KR100872524B1 - Method for manufacturing rigid-flex printed wiring board - Google Patents

Abstract

The manufacturing method of the rigid-flex printed wiring board which has an inner layer flexible wiring board which overlaps a coverlay on an inner layer copper clad laminated board, and whose outer surface is a flexible member, an outer layer rigid wiring board which one surface is made of an inflexible member, and an adhesive member, A step of alkali treating both outer surfaces of the inner layer flexible wiring board, and a step of stacking the outer layer rigid wiring board on the outer surfaces of the inner layer flexible wiring board subjected to the alkali treatment, respectively, through the adhesive member. .

Wiring board, alkali, adhesive part

Description

Manufacturing method of rigid flex printed wiring board {Method for manufacturing rigid-flex printed wiring board}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a rigid flex printed wiring board, and more particularly, to a rigid flex printed wiring board having a structure in which an inner layer FPC is inserted into an outer layer RPC through an adhesive, and the adhesive can exhibit excellent adhesion strength. It is about a method.

First, a conventional shield formation process will be described by taking a rigid-flex (R-F) three-layer printed wiring board shown in a schematic cross-sectional view in FIGS. 7A to 7D and FIGS. 8A and 8B as an example. However, the order of (1) to (8) shown below is a general purpose one, and may be slightly reversed with respect to this order, and the contents thereof are not limited at all.

(1) The circuit 112 'is formed by processing the conductive member 112 in the inner layer CCL 110 (FIG. 7A) formed by providing the conductive member 112 on one surface of the electrically insulating flexible base 111. FIG. do. This obtains the inner layer CCL 110 'provided with the circuit 112' (FIG. 7B). Here, CCL means copper-clad laminate.

(2) A coverlay (hereinafter also referred to as CL) 120 is adhered on the surface where the circuit 112 'of the inner layer CCL 110' is provided (attached CL to the CCL formed circuit by heat press), An inner layer FPC (hereinafter also referred to as inner layer substrate) 130 is obtained (FIG. 7C). Here, the coverlay 120 is provided with the adhesive layer 122 on one surface of the electrically insulating flexible base 121. Here, FPC means a flexible printed circuit.

(3) An adhesive member 140 is attached on the rigid base material 151 of the outer layer RPC (hereinafter also referred to as outer layer substrate) 150 (FIG. 8B). Here, the outer substrate 150 is provided with a conductive member 152 on one surface of the electrically insulating rigid substrate 151 (Fig. 8A). Moreover, RPC means a rigid printed circuit.

(4) The outer layer substrates 150A and 150B are laminated on the upper and lower surfaces of the inner layer substrate 130 through the bonding members 140A and 140B (hereinafter also referred to as a laminated cure). As a result, a structure in which the inner substrate 130 including the FPC is sandwiched by the two outer substrates 150 including the RPC through the adhesive member 140 can be obtained (FIG. 7D).

(5) A hole is drilled in the substrate (hereinafter also referred to as NC drilling treatment: not shown). The structure in which the inner layer substrate 130 is inserted into the outer layer substrates 150A and 150B is subjected to mechanical processing for drilling holes for interlayer conduction.

(6) Through hole plating is formed (not shown). The inner surface of the hole for interlayer conduction is plated to form a through hole. As a result, conduction between the inner layer substrate 130 and the outer layer substrates 150A and 150B is achieved.

(7) An outermost layer circuit is formed (not shown). For example, a circuit is formed by etching the conductive member 152A forming the outermost layer of the outer layer substrate 150A.

(8) A resist is formed on the outer layer substrates 150A and 150B (not shown). In order to protect the outermost layer circuit formed by the above (7), an insulating layer made of a resist is provided to cover the outer surfaces of the outer layer substrates 150A and 150B, that is, the surface on which the outermost layer circuit is provided.

In the normal printed wiring board (FIG. 9) manufactured by the said process, the structure which combined and laminated | stacked and arrange | positioned using several kinds of members which consist of different materials is employ | adopted. Therefore, when the adhesion between the specific members is low, there is a fear that peeling may finally occur between the specific members due to environmental tests such as heat cycles or changes over time. For example, when peeling with copper foil and polyimide (between PI), since insulation is bad and it is difficult to use as a printed wiring board, it is not preferable. Therefore, in a multilayer printed wiring board, it is calculated | required to attach each member with appropriate adhesive force.

In the conventional manufacturing method, after the inner layer substrate 130 and the outer layer substrate 150B are attached, for example, the adhesion strength of the adhesive member 140B corresponding to this attachment portion may be weak. In this case, as shown in FIG. 10, peeling easily occurs between the inner layer substrate 130 and the outer layer substrate 150B. As a step located later than this attaching step, for example, the chemical liquid at the time of etching or developing may invade and the yield may greatly decrease. As a result, there exists a possibility of causing the fall of the reliability of the printed wiring board (henceforth a completed board | substrate) shipped as a product.

As a manufacturing method which solves the said subject, for example, (a) the method of modifying a polyimide surface by alkali-processing after discharging a polyimide (Unexamined-Japanese-Patent No. 5-279497), (b) low temperature plasma After the treatment, a method of surface-modifying the polyimide with an alkaline chemical solution (Japanese Patent Laid-Open No. Hei 6-32926), and (c) a method of treating the polyimide film with an alkaline solution and then treating with an acid solution (Japanese Patent Laid-Open No. 7-A). 03055), (d) a method of performing a plasma treatment on the surface of a polyimide film in an inert gas atmosphere, followed by plasma treatment on the same surface (JP-A-8-3338), (e) a polyimide resin surface The method of modifying a surface by irradiating the ultraviolet-ray in the presence of a 1st oxidizing agent, and then etching with a 2nd oxidizing agent (Unexamined-Japanese-Patent No. 9-157417) is mentioned. Furthermore, the polyimide in each document corresponds to the electrically insulating flexible base 111 constituting the inner layer substrate 130 described above.

The above-mentioned well-known documents (a) to (e) describe only surface treatment such as alkali treatment or plasma treatment in order to improve adhesion, and detailed descriptions such as "chemical concentration", "treatment temperature", "treatment time", and the like. Treatment conditions are not specified. That is, the surface treatment which optimized various treatment conditions is not described at all.

(f) A multilayer wiring board suitable for flip chip mounting that can withstand thermal shock and a method of manufacturing the same have been described, and a range suitable for the elastic modulus of the adhesive layer, the coefficient of linear expansion, and the blending of the material of the adhesive has been disclosed. -298369).

(g) A multilayer printed wiring board is described in which via holes are not easily peeled off from a lower conductive circuit, and a range suitable for the particle diameter, weight blending, etc. of the epoxy resin serving as the adhesive layer is disclosed. 46066).

(h) A multilayer printed wiring board having excellent adhesive strength between a conductor layer and an insulating layer is described, and a method of simply roughening is disclosed (Japanese Patent Laid-Open No. 10-70367). .

(i) The adhesive for flexible printed wiring boards is described, and the material mix of an adhesive agent is disclosed (Unexamined-Japanese-Patent No. 2001-164226).

Although well-known documents of (f) to (i) clearly describe the type, compounding, and surface treatment of the adhesive in the adhesive used in the printed wiring board of the prior art, mention is made on the improvement of the adhesion under optimum conditions. One cannot be found.

In recent years, in the technical field of a printed wiring board, multilayering has progressed further, for example, development of the multilayer board of more than 50 layers is performed. In particular, with light and short size reduction of electronic devices, a rigid flex printed wiring board which connects a rigid wiring board through a flex wiring board or superimposes a rigid wiring board on one part or all part of a flex wiring board is calculated | required, for example. Therefore, in the multilayered printed wiring board, it is expected to establish clear processing conditions for the processing method of the member surface on which the adhesive is to be provided.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a structure in which an inner layer substrate or an outer layer substrate is stacked through an adhesive member, and a rigid flex printed wiring board capable of suppressing peeling generated between the adhesive member and the inner layer substrate can be suppressed. It is an object to provide a method.

According to one aspect of the present invention, there is provided a method of manufacturing a rigid flex printed wiring board, wherein an inner layer flexible wiring board including a coverlay on an inner layer copper clad laminate and an outer surface of which is made of a flexible member, and an outer layer rigid wiring board and an adhesive member of which one surface is made of a flexible member. A method of manufacturing a rigid flex printed wiring board comprising: a process (alpha) of alkali treatment of both outer surfaces of the inner layer flexible wiring board and both outer surfaces of the inner layer flexible wiring board subjected to alkali treatment, The process (beta) which laminates an outer layer rigid wiring board, respectively is provided.

In the method for manufacturing a rigid flex printed wiring board according to the present invention, a step γ of washing the outer surfaces of the inner layer flexible wiring board subjected to alkali treatment between the step α and the step β with water washing with calcium addition water. It may be further provided.

In the method for manufacturing a rigid flex printed wiring board according to the present invention, the alkali treatment concentration in the step α may be 0.25 wt% or more and less than 10.0 wt%.

In the method for manufacturing a rigid flex printed wiring board according to the present invention, the alkali treatment time in the step α may be 30 sec or more and 120 sec or less.

In the method for manufacturing a rigid flex printed wiring board according to the present invention, the alkali treatment liquid temperature in the step α may be 25 ° C. or more and less than 55 ° C.

In the method for manufacturing a rigid flex printed wiring board according to the present invention, the calcium concentration in the step γ may be in the range of 20 ppm to 1000 ppm.

In the method of manufacturing a rigid flex printed wiring board according to the present invention, first, in step α, the surface layer of the flexible member (for example, polyimide) that forms both outer surfaces of the inner layer FPC by alkali treating both outer surfaces of the inner layer FPC (inner layer substrate). Reform wealth. Subsequently, in step β, the outer layer RPC is laminated on both outer surfaces of the inner layer FPC modified by alkali treatment so that the non-flexible member (for example, glass epoxy) comes into contact with each other via an adhesive member. As a result, the adhesive member can have excellent adhesion to both outer surfaces of the modified inner layer FPC (inner layer substrate).

In other words, in the manufacturing method according to the present invention, since the adhesive member significantly improves the adhesion between the inner layer FPC and the outer layer RPC by performing alkali treatment only on the flexible inner layer FPC, a rigid flex print having excellent reliability and stable adhesion. Contributes to the supply of wiring boards.

According to the present invention, the inner layer substrate constituting the printed wiring board is subjected to alkali treatment (step α) to modify the surface of the inner layer substrate, and then the inner layer substrate and the outer layer substrate are laminated (step β) through an adhesive layer, thereby providing high reliability. It becomes possible to manufacture a printed wiring board having excellent and stable adhesion. This manufacturing method is particularly effective for a printed wiring board made by combining various different materials, that is, a rigid flex printed wiring board in which an inner layer board is a flexible wiring board and an outer layer board is a rigid wiring board. However, it goes without saying that the manufacturing method according to the present invention is also effective in printed wiring boards of various shapes such as single-sided and multi-layered single-sided and multilayered types.

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment of the rigid flex printed wiring board which concerns on this invention is described based on drawing.

1A to 1D are schematic cross-sectional views showing an example of a method of manufacturing a rigid flex printed wiring board according to the present invention, in which components are exaggerated and drawn appropriately. 2A and 2B are typical sectional drawing which shows an example of the manufacturing method of the outer layer RPC which comprises the rigid flex-printed wiring board of FIGS. 1A-1D.

In the manufacturing method according to the present invention, as shown in FIG. 1D, the cover layer 20 is stacked on the inner layer CCL 10 ', and both outer surfaces are made of polyimide, and the inner layer FPC 30 is formed of glass epoxy. It is applied to a rigid flex printed wiring board provided with at least the outer layer RPCs 50A, 50B and the adhesive layer 40. In addition, CCL, F25PC, and RPC are the abbreviations of Copper-Clad Laminate, Flexible Printed Circuit, and Rigid Printed Circuit, respectively.

Here, although the manufacturing method is demonstrated in detail, taking a 3-layer printed wiring board as an example of a rigid flex printed wiring board, unless the alkali treatment effect | action and effect which concern on this invention are impaired, of (1)-(8) shown below: Of course, the order can be reversed.

(1) A circuit 12 'is formed in the inner layer CCL 10. As the inner layer CCL 10, a circuit 12 ′ was formed by etching the copper foil 12 using a copper foil 12 provided on one surface of a flexible base material 11 made of polyimide (FIG. 1A). Then, an inner layer CCL 10 'provided with a circuit is obtained (FIG. 1B).

(2) The coverlay 20 is adhere | attached on the surface in which the circuit 12 'of the inner layer CCL 10 was provided (CL is attached to the CCL which formed circuit by heat press). Here, as the coverlay 20, an adhesive layer 22 is provided on one surface of the flexible base material 21 made of polyimide, and the inner layer substrate 10 'and the coverlay are formed through the adhesive layer 22. By stacking 20, an inner layer FPC (hereinafter also referred to as an inner layer substrate) 30 is obtained (FIG. 1C).

(3) Alkali treatment of both outer surfaces of the inner layer substrate 30 (hereinafter referred to as step α). Here, in the apparatus where the line speed is managed, the alkaline aqueous solution in which the concentration and temperature are uniformly managed on both outer surfaces of the inner layer FPC 30 is sprayed onto the substrate by a shower method so that both outer surfaces of the inner layer FPC 30 are sprayed. Alkali treatment. Thereby, the inner substrate 30 subjected to alkali treatment is obtained.

(4) Aside from the inner layer substrate 30, it is prepared to attach an adhesive member 40 made of an adhesive sheet to an outer layer RPC (hereinafter also referred to as an outer layer substrate) 50. As the outer layer substrate 50, an adhesive member (not shown on the rigid substrate 51 of the outer layer substrate 50 using the copper foil 52 provided on one side of the rigid substrate 51 made of glass epoxy (FIG. 2A)). 40) is obtained by attaching (FIG. 2B).

(5) The outer layer substrate 50 of the above (4) is laminated on both outer surfaces of the inner layer substrate 30 subjected to alkali treatment in the above (3), respectively through an adhesive member 40 made of an adhesive sheet (hereinafter, Step β (lamination cure)). As shown in FIG. 2B, two outer substrates 50A and 50B formed by attaching the adhesive members 40A and 40B, respectively, are prepared. In stacking, the two adhesive substrates 40A and 40B provided on the two outer substrates 50A and 50B are stacked on both surfaces of the inner layer substrate 30 so as to be in contact with each other (FIG. 1D). When this stacking is appropriate, it may be pressurized or heated in the inward direction from the outside of the outer layer substrates 50A and 50B.

By the said process (1)-(5), the rigid flex 3-layer printed wiring board shown to FIG. 1D is produced. Moreover, although not shown, the following steps (6) to (9) are appropriately performed on the three-layer printed wiring board of FIG. 1D.

(6) A hole is drilled into the substrate (hereinafter also referred to as NC drilling process). Mechanical processing is performed to drill holes for interlayer conduction of the structure in which the inner layer substrate 30 is fitted to the outer layer substrates 50A and 50B (not shown).

(7) Through-hole plating is formed. The inner surface of the hole for interlayer conduction is plated to form a through hole. This conducts the inner and outer layers with electricity (not shown).

(8) An outermost layer circuit is formed. For example, a circuit is formed by etching the copper foil 50A constituting the outermost layer of the outer layer substrate 50A (not shown).

(9) A resist is formed on the outer layer substrates 50A and 50B. In order to protect the outermost layer circuit formed by the above (7), an insulating layer made of a resist is provided to cover the outer surface of the outer layer substrate, that is, the surface on which the outermost layer circuit is provided (not shown).

The manufacturing method of the rigid flex printed wiring board which concerns on this invention comprises the process (alpha) and the process (beta) at least in the process (1)-(9) mentioned above. By having these two processes α and β, the adhesive layer can have excellent adhesion to both outer surfaces of the modified inner layer FPC. Therefore, the manufacturing method of the present invention can improve the adhesion between the inner layer FPC and the outer layer RPC, thereby enabling the manufacture of a rigid flex printed wiring board with excellent reliability and stable adhesion.

The action of the adhesive force obtained by the alkali treatment of the step α is further improved by defining all the conditions of the alkali treatment. For example, the preferable range of alkali treatment concentration (wt%) is 0.25 or more and less than 10.0, More preferably, it is 0.25 or more and 4.0 or less. Moreover, the preferable range of alkali treatment time (sec) is 30 or more and 120 or less. Moreover, the preferable range of alkali treatment liquid temperature (degreeC) is 25 or more and less than 55.

In addition to this, step γ may be provided between the step α and step β in which both sides of the inner layer FPC subjected to the alkali treatment are washed with water using calcium-added water. By adding process (gamma), the preferable range of each alkali treatment condition can be expanded. This improves the degree of freedom of chemical management in mass production, or indicates a process control relaxation, thereby enabling the construction of an inexpensive and stable manufacturing line.

The above action obtained by the calcium addition water of step γ is further improved by defining the concentration. The preferable range of calcium concentration (ppm) is 20 or more, and 250 or more are more preferable. Moreover, between step α (alkaline treatment) and step γ (washing with calcium-added water) or between step γ and step β (laminated cure), for example, washing with water using RO water, ion-exchanged water or pure water. It is desirable to make.

Although the chemical liquid used for alkali treatment is given the example which used the sodium hydroxide aqueous solution in the Example mentioned later, a variety and a composition are not specifically limited. In addition, although calcium addition water is given the example which used the calcium chloride aqueous solution in the Example mentioned later, a variety and a composition are not specifically limited.

Example

Hereinafter, the results of evaluating all the conditions of the alkali treatment and the calcium concentration of the calcium-added water in detail from the viewpoint of modifying the surface of the inner substrate by improving the adhesion of the inner layer substrate by performing an alkali treatment on the inner layer substrate will be described in detail. Let's do it.

(Example 1)

In this example, sodium hydroxide aqueous solution (NaOH (aq)) is used as the chemical liquid used in the alkali treatment, and the alkali treatment concentration is changed in the range of 0.1 to 0.1 wt%, and the above-mentioned steps (1) to (5) By this, the rigid-flex 3-layer printed wiring board which consists of a structure shown in FIG. 1D was produced. In that case, the manufacturing conditions other than alkali treatment concentration were made the same. Table 1 summarizes the manufacturing conditions. Moreover, the printed wiring board produced in this example is called sample A.

 ◆ Materials of printed wiring board [Inner layer CCL] Double-sided copper foil 18μm, Polyimide 25μm, Adhesive 10μm [Coverlay (CL)] Polyimide 25μm, Adhesive 25μm [Outer layer RPC] Single-side copper foil 18μm, Glass epoxy 100μm [Adhesive sheet] 25μm  ◆ Chemical liquid treatment conditions of Sample A [Alkali treatment] Concentration: 0.1 to 10.0 [wt%], Liquid temperature: 35 [° C], Time: 60 [sec] [RO water washing] Liquid temperature: Room temperature, Time: 30 [sec] [ Calcium-added water washing] Concentration: 500 [ppm], liquid temperature: room temperature, time: 45 [sec], [RO washing] liquid temperature: room temperature, time: 30 [sec]

The peeling strength test based on JIS C 6471 was performed about the sample A produced by changing alkali treatment density | concentration. At that time, the tensile speed was 50 mm / min, and the temperature was normal temperature (room temperature). And peeling strength (called peeling strength) (N / cm) was computed based on JIS C 5016 8.1.6.

3 is a graph showing the peeling strength of Sample A prepared by changing the alkali treatment concentration. However, FIG. 3 also shows the results (specified no treatment) of samples not subjected to alkali treatment for comparison. Moreover, peeling strength is an average value of the numerical values obtained from ten samples, unless there is a notice.

In FIG. 3, it became clear from the following points.

(1a) When the alkali treatment concentration (wt%) is lower than 0.1, since the peeling strength is low, it is considered that the alkali treatment is insufficient.

(1b) In contrast, when the alkali treatment concentration (wt%) is higher than 10.0, the alkali treatment is considered to be excessive because the peeling strength is similarly low.

(1c) It is suggested that an improvement in peeling strength can be obtained by performing an alkali treatment in an alkali treatment concentration (wt%) of 0.25 or more and less than 10.0. In particular, when the alkali treatment concentration is in the range of 0.25 or more and 4.0 or less, it is more preferable because the peeling strength of about 3 times or more can be stably obtained compared with no treatment.

Therefore, it was found that in order for the printed wiring board to have more stable peeling strength, it is necessary to keep the alkali treatment concentration in an appropriate range.

(Example 2)

In this example, the alkali treatment time is changed to a range of 10 to 60Osec using an aqueous sodium hydroxide solution (NaOH (aq)) as the chemical liquid used for the alkali treatment, and shown in FIG. 1D by the steps (1) to (5). The rigid flex 3-layer printed wiring board which consists of one structure was produced. At that time, production conditions other than alkali treatment time were made the same. Table 2 summarizes the manufacturing conditions. The printed wiring board produced in this example is called sample B.

 ◆ Materials of printed wiring board [Inner layer CCL] Double-sided copper foil 18μm, Polyimide 25μm, Adhesive 10μm [Coverlay (CL)] Polyimide 25μm, Adhesive 25μm [Outer layer RPC] Single-side copper foil 18μm, Glass epoxy 100μm [Adhesive sheet] 25μm  ◆ Chemical solution treatment condition of Sample B [Alkali treatment] Concentration: 1.0 [wt%], Liquid temperature: 35 [° C], Time: 10 to 600 [sec] [RO water washing] Liquid temperature: Room temperature, Time: 30 [sec] [ Calcium-added water washing] Concentration: 500 [ppm], liquid temperature: room temperature, time: 45 [sec], [RO washing] liquid temperature: room temperature, time: 30 [sec]

The peeling strength (referred to as peeling strength) (N / cm) was computed about the sample peeling strength test similarly to Example 1 about the sample B produced by changing alkali treatment time.

4 is a graph showing the peeling strength of Sample B prepared by changing the alkali treatment time. However, in FIG. 4, the result (specified as no treatment) of the sample which has not been treated with alkali is also shown for comparison. Moreover, peeling strength is an average of the numerical values obtained from ten samples, unless there is particular notice.

In Fig. 4, the following points became apparent.

(2a) When the alkali treatment time (sec) is shorter than 30, since the peeling strength is lowered by 20, it is considered that the alkali treatment is insufficient.

(2b) On the contrary, when the alkali treatment time (sec) is longer than 120, the peeling strength is similarly lowered, so it is considered that the alkali treatment is excessive.

(2c) When the alkali treatment time (sec) is in the range of 30 or more and 120 or less, it is more preferable because the peeling strength of about 8 times or more can be stably obtained compared with no treatment.

Therefore, in order for a printed wiring board to have more stable peeling strength, it turned out that it is necessary to make alkali treatment time into an appropriate range.

(Example 3)

In this example, the alkali treatment temperature (liquid temperature) is changed in the range of 15-55 degreeC using the sodium hydroxide aqueous solution (Na0H (aq)) as a chemical liquid used by alkali treatment, and the process (1)-(5) mentioned above. The rigid-flex 3-layer printed wiring board which consists of a structure shown in FIG. 1D was produced. At that time, production conditions other than alkali treatment temperature (liquid temperature) were made the same. Table 3 summarizes the fabrication conditions. Moreover, the printed wiring board produced in this example is called sample C.

 ◆ Materials of printed wiring board [Inner layer CCL] Double-sided copper foil 18μm, Polyimide 25μm, Adhesive 10μm [Coverlay (CL)] Polyimide 25μm, Adhesive 25μm [Outer layer RPC] Single-side copper foil 18μm, Glass epoxy 100μm [Adhesive sheet] 25μm  ◆ Chemical liquid treatment conditions of Sample C [Alkali treatment] Concentration: 1.0 [wt%], Liquid temperature: 15 to 55 [° C], Time: 60 [sec] [RO water washing] Liquid temperature: Room temperature, Time: 30 [sec] [ Calcium-added water washing] Concentration: 500 [ppm], liquid temperature: room temperature, time: 45 [sec], [RO washing] liquid temperature: room temperature, time: 30 [sec]

Peeling strength test (the peeling strength) (N / cm) was computed on the sample peeling test similar to Example 1 about the sample C produced by changing alkali treatment temperature (liquid temperature).

5 is a graph showing the peeling strength of Sample C prepared by changing the alkali treatment temperature (liquid temperature). 5, the results (specified that there is no treatment) of the sample which did not carry out the alkali treatment are also shown for the comparison. Moreover, peeling strength is an average value of the numerical values obtained from ten samples, unless there is particular notice.

5, the following points became clear.

(3a) When alkali treatment temperature (liquid temperature) is lower than 25 degreeC, since the peeling strength is low, it is thought that alkali treatment is inadequate.

(3b) On the contrary, when alkali treatment temperature (liquid temperature) is higher than 55 degreeC, since the peeling strength is similarly low, it is considered that alkali treatment is excessive.

(3c) When the alkali treatment temperature (liquid temperature) is in the range of 25 or more and 55 or less, more preferably about 8 times or more of peeling strength can be stably obtained compared to no treatment, and more preferable.

Therefore, in order to have a more stable peeling strength of a printed wiring board, it turns out that it is necessary to make alkali treatment temperature (liquid temperature) into an appropriate range.

(Example 4)

In this example, the calcium concentration in the step γ in which both outer surfaces of the inner layer FPC subjected to the alkali treatment, washed after the alkali treatment (step α) is washed with water using calcium-added water is changed to a range of 0 to 1000 ppm, and the above-mentioned. By the steps (1) to (5), a rigid flex three-layer printed wiring board having the configuration shown in Fig. 1D was produced. At that time, the alkali treatment concentration was changed within the range of 0.1 to 10 wt% using an aqueous sodium hydroxide solution (NaOH (aq)) as a chemical solution used in the alkali treatment (step α). The manufacturing conditions other than the alkali concentration and the calcium concentration of the calcium-added water were made the same, without changing the point.

Table 4 summarizes the fabrication conditions. Moreover, the printed wiring board produced in this example is called sample D.

 ◆ Materials of printed wiring board [Inner layer CCL] Double-sided copper foil 18μm, Polyimide 25μm, Adhesive 10μm [Coverlay (CL)] Polyimide 25μm, Adhesive 25μm [Outer layer RPC] Single-side copper foil 18μm, Glass epoxy 100μm [Adhesive sheet] 25μm  ◆ Chemical liquid treatment conditions of Sample D [Alkali treatment] Concentration: 0.1 to 10.0 [wt%], liquid temperature: 35 [° C.], time: 60 [sec] [RO water washing] Liquid temperature: room temperature, time: 30 [sec] [ Calcium-added water washing] Concentration: 0 to 1000 [ppm], liquid temperature: room temperature, time: 45 [sec], [RO washing] liquid temperature: room temperature, time: 30 [sec]

Peeling strength test (the peeling strength) (N / cm) was computed similarly to Example 1 about the sample D produced by changing the alkali treatment density | concentration and the calcium concentration of calcium addition water.

6 is a graph showing the peeling strength of Sample D prepared by changing the alkali treatment concentration and the calcium concentration of calcium-added water. However, also for the comparison, the result (specified that there is no treatment) of the sample which did not give alkali treatment was also published for the comparison. Moreover, peeling strength is an average value of the numerical values obtained from ten samples, unless there is a notice.

6, the following points became apparent.

(4a) When the water treatment with calcium addition water is not performed (focus on the bar graph with calcium concentration Oppm), the peeling strength is increased only in a narrow range where the alkali treatment concentration (wt%) is 1.O or more and less than 4.0. It shows a tendency, and about 8 times or more peeling strength is obtained compared with no treatment. On the other hand, the peeling strength in the area | region of 0.5 wt% or less or the area | region of 4.0 wt% or more hardly changes compared with the result of not giving alkali treatment (it describes as no treatment).

(4b) In the case of washing with water using calcium-added water (concentrating on a bar graph with calcium concentration of 20 to 100 ppm), the peeling strength is increased in a wide range of alkali treatment concentration (wt%) of less than 0.25 to 10.0. For example, the range of alkali treatment concentration which can obtain about 8 times or more of peeling strength compared with no treatment is greatly expanded to 0.25 to 2.0 wt%.

(4c) From the result of setting the alkali treatment concentration to 4.0 wt%, it can be seen that when the calcium concentration is 20 ppm or more, the peeling strength of about 2 times or more can be obtained compared with no treatment. When the calcium concentration is 250 ppm or more, more preferably about 3 times or more peeling strength can be stably obtained compared to no treatment.

Therefore, in order for the printed wiring board to have a more stable peeling strength, it was found that it is effective to carry out an alkali treatment and then perform a water washing treatment using calcium-added water.

Moreover, it became clear that the water washing process using calcium addition water brings about the effect which expands the alkaline treatment optimal range. At that time, calcium concentration (ppm) becomes like this. Preferably it is 20 or more, More preferably, it is 250 ppm or more.

As mentioned above, although the preferable Example of this invention was described, this invention is not limited to these Examples. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the invention. The invention is not limited by the foregoing description, but only by the scope of the appended claims.

1A to 1D are schematic cross-sectional views showing an example of a method of manufacturing a rigid flex printed wiring board according to the present invention.

FIG. 2: A and 2B are typical sectional drawing which shows an example of the manufacturing method of outer layer RPC used for the printed wiring board of FIGS. 1A-1D.

3 is a graph showing the peeling strength of Sample A. FIG.

4 is a graph showing the peeling strength of Sample B. FIG.

5 is a graph showing the peeling strength of Sample C. FIG.

6 is a graph showing the peeling strength of Sample D. FIG.

7A to 7D are schematic cross-sectional views showing an example of a conventional method for manufacturing a rigid flex printed wiring board.

8A and 8B are schematic cross-sectional views showing an example of a manufacturing method of the outer layer RPC used for the printed wiring board of FIGS. 7A to 7D.

9 is a schematic cross-sectional view showing an example of a conventional rigid flex printed wiring board.

10 is a schematic cross-sectional view showing a state in which peeling occurs between the inner layer FPC and the adhesive member constituting the printed wiring board.

Claims (1)

A method for manufacturing a rigid flex printed wiring board having an inner layer flexible wiring board having a coverlay over an inner layer copper clad laminate and having an outer layer made of a flexible member, an outer layer rigid wiring board made of a non-flexible member on one surface, and an adhesive member, Alkali-processing both outer surfaces of the inner layer flexible wiring board, and A step β of laminating the outer layer rigid wiring board on the outer surfaces of the inner layer flexible wiring board subjected to the alkali treatment, respectively, via the adhesive member; The alkali treatment concentration in the step α is 0.25wt% or more and less than 10.0wt%, The alkali treatment time in the step α is 30 sec or more and 120 sec or less, The alkali treatment liquid temperature in the said process (alpha) is 25 degreeC or more and less than 55 degreeC, Furthermore, between the said process (alpha) and the said (beta), the process (gamma) which wash-washes both the outer surfaces of the said inner layer flexible wiring board which performed the said alkali treatment using calcium addition water is further provided, The calcium concentration in the said process (gamma) is a manufacturing method of the rigid flex printed wiring board in the range of 20 ppm-1000 ppm.

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