JPH0735414Y2 - Multilayer circuit board for mounting electronic components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a circuit board having two or more layers with cavities for housing electronic components such as semiconductor elements.

[Prior Art and its Problems] Conventionally, as a circuit board for mounting electronic parts, which is provided with a cavity for housing electronic parts such as semiconductor elements,
The structure shown in the figure was used. That is, a bonding pad a formed by aligning and forming an appropriate number of conductor patterns a ₁ , a ₂ , ..., A _i (i is an arbitrary integer) around the position where an electronic component such as a semiconductor element is mounted is provided. Circuit board A
A ring having a bonding pad b on which a through hole is formed and an appropriate number of conductor patterns b ₁ , b ₂ , ..., B _n (n is an arbitrary integer) are formed around the through hole. Circuit board B
Those having a structure in which the above are laminated and integrated have been used.

In recent years, due to the demand for higher densities, a structure in which circuit patterns are stacked in multiple stages to form cavities for accommodating electronic components in a staircase at the center and bonding pads are arranged at the stairs of each stage Is also being used.

In such a multilayer-structured electronic component mounting circuit board, high dimensional precision processing is required for high density. For example, a conductor foil pattern having a width of about 0.15 mm to 0.40 mm and a thickness of about 0.03 mm to 0.05 mm is formed on the step portion of the side wall of the kibity in an amount of about 0.15 mm.
Aligned at intervals of about mm to 0.40 mm, the ends are about 1.0 mm to 2.0 mm
It is necessary to perform processing with high dimensional accuracy, that is, forming bonding pads that are exposed to some extent.

By the way, a circuit board for mounting electronic parts having a multilayer structure is formed on a circuit board having a multilayer structure with a suitable number of circuit boards formed in a predetermined circuit pattern via a prepreg, and then a predetermined circuit board having a multilayer structure is formed. A method of punching a cavity for accommodating electronic components such as semiconductor elements in a stepwise manner by machining such as counterbores can be considered, but this method obtains a multilayer circuit board adopting an electronic component tower with high dimensional accuracy Although it can be done, it is not suitable for mass-produced products because it will be finished into stepped cavities by making use of high-precision cutting processing technology for each piece.

Further, as a method suitable for mass-produced products, when the circuit boards constituting each layer are integrally laminated using a prepreg, a suitable number of circuit boards having through holes of different sizes are preliminarily formed on the circuit boards. A method has been proposed in which a cavity is simultaneously formed by preparing a prepreg and stacking prepregs in the ascending order of the through holes, pressurizing and heating the prepreg, and integrally molding the prepreg into a multilayer structure. This method is suitable for mass production because a large number of pieces can be processed at one time, but when integrated into a multilayer structure, the resin of the prepreg flows out to the bonding pad a of the cavity as shown in FIG. There is a problem that it is easy to occur and it is difficult to obtain high dimensional accuracy.

This invention has been made in view of the above points, and the purpose of this invention is to stack circuit boards in two or more steps and heat / pressurize them to integrally laminate them.
Provided is a multilayer circuit board adopting an electronic parts tower in which a resin of a prepreg does not flow out to a bonding pad portion of a cavity even when a manufacturing method of simultaneously forming a cavity for housing an electronic part is used.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a circuit board having a through hole formed on the circuit board through a prepreg through an N
(N is an integer of 2 or more) Multilayers for mounting electronic parts with a cavity formed in the center by stacking them in layers and heating / pressurizing them to form an adhesive layer with prepreg between circuit boards for integration. In the circuit board, an annular spacer formed of a laminated body having a low elastic body layer and a high elastic body layer in the thickness direction is bonded and integrated between the circuit boards and inside the adhesive layer by the prepreg. It was provided.

[Operation] The prepreg in which the circuit boards having through holes formed on the circuit board are stacked in N (N is an integer of 2 or more) stages through the prepreg is used to transfer heat at the initial stage of heating / pressurizing. Since the speed is slow, only the applied pressure is applied and it is compressed and deformed, and it is pressed close to the thickness of the annular spacer. When the heat is gradually transferred to raise the temperature to a predetermined temperature, the resin content of the prepreg is once softened and becomes liquid, and then the adhesive layer is formed as the curing reaction proceeds, but the resin content of the prepreg becomes liquid. The resin liquid is caused to flow into the space around the prepreg by the applied pressure when it is formed, and is pressed down to the same thickness as the annular spacer, the upper surface of the annular spacer abuts the upper circuit board, and the lower surface of the lower circuit It comes into contact with the upper surface of the conductor pattern of the bonding pad portion of the substrate.
Then, a large number of pores surrounded by adjacent conductor patterns are formed on the lower surface of the annular spacer, and the resin liquid of the prepreg flows into the pores between the conductor patterns,
The viscosity resistance determined by the viscosity of the prepreg resin liquid, the cross-sectional area of the pores between the conductor patterns, the surface roughness of the pores between the conductor patterns, etc. is compared with several hundred cps even when the viscosity of the prepreg resin liquid is the smallest. Since the cross-sectional area of the pores between the conductor patterns is extremely small and is as small as several μm × several hundred μm, the viscous resistance becomes extremely large, and the prepreg resin liquid flows into the middle of the pores and stops. It does not flow to the inside surrounded by the annular spacer.

By using the annular spacer formed by the laminate having the low elastic layer and the high elastic layer with the low elastic layer side facing down, the pressure is applied to the space between the conductor patterns in the low elastic layer of the annular spacer. The elastic cross section that occupies a part of the conductor pattern can be caused to narrow the cross section of the pores formed between the conductor patterns, and therefore the necessary and sufficient viscous resistance value can be raised to prevent the liquid resin from flowing into the cavity. it can.

The resin liquid of the prepreg contacts the inner surface of the annular spacer, slightly enters the gap between the contact surfaces on the upper surface of the annular spacer, and contacts a part of the surface sandwiched between the conductor patterns on the lower surface of the annular spacer, Later, the annular spacer can be bonded and integrated inside the adhesive layer of the prepreg between the circuit boards.

If the upper and lower surfaces of the annular spacer are roughened, the friction coefficient of the contact surface becomes large when they come into contact with the upper and lower circuit boards, and the slipperiness associated with the liquefaction of the resin component of the prepreg is suppressed to prevent the upper and lower circuits. It is possible to prevent positional displacement between the substrates. Further, the adhesive strength of the annular spacer can be increased by increasing the adhesive area by roughening the upper and lower surfaces of the annular spacer.

Example An example will be described below with reference to FIGS. 1 and 2. First
The figure shows an example of a two-layer circuit board in which cavities for accommodating electronic components are formed in one step in a substantially square prism shape. FIG. 2 shows an example of a three-layer circuit board in which a cavity for accommodating an electronic component is formed in a shape in which two substantially square columnar portions are stacked. The number of circuit layers can be increased by using a double-sided circuit board or a multi-layer circuit board having two or more layers for the circuit board used in each stage.

The two-layer circuit board using electronic components shown in FIG. 1 is a circuit board A provided with bonding pads a formed by aligning and forming an appropriate number of conductor patterns around the position where electronic components such as semiconductor elements are mounted. And a ring-shaped circuit board B provided with a bonding pad b formed by forming a through hole φ having the same size as the outer diameter of the bonding pad a and forming an appropriate number of conductor patterns in an array around the through hole φ. A prepreg sheet C in which a through-hole ψ having a square cross-section having a diameter larger than that of the through-hole φ having a square cross-section of the circuit board B is formed, and an outer diameter inside the prepreg sheet C is slightly smaller than the through-hole ψ. Is a square annular spacer D having the same size as the through hole φ of the circuit board B.
It has a structure in which it is stacked in two stages via a sheet and is heated and pressed to form an adhesive layer C'by prepreg between the circuit boards A and B to be integrated.

The three-layer circuit board employing electronic components shown in FIG. 2 is a circuit board A provided with a bonding pad a formed by arranging an appropriate number of conductor patterns in an array around a position where an electronic component such as a semiconductor element is mounted. , An annular circuit board provided with a bonding pad b ₁ formed by forming a through hole φ ₁ having the same size as the outer diameter of the bonding pad a and forming an appropriate number of conductor patterns around the through hole φ _{1 in} an aligned manner. the B _1, prepreg sheet C ₁ and prepreg sheet C ₁ was formed a through-hole [psi ₁ of the large diameter of the cross section square than the through-hole phi ₁ of a square cross section of the circuit board B ₁ between
The outer diameter is slightly smaller than that of the through hole ψ ₁ , and the inner diameter is stacked via a square annular spacer D ₁ of the same size as the through hole φ ₁ of the circuit board B ₁ and further bonded onto this. An annular circuit board B provided with a bonding pad b ₂ formed by forming a through hole φ ₂ having the same size as the outer diameter of the pad 2 and forming an appropriate number of conductor patterns around the through hole φ _2.
2 , a prepreg sheet C ₂ in which a through hole ψ ₂ having a square cross section larger than the through hole φ _{2 having a} square cross section of the circuit board B ₂ is formed, and the through hole having an outer diameter inside the prepreg sheet C ₂ slightly smaller outside diameter inside diameter of the circuit board B ₂ the through hole phi ₂ and the circuit board a heated and pressed so stacked three stages through a rectangular annular spacer D ₂ of the same size B than [psi ₂ between _1, it is of the adhesive layer C ', were integrated to form a C "structure according to the prepreg between the circuit board B ₁ and B _2.

The annular spacer may be formed of the same material as the insulating resin of the circuit board, and may be any material as long as it has substantially the same characteristics as the insulating resin of the circuit board.

When one or both surfaces of the upper and lower surfaces of the annular spacer were roughened, for example, embossed, the positional displacement between the upper and lower circuit boards was extremely reduced, and the upper and lower surfaces of the annular spacer were bonded well. When the roughening of the annular spacer becomes excessively large, the resin liquid of the prepreg comes to flow out through the gap of the rough surface of the annular spacer, so that the degree of roughening is limited.

Further, the material of the annular spacer may be an insulating material, but if a material having a hardness higher than the hardness of the circuit board is selected, the wire bonding can be favorably performed.

In the above embodiment, the shape of the cavity for accommodating the electronic component is described as an example having a square cross section, but the shape of the cavity is appropriately set according to the type and shape of the electronic component, and the annular spacer The shape of will also be appropriately determined according to the shape of the cavity.

[Effects of the Invention] In the multilayer circuit board employing the electronic component of the present invention, the thickness of the adhesive layer made of the prepreg resin becomes constant depending on the thickness of the annular spacer, and it is easy to make the entire thickness to a desired value due to the dust. become.

Since the upper and lower circuit boards are supported by the annular spacer, the positional displacement between the upper and lower circuit boards is reduced.

The annular spacer can prevent the resin liquid of the prepreg from flowing out to the bonding pad portion.

If the annular spacer is formed of a laminate that has a low-elasticity layer and a high-elasticity layer in the thickness direction, the cross-sectional area of the pores between the conductor patterns can be narrowed, and the resin liquid of the prepreg flows out to the bonding pad section. Can be blocked.

When the upper and lower surfaces of the annular spacer are roughened, the adhesive condition of the upper and lower surfaces of the annular spacer is improved and the adhesive strength is also increased. Further, when the upper and lower surfaces of the annular spacer are roughened, the coefficient of friction with the upper and lower circuit boards becomes large, which contributes to the prevention of displacement between the circuit boards.

By making the hardness of the annular spacer larger than that of the circuit board, good wire bonding can be performed.

And so on.

[Brief description of drawings]

1 and 2 are sectional views for explaining an embodiment of the present invention, FIG. 3 (a) is a front view for explaining a conventional example, and FIG. 3 (b) is III of FIG. 3 (a). -III 'sectional view, FIG. 4 shows that it is an enlarged sectional view of the principal part for explaining the conventional example. A ... Circuit board, a ... Bonding pad of circuit board A,
B, B ₁ , B ₂ ... Each ring circuit board, b, b ₁ , B ₂ ... Each ring circuit board bonding pad, C, C ₁ , C ₂ ... Each prepreg sheet, C ', C "... Each Adhesive layer,
Ring spacers for D, D ₁ and D ₂ respectively.

Claims (1)

[Scope of utility model registration request] 1. A circuit board having a through hole formed in the circuit board through a prepreg through N (where N represents an integer of 2 or more).
By stacking them in stages, heating and pressing them to form an adhesive layer of prepreg between the circuit boards and integrating them,
In a multilayer circuit board for mounting electronic parts, which has a cavity for accommodating electronic parts in a central portion, in a thickness direction, a low elastic body layer is provided between circuit boards and inside an adhesive layer by a prepreg. A multi-layer circuit board for mounting electronic parts, characterized in that an annular spacer formed of a laminated body having a high-elasticity layer is integrally bonded and provided.