JP2019057694A - Manufacturing method of multilayer substrate, manufacturing method of component mounting substrate, multilayer substrate and component mounting substrate - Google Patents

Abstract

To provide a manufacturing method of a multilayer substrate which has the stable connection resistance value and high connection reliability in an interlayer connection part, and enables printing formation of a uniform insulation layer onto the interlayer connection part and component mounting, a manufacturing method of a component mounting substrate, the multilayer substrate and the component mounting substrate.SOLUTION: A manufacturing method of a multilayer substrate 100 includes: a process of forming a through hole 1 with punching processing so that a front surface circuit pattern 2 and a rear surface circuit pattern 3 are formed on the front surface and rear surface of an insulation substrate 4, and a portion of at least one circuit pattern on the front surface and rear surface of the insulation substrate 4 extends along the inner wall of the through hole 1 of the insulation substrate 4; and a process of forming an interlayer connection part 6 by filling the inside and circumference of the through hole 1 with the conductive paste by printing from both of the front surface and rear surface of the insulation substrate 4.SELECTED DRAWING: Figure 1B

Description

  The present disclosure relates to a multilayer board manufacturing method, a component mounting board manufacturing method, a multilayer board, and a component mounting board.

  The interlayer connection portion of the multilayer substrate needs to have connection reliability that can withstand thermal shock during heat treatment and soldering work in the component mounting process. For example, in Patent Document 1 and Patent Document 2, a circuit board having an interlayer connection portion with higher connection reliability than conventional by devising the shape of the through hole by punching and filling the through hole with a conductive paste And a circuit board manufacturing method.

JP 7-302962 A JP-A-10-51095

  However, in the technique of the above-mentioned patent document, the front and back surfaces of the interlayer connection part are not flat, and it is difficult to mount components on the interlayer connection part. In addition, for example, when a printable insulating resin is formed by a screen printing method or the like, there is no flatness on the front and back surfaces of the interlayer connection portion, so that the insulating layer is distorted or stepped on the front and back surfaces of the interlayer connection portion. . For this reason, voids, pinholes and the like are generated in the insulating layer, so that a uniform insulating layer cannot be formed, and there is a concern that the electrical insulation in the vicinity of the interlayer connection portion is lowered. Further, the interlayer connection portion of the multilayer substrate is required to have a stable connection resistance value in addition to connection reliability.

  Embodiments according to the present disclosure have a stable connection resistance value and high connection reliability in an interlayer connection, and a method for manufacturing a multilayer substrate capable of printing a uniform insulating layer on the interlayer connection and mounting components. It is an object of the present invention to provide a component mounting board manufacturing method, a multilayer board, and a component mounting board.

  In the method for manufacturing a multilayer substrate according to an embodiment of the present disclosure, a circuit pattern is formed on a front surface and a back surface of an insulating substrate, and a part of the circuit pattern on at least one of the front surface and the back surface of the insulating substrate is the insulating substrate. Forming the through hole by punching so as to extend along the inner wall of the through hole, and conductive paste by printing from both the front and back surfaces of the insulating substrate in and around the through hole. And forming an interlayer connection part.

  A component mounting board manufacturing method according to an embodiment of the present disclosure includes a step of forming a resist on the front and back surfaces of the multilayer board manufactured by the multilayer board manufacturing method described above, and a component on the multilayer board on which the resist is formed. Mounting.

  A multilayer substrate according to an embodiment of the present disclosure includes a circuit pattern provided on a front surface and a back surface of an insulating substrate, and an interlayer connection formed by filling a conductive paste in a through hole penetrating the insulating substrate and the circuit pattern. A part of the circuit pattern of at least one of the front surface and the back surface of the insulating substrate extending along the inner wall of the through hole of the insulating substrate, and the insulating substrate The portions of the interlayer connection portion on the front surface and the back surface are flat.

  A component mounting board according to an embodiment of the present disclosure is obtained by mounting a mounting component on the multilayer board described above.

According to the multilayer substrate manufacturing method of the embodiment according to the present disclosure, the interlayer connection portion has a stable connection resistance value and high connection reliability, and printing of an insulating layer on the interlayer connection portion and component mounting are possible. A multilayer substrate can be manufactured.
According to the method for manufacturing a component mounting board of the embodiment according to the present disclosure, a component mounting board having a stable connection resistance value and high connection reliability in an interlayer connection portion and having a high insulation property of an insulating layer is manufactured. Can do.
According to the multilayer substrate of the embodiment according to the present disclosure, the interlayer connection portion has a stable connection resistance value and high connection reliability, and an insulating layer can be printed on the interlayer connection portion and components can be mounted.
According to the component mounting board of the embodiment according to the present disclosure, the interlayer connection portion has a stable connection resistance value and high connection reliability, and the insulating layer has high insulation.

It is a top view showing typically the composition of the multilayer substrate concerning an embodiment. It is sectional drawing which shows typically the structure of the multilayer substrate which concerns on embodiment, and shows the cross section corresponded to the IB-IB line | wire of FIG. 1A. It is sectional drawing which shows the state before forming a circuit pattern in the manufacturing method of the multilayer substrate which concerns on embodiment. It is sectional drawing which shows the process of forming a circuit pattern in the manufacturing method of the multilayer substrate which concerns on embodiment. It is sectional drawing which shows the process of forming a through hole in the manufacturing method of the multilayer substrate which concerns on embodiment. It is sectional drawing which shows the process of forming the interlayer connection part in the manufacturing method of the multilayer board | substrate which concerns on embodiment, and is sectional drawing which shows the process of filling with an electrically conductive paste from the back surface of an insulated substrate. It is sectional drawing which shows the process of forming the interlayer connection part in the manufacturing method of the multilayer board | substrate which concerns on embodiment, and is sectional drawing which shows the process of filling with an electrically conductive paste from the surface of an insulated substrate. It is sectional drawing which shows the process of grind | polishing the site | part of the interlayer connection part in the manufacturing method of the multilayer substrate which concerns on embodiment. It is sectional drawing which shows typically the structure of the component mounting board which concerns on embodiment. It is sectional drawing which shows the multilayer substrate before forming the resist in the manufacturing method of the component mounting board which concerns on embodiment. It is sectional drawing which shows the process of forming a resist in the manufacturing method of the component mounting board | substrate which concerns on embodiment, and is sectional drawing which shows the process of forming a resist on the surface of a multilayer substrate. It is sectional drawing which shows the process of forming the resist in the manufacturing method of the component mounting board | substrate which concerns on embodiment, and is sectional drawing which shows the process of forming a resist in the back surface of a multilayer substrate. It is sectional drawing which shows the process of mounting components in the manufacturing method of the component mounting board which concerns on embodiment, and is sectional drawing which shows the process of forming an contact bonding layer. It is sectional drawing which shows the process of mounting components in the manufacturing method of the component mounting board which concerns on embodiment, and is sectional drawing which shows the state after mounting components. It is an image which shows the board | substrate for interlayer connection part evaluation before filling with the electrically conductive paste used in the Example. It is an image which expands and shows a part of Drawing 7A. It is a perspective view which shows typically the connection state of the interlayer connection part in the board | substrate for interlayer connection part evaluation after filling with the electrically conductive paste used in the Example.

<Embodiment>
Embodiments will be described below with reference to the drawings. However, the forms shown below exemplify a multilayer board manufacturing method, a component mounting board manufacturing method, a multilayer board, and a component mounting board for embodying the technical idea of the present embodiment. It is not limited to. In addition, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only. Note that the size and positional relationship of the members shown in each drawing may be exaggerated for clarity of explanation.

[Multilayer substrate]
First, the multilayer substrate according to the present embodiment will be described.
FIG. 1A is a plan view schematically showing the configuration of the multilayer substrate according to the embodiment. 1B is a cross-sectional view schematically showing the configuration of the multilayer substrate according to the embodiment, and shows a cross section corresponding to the line IB-IB in FIG. 1A.

  In the multilayer substrate 100, the conductive paste is filled into the insulating substrate 4, the front surface circuit pattern 2 provided on the surface of the insulating substrate 4, the back surface circuit pattern 3 provided on the back surface of the insulating substrate 4, and the through hole 1. And an extended portion 20 in which a part of the surface circuit pattern 2 extends along the inner wall of the through hole 1 of the insulating substrate 4.

As the insulating substrate 4, one or a plurality of glass cloths are impregnated with a thermosetting insulating resin such as an epoxy resin, and the glass epoxy, film-like polyimide, or liquid crystal polymer in which the thermosetting insulating resin is cured. Etc. The insulating substrate 4 is generally manufactured as a double-sided copper-clad laminate with copper foil attached to both sides.
When the insulating substrate 4 is glass epoxy, the thickness can be 50 to 1000 μm. Moreover, when the insulating substrate 4 is a polyimide, thickness can be 12-50 micrometers. As the insulating substrate 4, it is possible to use a plate having a certain thickness to a thin plate.

  The surface circuit pattern 2 is formed on the surface of the insulating substrate 4. The back circuit pattern 3 is formed on the back surface of the insulating substrate 4. The front surface circuit pattern 2 and the back surface circuit pattern 3 are formed by wiring in a desired shape. The front surface circuit pattern 2 and the back surface circuit pattern 3 are made of a metallic material such as copper.

  The thickness of the front surface circuit pattern 2 and the back surface circuit pattern 3 is preferably 12 to 70 μm. If the thickness of the front surface circuit pattern 2 and the back surface circuit pattern 3 is 12 μm or more, the front surface circuit pattern 2 and the back surface circuit pattern 3 are easily formed. On the other hand, if the thickness is 70 μm or less, the multilayer substrate 100 can be thinned.

  The through hole 1 is formed so as to penetrate the front surface circuit pattern 2, the insulating substrate 4, and the back surface circuit pattern 3. The diameter of the through hole 1 is, for example, 0.2 to 0.3 mm.

The interlayer connection portion 6 is a portion that electrically connects the front surface circuit pattern 2 and the back surface circuit pattern 3. The interlayer connection 6 is formed by filling the through hole 1 with a conductive paste. In addition, the interlayer connection portion 6 is formed by filling a conductive paste in and around the through-hole 1 and curing it in a state where it is sufficiently in contact with the front surface circuit pattern 2 and the back surface circuit pattern 3. Here, the periphery of the through-hole 1 is the vicinity of the through-hole 1, for example, within 1 mm, preferably within 0.3 mm, more preferably within 0.1 mm from the through-hole 1.
The interlayer connection portion 6 is formed by filling the through hole 1 with a conductive paste, thereby improving connection reliability against thermal shock in a process of mounting components and the like.

The interlayer connection portion 6 is formed in a convex shape on the front surface and the back surface of the insulating substrate 4. Further, the interlayer connection portion 6 covers a part of the front surface circuit pattern 2 and the back surface circuit pattern 3. In the present embodiment, the interlayer connection portion 6 includes a portion covering the front surface circuit pattern 2 and the back surface circuit pattern 3.
That is, the interlayer connection part 6 is formed at both ends of the in-hole filling parts 5a and 6a filled in the through hole 1 and the in-hole filling parts 5a and 6a. And have. Here, the through hole 1 includes a case where only the in-hole filling portion 5a or only the in-hole filling portion 6a is filled.

As the conductive paste, for example, a mixture of a filler such as flaky, scaly, or bark-like silver powder or copper powder and a thermosetting binder resin can be used.
Further, as the conductive paste, it is preferable to use a paste having a volume resistivity as low as possible and a low content of binder resin or solvent component.
For example, it is preferable to use a conductive paste having a volume resistivity of 2 × 10 ^{−5 to} 1.5 × 10 ⁻⁴ Ω · cm and a binder resin content of 3 to 10% by mass. With such a conductive paste, the resistance value of the interlayer connection portion 6 becomes smaller and the variation in resistance value becomes smaller. The volume resistivity is more preferably about 7.5 × 10 ⁻⁵ Ω · cm, and the binder resin content is more preferably 6 to 7% by mass. Moreover, it is preferable to use a conductive paste having a solvent content of 0 to 1% by mass, for example.

  The conductive paste preferably has a small thermal shrinkage at the time of curing. Specifically, it is preferable that the mass reduction rate during curing is 1% or less. Such a conductive paste makes it easier to control the flatness in the out-of-hole flat plate portion 6b serving as the surface of the interlayer connection portion 6 described later and the out-of-hole flat plate portion 5b serving as the back surface. Here, since the conductive paste is filled from the back side of the insulating substrate 4 first, even if the conductive paste filled in the hole filling portion 5a contracts, the conductive paste is filled again from the front side of the insulating substrate 4 Therefore, the recess of the out-hole flat plate portion 6b on the surface of the insulating substrate 4 can be reduced, and the out-of-hole flat plate portion 6b can be flattened.

The multilayer substrate 100 has an extended portion 20 in which a part of the surface circuit pattern 2 extends along the inner wall of the through hole 1 of the insulating substrate 4. That is, in the multilayer substrate 100, the extending portion 20 is formed by pushing a part of the surface circuit pattern 2 when forming the through hole 1. The extended portion 20 is formed so that the end portion on the through hole 1 side of the surface circuit pattern 2 extends toward the inner layer of the insulating substrate 4 and is in close contact with the insulating substrate 4 inside the through hole 1. .
In the present embodiment, since the multilayer substrate 100 has the extended portion 20, the contact area between the in-hole filling portions 5a and 6a formed of the conductive paste and the surface circuit pattern 2 becomes wider than a normal through hole. For this reason, the resistance value of the interlayer connection 6 is lowered and the resistance value is stabilized.

  The length of the extended portion 20, that is, the length of the part of the surface circuit pattern 2 located on the inner wall of the through hole 1 (length in the vertical direction) is preferably 5 to 35 μm. If the length of the extension part 20 is 5 μm or more, the contact area between the hole filling parts 5a, 6a and the surface circuit pattern 2 becomes wider. Therefore, in the multilayer substrate 100, the resistance value of the interlayer connection portion 6 is easily lowered and the resistance value is more easily stabilized. On the other hand, if the length of the extension part 20 is 35 μm or less, the extension part 20 is more easily formed.

The portions of the interlayer connection 6 on the front and back surfaces of the insulating substrate 4 are formed flat. That is, the upper surfaces of the convex portions (out-hole plate portions 5b, 6b) on the front surface and the back surface of the interlayer connection portion 6 are formed flat.
Here, “flat” means that the thickness difference between the thinnest part and the thickest part of the out-hole flat plate part 6b is 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less.

It is preferable that the thickness of the flat part of the interlayer connection part 6, that is, the thickness of the out-of-hole flat plate part 6 b serving as the surface of the insulating substrate 4 and the out-of-hole flat plate part 5 b serving as the back surface is 10 to 30 μm. When the thickness of the out-hole flat plate portions 5b and 6b is 10 μm or more, the interlayer connection portion 6 is easily formed. On the other hand, if the thickness of the out-hole flat plate portions 5b and 6b is 30 μm or less, the thickness of the multilayer substrate 100 can be reduced. The thickness of the out-hole flat plate portion 6b on the surface of the insulating substrate 4 is the thickness from the upper surface of the surface circuit pattern 2 to the upper surface of the out-of-hole flat plate portion 6b on the surface of the insulating substrate 4. Further, the thickness of the out-of-hole flat plate portion 5 b on the back surface of the insulating substrate 4 is the thickness from the upper surface of the back surface circuit pattern 3 to the upper surface of the out-of-hole flat plate portion 5 b on the back surface of the insulating substrate 4.
The thickness of the out-hole flat plate portions 5b and 6b can be controlled by the amount of the conductive paste when filling the through-hole 1. Moreover, it can control by grind | polishing the flat-plate part 5b, 6b outside a hole.

As described above, in the present embodiment, in the multilayer substrate 100, the out-of-hole flat plate portion 6b serving as the surface of the interlayer connection portion 6 and the out-of-hole flat plate portion 5b serving as the back surface are formed flat.
The interlayer connection portion 6 of the multilayer substrate 100 needs to have a connection reliability that can withstand heat shock during a component mounting process and thermal shock during soldering. In conventional multilayer substrates, through-hole connection by plating is often used. However, in such a multilayer substrate, a crack is generated in the corner portion of the through hole due to the stress generated by the difference between the thermal expansion coefficient of the substrate in the thickness direction of the substrate and the thermal expansion coefficient of the plating, thereby reducing connection reliability. Therefore, for example, as described in Patent Document 1 and Patent Document 2 described in the background art, a connection method for filling a through-hole with a conductive paste is proposed for through-hole connection by plating.

  In Patent Document 1 and Patent Document 2, the connection portion is formed by the conductive paste embedded in the through hole. However, the conductive paste is insufficiently filled in the through hole. When cured, the binder resin undergoes thermal shrinkage. For this reason, the front and back surfaces of the interlayer connection portion are not flat, and it is difficult to mount components on the interlayer connection portion. Therefore, conventionally, the interlayer connection part and the component mounting part are arranged separately. However, there is a problem that the substrate area increases due to this.

  Further, in the interlayer connection portions as in Patent Document 1 and Patent Document 2, the insulating layer provided on the interlayer connection portion is also restricted. Specifically, for example, when a printable insulating resin is formed by a screen printing method or the like, voids and pinholes are generated in the concave portions of the interlayer connection portion because the front and back surfaces of the interlayer connection portion are not flat. . For this reason, a uniform insulating layer cannot be formed, and there is a concern that the electrical insulation in the vicinity of the connecting portion is lowered. Therefore, the actual situation is that a coverlay film or the like having an adhesive having a thickness that can follow the unevenness of the front and back surfaces of the multilayer substrate is attached. However, when a coverlay film or the like having an adhesive is attached, there is a problem that the total thickness of the substrate is increased by an amount corresponding to the thickness of the adhesive.

  In particular, in an LED mounting substrate, the insulating layer on the substrate surface must be white, reflectivity, light resistance, and the like. However, in a coverlay film made of a polyimide resin having a general adhesive layer, there is a problem that the polyimide resin undergoes photodegradation in an LED continuous lighting test. Therefore, the actual situation is that the required characteristics of customers cannot be satisfied.

  Here, the requirements for circuit boards from customers are increasing year by year, and in particular, many electronic devices are becoming smaller, thinner, and lighter in order to reduce the board area including components. There are increasing demands for higher density and thinner insulating layers. However, a multilayer board having a conventional connection structure cannot meet these requirements.

  In the present embodiment, in the multilayer substrate 100, since the out-of-hole flat plate portion 6b serving as the front surface of the interlayer connection portion 6 and the out-of-hole flat plate portion 5b serving as the back surface are flat, it is easy to form a resist on the inter-layer connection portion 6. Therefore, the insulating property is high, and the component mounting on the interlayer connection portion 6 is easy.

[Multilayer substrate manufacturing method]
Next, an example of a method for manufacturing a multilayer substrate according to the present embodiment will be described.
FIG. 2A is a cross-sectional view illustrating a state before the circuit pattern is formed in the method for manufacturing a multilayer substrate according to the embodiment. FIG. 2B is a cross-sectional view illustrating a process of forming a circuit pattern in the method for manufacturing a multilayer substrate according to the embodiment. FIG. 2C is a cross-sectional view illustrating a process of forming a through hole in the method for manufacturing a multilayer substrate according to the embodiment. FIG. 3A is a cross-sectional view showing a step of forming an interlayer connection part in the method for manufacturing a multilayer substrate according to the embodiment, and is a cross-sectional view showing a step of filling a conductive paste from the back surface of the insulating substrate. FIG. 3B is a cross-sectional view showing a step of forming an interlayer connection part in the method for manufacturing a multilayer substrate according to the embodiment, and is a cross-sectional view showing a step of filling a conductive paste from the surface of the insulating substrate. FIG. 3C is a cross-sectional view showing a step of polishing a portion of the interlayer connection portion in the method for manufacturing a multilayer substrate according to the embodiment.
The same number is assigned to the squeegee and the mask in each process, but the physical same thing is not used, only the function and properties are common, and different sizes and materials are used. be able to.

  The method of manufacturing a multilayer substrate according to the present embodiment includes a step of forming a circuit pattern, a step of forming a through hole, a step of forming an interlayer connection, and a step of polishing a portion of the interlayer connection. Perform in this order. Note that the material and arrangement of each member are the same as described in the description of the multilayer substrate 100 described above, and thus the description thereof will be omitted as appropriate.

(Process for forming a circuit pattern)
The step of forming the circuit pattern is a step of forming the front surface circuit pattern 2 and the back surface circuit pattern 3 on the front and back surfaces of the insulating substrate 4.

In this step, for example, first, one or more sheet-like glass cloths are impregnated with an epoxy resin, the front surface copper foil 2a is bonded to the front surface, and the back surface copper foil 3a is bonded to the back surface to cure the epoxy resin. A commercially available double-sided copper-clad laminate is prepared. Next, the front surface copper foil 2 a and the back surface copper foil 3 a are etched to form the front surface circuit pattern 2 and the back surface circuit pattern 3.
In addition, you may join the surface copper foil 2a to the surface of the insulated substrate 4, and the back surface copper foil 3a to the back surface, without using a commercially available double-sided copper clad laminated board. Moreover, you may purchase the double-sided copper clad laminated board in which the surface circuit pattern 2 and the back surface circuit pattern 3 were formed previously.

(Process for forming through holes)
The step of forming the through hole is a step of forming the through hole 1 by punching so that a part of the surface circuit pattern 2 of the insulating substrate 4 extends along the inner wall of the through hole 1 of the insulating substrate 4.

In this step, punching processing is performed by inserting a punching pin (punch) 14 from the front surface side of the insulating substrate 4 at a portion of the insulating substrate 4 where the front surface circuit pattern 2 and the rear surface circuit pattern 3 are present. The through hole 1 having a diameter of 2 to 0.3 mm is formed. Here, when the through hole 1 is formed, a part of the surface circuit pattern 2 extends along the inner wall of the through hole 1 of the insulating substrate 4. That is, the end portion of the surface circuit pattern 2 extends by being forcibly pushed toward the inner layer of the insulating substrate 4, and the extension portion 20 is formed inside the through hole 1.
In the punching process, it is preferable to adjust the length of the extended portion 20 to be 0.05 to 0.5 times, preferably 0.1 to 0.4 times the thickness of the insulating substrate 4. Moreover, in punching, it is preferable to adjust so that the length of the extension part 20 may be 5-35 micrometers.

  The length of the extending portion 20 is mainly adjusted by adjusting the diameter of the punch and the diameter of the die (punch receiving side) that constitute the punching pin. Although depending on the thickness and material of the front surface circuit pattern 2 and the back surface circuit pattern 3, for example, for a punch diameter of 0.2 to 0.3 mm, it is preferable to set the die diameter to about 0.21 to 0.32 mm. A gap of about 0.005 to 0.01 mm is set between the punch and the die.

(Process for forming interlayer connection)
The step of forming the interlayer connection portion is a step of forming the interlayer connection portion 6 by filling the inside and the periphery of the through hole 1 with the conductive paste 6c by printing from both the front surface and the back surface of the insulating substrate 4. Here, the conductive paste 6c is filled in the order of the back surface and the front surface of the insulating substrate 4, but the conductive paste 6c may be filled in the order of the surface and the back surface of the insulating substrate 4.

  In this step, first, the conductive paste 6c is filled into the through hole 1 from the back surface of the insulating substrate 4 through the mask 11 by screen printing. The screen printing conditions are, for example, a clearance of 0 to 2 mm, a metal mask 11 having a thickness of 20 to 300 μm and an opening hole diameter of φ 0.2 to 0.5 mm, or a screen mask 11 having a thickness of 150 to 400 mesh and an emulsion thickness of 10 to 20 μm. And a urethane rubber squeegee 40 having a hardness of 70 to 80, an effective squeegee angle of 15 to 30 degrees, a printing pressure of 0.2 to 0.4 MPa, a squeegee speed of 10 to 50 mm / sec, and squeegee reciprocal printing. . Of the front and back surfaces of the insulating substrate 4, the surface to be printed first is the reciprocating printing, whereby the through-hole 1 can be more easily filled with the conductive paste 6 c. In addition, when the thickness of the insulating substrate 4 is thin or the through hole 1 is large, the conductive paste 6c is filled in the through hole 1 even in the squeegee one-way printing, and therefore the squeegee one-way printing may be used.

  Thereafter, the conductive paste 6c is heated and temporarily cured at a constant temperature of, for example, 80 to 120 ° C. for 15 to 30 minutes. The temporary curing of the conductive paste 6c is preferably in a state where the surface of the conductive paste 6c is dried, and the conductive paste 6c after the temporary curing is preferably in an insulator state.

The reason why the pre-cured conductive paste 6c is preferably in an insulating state will be described below.
The conductive paste 6c printed from the back surface and the conductive paste 6c formed from the front surface are connected by screen printing from the front surface of the next step. At this time, if the conductive paste 6c printed and formed from the back surface is excessively hardened, the conductive paste 6c printed from the back surface and the conductive paste 6c formed from the front surface are connected. There is a case where the conductive state of the interface is deteriorated. When the conduction state is deteriorated, quality problems such as an increase in connection resistance value and a decrease in connection reliability against thermal shock occur. Therefore, it is preferable that the electrically conductive paste 6c after temporary curing is in an insulator state.

The following method can be used to bring the conductive paste 6c after temporary curing into an insulating state.
First, a heat treatment test is performed using a sample in which the conductive paste 6c is line printed in advance. Then, under what conditions with respect to the heating temperature and heating time, (1) how hard the conductive paste 6c is, and (2) how much the resistance value of the line is, is temporarily cured Derive conditions. Thereby, the temporary hardening conditions used as the state of an insulator are determined. It is also possible to proceed to the next step without pre-curing at all. However, when the conductive paste 6c in the wet state is exposed on the substrate surface, it is adsorbed on the printing table or the suction paper in the next step, which causes problems such as the conductive paste 6c being peeled off from the substrate. Therefore, it is preferable that the conductive paste 6c printed from the back surface is temporarily cured.

  In this way, first, the joined body portion 5 having the in-hole filling portion 5a and the out-hole flat plate portion 5b on the back surface of the insulating substrate 4 is formed. In FIG. 3A, for convenience, the bonded body portion 5 is illustrated as a state after the conductive paste 6c is temporarily cured.

  Subsequently, the conductive paste 6c is printed and formed from the surface of the insulating substrate 4 through the mask 11 by a screen printing method. As the conductive paste 6c, the same paste as the conductive paste 6c printed and filled from the back surface of the insulating substrate 4 can be used. The screen printing conditions are, for example, a clearance of 0 to 2 mm, a metal mask 11 having a thickness of 20 to 50 μm and an opening hole diameter of 0.2 to 0.5 mm, or a screen mask 11 having a thickness of 150 to 400 mesh and an emulsion thickness of 10 to 20 μm. And a squeegee 40 of urethane rubber having a hardness of 80, and an squeegee effective angle of 15 to 70 degrees, a printing pressure of 0.1 to 0.4 MPa, a squeegee speed of 10 to 100 mm / sec, and squeegee one-way printing.

Thereafter, the conductive paste 6c is heated and cured at a constant temperature of 180 to 200 ° C. for 45 to 90 minutes. Thereby, the interlayer connection part 6 which electrically connects the front surface circuit pattern 2 and the back surface circuit pattern 3 is formed. In FIG. 3B, for convenience, the interlayer connection portion 6 is illustrated as a state after the conductive paste 6c is cured.
When the conductive paste 6c is filled in the order of the front surface and the back surface of the insulating substrate 4, the above-described screen printing method conditions from the back surface and the screen printing method conditions from the front surface may be interchanged.

  In the present embodiment, in the step of filling the conductive paste 6c, the conductive paste 6c is filled into the through hole 1 from both the front and back surfaces of the insulating substrate 4 by printing, so that the surface of the insulating substrate 4 is filled. And the site | part of the hole outside flat plate parts 5b and 6b of the interlayer connection part 6 in a back surface can be made flat.

(Process of polishing the part of the interlayer connection)
The step of polishing the portion of the interlayer connection portion is a step of flatly polishing the portion of the interlayer connection portion 6 on the front and back surfaces of the insulating substrate 4. That is, this step is a step of polishing the upper surfaces of the out-of-hole flat plate portions 5b and 6b so that the upper surfaces of the out-of-hole flat plate portions 5b and 6b on the front surface and the back surface of the interlayer connection portion 6 become flatter.

  From the relationship between the electrode shape and thickness of the mounting component 10 and the thickness of the surface resist 7, the interlayer connection portion 6 may be subjected to a polishing process before the surface resist 7 is printed and formed as necessary. In that case, physical polishing with the ceramic buff 30 is preferable. By performing the polishing process of the interlayer connection portion 6, the portions of the out-hole plate portions 5 b and 6 b of the interlayer connection portion 6 can be further flattened. In addition, the process of grind | polishing the site | part of an interlayer connection part does not need to be performed as an essential process.

[Component mounting board]
Next, the component mounting board according to the present embodiment will be described.
FIG. 4 is a cross-sectional view schematically showing the configuration of the component mounting board according to the embodiment.
The component mounting substrate 101 includes a multilayer substrate 100, a surface resist 7 provided in a partial region on the surface of the multilayer substrate 100, a back surface resist 8 provided on the back surface of the multilayer substrate 100, and the surface of the multilayer substrate 100. A mounting component 10 is provided on the interlayer connection portion 6 via an adhesive layer 9 that is a solder paste.

  The surface resist 7 is formed around the mounting component 10. That is, the surface resist 7 is provided on the surface circuit pattern 2 excluding the interlayer connection portion 6 and the vicinity thereof. The back resist 8 is formed so as to cover the back circuit pattern 3 and the interlayer connection 6.

  As the front surface resist 7 and the back surface resist 8, for example, a general one obtained by mixing a copolymer resin such as epoxy with a solvent or an antifoaming agent, or a whitened one obtained by adding a filler such as titanium oxide is used. it can. The front surface resist 7 and the back surface resist 8 become insulating layers. The thicknesses of the front surface resist 7 and the back surface resist 8 are, for example, 10 to 30 μm. The thickness of the surface resist 7 is preferably equal to or thicker than the thickness of the out-hole flat plate portion 6b. This is because the height of the adhesive layer 9 can be suppressed and the height of the mounting component 10 can be reduced by making the thickness of the out-hole flat plate portion 6 b thinner than the thickness of the surface resist 7. The thickness of the out-hole flat plate portion 6b is, for example, preferably about 0.5 to 0.9 times, and more preferably about 0.6 to 0.8 times the thickness of the surface resist 7. By setting the thickness of the out-hole flat plate portion 6b to 0.5 times or more, the thickness of the interlayer connection portion 6 can be suppressed, and by setting it to 0.9 times or less, the electrical conductivity can be kept high. The thicknesses of the front surface resist 7 and the back surface resist 8 may be the same or different.

  As a material of the adhesive layer 9, for example, Sn—Ag—Cu, Au, Ag, Cu, Sn, Bi, or an alloy thereof can be used. Examples of the mounting component 10 include an LED, a chip resistor, and a capacitor.

[Manufacturing method of component mounting board]
Next, a method for manufacturing the component mounting board according to the present embodiment will be described.
FIG. 5A is a cross-sectional view illustrating the multilayer substrate before the resist is formed in the method for manufacturing the component mounting substrate according to the embodiment. FIG. 5B is a cross-sectional view showing a step of forming a resist in the method for manufacturing a component mounting board according to the embodiment, and is a cross-sectional view showing a step of forming a resist on the surface of the multilayer board. FIG. 5C is a cross-sectional view showing a step of forming a resist in the method for manufacturing a component mounting board according to the embodiment, and is a cross-sectional view showing a step of forming a resist on the back surface of the multilayer board. FIG. 6A is a cross-sectional view illustrating a process of mounting a component in the method for manufacturing a component mounting board according to the embodiment, and is a cross-sectional view illustrating a process of forming an adhesive layer. FIG. 6B is a cross-sectional view illustrating a process for mounting a component in the method for manufacturing a component mounting board according to the embodiment, and is a cross-sectional view illustrating a state after the component is mounted. The front resist before curing is 7c, and the back resist before curing is 8c.

  The method for manufacturing a component mounting board according to the present embodiment includes, as an example, a step of forming a resist on the multilayer substrate described above and a step of mounting components, which are performed in this order. Note that the material and arrangement of each member are as described in the description of the component mounting board, and therefore the description thereof will be omitted as appropriate.

(Process for forming resist)
The step of forming the resist is a step of forming the front surface resist 7 and the back surface resist 8 on the front surface and the back surface of the multilayer substrate 100. Here, the front surface resist 7 and the back surface resist 8 are formed in the order of the front surface and the back surface of the multilayer substrate 100, but the back surface resist 8 and the front surface resist 7 may be formed in the order of the back surface and the front surface of the multilayer substrate 100.

  In this step, first, the surface resist 7 is formed on the surface circuit pattern 2 of the multilayer substrate 100 by a screen printing method using the screen mask 12 and the surface resist 7c on which a desired coating pattern is formed.

  Screen printing conditions are, for example, a clearance of 0.5 to 5.0 mm, a screen mask 12 of 100 to 400 mesh, an emulsion thickness of 10 to 20 μm, and a urethane rubber squeegee 40 of hardness 60 to 80, and a squeegee effective. An angle of 60 to 80 degrees, a printing pressure of 0.2 to 0.4 MPa, a squeegee speed of 20 to 100 mm / sec, and squeegee one-way printing can be used. Thereafter, the surface resist 7 is heated and cured at 50 to 250 ° C. for 5 to 60 minutes.

  Subsequently, the back resist 8 is formed on the back circuit pattern 3 by a screen printing method using the screen mask 12 and the back resist 8c. The back resist 8 can be the same as the resist printed and formed from the surface of the insulating substrate 4, and the screen printing conditions can be the same as those during the printing of the front resist 7. Thereafter, the back resist 8 is heated and cured at 50 to 250 ° C. for 5 to 60 minutes. Thereby, an insulating layer is formed in a desired range of the front surface circuit pattern 2 and the back surface circuit pattern 3.

(Process for mounting components)
The step of mounting the component is a step of mounting the component on the multilayer substrate 100 on which the front surface resist 7 and the back surface resist 8 are formed.

  In this step, first, the solder paste 9c is printed using the metal mask 13 and the squeegee 40 each having an opening in a component mounting portion, and the adhesive layer 9 is formed. Next, the mounting component 10 is placed on the adhesive layer 9, the adhesive layer 9 is cured, and the mounting component 10 is connected and fixed to the multilayer substrate 100.

  In this example, the solder paste 9c is directly applied on the interlayer connection portion 6, but from the viewpoint of the bonding strength of the component, the mounting portion of the component may be subjected to a plating process or an organic rust prevention process in advance.

  As described above, according to the present embodiment, the interlayer connection portion 6 is formed by filling the through hole 1 with the conductive paste 6c. Here, paying attention to the difference in thermal expansion coefficient between the material used for the interlayer connection portion 6 and the substrate insulating resin, the difference in thermal expansion coefficient between the conductive paste 6c containing the binder resin and the insulating resin material of the insulating substrate 4 is The difference in thermal expansion coefficient between the plating metal and the insulating resin material of the substrate in the through-hole connection by plating that is generally used is small. Therefore, since the stress during thermal shock is suppressed, the connection reliability of the multilayer substrate 100 in the process of mounting components and the like is improved.

  Further, an extending portion 20 in which a part of the surface circuit pattern 2 extends along the inner wall of the through hole 1 of the insulating substrate 4 is formed by punching. As a result, the contact area between the hole filling portions 5a, 6a formed of the conductive paste 6c filled in and around the through hole 1 and the surface circuit pattern 2 becomes wider than that of a general connection portion structure. Therefore, the resistance value of the interlayer connection portion 6 is reduced, and the variation in resistance value is also reduced. Further, since the front and back surfaces of the interlayer connection 6 are flat, it is easy to form the surface resist 7 and the back resist 8 on the interlayer connection 6 and to mount components. Therefore, it is possible to improve the insulation of the interlayer connection portion 6 in the multilayer substrate 100 and increase the component mounting density. In addition, the accuracy of the mounting position of the mounting component 10 and the accuracy of the inclination, which are particularly important in mounting LED components, can be ensured by the flatness of the front and back surfaces of the interlayer connection portion 6. Further, it can be applied to a flexible substrate having a thin insulating layer, and can contribute to downsizing, thinning, and narrowing the frame of electronic devices and displays.

Examples will be described below.
FIG. 7A is an image showing an interlayer connection evaluation substrate before filling with a conductive paste used in the example. FIG. 7B is an image showing a part of FIG. 7A in an enlarged manner. FIG. 7C is a perspective view schematically showing a connection state of the interlayer connection portion in the interlayer connection portion evaluation substrate after being filled with the conductive paste used in the example.

  The interlayer connection portion was evaluated using the interlayer connection portion evaluation substrate. The board for evaluating the interlayer connection part has a board outer dimension of 40 mm × 190 mm, and 40 interlayer connection parts are connected in series at 140 locations in a daisy chain at intervals of 0.9 mm between the upper left and lower left measurement lands. It is a structure that connects columns. The total number of interlayer connection portions in one substrate is 5600. In addition, as for the board | substrate for an interlayer connection part evaluation, 6 pieces with a through-hole diameter of 0.25 mm and 3 pieces with a through-hole diameter of 0.2 mm were produced in total.

The substrate for evaluating the interlayer connection portion was manufactured by the method for manufacturing a multilayer substrate described above. Specifically, it is as follows.
First, a copper foil having a thickness of 35 μm was bonded to the front and back surfaces of an insulating substrate (glass epoxy) having a thickness of 400 μm, and the total thickness of the multilayer substrate in the interlayer connection portion was set to 470 μm. Next, the copper foil on both sides was etched to form a front surface circuit pattern and a back surface circuit pattern. Next, punching was performed from the surface side of the insulating substrate with a punching pin to form a through hole having a through hole diameter of 0.25 mm and a through hole diameter of 0.2 mm.

Next, the conductive paste was filled into the through holes by screen printing from the surface of the insulating substrate through the mask. The conditions for screen printing are a clearance of 0 to 1 mm, a metal mask with a thickness of 20 to 30 μm, an opening hole diameter of 0.3 and 0.35 mm, and a urethane rubber squeegee with a hardness of 80. The pressure was 0.3 MPa, the squeegee speed was 10 mm / sec, and the squeegee reciprocating printing was performed. Thereafter, the conductive paste was heated at a constant temperature of 120 ° C. for 30 minutes to be temporarily cured. As the conductive paste, a mixture of flaky silver and flaky silver-coated copper powder filler and a thermosetting binder resin was used. As the conductive paste, the volume resistivity is 7.5 × 10 ⁻⁵ Ω · cm, the binder resin content is 6 to 7% by mass, the solvent content is 0% by mass, and the mass reduction rate upon curing is 1 Less than% was used.

Subsequently, a conductive paste similar to that printed and filled from the front surface was printed by screen printing from the back surface of the insulating substrate through a mask. The conditions for screen printing are a clearance of 0 to 1 mm, a metal mask with a thickness of 20 to 30 μm, an opening hole diameter of 0.3 and 0.35 mm, and a urethane rubber squeegee with a hardness of 80. The pressure was 0.4 MPa, the squeegee speed was 10 mm / sec, and squeegee one-way printing. Thereafter, the conductive paste was cured by heating at a constant temperature of 200 ° C. for 60 minutes.
Thereby, the interlayer connection part which electrically connects a front surface circuit pattern and a back surface circuit pattern was formed.

  As a result of analyzing the substrate for evaluating an interlayer connection obtained in this way, a conduction failure point was not detected. The through hole diameter φ0.25 mm interlayer connection is 6.8 to 7.6 mΩ (n = 3 substrate), and the through hole diameter φ0.2 mm interlayer connection is 10.1 to 12.9 mΩ (n = 3 substrate). ) Connection resistance value. This is an appropriate resistance value calculated from the dimensions of the connecting portion and has little variation, and this analysis confirmed that there was no problem in use.

  Subsequently, a 260 ° C. solder dip (repeated 10 times) heat resistance test and a 260 ° C. reflow treatment (repeated 10 times) heat resistance test were performed using the obtained interlayer connection evaluation board. As a result, the resistance change rate was less than 10% for both the interlayer connection portion evaluation substrates having through-hole diameters of 0.2 mm and 0.25 mm, and it was confirmed that there was no problem in use.

  The height of the conductive paste from the surface of the copper foil in the interlayer connection portion (thickness of the plate portion outside the hole) was about 10 to 30 μm as a result of measurement using a step gauge, a microscope, or the like.

  The multilayer board manufacturing method, the component mounting board manufacturing method, the multilayer board, and the component mounting board according to the present embodiment have been specifically described with reference to the embodiments for carrying out the invention. It is not limited to these descriptions, and should be widely interpreted based on the description of the scope of claims. Further, various changes and modifications based on these descriptions are also included in the spirit of the present invention.

  For example, the multilayer substrate 100 has an extended portion 20 in which a part of the surface circuit pattern 2 extends along the inner wall of the through hole 1 of the insulating substrate 4. However, a part of the back circuit pattern 3 may have an extending portion that extends along the inner wall of the through hole 1 of the insulating substrate 4. Moreover, you may have an extension part in both the surface side of the insulated substrate 4, and a back surface side.

Further, for example, in the method for manufacturing a multilayer substrate, in the step of forming the interlayer connection portion, printing from the surface of the insulating substrate 4 (printing of a surface to be printed later) is one-way printing, but may be reciprocal printing.
In addition, the multilayer substrate manufacturing method and the component mounting substrate manufacturing method may include other steps between or before and after each step as long as they do not adversely affect each step. For example, a foreign matter removing step for removing foreign matter mixed in during manufacturing may be included.

  The multilayer substrate and the component mounting substrate according to the embodiment of the present disclosure can be used for electronic devices, displays, and the like.

DESCRIPTION OF SYMBOLS 1 Through-hole 2 Front surface circuit pattern 2a Front surface copper foil 3 Back surface circuit pattern 3a Back surface copper foil 4 Insulation board | substrate 5 Junction part 5a, 6a Filling part 5b, 6b Outer flat plate part 6 Interlayer connection part 6c Conductive paste 7, 7c Front surface resist 8, 8c Back surface resist 9 Adhesive layer 9c Solder paste 10 Mounting component 11 Mask 12 Screen mask 13 Metal mask 14 Punching pin 20 Extension part 30 Ceramic buff 40 Squeegee 100 Multilayer substrate 101 Component mounting substrate

Claims (10)

Punching so that circuit patterns are formed on the front and back surfaces of the insulating substrate, and a part of the circuit pattern of at least one of the front and back surfaces of the insulating substrate extends along the inner wall of the through hole of the insulating substrate. Forming the through hole by processing;
And a step of filling the conductive paste by printing from both the front surface and the back surface of the insulating substrate inside and around the through-hole to form an interlayer connection portion.   The method for manufacturing a multilayer substrate according to claim 1, wherein after the step of forming the interlayer connection portion, a step of flatly polishing the portion of the interlayer connection portion on the front surface and the back surface of the insulating substrate is performed. 2. The method for producing a multilayer substrate according to claim 1, wherein the conductive paste has a volume resistivity of 2 × 10 ^{−5 to} 1.5 × 10 ⁻⁴ Ω · cm and a binder resin content of 3 to 10 mass%. .   3. The method for manufacturing a multilayer substrate according to claim 1, wherein printing of a surface to be printed first is reciprocal printing and printing of a surface to be printed later is one-way printing among the front and back surfaces of the insulating substrate.   The insulating substrate is a glass epoxy having a thickness of 50 to 1000 μm or a polyimide having a thickness of 12 to 50 μm, and the thickness of the circuit pattern formed on the front and back surfaces of the insulating substrate is 12 to 70 μm. The manufacturing method of the multilayer substrate as described in any one of Claims 1-4. Forming a resist on the front surface and the back surface of the multilayer substrate manufactured by the multilayer substrate manufacturing method according to any one of claims 1 to 5;
Mounting the component on the multilayer substrate on which the resist is formed. Circuit patterns provided on the front and back surfaces of the insulating substrate, interlayer connection portions formed by filling the insulating substrate and through holes penetrating the circuit pattern with conductive paste, and the front and back surfaces of the insulating substrate A part of at least one of the circuit patterns extending along the inner wall of the through hole of the insulating substrate, and
A multilayer substrate in which portions of the interlayer connection portion on the front surface and the back surface of the insulating substrate are flat. The multilayer substrate according to claim 7, wherein the conductive paste has a volume resistivity of 2 × 10 ^{−5 to} 1.5 × 10 ⁻⁴ Ω · cm and a binder resin content of 3 to 10% by mass.   The insulating substrate is a glass epoxy having a thickness of 50 to 1000 μm or a polyimide having a thickness of 12 to 50 μm, and the thickness of the circuit pattern formed on the front and back surfaces of the insulating substrate is 12 to 70 μm. Item 9. The multilayer substrate according to Item 7 or Item 8.   The component mounting board | substrate with which the mounting component was mounted in the multilayer substrate as described in any one of Claims 7-9.