JP2021177535A - Manufacturing method of circuit board - Google Patents

Abstract

To provide a technology that generates an efficient circuit pattern in a manufacturing method of a circuit board having a heat dissipation function.SOLUTION: A manufacturing method of a heat dissipation substrate 10 (circuit board) includes the steps of providing a metal layer 20A on an insulating layer 11 (insulating substrate), and forming a circuit pattern by patterning the metal layer 20A, and the step of forming the circuit pattern 20 includes a step of cutting the metal layer 20A by linearly moving a cutting blade having a cutting width of 20 mm or more.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for manufacturing a circuit board.

The market for power modules equipped with electronic components such as IGBT elements is expanding. Power modules are required to have high reliability and high heat resistance. As a technique of this kind, various developments have been made in a circuit board having a heat dissipation function (also referred to as a heat dissipation board), and for example, the technique described in Patent Document 1 is known. Patent Document 1 discloses a power module in which a semiconductor element is mounted on a support such as a lead frame, and the support and a heat radiating plate connected to a heat sink are bonded by an insulating resin layer.

Japanese Unexamined Patent Publication No. 2011-216619

In recent years, the demand for such circuit boards has been increasing, and the demand for cost reduction is increasing accordingly. The technology disclosed in Patent Document 1 is not a technology in consideration of cost reduction, and a new technology has been required because it cannot sufficiently meet such a demand.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a technique for efficiently forming a circuit pattern in a method for manufacturing a circuit board having a heat dissipation function.

According to the present invention
The process of providing a metal layer on the insulating substrate and
The process of forming a circuit pattern by patterning the metal layer and
Have,
The step of forming the circuit pattern includes a step of cutting the metal layer by linearly moving a cutting blade having a cutting width of 20 mm or more.
A method for manufacturing a circuit board can be provided.

According to the present invention, it is possible to provide a technique for efficiently forming a circuit pattern in a method for manufacturing a circuit board having a heat dissipation function.

It is a top view of the heat dissipation substrate which concerns on embodiment. It is sectional drawing of the heat dissipation substrate which concerns on embodiment. It is a chart figure which shows the manufacturing process of the heat dissipation substrate which concerns on embodiment in the plan view. It is a chart figure which shows the manufacturing process of the heat dissipation substrate which concerns on embodiment in the cross-sectional view.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Outline of heat dissipation board>
FIG. 1 is a plan view of the heat radiating substrate 10. FIG. 2 is a cross-sectional view of the heat dissipation substrate 10.
As shown in the figure, the heat radiating substrate 10 is a circuit board on which electronic components of a heating element and the like are mounted, and is composed of a metal substrate 12, an insulating layer 11, and a circuit pattern 20, as shown in FIG. It is a laminated board (laminated body) laminated in this order from the bottom. Electronic components and the like are mounted on the circuit pattern 20. Further, the heat radiating substrate 10 includes a first region 80 on the right side of the drawing in which the circuit pattern 20 is formed, and a second region 90 on the left side of the drawing in which the circuit pattern 20 is not formed.

The total thickness T0 of the heat radiating substrate 10 is not particularly limited, but is preferably 300 μm or more and 5000 μm or less, and more preferably 1000 μm or more and 4000 μm or less.

<Metal substrate 12>
The metal substrate 12 is a layer made of a metal material. In the present embodiment, an insulating layer 11 is formed on the upper surface thereof, and heat radiation means such as heat radiation fins and radiators are appropriately attached to the lower surface.

The thickness T1 of the metal substrate 12 is not particularly limited, but is the thickest among the elements (insulating layer 11, metal substrate 12, circuit pattern 20) laminated on the heat radiating substrate 10, and is 10 to 90 with respect to the total thickness T0. % Is preferable.

The metal material constituting the metal substrate 12 is not limited to a specific type, and for example, copper, a copper alloy, aluminum, an aluminum alloy, or the like can be used.
The upper limit of the thickness T1 of the metal substrate 12 is, for example, 20.0 mm or less, preferably 5.0 mm or less. By using the metal substrate 12 having a thickness T1 equal to or less than this value, the heat dissipation substrate 10 as a whole can be made thinner. Further, it is possible to improve the workability in the outer shape processing, the cutting process, and the like of the heat radiating substrate 10.
The lower limit of the thickness T1 of the metal substrate 12 is, for example, 0.1 mm or more, preferably 0.5 mm or more, and more preferably 1.0 mm or more. By using the metal substrate 12 having a value equal to or higher than this value, the heat dissipation property of the heat radiating substrate 10 as a whole can be improved.

<Insulation layer 11>
The insulating layer 11 is a layer of a resin substrate mainly made of a resin material, and has a function of insulating the metal substrate 12 and the circuit pattern 20. A ceramic substrate (aluminum nitride substrate, silicon nitride substrate, or the like) may be used as the insulating layer 11.

The resin material constituting the insulating layer 11 is not limited to a specific type, but is, for example, a thermosetting resin such as an epoxy resin, a phenol resin, a urea resin, a melamine resin, a polyester (unsaturated polyester) resin, or a polyimide resin. , Silicone resin, polyurethane resin and the like. As the resin material, one or more of these resins can be mixed and used.

A filler composed of particles having electrical insulation and high thermal conductivity can also be mixed in the resin material constituting the insulating layer 11. Examples of the constituent material of the particles of the filler include metal oxides such as alumina and nitrides such as boron nitride.

The thickness T2 of the insulating layer 11 is appropriately set according to the purpose, but from the viewpoint of more effectively transferring the heat from the electronic components to the metal substrate 12 while improving the mechanical strength and heat resistance. The thickness T2 of the insulating layer 11 is preferably 40 μm or more and 400 μm or less, and more preferably 80 μm or more and 300 μm or less from the viewpoint of further excellent balance between heat dissipation and insulation in the entire heat radiation substrate 10. By setting the thickness T2 of the insulating layer 11 to be equal to or less than the above upper limit value, it is possible to facilitate the transfer of heat from the electronic components to the metal substrate 12. Further, by setting the thickness T2 of the insulating layer 11 to the above lower limit value or more, it is possible to sufficiently alleviate the generation of thermal stress due to the difference in the coefficient of thermal expansion between the metal substrate 12 and the insulating layer 11. Further, the insulating property of the heat radiating substrate 10 is improved.

In the present embodiment, the region of the upper surface of the insulating layer 11 corresponding to the first region 80 in which the circuit pattern 20 described above is formed is the first insulating layer upper surface 11a, and the second region in which the circuit pattern 20 is not formed is formed. The region of the insulating layer 11 corresponding to 90 will be described as the second insulating layer upper surface 11b.

<Circuit pattern 20>
The circuit pattern 20 is made of a conductive metal material, and is electrically connected to an electronic component (LED or the like) of a heating element by, for example, solder. For example, copper can be preferably used as the metal material constituting the circuit pattern 20. As a result, the resistance value of the circuit pattern 20 becomes relatively small. At least a part of the circuit pattern 20 may be covered with a solder resist layer.

The circuit pattern 20 is formed, for example, by processing a metal layer (metal foil) laminated on the upper surface 11a of the insulating layer 11 of the insulating layer 11 into a predetermined pattern by cutting and etching. The forming process will be described later in FIGS. 3 and 4, but in this embodiment, rolled copper is used as the metal layer 20A (see FIGS. 3 and 4).
The lower limit of the thickness T3 of the circuit pattern 20 is, for example, 0.3 mm or more. If it is more than such a value, it is possible to suppress heat generation of the circuit pattern even in an application requiring a high current. The upper limit of the thickness T3 of the circuit pattern 20 is, for example, 5.0 mm or less, preferably 4.0 mm or less, and more preferably 3.0 mm or less. If it is less than such a numerical value, the circuit workability can be improved, and the thickness of the entire substrate can be reduced.

<Features of circuit pattern 20>
Here, the specific shape of the circuit pattern 20 will be described. In the present embodiment, as described in the manufacturing process of FIG. 4, the metal layer 20A of rolled copper provided on the insulating layer 11 is efficiently processed by cutting and etching to form a desired circuit pattern 20. be able to.

Generally, due to the etching process when forming the circuit pattern 20, the metal layer side surface 23 has a sewn portion on the boundary region (region from the interface to a predetermined height) with the insulating layer 11 (first insulating layer upper surface 11a). 23a is formed. The threaded portion 23a has a threaded shape having a gentler surface (a gentle curve in the cross section) toward the upper surface 11a side of the insulating layer. In the present embodiment, the position where the sewn shape is formed is determined by performing a cutting step before the etching step to reduce the region of the sewn shape. In other words, the region of the metal layer side surface 23 that is substantially vertical is increased. For example, it is a region from the upper surface 11a of the insulating layer 11 of the insulating layer 11 to a position of 0.4D in the vertical direction, preferably a region of 0.3D, and more preferably a region of 0.2D.

A straight line portion is formed in a region above the sewn-shaped region of the metal layer side surface 23 as a region having a straight line having the inclination angle θ continuously below the average roughness of the surface in the cross section. That is, the straight line portion can be said to be a region (that is, a vertical portion) in which the tangent line is formed substantially perpendicular to the above-mentioned inclination angle θ (for example, 80 degrees or more and 100 degrees or less).

Here, the height (thickness) of the circuit pattern 20 is b, and the width between adjacent circuit patterns 20 is a. However, the width a is the distance between the central portions in the height direction on the side surface of the metal layer of each circuit pattern 20. Under this condition, the aspect ratio b / a has a region of 0.2 or more and 5 or less. In other words, the region is a region in which the width a between the circuit patterns 20 is relatively narrow with respect to the height D (b) of the circuit pattern 20. As a result, since the width between the circuit patterns 20 can be provided to be narrower than that of the conventional one, the area of the circuit pattern 20 can be increased and the heat dissipation performance can be improved. In addition, the degree of freedom in the pattern shape of the circuit pattern 20 is increased. That is, the degree of freedom in heat dissipation design is increased, and the controllability of the heat distribution of the entire heat dissipation substrate 10 when an electronic component or the like is mounted and driven in the circuit pattern 20 is improved.

<Manufacturing method of heat dissipation substrate 10>
3 and 4 are charts showing a manufacturing process of the heat radiating substrate 10. FIG. 3 is a plan view and FIG. 4 is a cross-sectional view.

(S10: Laminated body preparation step)
A laminated plate 10A in which a metal substrate 12, an insulating layer 11, and a metal layer 20A are laminated is prepared in this order from the bottom. The metal layer 20A becomes a circuit pattern 20 by being processed by the following steps (S12 to S16).
As a method for producing the laminated board 10A, a known method can be used. For example, using the metal substrate 12 as a carrier, a liquid material (varnish-like material) as a constituent material of the insulating layer 11 is applied onto the metal substrate 12 having a thickness of T1 by, for example, a spray method.
Then, the liquid material on the metal substrate 12 is dried by natural drying or forced drying. As a result, the insulating layer 11 having a thickness of T2 is obtained. At this time, the insulating layer 11 may not be completely cured (so-called B stage state).

Next, a metal layer 20A having a thickness of T3'is formed on the insulating layer 11 (that is, the upper surface 11a of the insulating layer). That is, a metal layer 20A to be a circuit pattern 20, for example, rolled copper is laminated on the first insulating layer upper surface 11a and the second insulating layer upper surface 11b of the insulating layer 11 by a hot pressure press or the like. As a result, the laminated board 10A is obtained. The thickness T3'of the metal layer 20A is set in consideration of the etching process described later.

In the present embodiment, as the metal layer 20A, the first metal layer 20A1 in the region on the right side in the drawing, which is the circuit pattern 20, and the second metal layer 20A2 to be finally removed are integrally provided. The area of the second metal layer 20A2 is 5% or more and 50% or less of the area of the insulating layer 11.

(S12: Non-circuit pattern area cutting process)
Subsequently, the second metal layer 20A2 is cut by moving it linearly using a wide cutting blade to obtain a non-circuit pattern cutting region 20A3 in which a metal layer having a predetermined thickness remains.
Here, "wide" means that the cutting width is 20 mm or more. As such a cutting blade, there is a flat cutting type cutting blade having a blade width of 20 mm or more. Further, an end mill having a blade diameter (diameter) of 20 mm or more may be used.
Since the non-circuit pattern cutting region 20A3 is melted and removed in the etching process described later, it is not necessary to consider the surface roughness and the like. Therefore, the second metal layer 20A2 can be quickly cut with a wide cutting width.

(S14: Circuit pattern cutting process)
Subsequently, using a router, the metal layer 20A of the above-mentioned laminated plate 10A, here, the first metal layer 20A is cut so as to have a desired pattern. A provisional circuit pattern 20A4 is formed on the insulating layer 11 by leaving a metal layer (thin copper portion 20B1) having a predetermined thickness for a portion that is not a pattern. That is, if all the patterns are formed by cutting, the insulating layer 11 may be damaged. Therefore, a metal layer (thin copper portion 20B1) having a predetermined thickness is left with a margin. As a result, the laminated plate 10C having the provisional circuit pattern 20A4 in the region on the right side in the drawing of the insulating layer 11 can be obtained. It is desirable that the thickness of the thin copper portion 20B1 and the non-circuit pattern cutting region 20A3 are about the same in consideration of the efficiency of the etching process.

(S16: Etching process)
Further, by etching the laminated plate 10B having the provisional circuit pattern 20A4, the remaining metal layer of the non-circuit pattern cutting region 20A3 and the metal layer of the provisional circuit pattern 20A4 (thin copper portion 20B1) are melted, and a desired one is desired. By forming the pattern, the final circuit pattern 20 is obtained.
That is, the circuit pattern 20 is laminated on the first insulating layer upper surface 11a of the insulating layer 11 on the right side in the drawing, and the first insulating layer upper surface 11a on the left side in the drawing is not covered with the metal layer and the insulating layer 11 Is completely exposed.

<Effect of embodiment>
The features and effects of the embodiments are summarized as follows.
(1) The method of manufacturing the heat radiating board 10 (of the circuit board) is as follows.
A step of providing the metal layer 20A on the insulating layer 11 (insulating substrate) (laminate preparation step S10) and
The steps (S12 to S16) of forming a circuit pattern by patterning the metal layer 20A, and
Have,
The step of forming the circuit pattern 20 includes a step of linearly moving a cutting blade having a cutting width of 20 mm or more to cut the metal layer 20A (non-circuit pattern region cutting step S12).
That is, when forming a circuit pattern 20, when removing a relatively large region of the metal layer 20A, the region is removed by using a wide cutting blade prior to the etching step S16 (non-circuit). Pattern region cutting step S12), and then the region corresponding to the circuit pattern 20 is finely cut with a router (circuit pattern cutting step S14) and etched (etching step S16).
As a result, the metal layer can be quickly removed in the region where the circuit pattern 20 is densely packed and the circuit pattern 20 is not formed. Therefore, it is possible to reduce the cost while maintaining the quality of the heat radiating substrate 10.
(2) In the step (S12) of cutting the metal layer 20A with the cutting blade, the metal layer (the second metal layer 20A2 to be finally removed) of 5% or more and 50% or less of the area of the insulating layer 11 is cut.
(3) In the step of cutting the metal layer 20A with the cutting blade (non-circuit pattern area cutting step S12), when the cutting blade is a plan cutting type cutting blade, the cutting blade is cut with a cutting blade having a blade width of 20 mm or more.
(4) In the step of cutting the metal layer 20A with a cutting blade (non-circuit pattern region cutting step S12), when the cutting blade is an end mill, it is cut with a cutting blade having a diameter of 20 mm or more.
(5) The insulating layer 11 is made of a resin substrate.
(6) The metal layer 20A is made of rolled copper.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than the above can be adopted.

10 Heat dissipation substrate 10A, 10B, 10C Laminated plate 11 Insulation layer 11a First insulation layer upper surface 11b Second insulation layer upper surface 12 Metal substrate 20 Circuit pattern 20A1 First metal layer 20A2 Second metal layer 20A3 Non-circuit pattern cutting Region 20A4 Provisional circuit pattern 80 First region 90 Second region

Claims (6)

The process of providing a metal layer on the insulating substrate and
The process of forming a circuit pattern by patterning the metal layer and
Have,
The step of forming the circuit pattern includes a step of cutting the metal layer by linearly moving a cutting blade having a cutting width of 20 mm or more.
How to manufacture a circuit board. The step of cutting the metal layer with the cutting blade is
The method for manufacturing a circuit board according to claim 1, wherein the metal layer of 5% or more and 50% or less of the area of the insulating substrate is cut. The step of cutting the metal layer with the cutting blade is
The method for manufacturing a circuit board according to claim 1 or 2, wherein when the cutting blade is a flat cutting type cutting blade, the cutting blade is used for cutting with a cutting blade having a blade width of 20 mm or more. The step of cutting the metal layer with the cutting blade is
The method for manufacturing a circuit board according to claim 1 or 2, wherein when the cutting blade is an end mill, the cutting blade is used for cutting with a cutting blade having a diameter of 20 mm or more. The method for manufacturing a circuit board according to any one of claims 1 to 4, wherein the insulating substrate is made of a resin substrate. The method for manufacturing a circuit board according to any one of claims 1 to 5, wherein the metal layer is made of rolled copper.

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