JP2649252B2 - Multilayer printed wiring board - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a multilayer printed wiring board having excellent mechanical strength, in which the number of laminated conductor layers is particularly odd, and a part of the conductor is composed of an electronic component or other component. The present invention relates to a multilayer printed wiring board on which electrodes for electrical connection to a printed wiring board are formed.

(Prior Art) In recent years, the density of a multilayer printed wiring board for mounting an electronic part has been remarkably increased, and the basic trend thereof corresponds to specifications such as the density of a semiconductor element at a customer. That is, there are functional units and miniaturization in the multilayer printed wiring board, an increase in the number of input / output terminals, and miniaturization of terminal processing.

Therefore, even for a multilayer printed wiring board on which these semiconductor elements are mounted, it is necessary to increase the required wiring channels per unit area, and to increase the number of layers and the thickness of the printed circuit board itself.

Further, functionally, printed wiring boards are being considered as functional unit units because they facilitate maintenance in the market and improve production yield.

In general multilayer printed wiring boards, in order to increase wiring efficiency, if the horizontal direction of one layer is the flow direction of wiring, the other layer is the flow of wiring in the vertical direction, so the number of conductor layers is almost even, Is formed.

Further, the power supply layer and the ground layer as the conductor layers are expected to have a shielding effect, and are often formed in pairs with respect to the signal layer. In any case, the functional conductor layers are formed in even numbers.

The reason is that a multilayer printed wiring board is formed by laminating a resin impregnated glass cloth (prepreg), a copper foil for an outer layer, and a copper-clad laminate. This is because, due to curing shrinkage of the prepreg at the time of pressing, stress is left on the formed substrate, and warping and twisting of the laminated substrate cannot be avoided. Thus, high-multilayer printed wiring boards having odd-numbered conductor layers formed by prepreg lamination have hardly been manufactured.

(Problems to be Solved by the Invention) However, as described above, when the configuration of a general multilayer printed wiring board is adopted, taking odd layers such as three layers, five layers, and seven layers has no cost merit. Although the storage of wiring is enough because warpage and twisting are easy to occur,
There is a problem that an even-numbered conductor layer, which is one layer higher than the four-layer, six-layer, and eight-layer configuration, must be used, and a costly layer configuration that uses a lot of base materials must be used.

That is, the inner layer core base material uses a copper foil layer on the front and back, it is always an even number, and even if a single-sided copper-clad laminate is used to make an odd conductor layer, the basic material composition is The cost remained the same, and warpage and twisting were likely to occur.

Also, when trying to form a multilayer structure with a thin plate thickness, the mechanical strength is insufficient with only a glass cloth-resin impregnated material, which is a general material for printed wiring boards, and mounting of surface-mounted components (surface-mounted components) in a large size. There was a difficult problem.

Furthermore, when the printed wiring board is considered as a unit functional unit, the electrical connection electrodes with the outside of the printed wiring board are formed as contact fingers aligned with the ends, and are connected to electronic components and other printed wiring boards. One system was constituted by a large number of printed wiring boards.

For this reason, the connector and wiring cable area occupies a considerable area for the printed wiring board, and it is necessary to increase the storage volume even though the printed wiring board is densely wired and mounted. I couldn't.

As a result of intensive studies conducted by the present inventors to solve the above problems, it has been newly found that using a lead frame material as a conductor and using it as a conductor layer of a multilayer printed wiring board produces good results. The present invention has been completed.

The object of the present invention is a multilayer printed wiring board having an odd-numbered conductor layer having excellent mechanical strength without warping or twisting of a substrate at a bottom cost, and particularly a lead frame material used as a conductor as an input / output electrode. It is an object of the present invention to provide a multilayer printed wiring board which has a fine input / output and is capable of interconnecting high-density printed wiring boards without requiring connectors and cables when interconnecting the printed wiring boards.

(Means for Solving the Problems) Means taken by the present invention to solve the above problems are:
Referring to FIG. 1 to FIG. 7 corresponding to the embodiment, a multilayer printed wiring board (10) having a plurality of conductor layers, and an intermediate conductor layer (5) made of a lead frame material; A multilayer printed wiring board (10), comprising: a conductor layer (3) symmetrically provided on both surfaces of the intermediate conductor layer (5) via an insulating layer.

Then, the multilayer printed wiring board ′ (1
The following can be considered as a more specific mode of 0). That is, the other conductor layers (3) are provided symmetrically on both surfaces of the intermediate conductor layer (5) made of a lead frame material via an insulating layer, and the conductor layers (3) and (5) are odd. It must be a multilayer printed wiring board (10).

The multilayer printed wiring board (10), wherein the intermediate conductor layer (5) is an electrode for electrical connection with an electronic component of the multilayer printed wiring board (10).

The multilayer printed wiring board (1) characterized in that the electrical connection electrode protrudes from the multilayer printed wiring board (10).
0).

The means adopted by the present invention described above will be described in detail with reference to the specific examples shown in the drawings.

First, the multilayer printed wiring board (10) has an intermediate conductor layer (5) formed of a lead frame material. For example, a circuit is formed by etching or stamping a copper-based or 42-alloy-based material, and another conductor layer (3) is symmetrically provided on both surfaces of the intermediate conductor layer (5) and laminated with a prepreg serving as an insulating layer. It is formed by pressing.

340m similar to a printed wiring board as an example of lamination
By using a large lead frame material having a size of mx 510 mm and press-forming using a guide hole, high positional accuracy between layers can be secured.

The lead frame material used here may be any material that is used as an external input / output outer lead (6) of a general semiconductor element. Preferably, a copper-based material, such as glass epoxy or glass polyimide material, which is close to the thermal expansion in the vertical and horizontal directions of a general printed wiring board material is preferable. This is because the reliability of the connection between the plating of the through hole (4) and the lead frame material can be increased, and the etching process and pattern forming process of the printed wiring board can be shared. A thickness of 0.1 to 0.25 mm is particularly easy to use.

For circuit formation, punching with a die is effective if a large number of small patterns are formed with respect to the manufacturing work size, and low-cost processing is possible.

The copper-clad laminate (1) and adhesive (2) used here
Is preferred to be impregnated with glass cloth-resin such as epoxy, triazine, polyimide, etc.In short, it is a large size that is a feature of the printed wiring board, as long as it is an insulating material that can be processed by etching, plating, etc. using copper foil etc. Good.

Furthermore, in this multilayer printed wiring board (10),
By using the lead frame material as a conductor and projecting from the multilayer printed wiring board (10), it is used as an electrode for electrical connection with the motherboard (11).

This has the same function as a case where a so-called F-clip lead is inserted into a contact finger (8) for electrical connection with the outside of the printed wiring board.

(Operation of the Invention) The present invention has the following operation by adopting the above means.

(A) Since the other conductor layers (3) are provided symmetrically on both surfaces of the intermediate conductor layer (5) via the insulating layers, warping and twisting are small even in odd-numbered conductor layers. This is because the lead frame material is connected to the intermediate conductor layer (5) without using much copper-clad laminate (1).
Since the prepreg (2) serving as an insulating layer in the laminated structure can be arranged symmetrically with respect to the center of the laminated structure, the stress of the substrate shrinkage during the lamination heating press is balanced and canceled. is there.

Also, the copper-clad laminate (1) is not necessarily used as the conductor layer (3).
Since the material is not used, the material cost is low, and the processing method and the stamping method can be performed, thereby further reducing the processing cost.

(B) Since the intermediate conductor layer (5) uses a lead frame material having excellent mechanical strength instead of a mere metal foil, the intermediate conductor layer (5) is thin, but resistant to bending and bending. Since the conductor layer (3) is thick, the heat capacity is increased, and the heat uniformity is not high. Further, a large current can flow.

This is because the workability of the copper clad laminate (1) and the strength and characteristics of the lead frame material are combined.

(C) By making the lead frame material protrude from the multilayer printed wiring board (10), the lead frame is not used as a simple conductor layer, but is actively used for external electrical connection. It is unnecessary to mount the connector on the motherboard (11) using the connector with the finger (8). In other words, the use of the intermediate conductor layer (5) as the outer lead (6) is provided with the input / output leads even though the multilayer printed wiring board (10) is used, and has the effect of enabling high-density mounting.

(Examples) Next, the present invention will be described in detail according to each embodiment shown in the drawings and a conventional example.

(Conventional Example) FIGS. 1 and 2 show a conventional example of a six-layer conductor layer. In FIG. 1, three copper-clad laminates (1) having a pattern formed thereon are prepared, laminated through an adhesive layer (2), and then subjected to a printed wiring board manufacturing process such as a hole plating process. FIG. 2 is a cross-sectional view of a substrate that has been bent. As can be seen from this manufacturing process, three inner core materials (1) and the cost of the etching process are required and the cost is high. Further, as described above, the layer configuration is inevitably an even number step.

FIG. 2 shows a case where two core materials (1) are used and the outer layer is formed of copper foil. In any case, the copper foil of a specific layer must be completely formed to form an even-numbered conductor layer. Or the cost is high due to the etching removal, or an asymmetric configuration using a single-sided copper-clad laminate (1) is used, and the stress remains,
It is inevitable to have a layer structure that is easy to warp and twist.

FIG. 3 is a diagram of a contact finger (8) of a terminal for making an electrical connection with a conventional external component.
It is 3.81 mm and is connected to other printed wiring boards using a medium such as a connector.

Embodiment 1 FIG. 4 shows an embodiment of the present invention, which is another layer (10) having five conductor layers (3) and (5). As the core material, two 0.4mm thick IR-4 copper-clad laminates (1) are configured on the outer layer side, and a 0.25mm copper lead frame material (trade name: HSM) manufactured by Mitsubishi Shindoh is stamped. The circuit formed in this way is used as an intermediate conductor layer (5). This circuit formation may naturally be performed by etching, and a processing method that provides the optimum cost in consideration of the amount may be selected.

In the present embodiment, the intermediate conductor layer (5) is electrically connected to the intermediate conductor layer (5) by the through hole (4). However, as long as the electrical connection is established, the connection may be a solder connection using an access hole.

With the above configuration, the laminated structure is symmetrical even though it is an odd-numbered layer, and the laminated formed product is good without warpage or twisting, and at the same time uses a 0.25 mm thick lead frame material, , Better mechanical strength than copper foil,
The increased electric capacity and the excellent thermal conductivity make it possible to mount high-density and high-power components.

Embodiment 2 FIG. 5 shows a thin three-layer multilayer printed wiring board (10) according to the present invention. This configuration is for a case where a lead frame material larger than the adhesive (3) which has been etched and laminated in advance is used. The lead frame material used is
42 alloy lead frame material of 0.25mm thickness, using DF42 material manufactured by Daido Steel Co., Ltd., adhesive layer (3) Pre-preg of busmalade triazine 0.1mm manufactured by Mitsubishi Gas Chemical Company
Two sheets on one side are laminated with an 18 μm electrolytic copper foil.

A part of the intermediate conductor layer (5) protrudes from the substrate, and is electrically connected to a printed wiring board circuit through a through hole. The protrusion is formed as a lead (6) for electrical connection with the circuit board and other electronic components and devices.

This embodiment is a multilayer printed wiring board which is thin and has excellent mechanical strength because it does not use the core material (1) but has a three-layer structure.

FIG. 6 shows an embodiment in which a surface-mounted electronic component (20) is mounted on the multilayer printed wiring board of FIG. 5, and a through hole (4) of a motherboard (11) is directly inserted and mounted by an outer lead (6). This eliminates the need for connectors and allows for the interconnection of higher density multilayer printed wiring boards.

Embodiment 3 FIG. 7 shows an embodiment of a multilayer printed wiring board having a five-layer structure according to the present invention. In this embodiment, a bare chip (21) as a mounting component is wire-bonded with a gold wire (30) to perform printed wiring. While electrically connected to the board,
The passive element (22) of the chip on the back side is mounted by connection of solder (31), and then molded and sealed with resin. At this time, the lead frame material used as the inner layer conductor protrudes more than the molding resin (7) for sealing, and works very effectively as a heat radiation area for electronic components. At this time, the intermediate conductor layer (5) and the multilayer printed wiring board (10) may be connected on a circuit or may be independent.

(Effect of the Invention) In summary, according to the present invention, as exemplified in the above embodiments, “a multilayer printed wiring board having a plurality of conductor layers, and an intermediate conductor layer made of a lead frame material; A multilayer printed wiring board characterized by comprising a conductor layer symmetrically provided on both surfaces of an intermediate conductor layer via an insulating layer. " Even with an odd-numbered conductor layer, it is possible to provide a multilayer printed wiring board (10) which is free from warping and twisting and has excellent thermal characteristics with a simple structure.

That is, the multilayer printed wiring board (10) has the following specific effects.

(A) A layer configuration that does not necessarily require an even-numbered conductor layer due to the necessity of accommodating wiring, and thus, when a multilayer printed wiring board (10) having a small number of layers is laminated and formed, a simple configuration and a low cost can be achieved. In addition, a multilayer printed wiring board (10) free of warpage and twist can be manufactured.

(B) In addition, since a lead frame material is used for the intermediate conductor layer (5), unlike a simple metal conductor layer, the mechanical strength can be improved even with a thin plate, and the heat conductivity is improved by the lead frame conductor layer. There are advantages to be improved.

(C) Further, by protruding the lead frame conductor layer from the multilayer printed wiring board (10), it can be used as an electrical input / output terminal of the circuit. Depending on the way of the outer lead (6), SIP, DIP, QFP It is possible to input and output types. That is, it can be mounted at high density without using a connector, and is very effective especially in the case of having an odd number of conductor layers as compared with the structure of the conventional multilayer printed wiring board. Is formed, the printed wiring board as a functional unit can be organically connected to a high degree.

[Brief description of the drawings]

1 and 2 are sectional views of a conventional multilayer printed wiring board, and FIG. 3 is a perspective view of an input / output electrode portion of the conventional printed wiring board. 4 and 5 are cross-sectional views of the multilayer printed wiring board according to the present invention, and FIG. 6 is a diagram in which electronic components are mounted on the multilayer printed wiring board of FIG. 5 and leads are mounted on another printed wiring board (mother board). It is the perspective view which inserted and mounted. FIG. 7 is a vertical cross-sectional view showing an embodiment in which a bare chip or the like is mounted and a molded component mounting form is added. DESCRIPTION OF SYMBOLS 1 ... copper-clad laminate (inner core material), 2 ... adhesive layer (insulating layer), 3 ... conductor layer, 4 ... through hole, 5 ...
... Intermediate conductor layer, 6 ... Lead frame protrusion (outer lead), 7 ... Mold resin, 8 ... Contact finger, 10 ... Multilayer printed wiring board, 11 ... Mother board, 20 ... Electronic parts with surface , 21 ... Bear chip, 22 ...
... Chip passive element, 30 ... Gold wire, 31 ... Solder.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Takeshi Takeyama 300, Aoyagi-cho, Ogaki-shi, Gifu IBIDEN Corporation Aoyagi Factory (56) References JP-A-63-52460 (JP, A) JP-A-62-101064 (JP, A) JP-A-63-29566 (JP, A) JP-A-61-285788 (JP, A) JP-A-1-199497 (JP, A) JP-A-1-187995 (JP, A)

Claims (1)

(57) [Claims] 1. A multilayer printed wiring board having a plurality of conductor layers, comprising: an intermediate conductor layer made of a lead frame material; and conductor layers symmetrically provided on both surfaces of the intermediate conductor layer via insulating layers. A multilayer printed wiring board characterized by being constituted.