JP2009224358A - Flexible printed wiring board and optical transmission/reception module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible printed board which can transmit a high-frequency signal without causing loss and enables three-dimensional arrangement of electronic components, and to provide an optical transmission/reception module. <P>SOLUTION: The flexible printed wiring board has a structure in which a woven fabric made of an insulative material having ≥10 GPa Young's modulus and ≤1×10<SP>-5</SP>linear expansion coefficient is used as a core material, and a base material made of an insulative high polymer material having ≤4 relative dielectric constant and ≤0.005 dielectric dissipation factor is laminated on both surfaces of the woven fabric. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a flexible printed wiring board for connecting electrodes of an electronic component, and an optical transmission / reception module in which an optical element and an electronic component are mounted on a flexible rigid board having the printed wiring board.

  Generally, in order to reduce the size of an electronic product, it is important to three-dimensionally arrange each electronic component in the housing. In order to three-dimensionally arrange electronic components at desired positions, it is necessary that the printed wiring board that electrically connects the electronic components has flexibility. Conventional flexible printed wiring boards are called flexible printed wiring boards, flexible substrates, and the like, and are made of polyimide, polyester, or the like as a base material for an insulating layer. In addition, a printed wiring board in which the flexible board is connected to a rigid rigid wiring board as a flexible part that can be bent is called a flexible rigid printed wiring board, a flex rigid board, or the like. (For example, refer to Patent Document 1, Patent Document 2, and Patent Document 3).

JP 2004-193433 A JP-A-7-193370 Japanese Patent Laid-Open No. 5-243738

  When a conventional flexible printed wiring board is applied to an optical transmission / reception module, high-frequency signal transmission is performed between the optical element and the electronic circuit through a line formed on the flexible printed wiring board. In order to transmit high-frequency signals without loss, it is necessary to reduce the relative permittivity and dielectric loss tangent of the insulating material that constitutes the printed wiring board. is important.

  However, polyimide, which is an insulating material that constitutes a conventional flexible printed wiring board, has a relative dielectric constant of about 3.5, but has a large dielectric loss tangent of 0.01, resulting in a large loss in high-frequency signal transmission. However, there was a problem that noise was easily applied to optical transmission and reception.

  In addition, since the conventional flexible rigid substrate has a structure in which the rigid substrate is attached from both sides of the flexible substrate, the vias that connect each layer in the rigid substrate are an insulating layer of the rigid substrate made of glass fiber and epoxy resin, and polyimide. It penetrates through the insulating layer of the flexible substrate. In this case, since the thermal expansion of the insulating layer of the rigid substrate and the insulating layer of the flexible substrate are different, there has been a problem that the via conductor is cracked when the temperature difference is repeated in the market and the reliability is lowered.

  Further, conventionally, as a base material for an insulating layer of a rigid substrate, a material in which an inorganic filler is contained in a tetrafluoroethylene resin (hereinafter referred to as polytetrafluoroethylene) having a small relative dielectric constant and dielectric loss tangent is used. However, it is poor in flexibility as a base material for the insulating layer of the flexible substrate. In order to make this a flexible substrate that can be bent, it is necessary to make the substrate very thin, but there is a problem that the bending strength is poor.

  The present invention has been made to solve the above-described problem, and can be used to transmit a high-frequency signal without loss even when applied to an optical transceiver module or the like, and can be used as a flexible part of a flexible rigid board. An object of the present invention is to provide a flexible printed wiring board capable of improving the bonding reliability of the solder joint portion.

  In the printed wiring board having flexibility according to the present invention, a woven fabric made of an insulating material is used as a core material, and a base material made of an insulating thermoplastic polymer material is laminated on both surfaces of the woven fabric. is there.

  According to the present invention, even when applied to an optical transceiver module used as a flexible portion of a flexible rigid substrate, a high-frequency signal transmission with low loss is possible, and the flexibility that can improve the reliability of a solder joint portion. A printed wiring board having the characteristics can be realized.

Embodiment 1 FIG.
The first embodiment will be described with reference to the drawings. FIG. 1A is a top view showing a flexible printed wiring board according to Embodiment 1, and FIG. 1B is a cross-sectional view taken along the line AA.

In FIG. 1, the insulating layer 2 of the flexible printed wiring board 1 is a woven fabric made of a low thermal expansion material having a high rigidity with a Young's modulus of 10 GPa or more and a linear expansion coefficient of 1 × 10 ⁻⁵ or less. A base material made of an insulating polymer material 21 having a low dielectric constant of 4 or less and a dielectric loss tangent of 0.005 or less and a low dielectric loss on both surfaces of the woven fabric 22 with 22 as a core material. Are stacked. A circuit pattern layer 3 containing copper is provided on both surfaces of the insulating layer 2, and a resist 23 is provided as a protective film on a part of the circuit pattern layer 3. The exposed portion of the circuit pattern layer 3 without the resist 23 is electrically connected to the outside.

  As the polymer material 21 having a low dielectric constant and low dielectric loss, polytetrafluoroethylene, bismaleimide triazine, liquid crystal polymer, or the like is used. Further, as the woven fabric 22 having high rigidity and low thermal expansion, glass fiber, aramid fiber, or the like is used.

  In order to provide flexibility, the woven fabric 22 is disposed at the center of the insulating layer 2 in the cross-sectional direction, and the thickness of the insulating layer 2 in the cross-sectional direction is reduced. For example, if the thickness is 0.12 mm or less, there is no problem even if the curvature radius is 1.5 mm.

  The flexible printed wiring board 1 configured as described above uses a polymer material 21 having a low dielectric constant and low dielectric loss, such as polytetrafluoroethylene, as the base material of the insulating layer 2. Therefore, even when applied to an optical transceiver module or the like, high-frequency signal transmission with little loss is possible. In addition, since the highly rigid woven fabric 22 such as glass fiber is disposed in the central portion in the cross-sectional direction of the insulating layer 2, the cross-sectional thickness of the insulating layer 2 can be reduced in order to increase flexibility. Thus, a highly reliable bendable flexible substrate can be realized without impairing the strength of the printed wiring board.

  In the first embodiment, the resist 23 is provided on both surfaces of the flexible printed wiring board 1, but the resist 23 may not be provided.

Embodiment 2. FIG.
FIG. 2 is a cross-sectional view showing a flexible rigid substrate using a flexible printed wiring board according to Embodiment 2, and FIG. 3 is a cross-sectional flow diagram showing an example of the manufacturing method. In the figure, the same reference numerals as those of the first embodiment shown in FIG.

  In FIG. 2, the structure of the flexible rigid board | substrate 11 comprised by affixing the rigid rigid wiring board 4 on a part of both surfaces of the printed wiring board 1 which has flexibility is shown. A portion of the printed wiring board 1 having flexibility that is not sandwiched between the rigid wiring boards 4 is a flexible portion that can be bent. In order to electrically connect the rigid circuit board 4 and the circuit pattern layers 31 and 32 of the flexible printed wiring board 1, penetrating vias 7 (also referred to as through holes) are provided.

  The flexible rigid substrate 11 using the flexible printed wiring board 1 configured as described above is configured such that a woven fabric 22 made of a material having high rigidity and low thermal expansion, such as glass fiber, is provided in a cross-sectional direction of the insulating layer 2. Therefore, consistency with the thermal expansion coefficient of the rigid wiring board 4 can be obtained. Thereby, in the flexible rigid substrate 11, it is possible to reduce the thermal stress generated due to the difference in thermal expansion of each member. Therefore, no crack is generated in the conductor of the via 7, and the highly reliable flexible rigid substrate 11. Can be realized.

  The flexible printed wiring board 1 uses the polymer material 21 having a low dielectric constant and a low dielectric loss as the base material of the insulating layer 2, and is therefore exactly the same as in the first embodiment. Needless to say, an effect can be obtained.

  Further, the insulating layer 2a of the rigid wiring board 4 can be made of the same material as the insulating layer 2 of the printed wiring board 1 having flexibility. As a result, the thermal expansion coefficient can be further matched, and even when applied to an optical transceiver module or the like, high-frequency signal transmission with even less loss is possible.

An example of a method for manufacturing the flexible rigid substrate 11 as described above will be described with reference to a cross-sectional flowchart shown in FIG.
In FIG. 3A, a flexible printed wiring board 1 having copper 8 stretched on both sides is prepared.
In FIG. 3B, a hole is formed at a predetermined position in the flexible printed wiring board 1 by drilling or laser processing, and a copper plating 81 is formed on the entire surface of both surfaces.

In FIG. 3 (c), a resist (not shown), which is a photosensitive material, is formed on the entire surface, and then exposed and developed. After the resist is formed at a predetermined position, it is exposed with a ferric chloride aqueous solution or the like. The copper that has been dissolved is removed by dissolution, and the resist is removed. As a result, the circuit pattern 31 and the via 71 serving as a through hole are formed on the surface of the flexible printed wiring board 1.
In FIG. 3D, a cover sheet 51 is bonded and laminated on both surfaces of a flexible printed wiring board 1 with an adhesive 52.

In FIG. 3E, a prepreg 6 processed into a predetermined shape and a rigid wiring board 4 are arranged and laminated on a part of both surfaces of a flexible printed wiring board 1.
3 (f), a rigid wiring board 4 sandwiching a flexible printed wiring board 1 is drilled or laser-processed to form holes at predetermined positions, and copper plating (not shown) is performed on both surfaces. Z.) is formed. Furthermore, after forming a resist (not shown), which is a photosensitive material, on the entire surface, exposure and development are performed to form a resist at a predetermined position, and then the exposed copper is dissolved with a ferric chloride aqueous solution or the like. Remove and remove the resist. As a result, the via 7 for electrically connecting the circuit pattern layer 32 and the circuit pattern 31 of the flexible printed wiring board 1 to the rigid wiring board 4 of the flexible rigid board 11 is formed. Complete.

Embodiment 3 FIG.
4 is a perspective view showing an optical transmission / reception module using a flexible printed wiring board according to Embodiment 3, and FIG. 5 is an optical element on a flexible rigid board using the flexible printed wiring board. It is a perspective view which shows the optical transmission / reception module with which the electronic component was mounted. In the figure, the same reference numerals as those in the first or second embodiment shown in FIGS. 1 to 3 denote the same or corresponding components.

  In FIG. 4, the optical transceiver module 9 a is electrically connected to the wiring board 93 on which the optical element 91 and the electronic component 92 are mounted by the flexible printed wiring board 1 shown in the first embodiment. Yes. Optical elements 91 and support bases 95 that support the wiring board 93 are three-dimensionally arranged at predetermined positions of the housing 94. Since the wiring board 93 on which the optical element 91 and the electronic component 92 are respectively mounted is connected via the flexible printed wiring board 1, each component can be arranged at an arbitrary position.

  Since the flexible printed wiring board 1 uses a polymer material having a low dielectric constant and a low dielectric loss as the base material of the insulating layer, the same effect as in the first embodiment is obtained. Needless to say, the optical transmission / reception module 9a capable of high-performance optical transmission / reception can be realized.

  In FIG. 5, the optical transceiver module 9b uses the flexible rigid board 11 shown in the second embodiment, and the optical element 91 and the electronic component 92 are mounted on the rigid wiring board portion. It can be placed at any position.

  In addition, since the flexible part of the flexible rigid board | substrate 11 is comprised with the printed wiring board 1 which has flexibility shown in Embodiment 1, it says that the completely same effect as Embodiment 1 can be acquired. Needless to say, the same effects as those of the second embodiment can be obtained.

FIG. 3 is a configuration diagram showing a flexible printed wiring board in the first embodiment. 6 is a cross-sectional view showing a flexible rigid board using a flexible printed wiring board in Embodiment 2. FIG. 10 is a cross-sectional flow diagram illustrating an example of a method for manufacturing a flexible rigid board using a flexible printed wiring board according to Embodiment 2. FIG. FIG. 11 is a perspective view showing an optical transceiver module using a flexible printed wiring board in Embodiment 3. FIG. 10 is a perspective view showing an optical transceiver module in which an optical element and an electronic component are mounted on a flexible rigid board using a flexible printed wiring board according to Embodiment 3.

Explanation of symbols

1 flexible printed wiring board,
2, 2a insulating layer,
4 Rigid wiring board,
9a, 9b optical transceiver module,
11 Flexible rigid board,
21 polymer materials,
22 Woven cloth,
91 optical elements,
92 Electronic components

Claims (7)

Using a woven fabric made of an insulating material as a core material,
A flexible printed wiring board having a base material made of an insulating thermoplastic polymer material laminated on both sides of the woven fabric.   2. The flexible printed wiring board according to claim 1, wherein the polymer material is a material having a relative dielectric constant of 4 or less and a dielectric loss tangent of 0.005 or less.   The flexible printed wiring board according to claim 2, wherein the polymer material is composed of any one of polytetrafluoroethylene, bismaleimide triazine, and a liquid crystal polymer. 4. The flexible printed wiring according to claim 1, wherein the woven fabric has a Young's modulus of 10 GPa or more and a linear expansion coefficient of 1 × 10 ⁻⁵ or less. ^5. Board.   5. The flexible printed wiring board according to claim 4, wherein the woven fabric is made of any one of glass fiber and aramid fiber. A rigid wiring board is provided on a part of both surfaces of the flexible printed wiring board according to any one of claims 1 to 5,
An optical transceiver module, wherein an optical element and an electronic component are mounted on a flexible rigid board using the printed wiring board having flexibility as a flexible part. The flexible rigid board is composed of a first rigid wiring board and a second rigid wiring board electrically connected via the flexible printed wiring board,
The optical element is mounted on a first rigid wiring board,
The optical transceiver module according to claim 6, wherein the electronic component is mounted on a second rigid wiring board.

Images