet 1, substrate material sheet 1, cover plate 2, cover plate 2, substrate material sheet 1, substrate material sheet 1, and cover plate 2.

[0100] Since the width of all the wiring 11 crossing the bend line 12 becomes wider at the portion crossing the bend line 12 than the width on both sides or front and back in its length direction, the risk of damage such as wire breakage is very small even if the wiring 11 is bent together with the substrate material sheet 1.

[0101] Next, the fixed procedures will be implemented.

[0102] In the fixing process, the base material sheet 1 and the cover plate 2, which have undergone the bending process, are fixed.

[0103] This fixing process is performed by heating the bent substrate material sheet 1 and the cover plate 2. During the fixing process, not only are the substrate material sheet 1 and the cover plate 2 heated, but the folded substrate material sheet 1 and the cover plate 2 can also be bent from... Figure 6 (C) shows the face and Figure 6 (D) shows the two surfaces clamping each other to apply pressure. This is the case in this embodiment.

[0104] The heating and pressurizing conditions for the substrate material sheet 1 and the cover plate 2 can be adjusted according to the thickness and melting point of the materials. The heating and pressurizing conditions described below are an example where the thermoplastic resins constituting the substrate material sheet 1 and the cover plate 2 are both liquid crystal polymers. More precisely, the substrate material sheet 1 is a liquid crystal polymer with a melting point of 335°C, and the cover plate 2 is a liquid crystal polymer with a melting point of 280°C. The reason for choosing a resin with a lower melting point than the liquid crystal polymer constituting the thermoplastic resin of the substrate material sheet 1 as the thermoplastic resin constituting the cover plate 2 is that, during the fixing process, by preferentially softening the cover plate 2 compared to the substrate material sheet 1, the softened and fluidized liquid crystal polymer constituting the cover plate 2 effectively fills the gaps between adjacent substrate material sheets 1 and cover plates 2 (where unevenness sometimes exists due to wiring 11) or between adjacent cover plates 2. Thus, in this application, thermoplastic resins that constitute the matrix material sheet 1 and the cover plate 2 can be selected respectively, such that the melting point of the thermoplastic resin constituting the cover plate 2 is lower than the melting point of the thermoplastic resin constituting the matrix material sheet 1.

[0105] For example, heating of the substrate material sheet 1 and the cover plate 2 can be carried out using a general pressurization device.

[0106] (1) First, the temperature of the substrate material sheet 1 and the cover plate 2 is raised from room temperature to a temperature at which the thermoplastic resin constituting them (especially the thermoplastic resin constituting the cover plate) softens slightly, for example, 150°C, and this temperature is maintained for several minutes. The purpose of this step is to fill the gap between adjacent substrate material sheets 1 and cover plates 2, or between adjacent cover plates 2, to a certain extent by softening at least one of the substrate material sheets 1 and cover plates 2, using the softened and fluidized thermoplastic resin.

[0107] (2) Next, the temperature of the substrate material sheet 1 and the cover plate 2 is raised to a temperature close to the melting point of the thermoplastic resin constituting them (especially the thermoplastic resin constituting the cover plate), for example, 290°C, and this temperature is maintained for about 30 minutes. The purpose of this process is to further soften at least the cover plate 2 of the substrate material sheet 1 and the cover plate 2, and to use the softened and fluidized thermoplastic resin to practically completely fill the gap between adjacent substrate material sheets 1 and cover plates 2, or the gap between adjacent cover plates 2.

[0108] (3) Finally, the temperature of the substrate material sheet 1 and the cover plate 2 is cooled to, for example, room temperature. This process causes the thermoplastic resin that effectively fills the gap between adjacent substrate material sheets 1 and cover plates 2, or between adjacent cover plates 2, to harden. As a result, the gap between adjacent substrate material sheets 1 and cover plates 2, or between adjacent cover plates 2, becomes a state in which the thermoplastic resin effectively fills the gap, and the adjacent substrate material sheets 1 and cover plates 2, or adjacent cover plates 2, become a state in which they are mutually fixed.

[0109] When performing the above-mentioned steps (1) to (3), the base material sheet 1 and the cover plate 2 are pressurized in the pressurizing device.

[0110] In this embodiment, for example, no pressure is applied for a period of time from the start of the process described in (1). During the time from near the middle of the period in which the temperature of the substrate material sheet 1 and the cover plate 2 is maintained at 150°C until the end of the process, for example, the substrate material sheet 1 and the cover plate 2 are pressurized at 3 MPa and the pressure is kept constant. This is to allow the gaps between adjacent substrate material sheets 1 and cover plates 2, or between adjacent cover plates 2, to be better filled by the fluidized thermoplastic resin.

[0111] Furthermore, from the start of process (2) above until the end of process (3), the substrate material sheet 1 and the cover plate 2 are pressurized at a constant pressure of 1 MPa. The reason for making the pressure at this time smaller than the pressure applied during the time period in process (1) when the temperature of the substrate material sheet 1 and the cover plate 2 is maintained at 150 degrees (in this example, as mentioned above, the pressure is 3 MPa) is that although constant pressure is required in order to better utilize the fluidized thermoplastic resin to fill the gap between adjacent substrate material sheet 1 and cover plate 2, or between adjacent cover plates 2, there is a risk that the fluidized thermoplastic resin will leak out from the gap between adjacent substrate material sheet 1 and cover plate 2, or between adjacent cover plates 2, when the pressure is applied too strongly.

[0112] As described above, in the folded base material sheet 1 and cover plate 2 after the bending process is completed, the material becomes... Figure 6 (C) shows the surface to Figure 6(D) shows a stacked state in which the substrate material sheet 1 and the cover plate 2 are layered in the following order: cover plate 2, substrate material sheet 1, substrate material sheet 1, cover plate 2, cover plate 2, substrate material sheet 1, substrate material sheet 1, and cover plate 2. By heating, at least a portion of the cover plate 2 melts and hardens after heating. In this embodiment, a portion of the substrate material sheet 1 also melts and hardens after heating. Thus, in each of the aforementioned layers contained in the folded substrate material sheet 1 and cover plate 2, adjacent substrate material sheets 1 and cover plates 2, adjacent substrate material sheets 1 and substrate material sheets 1, and adjacent cover plates 2 and cover plates 2 are fused together.

[0113] Thus, when the fixing process is completed, the folded base material sheet 1 and cover plate 2 are fixed into a plate shape.

[0114] After the fixed process is completed, the electronic component installation process is carried out.

[0115] Electronic components include IC chips, BGAs, CSPs, resistors, capacitors, etc., which can be appropriately selected according to the performance requirements of the multilayer substrate.

[0116] The electronic component 3 is connected in a conductive state to the wiring 11 on the surface of the substrate material sheet 1 included in the plate-shaped substrate material sheet 1 and the cover plate 2, which are disposed in a fixed state after the fixed process is completed. Figure 7 (A), (B)), thus, are fixed to the substrate material sheet 1.

[0117] Electronic component 3 is inserted into the hole 21 passing through the cover plate 2, and the terminals protruding from electronic component 3 are soldered to wiring 11, for example, using soldering. This connects electronic component 3 to wiring 11 in a conductive state. Since electronic component 3 needs to be inserted into hole 21 to fix it relative to wiring 11, hole 21 needs to be larger than electronic component 3. This is because otherwise, there would be risks that when mounting electronic component 3 to the substrate material sheet 1 via hole 21, pressure would be applied during insertion, potentially damaging electronic component 3, or making it difficult to move electronic component 3 horizontally relative to the surface of substrate material sheet 1. Furthermore, in order to enable conductive connection between electronic component 3 and wiring 11, hole 21 needs to be shaped to expose the end of wiring 11 from the periphery of hole 21. Hole 21 in this embodiment is such a shape.

[0118] Alternatively, closely adjacent holes 21 can be combined to form a single hole 21. For example, in Figure 7 (A) Two holes 21 that are smaller than the other holes 21 located side by side on the left and right sides can be combined into one hole. In this case, two electronic components 3 are installed in one hole 21.

[0119] All predetermined electronic components 3 are fixed to the substrate material sheet 1, and a circuit is formed by wiring 11 and electronic components 3, thereby completing the multilayer substrate.

[0120] In the multilayer substrate manufactured according to this embodiment, except for the bent portion, the substrate material sheet 1 and the cover plate 2 are actually parallel. In addition, the number of overlapping substrate material sheets 1 and cover plates 2 (the sum of their numbers) is the same in all parts of the multilayer substrate (8 sheets in this embodiment). The multilayer substrate having such a structure is formed into a plate shape.

[0121] In the multilayer substrate manufactured using this multilayer substrate manufacturing method, the surface of the substrate material sheet 1, except for the portion where the hole 21 is formed, is covered by the cover plate 2. As a result, since the wiring 11 is protected by the cover plate 2, the wiring 11 is less likely to break.

[0122] <Variation Example 1>

[0123] The manufacturing method of the multilayer substrate in Variation 1 is almost the same as that of the multilayer substrate manufacturing method described in the embodiments.

[0124] The multilayer substrate is manufactured using substrate material sheet 1, cover plate 2 and electronic components 3 as raw materials.

[0125] The structure of the substrate material sheet 1 and the cover plate 2 remains essentially unchanged in Modified Example 1 and the above-described embodiments. However, Figure 4 The hole 21 on the lower right of the cover plate 2 shown is slightly smaller in the modified example 1. In addition, the position of the hole 21 is slightly closer to the lower left corner of the cover plate 2.

[0126] In addition, in modified example 1, the structure of the wiring 11 provided on the surface of the substrate material sheet 1 is appropriately modified as the position and size of the hole 21 are changed.

[0127] In Modification 1, the same overlapping process as in the above-described embodiment is also performed.

[0128] Furthermore, in Modification 1, the same bending process as in the above-described embodiment is performed. In the above embodiment, the overlapping substrate material sheet 1 and cover plate 2 are bent twice; similarly, in Modification 1, the substrate material sheet 1 and cover plate 2 are bent twice. As a result, the substrate material sheet 1 and cover plate 2 become as follows: Figure 8 The states shown in (A) and (B). Figure 8 (A) and (B) are based on Figure 6 Figures based on (C) and (D).

[0129] In the bending process of Modified Example 1, from this state, the overlapping base material sheet 1 and cover plate 2 are bent again. This third bending follows... Figure 8 The bends 12 and 22 shown in (A) and (B) are used.

[0130] The third bend, Figure 8 In (A), the portion of the overlapping substrate material sheet 1 and cover plate 2 that is lower than the laterally extending bend lines 12 and 22 is oriented towards the portion along the laterally extending bend lines 12 and 22. Figure 8 (A) is folded back in the inward direction. Thus, the substrate material sheet 1 and the cover plate 2 become... Figure 8 The states shown in (C) and (D). Figure 8 (C) and (D) are respectively from and Figure 8 (A) and (B) are images of the substrate material sheet 1 and cover plate 2 viewed from the same direction.

[0131] This concludes the bending process for variation example 1.

[0132] In this case, after the bending process is completed, all seven holes 21 of the cover plate 2 are exposed to the outside.

[0133] Furthermore, in this case, all parts of the base material sheet 1 and the cover plate 2 after the bending process are actually parallel, except for the bent parts.

[0134] Furthermore, for the substrate material sheet 1 and cover plate 2 that are bent in this way, the upper portion of the bent substrate material sheet 1 and cover plate 2 becomes a state where the substrate material sheet 1 and cover plate 2 are stacked together in a total of 8 pieces, and the lower portion becomes a state where the substrate material sheet 1 and cover plate 2 are stacked together in a total of 16 pieces. As a result, in modified example 1, the substrate material sheet 1 and cover plate 2 after the bending process have Figure 8 (E) shows the step difference, in other words, the cross section with a step shape.

[0135] Subsequently, in Modified Example 1, the multilayer substrate is completed by performing the fixing process and the electronic component mounting process in the same manner as in the above-described embodiment.

[0136] The completed multilayer substrate, in addition to housing electronic component 3, contains other components such as... Figure 8 The substrates shown in (C), (D), and (E) are as follows. As a result, the multilayer substrate manufactured using the manufacturing method of Modified Example 1 has... Figure 8 (E) shows the step difference, in other words, the cross section with a step shape.

[0137] <Variation Example 2>

[0138] The manufacturing method of the multilayer substrate in Variation Example 2 is almost identical to the manufacturing method of the multilayer substrate described in the embodiments.

[0139] The multilayer substrate is manufactured using substrate material sheet 1, cover plate 2 and electronic components 3 as raw materials.

[0140] The structures of the substrate material sheet 1 and the cover plate 2 remain essentially unchanged in Modified Example 2 and the above-described embodiments. However, in Modified Example 2, both the substrate material sheet 1 and the cover plate 2 are square.

[0141] Although the entire substrate material sheet 1 in Modified Example 2 is not shown again, it is provided with the same wiring 11 as in the above embodiment.

[0142] In variation 2, the overlapping process is performed in the same manner as in the above-described embodiment. Figure 9 In the same manner as in the embodiment described above, holes 21 are provided on the cover plate 2. The number of holes 21 is 8 in variant example 2, but it is not limited to this.

[0143] In addition, in variation 2, the bending process is performed after the overlapping process, just like in the above-described embodiment. Figure 9 The dashed line 22A shown is the convex fold line where the substrate material sheet 1 and the cover plate 2 are folded forward, and the double-dotted line 22B is the concave fold line where the substrate material sheet 1 and the cover plate 2 are folded backward.

[0144] In this embodiment, the substrate material sheet 1 and the cover plate 2 simultaneously undergo convex folding along the convex fold line 22A and concave folding along the concave fold line 22B, thereby... Figure 10 (A) state after Figure 10 The state of (B) is folded to Figure 10 (C) shows a plate-like shape. This folding method is commonly used in origami. Additionally, in Figure 10 In (B), the center of the substrate material sheet 1 and the cover plate 2 is located near the front side of the paper surface, and the edges of the substrate material sheet 1 and the cover plate 2 are located on the inside side of the paper surface.

[0145] This concludes the bending process for variation example 2.

[0146] In this case, after the bending process is completed, all eight holes 21 of the cover plate 2 are exposed to the outside. Figure 11 ).in addition, Figure 11 (A) is a diagram showing one side of the base material sheet 1 and cover plate 2 in deformation example 2, which has become plate-shaped after the bending process is completed. Figure 11 (B) is a diagram of the other side.

[0147] Furthermore, in this case, all parts of the base material sheet 1 and the cover plate 2 after the bending process are actually parallel, except for the bent parts.

[0148] Subsequently, in Modification 2, the multilayer substrate is completed by performing the fixing process and the electronic component mounting process in the same manner as in the above-described embodiments.

[0149] The completed multilayer substrate, in addition to housing electronic component 3, contains other components such as... Figure 10 (C) and Figure 11 The substrate shown. As a result, the multilayer substrate manufactured using the manufacturing method of Modified Example 2 becomes a plate-shaped right-angled isosceles triangle on the surface and back side where electronic components 3 are mounted.

[0150] <Variation Example 3>

[0151] The manufacturing method of the multilayer substrate in Modified Example 3 is the same as that in Modified Example 2, except that the bending methods of the substrate material sheet 1 and the cover plate 2 in the bending process are different.

[0152] The multilayer substrate is manufactured using substrate material sheet 1, cover plate 2 and electronic components 3 as raw materials.

[0153] The structure of the substrate material sheet 1 and the cover plate 2 is basically the same as that in variation example 3 and variation example 2. In variation example 3, both the substrate material sheet 1 and the cover plate 2 are square.

[0154] Although the entire surface of the substrate material sheet 1 in Modified Example 3 is no longer shown in the figure, it is provided with the same wiring 11 as in the above-described embodiment.

[0155] In Modification 3, the overlapping process is performed in the same manner as in Modification 2. Figure 12 In the cover plate 2, holes 21 are provided in the same manner as in the above embodiment. The number of holes 21 is 8 in variant example 3, but it is not limited to this.

[0156] In addition, in variation 3, the bending process is performed after the overlapping process, just like in the above-described embodiment. Figure 12 The dashed line 22A shown is the convex fold line where the substrate material sheet 1 and the cover plate 2 are folded forward, and the double-dotted line 22B is the concave fold line where the substrate material sheet 1 and the cover plate 2 are folded backward.

[0157] In this embodiment, the substrate material sheet 1 and the cover plate 2 are simultaneously folded along the convex fold line 22A and folded along the concave fold line 22B, from... Figure 13 (A) state after Figure 13 The state of (B) is folded to Figure 13(C) shows a plate-like shape. This folding method is commonly used in origami. Additionally, in Figure 13 In (B), the center of the substrate material sheet 1 and the cover plate 2 is located near the front side of the paper surface, and the edges of the substrate material sheet 1 and the cover plate 2 are located on the inside side of the paper surface.

[0158] This concludes the bending process for variation example 3.

[0159] In this case, after the bending process is completed, all eight holes 21 of the cover plate 2 are exposed to the outside. Figure 14 ).in addition, Figure 14 (A) is a view of one side of the base material sheet 1 and cover plate 2 of the deformed example 3, which has become a plate after the bending process is completed. Figure 14 (B) is a diagram of the other side.

[0160] Furthermore, in this case, all parts of the base material sheet 1 and the cover plate 2 after the bending process are actually parallel, except for the bent parts.

[0161] Subsequently, in Modification 3, the multilayer substrate was completed by performing the fixing process and the electronic component mounting process in the same manner as in the above-described embodiment.

[0162] The completed multilayer substrate, in addition to housing electronic component 3, contains other components such as... Figure 13 (C) and Figure 14 The substrate shown. As a result, the multilayer substrate manufactured using the manufacturing method of Modified Example 3 becomes a square plate-shaped substrate on which electronic components 3 are mounted on the surface and back.

[0163] <Variation Example 4>

[0164] The manufacturing method of the multilayer substrate in Modification Example 4 is the same as that in Modification Example 2, except that the bending method of the substrate material sheet 1 and the cover plate 2 in the bending process is different, and the implementation method of the fixing process is different.

[0165] The multilayer substrate is manufactured using substrate material sheet 1, cover plate 2 and electronic components 3 as raw materials.

[0166] The structures of the substrate material sheet 1 and the cover plate 2 remain essentially unchanged in modified examples 4 and 2. In modified example 4, both the substrate material sheet 1 and the cover plate 2 are square.

[0167] Although the entire substrate material sheet 1 in Modified Example 4 is not shown in the figure, it is provided with the same wiring 11 as in the above-described embodiment.

[0168] In variation 4, the overlapping process is performed in the same manner as in variation 2. Figure 15 In the cover plate 2, holes 21 are provided in the same manner as in the above-described embodiment. The number of holes 21 is 10 in variant example 4, but it is not limited to this.

[0169] In addition, in variation 4, the bending process is performed after the overlapping process, just like in the above-described embodiment. Figure 12 The dashed line 22A shown is the convex fold line where the substrate material sheet 1 and the cover plate 2 are folded forward, and the double-dotted line 22B is the concave fold line where the substrate material sheet 1 and the cover plate 2 are folded backward.

[0170] In this embodiment, the substrate material sheet 1 and the cover plate 2 are simultaneously folded along the convex fold line 22A and concave folded along the concave fold line 22B, thereby... Figure 16 (A) state after Figure 16 The state of (B) is folded to Figure 16 (C) shows a plate-like shape. This folding method is commonly used in origami. Additionally, in Figure 16 In (B), the centers of the substrate material sheet 1 and the cover plate 2 are located near the front side of the paper surface, while the edges of the substrate material sheet 1 and the cover plate 2 are located on the inside side of the paper surface. Additionally, in Figure 16 In (B), the depiction of the hole 21 on the cover plate 2 and the wiring 11 in the substrate material sheet 1 exposed from the hole 21 is omitted.

[0171] This concludes the bending process for variation example 4.

[0172] In the case of variation 4, the base material sheet 1 and cover plate 2 after the bending process have the following shape: in the plan view, right-angled isosceles triangles of the same size extending in four symmetrical directions are connected in such a way that the non-hypotenuse sides of the right-angled isosceles triangles coincide (see reference). Figure 16 (C) Figure 17 ).

[0173] In this case, after the bending process is completed, all 10 holes 21 of the cover plate 2 are exposed. This is because all 10 holes 21 are located on any two sides of the four plate-like portions of the aforementioned right-angled isosceles triangle after the bending process. Furthermore, Figure 17 This is a perspective view of the base material sheet 1 and cover plate 2 of deformation example 4 after the bending process is completed.

[0174] In Modification 4, after the bending process, a portion of the base material sheet 1 and the cover plate 2 become non-parallel in relation to the other parts of the base material sheet 1 and the cover plate 2. Therefore, in Modification 4, after the bending process, the base material sheet 1 and the cover plate 2 have a three-dimensional shape.

[0175] Subsequently, in Modification 4, the multilayer substrate is completed by performing the fixing process and the electronic component mounting process in the same manner as in the above-described embodiment.

[0176] However, in this embodiment, the fixing process is performed four times for each of the aforementioned right-angled isosceles triangle plate-shaped portions. Pressure is applied and heat is applied to each right-angled isosceles triangle plate-shaped portion. By doing so, the substrate material sheet 1 and cover plate 2 that abut against each other, and the substrate material sheet 1 and substrate material sheet 1 that abut against each other, are respectively fixed at the four plate-shaped portions.

[0177] The completed multilayer substrate, in addition to housing electronic component 3, contains other components such as... Figure 16 (C) and Figure 17 The substrate shown. As a result, the multilayer substrate manufactured using the manufacturing method of Modified Example 4 has the three-dimensional structure described above.

[0178] Additionally, in the case of a plan view, the angles between adjacent plate-like portions of each right-angled isosceles triangle ( Figure 17 In this case, θ is basically 90 degrees, but since the plate-like parts of a right isosceles triangle can rotate about the non-hypotenuse side that coincides at the four plate-like parts, this angle is variable.

[0179] Explanation of reference numerals in the attached figures

[0180] 1. Matrix material sheet

[0181] 2. Cover plate

[0182] 3 Electronic components

[0183] 11 Wiring

[0184] 12. Bending lines

[0185] 21 holes

[0186] 22. Bend line

Claims

1. A method for manufacturing a multilayer substrate, wherein, include: The overlapping process involves overlapping the cover plate onto the surface of the base material sheet, wherein the outline of the base material sheet matches the outline of the cover plate. The base material sheet is a rectangular sheet made of thermoplastic resin that has insulation properties. Conductive wiring is arranged appropriately on the surface of the base material sheet. The cover plate is a sheet that is substantially the same shape and size as the base material sheet. The cover plate has at least one hole at the location where electronic components will be placed. The cover plate is made of thermoplastic resin and has insulation properties. The bending process involves bending and folding the overlapping substrate material sheet and the cover plate with the holes exposed to the outside. The fixing process involves heating the folded base material sheet and the cover plate to melt at least a portion of the cover plate, followed by cooling and hardening, thereby fixing the adjacent base material sheet and the cover plate. An electronic component mounting process, wherein the electronic component is fixed to the substrate material sheet exposed from the hole in such a state that the wiring of the electronic component inserted into the hole is in communication with the surface of the substrate material sheet exposed from the hole.

2. The method for manufacturing a multilayer substrate as described in claim 1, wherein, The substrate material sheet is square.

3. The method for manufacturing a multilayer substrate as described in claim 2, wherein, After the electronic component installation process is completed, the base material sheet and the cover plate are in the shape of a square or a right-angled isosceles triangle.

4. The method for manufacturing a multilayer substrate as described in claim 1, wherein, The bending process is performed so that all portions of the substrate material sheet and the cover plate after the electronic component mounting process are substantially parallel, except for the bent portions.

5. The method for manufacturing a multilayer substrate as described in claim 4, wherein, The bending process is performed such that the number of substrate material sheets and cover plates overlapped in a portion other than the bent portion after the electronic component mounting process is completed is different from the number of substrate material sheets and cover plates overlapped in other portions.

6. The method for manufacturing a multilayer substrate as described in claim 1, wherein, In the fixing process, adjacent cover plates among the overlapping base material sheets and cover plates are also fixed to each other.

7. The method for manufacturing a multilayer substrate as described in claim 1 or 5, wherein, In the fixing process, the overlapping substrate material sheets and the cover plate are pressurized and heated simultaneously.

8. The method for manufacturing a multilayer substrate as described in claim 1, wherein, Prior to the overlapping process, a wiring process is performed to lay the wiring on the surface of the substrate material sheet.

9. The method for manufacturing a multilayer substrate as described in claim 1 or 8, wherein, The width of the wiring at the bent portion of the substrate material sheet is wider than the width of the portions on both sides in the length direction.

10. The method for manufacturing a multilayer substrate as described in claim 1 or 9, wherein, The cover plate is thinner than the substrate material sheet.

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