JP2006332280A - Double-sided printed wiring board and its manufacturing method, and rigid-flex printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-sided flexible printed wiring board having a superior flexibility as a flexible board by fabricating it so that a cover lay and a copper foil may be laminated by one-time curing. <P>SOLUTION: On the polyimide insulation layer 11 side of a flexible single-sided CCL 10, the liquid-crystal polymer cover lay 22 is pasted which is formed with a wiring pattern 24 on one side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a double-sided printed wiring board used for a flexible printed circuit board of a rigid flex printed wiring board, a manufacturing method thereof, and a rigid flex printed wiring board.

  In recent years, there has been a demand for miniaturization of electronic devices, and accordingly, printed wiring boards used in electronic devices are increasingly required to be small, thin, light, and low in cost.

  Conventionally, it has been difficult for electronic devices to be significantly reduced in size due to restrictions in designing and manufacturing electronic components mounted on the electronic devices and printed wiring boards themselves. As a printed wiring that removes the restriction, a flexible substrate can be sandwiched between rigid substrates to form a substrate having a bent portion, whereby high-density mounting can be achieved. This substrate is called a rigid flex printed wiring board, and is very effective for downsizing electronic devices.

  A double-sided flexible printed wiring board is mainly used for the bent portion (flexible substrate portion) of the rigid flex printed wiring board.

  The double-sided flexible printed wiring board starts from a double-sided copper clad laminate (hereinafter referred to as “double-sided CCL”), and has a through-hole (hereinafter referred to as “through-hole”) at a predetermined position of the double-sided CCL by NC drilling or laser processing. ), And through-hole plating is performed so that the copper foils on the upper and lower layers (front and back layers) of the double-sided CCL are conductive, and then the copper foil is etched to form a wiring pattern on both sides. The insulating protective layer to be performed (completed by bonding the coverlay with a heating press (cure) (for example, Non-Patent Document 1).

  However, the double-sided flexible printed wiring board by through-hole plating increases the conductor thickness (copper foil thickness) of the wiring pattern by through-hole plating, so that the flexibility is lowered and the entire layer becomes thick. Not suitable for making patterns extremely thin.

  In addition, there is a problem that components cannot be mounted on the through holes in component mounting. In order to solve this problem, it is necessary to fill the through-hole with resin and further cover-plate, but this increases the number of steps and increases the cost, and it is difficult to obtain sufficient connection reliability.

  As a double-sided flexible printed wiring board using another manufacturing method that does not use through-hole plating, a through hole is made in a predetermined position of the resin film, the through hole is filled with a conductive paste, and copper foil is bonded to both sides of the resin film to cure. In addition, there is a technique in which a coverlay is cured after etching a copper foil to form a circuit (for example, Patent Document 1).

A double-sided flexible printed wiring board using a conductive paste for interlayer conduction can be expected to improve flexibility by using a thin copper foil. However, since the coverlay must be cured once more after the copper foil is cured, the number of steps increases. Generally, a vacuum is used for the carrier, but the process is relatively long, 30 minutes to 2 hours. Therefore, it is inevitable that the cost increases due to an increase in the number of times of curing. Also, depending on the resin, repeated heating and pressing may make it brittle and lower the mechanical strength and insulation.
Kiyoshi Takagi "Build-up multilayer printed wiring board technology", published by Nikkan Kogyo Shimbun, June 15, 2001, 2nd edition, pages 20-21 JP-A-10-84186

  The problem to be solved by the present invention is that, in a double-sided flexible printed wiring board, the lamination of the coverlay and the copper foil is only required to be cured once, the productivity is excellent, and the flexible substrate has excellent flexibility. Is to do.

  The method for manufacturing a double-sided printed wiring board according to the present invention includes a step of forming a first wiring pattern by etching a copper foil starting from a single-sided copper-clad laminate having a copper foil on one surface of an insulating substrate. And a step of opening a via hole in the insulating substrate of the single-sided copper clad laminate, a step of filling the via hole with a conductive paste, and one surface of the first insulating protective sheet in a semi-cured state having adhesiveness A step of bonding a copper foil to the substrate, a step of etching the copper foil bonded to one surface of the first insulating protective sheet to form a second wiring pattern, and the second wiring pattern. In the state where the second wiring pattern is located on the other surface side of the insulating base material of the single-sided copper-clad laminate, the first insulating protective sheet formed with the other side of the insulating base material Bonded to the surface in a fully cured state That at the same time, and a step of the one surface of the insulating base material of the single-sided copper-clad laminate, bonded cured state a second insulating protective sheet so as to cover the first wiring pattern.

  In addition, the method for manufacturing a double-sided printed wiring board according to the present invention uses a single-sided copper-clad laminate having a copper foil on one side of an insulating substrate as a starting material, and forms the first wiring pattern by etching the copper foil. A step of bonding an adhesive layer to the other surface of the insulating base material of the single-sided copper-clad laminate in a semi-cured state, and a via hole in the insulating base material and the adhesive layer of the single-sided copper-clad laminate. A step of opening, a step of filling the via hole with a conductive paste, a step of bonding a copper foil to one surface of a semi-cured first insulating protective sheet having adhesiveness, and the first insulating protective sheet Etching the copper foil bonded to one surface of the substrate to form a second wiring pattern; and forming the second insulating pattern on the first insulating protective sheet on which the second wiring pattern is formed. The wiring pattern of The first wiring pattern is insulatively coated on one surface of the insulating base material of the single-sided copper-clad laminate at the same time as being bonded to the adhesive layer in a fully cured state while being positioned on the surface side of the layer And a step of bonding the second insulating protective sheet in the fully cured state.

  In the method for manufacturing a double-sided printed wiring board according to the present invention, a sheet material having a lower water absorption rate than the insulating base material of the single-sided copper-clad laminate is used as the sheet material of the first insulating protective sheet and the second insulating protective sheet. Is used.

  In the method for manufacturing a double-sided printed wiring board according to the present invention, an insulating base made of a flexible resin is used as the insulating base of the single-sided copper-clad laminate, and the first insulating protective sheet and the second insulating protection are used. As the sheet, a liquid crystal polymer or a liquid crystal polymer as a main component and an insulating protective sheet are used.

  In the double-sided printed wiring board according to the present invention, the first insulating protective sheet in which the second wiring pattern is formed on the other surface of the insulating base material having the first wiring pattern on one surface, The second wiring pattern is bonded in a state of being located on the other surface side of the insulating base material of the single-sided copper clad laminate, and the first wiring is provided on one surface of the insulating base material. A second insulating protective sheet for insulatingly covering the pattern is bonded.

  Further, the double-sided printed wiring board according to the present invention has an adhesive layer on the other surface of the insulating base material having the first wiring pattern on one surface, and a second surface on the surface of the adhesive layer. A first insulating protective sheet on which a wiring pattern is formed, and the second wiring pattern is bonded to the surface of the adhesive layer of the single-sided copper-clad laminate; A second insulating protective sheet for insulatingly covering the first wiring pattern is bonded to one surface of the first wiring pattern.

  In the double-sided printed wiring board according to the present invention, the first insulating protective sheet and the second insulating protective sheet are made of a sheet material having a lower water absorption than the insulating base material.

  In the double-sided printed wiring board according to the present invention, the insulating base is composed of a flexible resin film, and the first insulating protective sheet and the second insulating protective sheet are liquid crystal polymer or resin mainly composed of liquid crystal polymer. It is comprised by.

  In the rigid flex printed wiring board according to the present invention, the insulating base is formed of a flexible resin film, and the first insulating protective sheet and the second insulating protective sheet are liquid crystal polymer or resin mainly composed of liquid crystal polymer. The above-mentioned double-sided printed wiring board constituted by the double-sided printed wiring board as a flexible substrate part, on at least one of the first insulating protective sheet and the second insulating protective sheet of the double-sided printed wiring board, Rigid substrate portions are stacked.

  Since the method for manufacturing a double-sided printed wiring board according to the present invention uses a single-sided copper-clad laminate as a starting material, it is easy to have a configuration of interlayer conduction with a conductive paste, and the lamination of an insulating protective sheet (coverlay) and copper foil is one. It only needs to be cured once, and is highly productive. Moreover, since there is no plating process, the wiring pattern can be kept thin, and the flexible substrate has excellent flexibility.

  One embodiment of a double-sided printed wiring board and a method for manufacturing the same according to the present invention will be described with reference to FIG.

  First, as shown in FIG. 1A, a flexible single-sided CCL (flexible single-sided copper-clad laminate) 10 is prepared as a starting material. The flexible single-sided CCL 10 has a copper foil 12 on one surface of a resin film 11 that forms an insulating substrate. The resin film 11 is made of a flexible material mainly composed of polyimide (PI) resin. When the thickness of the single-sided CCL 10 is large, the flexibility is lowered, and when it is thin, the handling becomes difficult and wrinkles occur. Therefore, the resin film 11 has a thickness of about 12 to 30 μm and the copper foil 12 has a thickness. The thickness is preferably about 3 to 25 μm. As the flexible single-sided CCL10, either a laminate method or a cast method can be used.

  As the first step, as shown in FIG. 1B, the copper foil 12 of the single-sided CCL 10 is etched to form a first wiring pattern (conductor pattern) 13.

  Next, as shown in FIG. 1C, the adhesive layer 14 is pasted (temporarily pasted) to the other surface of the resin film 11 of the single-sided CCL 10 in a semi-cured state by heating for a short time.

  The semi-cured state referred to here corresponds to a B stage state which is an intermediate stage between a varnish state called A stage and a complete cure called C stage in the curing reaction, and is once softened by reheating. Fully cured.

  As the adhesive layer 14, an adhesive resin film mainly composed of a thermoplastic polyimide containing a thermosetting epoxy or the like can be used. The adhesive layer 14 is not a film, and may be produced by applying a varnish. In order to maintain flexibility, it is preferable to use a material that is as thin as possible.

  The adhesive layer 14 can be omitted depending on the required adhesive strength of the first cover lay 22 described later.

  Next, as shown in FIG. 1D, a via hole 15 is opened at a predetermined position (interlayer conduction position). The via hole 15 is formed by drilling as a hole penetrating the resin film 11 and the adhesive layer 14. This drilling may be drilled, but is not suitable for finer circuits. Therefore, in order to open with high precision, a hole is formed by laser processing. As the laser processing machine, a CO2 laser, a UV-YAG laser, an excimer laser, or the like is used.

  Next, as shown in FIG. 1E, the via paste 15 is filled with the conductive paste 16 by a printing method. As the conductive paste 16, a paste containing a metal filler mainly composed of silver or copper is used.

  As shown in FIG. 1 (f), a copper foil 23 is temporarily attached to one surface of the first cover lay 22 having adhesiveness which is a first insulating protective sheet. The temporary attachment of the copper foil 23 refers to attaching the copper foil 23 to the semi-cured first cover lay 22.

  The fact that the first cover lay 22 is in a semi-cured state refers to an intermediate stage between a varnish state referred to as an A stage and a complete cure referred to as a C stage in the curing reaction, like the adhesive layer 14. The state corresponding to the B stage is once softened by reheating and then completely cured.

  By doing so, a large adhesive force can be obtained by an adhesive effect between the adhesive layer 14 and the first cover lay 22 in a later curing step.

  In the subsequent process, the copper foil 23 on the semi-cured first cover lay 22 is etched to form a circuit. Therefore, the first cover lay 22 is mainly made of a thermoplastic resin having acid resistance and alkali resistance. A resin film as a component is used.

  In particular, by using a liquid crystal polymer (LCP) that softens even below the glass transition temperature Tg or a resin mainly composed of a liquid crystal polymer for the first cover lay 22, the following points are better than other resins such as polyimide. Improved.

(1) Since the relative dielectric constant is lower than that of polyimide, the power loss of the signal can be reduced when the transmitted signal becomes a high frequency.

(2) Since the water absorption is lower than that of polyimide, peeling does not easily occur even under high temperature and high humidity, and reliability is improved.

  The first coverlay 22 may be polyetherimide (PEI), polyetheretherketone (PEEK), or the like in addition to the liquid crystal polymer.

  The thickness of the first cover lay 22 is preferably about 10 to 35 μm as a thickness that allows the first cover lay 22 to be embedded without bubbles, because the wiring pattern must be embedded.

  The copper foil 23 of the first cover lay 22 is etched to form a second wiring pattern (conductor pattern) 24.

  After the circuit is formed, the first cover lay 22 is arranged with the second wiring pattern 24 and the first wiring pattern 13 of the single-sided CCL 10 in a state where the second wiring pattern 24 is located on the surface side of the adhesive layer 14. Are aligned by image recognition so as to be electrically connected to each other by the conductive paste 16 of the via hole 15 and are laminated with high accuracy.

  Another cover lay, that is, a second cover lay 21 having adhesiveness, which is a second insulating protective sheet, is prepared, and this is attached to one surface (first wiring pattern 13) of the resin film 11 of the single side CCL 10. Are laminated on the surface on which is formed. Similarly to the first cover lay 22, the second cover lay 21 is preferably made of a liquid crystal polymer or a resin mainly composed of a liquid crystal polymer.

  Finally, as shown in FIG. 1 (g), a pressure of 1-5 MPa is applied using a vacuum press or a cureless machine, heated to 150-250 ° C. and held for 30 minutes to 2 hours. By doing so, the first cover lay 22 and the second cover lay 21 are collectively cured. That is, the first cover lay 22 and the second cover lay 21 are bonded together on both sides of the single-sided CCL 10 in a fully cured state. Thereby, the flexible double-sided printed wiring board 30 is completed.

  As described above, since the method for manufacturing a double-sided printed wiring board according to the present invention uses the single-sided CCL 10 as a starting material, the through-hole 15 can be easily drilled, and the structure of the interlayer conduction by the conductive paste 16 can be easily obtained. The lamination of the second coverlays 22 and 21 and the single-sided CCL 10 is only required to be cured once, and the productivity is excellent. Moreover, since there is no plating process, the wiring pattern can be kept thin, and the flexible substrate has excellent flexibility.

  In the flexible double-sided printed wiring board 30, the first cover lay 22 and the second cover lay 21 are made of a liquid crystal polymer or a resin mainly composed of a liquid crystal polymer, and absorb moisture from a polyimide resin constituting the resin film 11. Since the rate is low, the heat and moisture resistance of the flexible double-sided printed wiring board 30 is improved. Moreover, the distortion of the board | substrate at the time of lamination | stacking can be suppressed because the resin film 11 is a product made from polyimide resin whose glass transition temperature is higher than a liquid crystal polymer.

  One embodiment of a rigid flex printed wiring board using the flexible double-sided printed wiring board 30 as a flexible substrate portion and a method for manufacturing the same will be described with reference to FIG.

  First, as shown in FIG. 2A, a rigid CCL 40 in which a copper foil 42 is bonded to one side of an insulating layer 41 in which glass fiber is impregnated with an epoxy resin is attached to both sides of the flexible double-sided printed wiring board 30. The adhesive layers 43 are attached to the regions A and B of the first cover lay 22 and the surface of the second cover lay 21, respectively.

  Next, as shown in FIG. 2 (b), the via hole 44 penetrating the rigid CCL 40, the adhesive layer 43, and the first cover lay 22 or the second cover lay 21 of the flexible double-sided printed wiring board 30 is lasered. Drill holes by processing.

  Next, as shown in FIG. 2C, the inner surface of the via hole 44 is plated for interlayer conduction between the copper foil 42 of the rigid CCL 40 and the first wiring pattern 13 or the second wiring pattern 24. Then, an interlayer conductive portion 45 is formed by via hole plating.

  Next, as shown in FIG. 2 (d), the copper foil 42 of the rigid CCL 40 is etched to form a wiring pattern 46.

  Next, as shown in FIG. 2E, a rigid CCL 50 is further built up on each rigid CCL 40 with an adhesive layer 53, and the copper foil of the rigid CCL 50 is etched to form an outermost wiring pattern 56. The interlayer conductive portion 55 is also formed in the rigid CCL 50 by via hole plating. Thereby, the rigid flex printed wiring board 60 is completed.

  Since the rigid flex printed wiring board 60 uses the flexible double-sided printed wiring board 30, the flexible printed circuit board has excellent flexibility in the flexible board part, and the rigid board part can be easily and inexpensively attached to the flexible double-sided printed wiring board. It is possible to build up on both sides of the plate 30.

(A)-(g) is process drawing which shows one Embodiment of the double-sided printed wiring board by this invention, and its manufacturing method. (A)-(e) is process drawing which shows one embodiment of the rigid flex printed wiring board which used the double-sided printed wiring board by this invention as a flexible substrate part, and its manufacturing method.

Explanation of symbols

10 Flexible single-sided CCL
DESCRIPTION OF SYMBOLS 11 Resin film 12 Copper foil 13 1st wiring pattern 14 Adhesive layer 15 Via hole 16 Conductive paste 21 2nd coverlay 22 1st coverlay 23 Copper foil 24 2nd wiring pattern 30 Flexible double-sided printed wiring board 40 Rigid CCL
41 Insulating layer 42 Copper foil 43 Adhesive layer 44 Via hole 45 Interlayer conductive part 46 Wiring pattern 50 Rigid CCL
53 Adhesive layer 55 Interlayer conduction part 56 Wiring pattern 54 Rigid flex printed wiring board

Claims (9)

A step of forming a first wiring pattern by etching the copper foil, starting from a single-sided copper clad laminate having a copper foil on one side of the insulating substrate;
Opening a via hole in the insulating base material of the single-sided copper-clad laminate;
Filling the via hole with a conductive paste;
A step of bonding a copper foil to one surface of the semi-cured first insulating protective sheet having adhesiveness;
Etching the copper foil bonded to one surface of the first insulating protective sheet to form a second wiring pattern;
In the state where the second wiring pattern is positioned on the other surface side of the insulating base material of the single-sided copper-clad laminate, the first insulating protective sheet on which the second wiring pattern is formed, A second insulation protection is applied so as to cover the first wiring pattern on one surface of the insulating base of the single-sided copper-clad laminate at the same time as being bonded to the other surface of the insulating base in a fully cured state. A step of bonding the sheet in a fully cured state;
The manufacturing method of the double-sided printed wiring board which has this. A step of forming a first wiring pattern by etching the copper foil, starting from a single-sided copper clad laminate having a copper foil on one side of the insulating substrate;
Bonding the adhesive layer in a semi-cured state to the other surface of the insulating base of the single-sided copper-clad laminate;
Opening a via hole in the insulating base and the adhesive layer of the single-sided copper-clad laminate;
Filling the via hole with a conductive paste;
A step of bonding a copper foil to one surface of the semi-cured first insulating protective sheet having adhesiveness;
Etching the copper foil bonded to one surface of the first insulating protective sheet to form a second wiring pattern;
When the first insulating protective sheet on which the second wiring pattern is formed is bonded to the adhesive layer in a fully cured state in a state where the second wiring pattern is located on the surface side of the adhesive layer. At the same time, a step of pasting a second insulating protective sheet in a fully cured state on one surface of the insulating base of the single-sided copper-clad laminate so as to insulate the first wiring pattern;
The manufacturing method of the double-sided printed wiring board which has this.   Any one of Claims 1 and 2 which uses a sheet material with a low water absorption as the sheet material of the said 1st insulation protection sheet and the said 2nd insulation protection sheet compared with the said insulation base material of the said single-sided copper clad laminated board. A method for producing a double-sided printed wiring board according to claim 1.   An insulating base made of a flexible resin is used as the insulating base of the single-sided copper-clad laminate, and a liquid crystal polymer or a liquid crystal polymer is insulated from the main component as the first insulating protective sheet and the second insulating protective sheet. The manufacturing method of the double-sided printed wiring board of any one of Claims 1-3 which uses a protection sheet.   A first insulating protective sheet having a second wiring pattern formed on one surface is formed on the other surface of the insulating substrate having the first wiring pattern on one surface, and the second wiring pattern is formed on the one surface. A second insulation for laminating the first wiring pattern on one surface of the insulating base material, bonded to the other surface of the insulating base material of the copper clad laminate. Double-sided printed wiring board with a protective sheet attached.   A first insulation protection having an adhesive layer on the other surface of the insulating base material having the first wiring pattern on one surface, and a second wiring pattern formed on the one surface on the surface of the adhesive layer The sheet is bonded in a state where the second wiring pattern is located on the surface side of the adhesive layer of the single-sided copper-clad laminate, and the first wiring is formed on one surface of the insulating substrate. A double-sided printed wiring board on which a second insulating protective sheet for insulatingly covering a pattern is bonded.   The double-sided printed wiring board according to claim 5 or 6, wherein the first insulating protective sheet and the second insulating protective sheet are made of a sheet material having a lower water absorption than the insulating base material.   The said insulation base material is comprised by the flexible resin film, and the said 1st insulation protection sheet and the said 2nd insulation protection sheet are comprised by the resin which has a liquid crystal polymer or a liquid crystal polymer as a main component. Double-sided printed wiring board. The double-sided printed wiring board according to claim 8 is used as a flexible board part, and a rigid board part is laminated on at least one of the first insulating protective sheet and the second insulating protective sheet of the double-sided printed wiring board. Rigid flex printed wiring board.

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