JPH04290495A - Multi-layer flexible printed circuit board and its manufacture - Google Patents

Abstract

PURPOSE:To realize sufficient endorsement of quality after being bent with respect to a multi-layer flexible PCB. CONSTITUTION:A multi-layer flexible printed circuit board comprises inner layer patterns 21, 22 on a surface and a rear face of a core layer 20 having flexibility, further insulation layers 27, 28 having flexibility and further surface layer patterns 30, 31. A region 2 which is expected to be bent at the time of mounting has only the inner layer patterns 21,22 but has no surface pattern 30 and no through-hole 35. The surface layer pattern 30 and the through-hole 35 are exclusively provided on regions 5,6 which are not to be bent at the time of mounting.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer flexible printed wiring board and a method for manufacturing the same.

[0002]In recent years, information processing devices have become increasingly smaller. For this reason, the printed wiring board into which this device is incorporated is required to (1) have a structure that can be folded and incorporated into a narrow space, and (2) have a high-density wiring pattern.

0003

2. Description of the Related Art Conventional printed wiring boards include those that have a multilayer and rigid structure, and those that have a flexible but single layer structure.

0004

In the former case, since it has rigidity, the degree of freedom in assembling it into the device is restricted, and it is difficult to sufficiently respond to miniaturization of the device.

In the latter case, it is possible to arrange the device three-dimensionally along the inner wall of the housing of the device, making it possible to incorporate it into a narrow space, and is suitable for downsizing the device. Therefore, it is difficult to increase the density of wiring patterns.

[0006] Furthermore, in order to achieve flexible multi-layer construction, not only is the selection of materials important, but also the bonding process must be performed in a different manner from that for rigid printed wiring boards.

An object of the present invention is to provide a multilayer flexible printed wiring board that is flexible and realizes multilayering, and a method for manufacturing the same.

[0008]

[Means for Solving the Problems] The invention of claim 1 provides a core layer having flexibility, an inner layer pattern formed on the front and back surfaces of the core layer, and a surface layer covering the inner layer pattern. It has a cross-sectional structure consisting of a flexible insulating layer disposed on the back surface and a surface layer pattern formed on the surface of the insulating layer,
The area to be bent during mounting has only the inner layer pattern and does not have the surface layer pattern or the through holes.

[0009] In the invention according to claim 2, the inner layer pattern in the area to be bent is extended in the same direction as the direction in which the area to be bent is curved when it is bent, and the width thereof is smaller than the normal width. This is a configuration with a pattern of

According to a third aspect of the invention, the direction in which the inner layer pattern in the area to be bent extends is the same direction in which the area to be bent is curved when it is bent;
This pattern has a considerably wider width than a normal pattern.

The invention according to claim 4 includes an inner layer pattern forming step of forming an inner layer pattern on the front and back surfaces of a flexible core layer, and a step of forming an inner layer pattern covering the inner layer pattern formed by the inner layer pattern forming step. A temporary bonding step of temporarily bonding a flexible insulating sheet to the front and back surfaces to obtain a temporary bonded body in which the insulating sheet is temporarily bonded to the front and back surfaces of a core layer having an inner layer pattern; A main adhesion step of placing a metal sheet for forming a surface layer on the front and back surfaces of the obtained temporary bonded body and applying heat and pressure, a through hole forming step of forming a through hole, and the bonded metal for forming a surface layer pattern. It consists of a step of patterning the sheet to form a surface layer pattern. It is configured such that cushion paper, a first release film, a silicone rubber sheet, a second release film, and a press plate are stacked one on top of the other in this order, and then heated and pressed using a hot plate.

The invention according to claim 5 includes an inner layer pattern forming step of forming an inner layer pattern on the front and back surfaces of a flexible core layer, and a step of forming an inner layer pattern covering the inner layer pattern formed by the inner layer pattern forming step. A temporary bonding step of temporarily bonding a flexible insulating sheet to the front and back surfaces to obtain a temporary bonded body in which the insulating sheet is temporarily bonded to the front and back surfaces of a core layer having an inner layer pattern; A main adhesion step of placing a metal sheet for forming a surface layer on the front and back surfaces of the obtained temporary bonded body and applying heat and pressure, a through hole forming step of forming a through hole, and the bonded metal for forming a surface layer pattern. It consists of a step of patterning the sheet to form a surface layer pattern. The metal film, the third release film, the cushion paper, the first release film, the silicone rubber sheet, the second release film, and the press plate are stacked one on top of the other in this order, and then heated and pressed using a hot plate. This is what I did.

[0013]

In the first aspect of the invention, the structure in which both the core layer and the insulating layer are flexible makes the wiring board a multilayer structure and flexible.

[0014] By configuring the area to be bent to have only an inner layer pattern and no surface layer pattern or through holes, unnecessary stress is less likely to be applied to the pattern when it is bent, and even after bending. Ensure quality is not compromised.

In the invention of claim 2, the pattern of normal width allows free bending.

[0016] In the invention of claim 3, the considerably wide pattern maintains the folded state after being folded by its own rigidity.

In the fourth aspect of the present invention, the silicone rubber sheet applies pressing force from the hot plate uniformly over the entire surface of the metal sheet for forming the surface layer. The cushion paper absorbs the unevenness on the surface of the temporary bonded body and prevents the silicone rubber sheet from being affected by the unevenness on the surface of the temporary bonded body.

In the fifth aspect of the invention, the metal film prevents the surface layer forming metal sheet from being affected by the unevenness of the surface of the cushion paper.

[0019]

Embodiment FIG. 2 shows a four-layer flexible wiring board 1 which is an embodiment of the present invention.

In the figure, numerals 2, 3, and 4 are areas to be bent, which are portions to be bent when the printed wiring board 1 is mounted.

[0021] Reference numerals 5, 6, 7, and 8 are areas not to be bent, which are portions that are not bent and maintain their original planar state even during mounting.

As shown in FIG. 2, in this printed wiring board 1, both end portions of the bending area 2 and other bending areas 3, 4 are bent approximately vertically, and non-folding areas 5, 7, 6, 8 maintain a flat state, along the top surface, side surface, and bottom surface of the information processing device main body 10.
0, the housing 1 of the information processing device 11
It is mounted three-dimensionally along the inner wall of 2.

[0023] In this way, the printed wiring board 1
Since the device 11 is mounted in a narrow space along the inner wall of the device 2, a special space for mounting is not required, and the device 11 can be configured to be compact. This printed wiring board 1 has a pattern design that takes into consideration the area to be bent so that good quality can be maintained when the printed wiring board 1 is folded and mounted three-dimensionally as described above.

Next, the structure of the above printed wiring board 1 will be explained.

FIGS. 1 and 4 show the structure of part of the area 2 to be bent and areas 5 and 6 not to be bent on either side of the area 2 in FIG.

The core layer 20 is made of flexible polyimide and has a thickness t1 of 25 μm.

21 to 26 are inner layer patterns, and the core layer 2
0 and has a thickness t2 of 18 μm.

Reference numerals 27 and 28 denote flexible epoxy-based insulating layers, which are formed on the front surface 20a and back surface 20b of the core layer 20, covering the inner layer patterns 21 to 26, and have a thickness t3 of 50 μm. It is. The insulating layers 27 and 28 are made of flexible epoxy insulating sheets 52 and 53 (see FIG. 10), as will be described later.

30 to 33 are surface layer patterns formed on the insulating layers 27 and 28, and the thickness t4 is 18 μm.
It is.

Reference numerals 35 and 36 are through holes, which are formed to penetrate through the printed wiring board 1.

The inner layer patterns 21 to 26 constitute a power supply layer or a ground layer, and the surface layer patterns 30 to 33 constitute a signal layer.

Regarding the area 2 to be bent, no surface layer pattern or through holes are formed, and only inner layer patterns 21 and 22 are formed.

As shown in FIG. 4, the inner layer patterns 21 and 22 extend in the same direction as the direction 37 in which the area 5 to be bent extends in a curved manner when it is bent.

Furthermore, the inner layer patterns 21 and 22 are formed at the same location on the front and back surfaces of the core layer 20.

Furthermore, a plurality of inner layer patterns 21 (22) are formed in line.

Here, the width W1 of the inner layer patterns 21 and 22
is several hundred μm, which is the width of a normal pattern.

Therefore, the inner layer patterns 21 and 22 themselves have almost no rigidity. Therefore, the area 2 to be bent is in a state where it can be bent freely and can be restored to its original state.

As shown in FIG. 5, the area 2 to be bent is formed by forming the areas 2a and 2 at both ends of the area 2 to be bent.
b is bent at a substantially right angle, and the side surface 10 of the device main body 10
Implemented in accordance with a.

Looking at the part bent at a substantially right angle, there are only inner layer patterns 21 and 22, and the inner layer patterns 21 and 22 are located very close to the neutral plane 38 of the printed wiring board 1 that neither expands nor contracts. Therefore, the compressive and tensile stresses acting on the inner layer patterns 21 and 22 in this portion are considerably small, and the inner layer patterns 21 and 22 do not break.

Furthermore, the through holes 35 and 36 are located within the non-bending areas 5 and 6, respectively, and the stress caused by bending does not reach the through holes 35 and 36, so that no damage to the through holes 35 and 36 occurs. .

The surface layer patterns 30 to 33 are also located within the non-folding areas 5 and 6, and stress due to bending does not apply to them, and the surface layer patterns 30 to 33 do not break.

Therefore, the portion of the printed wiring board 1 extending from the above-mentioned non-folding areas 5 to 6 is folded and mounted without any loss in quality.

[0043] Even after being bent, a force is applied to the area 2 to be bent in the direction of restoring it to its original state.
When removed from the device 11, it returns to its original planar state.

Next, another portion 3 to be bent in FIG. 2 will be explained with reference to FIGS. 6 to 8.

In each figure, parts corresponding to those shown in FIGS. 1, 4, and 5 are given the same reference numerals.

[0046] The area 3 to be bent is the inner layer pattern 40.
, 41, and no through holes or surface layer patterns.

Furthermore, as shown in FIG. 7, the inner layer patterns 40 and 41 have a width W2 of 30 mm, which is quite wide, and when bent, they resist the restoring force generated by the core layer 20 and the insulating layers 27 and 28. It has excellent rigidity.

Therefore, when the area 3 to be bent is bent as shown in FIG. 8, the inner layer patterns 40, 41
It maintains the bent state shown in the figure due to its rigidity.

[0049] As a result, the printed wiring board 1 can be assembled in a state in which it has been bent in advance so that the areas 5 and 6 not to be bent are at right angles, and the mounting work of the printed wiring board 1 can be carried out that much more easily. be exposed.

[0050] Also, for maintenance etc., the printed wiring board 1
When the bent portion 3 is bent in the opposite direction when the printed wiring board 1 is removed, it is easily bent and the printed wiring board 1 is returned to its original planar state.

Furthermore, the inner layer patterns 40 and 41 are located very close to the neutral plane 42, and the stress caused by bending is extremely small, so that they do not break.

Further, the through hole 43 and the surface layer pattern 44 are located in the non-folding area 5, and the through hole 45 and the surface layer pattern 4 are located in another non-folding area 7, and the above-mentioned Even if it is bent, no stress is generated and no breakage occurs.

Further, in FIG. 1, another area 4 to be bent has the same structure as the area 3 described above.

Note that the non-folding areas 5 to 8 also have considerable flexibility.

Next, a method of manufacturing the above printed wiring board 1 will be explained with reference to FIG. 9.

First, an inner layer pattern forming step 50 is performed,
In FIGS. 1 and 6, inner layer patterns 21-
26, 40, 41 are formed. As the core layer having metal films on the front and back surfaces, Chissoflex manufactured by Chisso Corporation,
SG30R35 was used.

The next temporary bonding step 51 is performed.

Here, as shown in FIG. 10(A), inner layer patterns 21 to 26, 40, 4 are formed on the front and back surfaces of the core layer 20.
1 and temporarily bonded with flexible epoxy-based insulating sheets 52 and 53 to obtain a temporarily bonded body 54 shown in FIG. 10(B). As the insulating sheets 52 and 53, TFA-880 manufactured by Toshiba Chemical Corporation was used.

The temporary adhesion step 51 is performed as shown in FIG.
The pressure is maintained at a constant pressure of 10 kg/cm2 as shown by line I, and the temperature is heated to a maximum of 100°C as shown by line II.

Next, the main bonding step 55 is carried out as described later, and as shown in FIGS. Final adhesion is performed to obtain a final adhesive body 58.

Thereafter, a through hole forming step 59 is performed to form through holes 35 (see FIG. 1) in the main adhesive body 58 for electrically connecting the inner layer and the surface layer.

Finally, a surface layer pattern forming step 60 is performed to pattern the copper sheets 56 and 57 to form surface layer patterns 30 and 31 (see FIG. 1).

Next, the main bonding step 55 will be explained.

FIG. 13 shows an embodiment of the main bonding step 55.

As shown in the figure, cushion paper 70- made of high-quality paper is placed on the front and back sides of the temporary adhesive body 54 on which the copper sheets 56 and 57 for surface layer pattern formation are placed, starting from the temporary adhesive body 54 side. 1, 70-2, first release film 71-1
, 71-2, silicone rubber sheet 72-1, 70-2,
With the second release films 73-1, 73-2 and press plates 74-1, 74-2 stacked, the hot plate 75-1,
75-2 by heating and pressurizing.

[0066] As shown in FIG. 14, the heating and pressurization is carried out by keeping the pressure at a constant pressure of 20 kg/cm2 as shown by line III, and by heating up to a maximum temperature of 170°C as shown by line VI.

Next, in the main bonding step 55, the main bonded body 58 is bonded to prevent voids, bulges, wrinkles, cracks, etc.
How each of the above members functions will be explained.

I Regarding voids, bulges, and wrinkles, release films 71-1, 71-2, 73-1, 7 arranged on the upper and lower surfaces of silicone rubber sheets 72-1, 72-2
3-2 is the friction between the silicone rubber sheets 72-1, 72-2 and the press plates 74-1, 74-2, and the friction between the silicone rubber sheets 72-1, 72-2 and the cushion paper 70-1, 70-2.

As a result, when pressure is applied, the silicone rubber sheets 72-1 and 72-2 are uniformly stretched in all directions on the surface.

Therefore, the pressure P of the hot plates 75-1, 75-2
acts uniformly over the entire surface of the copper sheets 56, 57 via the press plates 74-1, 74-2 and the uniformly stretched silicone rubber sheets 72-1, 72-2.

As a result, the copper sheets 56 and 57 are pressed against the temporary bonding body 54 over the entire surface without leaving any air leakage residue between them and the temporary bonding body 54, and voids caused by the air leakage residue, etc. No swelling occurs.

[0072] Also, silicone rubber sheets 72-1, 72
If there are wrinkles on the silicone rubber sheets 72-1 and 72-2, the wrinkles will be transferred and wrinkles will occur on the surface of the main adhesive body 58, but in this embodiment, the silicone rubber sheets 72-1 and 72-2 are Since the silicone rubber sheets 72-1 and 72-2 are uniformly stretched, no wrinkles occur on the surface of the main adhesive body 58.

II Regarding cracks, cushion paper 70
-1, 70-2 is not interposed, Fig. 15(A)
As shown in FIG.
As shown by the reference numeral 76, the portion corresponding to 1 bites into the back surface of the silicone rubber sheet 72-1 in a convex manner.

This part becomes a mechanically engaged part, and when the silicone rubber sheet 72-1 is pushed and stretched in the plane direction, the force applied to the temporary adhesive body 54 causes the temporary adhesive body 54 to form a surface indicated by an arrow 77. A crack 78 may occur in the temporarily bonded body 54 due to the directional force acting thereon.

However, in this embodiment, the cushion paper 70
-1, 70-2 are interposed between the temporary adhesive body 54 and the silicone rubber sheets 72-1, 72-2, as shown in FIG.
5(B), the unevenness caused by the inner layer pattern 21 is absorbed by the surface 70-1a of the cushion paper 70-1 being concave as shown by the reference numeral 79, and does not reach the silicone rubber sheet 72-1. Silicone rubber sheet 72-1
maintain a flat surface.

[0076] Therefore, the silicone rubber sheet 72-1 stretches without exerting any force upon the temporary adhesive body 54 during stretching, and no cracks occur in the temporary adhesive body 54.

Next, another embodiment of the main bonding step 55 will be described with reference to FIG.

In addition to the embodiment shown in FIG. 13, this embodiment uses copper sheets 56, 57 and cushion paper 70-1, 70-2
In order from the temporary adhesive body 54 side, UTC (Ultra-Thin Copper) as a metal film is placed between
80-1, 80-2 and third release film 81-1,
81-2 is inserted, and the main lamination is performed under the same conditions as shown in FIG.

[0079] The third release films 81-1, 81-2 are made of cushion paper 70-1, 70-2 and UTC80-1,
80-2.

[0080] As a result, the cushion papers 70-1 and 70-2 are freely stretched during the main adhesion process.

First, the UTCs 80-1 and 80-2 absorb the influence of the unevenness on the surface of the cushion paper 70-1 and 70-2, and the influence of the unevenness does not reach the copper sheets 56 and 57.

As shown in FIG. 17, the UTCs 80-1 and 80-2 have an uneven surface 83a on one side of an Al sheet 82 with a thickness t10 of 40 μm and a thickness t11 of 9 μm.
It has a structure in which it is bonded to a copper foil 83 having .

This UTC 80-1 is stacked as shown in FIG. 18 and has the following functions.

[0084] First, the Al sheet 82 receives the influence of the unevenness 70-1a on the surface of the cushion paper 70-1, and the influence of the unevenness 70-1a causes the copper sheet 56 to
Make sure that it does not reach this level.

This prevents the unevenness 70-1a-1 on the surface of the cushion paper 70-1 from being transferred to the copper sheet 56.

As a result, the occurrence of wrinkles on the surface of the main adhesive body 58 is reliably prevented.

[0087]Secondly, the unevenness caused by the inner layer pattern 21 is received and absorbed to prevent the inner layer pattern 21 from being transferred to the cushion paper 70-1.

[0088] This prevents the influence of the elongation of the cushion paper 70-1 from being transmitted to the temporary adhesive body 54 (mainly adhesive body 58), making it difficult for cracks to occur.

■ Thirdly, the uneven surface 83 of the copper foil 83
a exhibits an anchor effect between it and the copper sheet 56. This anchor effect reduces the bending and stretching force acting on the temporarily bonded body 54.

As a result, cracks are less likely to occur in the temporarily bonded body 54.

The four-layer flexible printed wiring board 1 shown in FIG. 2 manufactured by the above manufacturing method has good characteristics as described below.

■ Solder heat resistance test No blistering or peeling occurred even after dipping at 260°C for 60 seconds.

■ Electrolytic corrosion test 35 V DC was applied at 60°C and 85% RH, and 1,00
After 0 hours had passed, the insulation resistance R was 10 8 Ω or more.

■ Peel strength 3-1 Under normal conditions, the insulating layer 27 (insulating sheet 52) of the surface layer pattern 30
The peel strength against was 2 kg/cm 2 .

The peel strength of the inner layer pattern 21 against the core layer 20 was 1.0 kg/cm 2 .

3-2 Insulating layer 27 (insulating sheet 52) of surface layer pattern 30 after soldering heat resistance (after floating at 260°C for 20 seconds)
The peel strength against was 18 kg/cm 2 .

The peel strength of the inner layer pattern 21 against the core layer 20 was 0.9 kg/cm 2 .

■ Bending resistance No abnormalities were observed even after 10 repetitions of bending with a bending radius of 2 mm (according to JISC5016).

[0099]

As explained above, according to the invention of claim 1, stress is not easily generated in the inner layer pattern even when the inner layer pattern is bent, and there is no surface layer pattern or through hole in the portion to be bent. There is no risk that stress will be generated in the surface layer pattern when it is bent, causing it to break at that part, or that through-holes will peel off. and reliability can be improved.

According to the second aspect of the invention, the area to be bent can be freely bent, and even in a complicatedly bent state, it is possible to mount the device.

According to the third aspect of the invention, since the printed wiring board is maintained in a folded state, it is possible to easily mount the printed wiring board on the device.

According to the invention of claim 4, the influence of the unevenness on the surface of the temporary adhesive body does not extend to the silicone rubber sheet, and the silicone rubber sheet can be expanded uniformly, thereby eliminating voids, bulges, and wrinkles. Furthermore, the main bonding can be performed without generating cracks.

According to the invention of claim 5, the silicone rubber sheet can be uniformly expanded without being affected by the unevenness of the surface of the temporary adhesive body, and the surface of the cushion paper can be expanded evenly. It is possible to limit the influence of the unevenness on the metal sheet for forming the surface layer, and the main adhesion can be performed in a state where the occurrence of wrinkles is further suppressed compared to the invention of claim 4.

[Brief explanation of the drawing]

FIG. 1 is a sectional view taken along line II in FIG. 2, showing an embodiment of a multilayer flexible printed wiring board of the present invention.

FIG. 2 is a diagram showing an embodiment of the multilayer flexible printed wiring board of the present invention.

FIG. 3 is a diagram showing a state in which the multilayer flexible printed wiring board of FIG. 2 is mounted.

FIG. 4 is a plan view of the multilayer flexible printed wiring board of FIG. 1;

FIG. 5 is a diagram showing the state of the area to be bent in FIG. 1 after mounting.

6 is a sectional view taken along the line VI-VI showing the internal structure of another intended bending region 3 in FIG. 1. FIG.

7 is a plan view of the area to be bent in FIG. 6; FIG.

8 is a diagram illustrating the state of the area to be bent in FIG. 6 after mounting; FIG.

9 is a diagram showing a manufacturing process of the multilayer flexible printed wiring board of FIG. 1. FIG.

10 is a diagram illustrating the temporary adhesion step in FIG. 9. FIG.

FIG. 11 is a diagram showing temporary bonding process conditions.

12 is a diagram illustrating the main bonding step in FIG. 9. FIG.

FIG. 13 is a diagram illustrating an example of a temporary adhesion process.

FIG. 14 is a diagram showing the conditions of the main bonding step.

FIG. 15 is a diagram illustrating the effect of cushion paper.

FIG. 16 is a diagram illustrating another example of the main bonding process.

FIG. 17 is a diagram showing the structure of UTC.

FIG. 18 is a diagram illustrating the effect of UTC.

[Explanation of symbols]

1 4-layer flexible wiring board 2, 3, 4 Areas to be bent 5 to 8 Areas to be not bent 10 Information processing device main body 11 Information processing device 12 Housing 20 Flexible polyimide core layers 21 to 26
, 40, 41 Inner layer patterns 27, 28 Flexible insulating layers 30 to 33 Surface layer patterns 35, 36, 43, 45 Through holes 38, 42
Neutral surface 50 Inner layer pattern forming process 51, 54 Temporary adhesion process 52, 53 Insulating sheet 55 Main adhesion process 56, 57 Copper sheet for surface layer pattern formation 58
Main adhesive body 59 Through-hole forming step 60 Surface layer pattern forming step 70-1, 70-2 Cushion paper 71-1, 71-2 First release film 72-1,
72-2 Silicone rubber sheet 73-1, 73-2
Second release film 74-1, 74-2 Press plate 75-1, 75-2 Hot plate 78 Crack 80-1, 80-2 UTC

Claims (5)

[Claims] 1. A core layer (20) having flexibility, and inner layer patterns (21, 22, 4) formed on the front and back surfaces of the core layer.
0, 41), a flexible insulating layer (27, 28) disposed on the front and back surfaces of the core layer covering the inner layer pattern, and a surface layer pattern (27, 28) formed on the surface of the insulating layer. 30,
It has a cross-sectional structure consisting of the above-mentioned inner layer pattern (21, 22, 40, 41) and has only the above-mentioned inner layer pattern (21, 22, 40, 41), and has the above-mentioned surface layer pattern ( 30, 31) and through holes (3
5, 36) A multilayer flexible printed wiring board characterized by having a structure not having. 2. The inner layer pattern (21, 22) in the area to be folded extends in the same direction as the direction in which the area to be bent is curved when it is bent, and has a width that is smaller than the normal width. The multilayer flexible printed wiring board according to claim 1, characterized in that the pattern (21, 22) has a pattern (21, 22). 3. The inner layer pattern (40, 41) in the area to be bent extends in the same direction in which the area to be bent is curved when it is bent;
The multilayer flexible printed wiring board according to claim 1, characterized in that the pattern (40, 41) has a width considerably wider than that of a normal pattern. 4. An inner layer pattern forming step (50) of forming an inner layer pattern on the front and back surfaces of the core layer having flexibility; A temporary adhesion step (temporary adhesion step) in which a flexible insulating sheet is temporarily adhered to the core layer having an inner layer pattern to obtain a temporary bonded body in which the insulating sheet is temporarily adhered to the front and back surfaces of the core layer having an inner layer pattern.
51), a main bonding step (55) of placing a metal sheet for surface layer formation on the front and back surfaces of the temporary bonded body obtained by the temporary bonding step and applying heat and pressure, and a through hole forming step of forming a through hole. (59) and a step (60) of patterning the bonded surface layer pattern forming metal sheet to form a surface layer pattern, and the main bonding step (55) is performed on the temporarily bonded body (54). On the front and back sides of the metal sheet for surface layer pattern formation (56, 57)
Starting from the side of the temporary adhesive body on which is placed the cushion paper (
70-1, 70-2), first release film (71-1
, 71-2), silicone rubber sheet (72-1, 72-
2) The second release film (73-1, 73-2) and press plate (74-1, 74-2) are stacked and heated and pressed using a hot plate (75-1, 75-2). A method for manufacturing a multilayer flexible printed wiring board, characterized by carrying out the following steps. 5. An inner layer pattern forming step (50) of forming an inner layer pattern on the front and back surfaces of the core layer having flexibility; A temporary adhesion step (temporary adhesion step) in which a flexible insulating sheet is temporarily adhered to the core layer having an inner layer pattern to obtain a temporary bonded body in which the insulating sheet is temporarily adhered to the front and back surfaces of the core layer having an inner layer pattern.
51), a main bonding step (55) of placing metal sheets for surface layer formation on the front and back surfaces of the temporary bonded body obtained by the temporary bonding step and applying heat and pressure, and a through hole forming step of forming through holes. (59) and a step (60) of patterning the bonded metal sheet for forming a surface layer pattern to form a surface layer pattern, and the main bonding step (55) is performed on the front and back surfaces of the temporarily bonded body. On the sides, in order from the side of the temporary adhesive body on which the metal sheet for surface layer pattern formation was placed, metal films (80-1, 80-2),
Third release film (81-1, 81-2), cushion paper (70-1, 70-2), first release film (7
1-1, 71-2), silicone rubber sheet (72-1,
72-2), second release film (73-1, 73-2)
) and press plates (74-1, 74-2) are stacked one on top of the other and heated and pressed using hot plates (75-1, 75-2).