JP2001185854A - Multilayered printed wiring board and producing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered printed wiring board which has a low-cost partially non-multilayered structure without requiring special materials, processing, working or skilled techniques, and a producing method therefor. SOLUTION: Concerning a multilayered printed wiring board, a dam member 14 for preventing a resin flow at the time of lamination is provided around the part where the number of layers is decreased. Thus, since the resin flow at the time of lamination can be effectively blocked without using special materials or processing, cost-down and yield improvement can be attained. The producing method for this multilayered printed wiring board has a process for forming a dam 14 for preventing resin flow by screen printing or the like corresponding to a notched part 13 for detaching a removal scheduled part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board and a method for manufacturing the same, and more particularly, to a rigid flex printed wiring board having a portion that is not partially multilayered.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become smaller, lighter, and more sophisticated, demands for printed wiring boards have been further increased. As a technical solution, a method of increasing the wiring density per layer, a method of forming a high multilayer printed wiring board, a build-up method of forming a connection between layers at an arbitrary position in an arbitrary layer, and mounting of a connector or the like There are a method of omitting the component (the component becomes unnecessary by absorbing the function of the mounted component into the printed wiring board), and a method of embedding the mounted component in the printed wiring board.

[0003] While some of the multilayer boards are based on multilayer boards,
There is a structure in which the number of layers is partially different, which partially includes a portion having a structure with a small number of layers.

A typical example is a multilayer board having a rigid structure as a whole, which is called a rigid-flex board partially provided with a flexible board.

Another example of a partial non-multilayer structure is a metal core multi-layer printed circuit board. In this metal core multi-layer printed circuit board, recesses are formed by counterboring after lamination.

The details of the conventional partial non-multilayer structure will be described below.

FIG. 6 is a sectional view showing the steps of a conventional method for manufacturing a rigid flex substrate. Here, a six-layer plate will be described as an example. FIGS. 6A to 6C show only one core substrate.

First, as shown in FIG. 6A, two core substrates 1 which are copper-clad laminates are prepared, and the layers corresponding to the second and fifth layers are selectively etched. The core pattern 2 is formed.

Next, a slit 3 is formed from the second layer and the fifth layer side so that the surface layer can be removed in the future, so that the insulating layer 1a is cut and stopped at the copper foil portion 1b. This slit processing is performed by press processing using a special mold, router processing, laser processing, or the like (FIG. 6B).

Next, a resin flow preventing sheet 4 is adhered to the part to be removed (FIG. 6C), and a blackening treatment, which is a surface roughening treatment for improving adhesion, is performed on the second and fifth layers. .

On the other hand, the flexible printed circuit board 5 constituting the third and fourth inner layers is patterned, then laminated with a cover lay, and subjected to a blackening process.

Further, with regard to the prepreg 6, portions to be removed in the future are removed by router processing.

[0013] The two core substrates 1 thus formed,
A setup operation is performed in which the flexible substrate 5 and the two prepregs 6 are positioned at predetermined positions so that the prepreg is sandwiched between the flexible substrate 5 and the core substrate 1 with the flexible substrate 5 as a center (FIG. 6D), and a press machine is used. A 6-layer plate is formed by performing lamination by pressing under a large pressure while heating using (FIG. 6D).

Next, a hole is formed in a place where a through hole is formed, and the surface layer including the through hole plating is patterned to obtain a multilayer printed board on which the through hole 7 and the surface layer pattern 8 are formed. FIG. 6 (e).
In this figure, the through-holes 7 are formed in a state where the respective layers are separated (before performing the lamination press) for easy understanding, but actually, the core substrate 1, the prepreg 6, and the flexible substrate Needless to say, the through holes are formed after all the elements 5 are brought into close contact with each other.

Next, a surface treatment such as solder resist coating, solder plating, and flux coating is performed, the outer shape is processed by a router or the like, and the slits 3 and the resin flow prevention sheet 4 are easily removed. 6 (e) is peeled off by pinching it in the direction of the arrow in FIG. 6 (e) to remove a desired portion of the core substrate to be removed, thereby forming a portion where only the flex substrate remains.

Finally, the product is shipped after completion inspection.

[0017]

However, such a conventional rigid flex printed board has the following various problems. That is, firstly, it is necessary to use a special material having a small resin flow as the prepreg, so that the material cost is increased. Secondly, such a prepreg material having a small resin flow is inferior in adhesiveness to the extent that the resin flow is suppressed as compared with a commonly used material, so that the surface is roughened by plasma as a special treatment for improving the adhesiveness. And the like, which further increases the cost and requires skill in manufacturing technology. Third, in order to perform lamination such that resin does not flow into the non-multilayered portion, special manufacturing technique skill is required, and manufacturers who can order are limited to manufacturers having this technique. Fourthly, since a cut is made in the core material, an etchant may enter the inside from the cut and cause damage to the flexible printed board during etching for forming a surface pattern. This requires extra work, such as performing an appropriate treatment and performing a seal for preventing the liquid from entering the cut portion, resulting in an increase in man-hours and an increase in cost. Fifth, when the core material is peeled along the cuts, there is a risk of causing damage such as cracks on the substrate end surface in the corresponding portion. Therefore, careful work is performed to avoid such a risk. Has been invited. Sixth, it is impossible for the cut to form a complicated shape such as a curve.

Another conventional technique is a metal core multilayer printed circuit board formed by subjecting only a desired portion to counterbore processing after lamination and exposing an inner layer substrate only at that portion. However, the following problem also occurs in a metal core multilayer printed circuit board that has a counterbore processing after the lamination. First, it is very difficult to obtain the accuracy in the depth direction of spot facing. Secondly, capital investment and man-hours for performing the spot facing are required, resulting in an increase in cost.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and does not require a special material, processing, work, and skill, and provides a low-cost multilayer printed wiring board having a partial non-multilayer structure. The purpose is to provide.

[0020]

According to the present invention, in a multilayer printed wiring board having a portion having a reduced number of layers, a dam member is provided around the portion having a reduced number of layers. It is characterized by.

The multilayer printed wiring board preferably has a flexible printed wiring board as an inner layer and a rigid printed wiring board as an outer layer, and is preferably a rigid flex printed wiring board in which the outer layer is partially removed.

It is preferable that the dam member is disposed corresponding to the slit processing portion for removing the outer layer, or disposed outside the slit processing portion for removing the outer layer.

It is preferable that the multilayer printed wiring board is formed entirely of a rigid substrate, and has a concave portion formed by removing the upper layer rigid substrate surrounded by the dam member.

It is preferable that the multilayer printed wiring board has a recess formed after multilayering.

A layer connected to a buried bump may be additionally formed as the outermost layer.

In such a multilayer printed wiring board, resin flow during multilayering can be effectively prevented without using a special material or processing, so that the cost is low, the yield is good, and the reliability is high.

According to the present invention, there is provided an electronic component package having the above-mentioned multilayer printed wiring board.

Further, according to the method for manufacturing a multilayer printed wiring board according to the present invention, a step of forming a cut for removing a portion to be removed in two rigid boards, and preventing resin flow corresponding to the cut Forming a dam member to be formed, a step of preparing a flexible printed wiring board forming an inner layer, a step of forming a prepreg in which a portion corresponding to the portion to be removed is removed, and one of the rigid substrates, a prepreg, A step of laminating the other of the flexible printed wiring board, the prepreg, and the rigid board, a step of forming upper and lower through holes, a step of forming a pattern of a front surface layer and a back surface layer, and a step of removing the rigid board. Removing step.

The step of forming the dam member is preferably a step of screen-printing the dam material.

By adopting such a method, it is possible to reduce the product cost because no special processing, work and skill are required.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view of each step showing a method of manufacturing a rigid flex board according to the first embodiment of the present invention. Here, a six-layer plate will be described as an example.

First, as shown in FIG. 1A, two copper-clad laminates as a core substrate 11 are prepared, and the layers corresponding to the second and fifth layers are selectively etched. The core pattern 12 is formed. It should be noted that FIG.
(B) and (c) show one of the core substrates.

Next, as shown in FIG. 1B, slits 13 are formed from the second and fifth layer surfaces so that the surface layer can be removed in the future, the insulating layer 11a is cut, and the copper foil portion is cut. Stop at 11b. This slit processing is performed by press processing using a special mold, router processing, laser processing, or the like. In addition, not only continuous slits but also fine holes can be arranged close to each other.

Next, a dam 14 for blocking resin flow is formed near the boundary between the multilayer portion and the flexible portion so as to surround the portion where the flexible substrate is to be exposed in the future (FIG. 1 (c)). The dam 14 is obtained by applying an epoxy resin as will be described later, for example, by screen printing using a screen of about 100, and curing the resin under a curing condition of, for example, 120 ° C. for about 2 hours.

The height of the dam 14 is such that the thickness of the glass cloth in the prepreg is 100 μm (110 μm after lamination).
Therefore, a thickness of about 70 to 300 μm is selected.

The necessary conditions for this dam are as follows. The width of the dam is 0.3-1.0
mm is desirable.

First, it must be softened before the prepreg. This is because in the laminating step, it is necessary to melt the prepreg before the prepreg and adhere to the core. Also,
Since it is necessary to prevent the flow of the prepreg softened as a dam, it is necessary to stop at the position without flowing even after softening.

As a material satisfying such conditions, for example, a glass transition temperature of 117 to 140 ° C. and 121 ° C.
The epoxy-based encapsulating resin having a gel time of 10 to 12 minutes is not limited to this.

The dam can be formed using a dispenser other than screen printing.

Subsequent to the dam printing process described above, a blackening process, which is a surface roughening process for improving adhesion, is performed on the second and fifth layers.

On the other hand, the flexible printed circuit board 15 forming the third and fourth inner layers is patterned, then a coverlay is laminated, and a surface roughening process such as a blackening process is performed.

Further, with respect to the prepreg 16, a portion to be removed in the future (a portion to be removed) is removed by router processing. The two core substrates 11 thus formed,
A set-up operation is performed in which the flexible substrate 15 and the two prepregs 16 are positioned at predetermined positions so that the prepreg 16 is sandwiched between the flexible substrate 15 and the core substrate 11 (FIG. 1D). When lamination is performed by pressing with a large pressure while heating using a machine, the resin of the prepreg is softened, and the flexible substrate and the core substrate are firmly bonded to each other, thereby forming a six-layer plate. The softened prepreg resin is prevented from moving by the dam member, and does not enter the portion of the core substrate to be removed. The formation position of the dam 14 is not limited to the illustrated position.

Next, a hole is formed in a place where a through-hole is formed, and the surface layer including the through-hole plating of this hole is patterned to obtain a multi-layer printed board on which a through-hole 7 and a surface layer pattern 8 are formed. FIG. 1 (e)).
In this figure, the through-holes 7 are formed in a state where the respective layers are separated (before performing the lamination press) for easy understanding, but actually, the core substrate 1, the prepreg 6, and the flexible substrate Needless to say, the through holes are formed after all the elements 5 are brought into close contact with each other.

Next, a surface treatment such as solder resist coating, solder plating, and flux coating is performed, the outer shape is processed by a router or the like, and the portion that is cut off by a slit is drawn in the direction of the arrow in FIG. When the core substrate is removed by pinching and removing, only the flex substrate remains in this portion. Finally, it is shipped after completion inspection.

The positional relationship between the dam and the slit is set at the same position as the position of the slit or at a position outside the removed portion with respect to the slit. At least a part of the dam may be in close contact with at least the surface on the six-layer plate side of the slopes on both sides of the slit, or the core pattern 12 forming surface side of the core substrate on the six-layer plate side.

As shown in FIG. 2 (a), when the dam is disposed at a position outside the slit, the cut portion is peeled off cleanly, but the etching liquid may enter from the slit when the surface pattern 18 is formed. is there. For this reason, whether sufficient control is performed so that the etchant does not enter the slit portion from the slit portion to the portion to be the flexible substrate,
It is necessary to provide sufficient protection for the flexible substrate surface. As protection, it is preferable to apply an etching resistant coat to the flexible substrate portion exposed after removing the punched portion.

When a dam is formed in accordance with the slit position as shown in FIG. 2B, the slit is completely closed, and a seal for preventing the etching liquid from entering the flexible substrate during pattern formation. To fulfill the role of
The flexible substrate can be effectively prevented from being etched. However, when the punched portion is peeled off, a part thereof is adhered to the dam, so that it is difficult to peel off, and even after peeling, the fractured surface has many irregularities. Further, in order to perform the peeling smoothly, it is necessary that the adhesive strength between the prepreg and the dam is larger than the adhesive strength between the core substrate and the dam, and the adhesive strength between the prepreg and the core substrate is larger than this strength.

FIG. 3 is a sectional view showing main steps in a second embodiment in which the present invention is applied to a rigid substrate partially having a small number of layers.

As shown in FIG. 3A, a dam 22 is formed on a lower rigid substrate 21 so as to surround a portion where an upper layer will be removed in the future. As described above, this dam 22 is obtained by printing and curing an epoxy resin by screen printing.

Next, the prepreg 23 partially removed corresponding to the portion to be removed is overlapped so that the end is located outside the dam (FIG. 3 (b)), and the upper layer is further removed. The rigid substrate 24 is set up on top of it (FIG. 3
(C)), lamination is performed by pressing while heating. At this time, slits 25 are previously formed in the upper rigid substrate 24 to be laminated.

By performing such lamination, since the prepreg does not exist in the portion to be removed, the upper rigid substrate 24 and the lower rigid substrate 21 are not bonded. Therefore, if the upper rigid substrate 24 to be removed is removed, the upper surface of the lower rigid substrate 21 is exposed in the recess.

In the multilayer printed wiring board thus obtained, for example, as shown in FIG. 4, an electronic component package comprising a core board (rigid board) 21 and a rigid board 24 prepared by the above-described method is used. By providing the component 22, a component (a chip component, a semiconductor chip, or the like) can be mounted in the concave portion 26 formed in the upper substrate, and a multilayer mounting is possible. That is, the wiring pattern 21a on the upper surface of the lower substrate 21 is exposed in the recess 26 (also referred to as a cavity), and the first element 31 is flip-chip mounted on this wiring pattern, and the pattern on the upper surface of the upper substrate 24a is formed. By mounting the second element 32 having a gull-wing type lead, multilayer mounting is possible. The first element 31 and the wiring pattern 21a of the lower substrate (rigid substrate) 21 are connected by bumps (not shown).

The second element 32 is not limited to the above. If the upper surface of the first element 31 is lower than the upper surface of the rigid substrate 24, the second element 3 of the BGA type is used.
2 can be mounted on the rigid board 24.

In this embodiment, a portion having a small number of layers can be formed without performing counterboring after lamination.

In this embodiment, the lower rigid substrate may be either a multilayer substrate or a single-layer substrate, a metal substrate having better heat dissipation, or a composite thereof. Further, the lower rigid substrate 21 may be a flex substrate. In this case, the flex substrate may be further extended outside the illustrated element mounting portion and bendable at that portion. Such a bent portion can also be formed by the manufacturing method of the present invention, and a desired bent portion on a single flex board, a high-density device having a device mounting portion requiring multilayer wiring can be provided. Implemented and
Due to the bent portion of the flex board, a wiring board having a high degree of ease of mounting can be obtained.

FIG. 4 shows an embodiment in which the elements are mounted in two stages. However, if the manufacturing method of the present invention is adopted, the recess formed in the lower substrate is made larger in size including the lower recess. By doing so, it is possible to mount the element in multiple layers with two or more stages of substrate portions having recesses (three or more stages for each substrate portion). Also in this case, if the dam 22 is provided in the peripheral part of each cavity, the prepreg resin can be prevented from seeping out to the bottom surface of the cavity, and the element can be mounted on each layer.

In any of these cases, the cavity forming section may remove unnecessary portions of the substrate sequentially from the top after laminating each layer. At this time, for example, if a part of the unnecessary part is opened with a drill and a jig is provided in the layer at the part, the unnecessary part can be easily separated.

In such a mode, the element to be mounted is G
The BA type is desirable, and the element mounted on at least the interior part other than the outermost layer is thinner than the surrounding multilayer substrate and has a thickness of 100 mm.
Desirably, it is processed to a thickness on the order of microns.
With such a configuration, higher-density mounting becomes possible.

The elements in each cavity, or only the element at the top, may be resin-sealed.

Further, in this embodiment, it is not always necessary to perform slit processing for facilitating removal of the upper rigid substrate, and the rigid substrate may be formed by spot facing. Even in this case, unlike the conventional case, the upper rigid plate in the area where the concave portion is to be formed is not bonded to the lower rigid plate, and there is a cavity having a thickness equivalent to the thickness of the prepreg 23. Since work control is not required, workability is improved.

FIG. 5 shows an example of a build-up substrate 40 according to the third embodiment in which a layer is further superimposed on the surface layer and the back surface layer of the rigid flex substrate according to the first embodiment by a silver paste bump method. It is shown.

In this embodiment, the second to seventh layers correspond to the first to sixth layers (rigid flex substrate 10) in FIG. 1, but the second layer (L2 in the figure; similarly, the n-th layer In the figure, between Ln (n is an integer of 1 to 8) and the third layer,
The layer and the seventh layer are connected by a silver bump 41. Further, a first layer on the front surface and an eighth layer on the back surface are laminated, and these are connected to the inner layers by silver bumps 42. The first and eighth layers have slits 43 formed on a rigid substrate of a rigid flex substrate.
Are formed. For this reason,
By these slits 43 and 44, the rigid substrate in the predetermined region and the layer on the back surface thereof are removed, and this portion can be made only the flex substrate.

Although the silver paste pump method has been described in this embodiment, the present invention can be applied to a build-up substrate using a laser via or photo via method.

In this embodiment, a printed wiring board having a large number of layers can be easily obtained.

In each of the above embodiments, the slits 13 and 25
Although the example of cutting into the substrates 11 and 24 and reaching the metal foil has been shown, the cutting to the metal foil is not necessarily required, and may be stopped in the middle of the substrate. In this case, there is little possibility that the substrate is broken along the slit during the process.

[0067]

As described above, according to the rigid flex type multilayer printed wiring board of the present invention, since the dam member for preventing the prepreg from flowing at the time of lamination is provided, the prepreg has low fluidity. Multilayer printed wiring that reduces costs and improves yield and reliability because there is no need to use expensive materials and no special treatment to improve adhesion or sticking work to prevent prepreg flow is required. It is possible to provide a board.

Further, according to the method of manufacturing a multilayer printed wiring board according to the present invention, since a step of forming a dam member for preventing a prepreg from flowing at the time of lamination is provided, an expensive prepreg having a low fluidity is used. There is no need to use any material, and special processing to increase the adhesion and sticking work to prevent the prepreg from flowing are also unnecessary, resulting in cost reduction by improving workability and reducing the number of work steps, and yield and reliability. Performance can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a process of manufacturing a multilayer printed wiring board according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a relationship between a positional relationship between a slit and a dam and a break in a wave.

FIG. 3 is a cross-sectional view illustrating a process of manufacturing a multilayer printed wiring board according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a state in which elements are mounted in multiple layers using the multilayer printed wiring board obtained by the process shown in FIG.

FIG. 5 is a cross-sectional view showing an example of a build-up board obtained by further laminating a multilayer printed wiring board obtained by the process shown in FIG. 1 with a silver paste bump method.

6A to 6C are cross-sectional views illustrating a method for manufacturing a conventional rigid flex substrate.

[Explanation of symbols]

 1, 11, 21 core substrate 2, 12 core pattern 3, 13, 25, 43 slit 4 resin flow prevention sheet 5, 15 flexible substrate 6, 16, 23 prepreg 7, 17, through hole 14, 22 dam

Continuing from the front page (72) Inventor Noriaki Sekine 1 Toshiba-cho, Fuchu-shi, Tokyo F-term in the Fuchu Plant of Toshiba Corporation 5E338 AA03 AA11 AA12 AA16 BB63 CC01 CD40 EE32 EE33 5E343 AA02 AA12 AA33 BB21 BB65 ER60 GG11 5E346 AA05 AA06 AA22 AA60 BB01 EE02 EE06 EE07 EE09 EE44 GG19 GG28 HH32 HH33

Claims (8)

[Claims] 1. A multilayer printed wiring board having a portion with a reduced number of layers in a part thereof, wherein a dam member is provided around the portion with a reduced number of layers. 2. The printed circuit board according to claim 1, wherein said multilayer printed circuit board has a flexible printed circuit board and a rigid printed circuit board, and is a rigid-flex printed circuit board with an outer layer partially removed. Multilayer printed wiring board. 3. The multilayer printed wiring board according to claim 1, wherein the multilayer printed wiring board is entirely formed of a rigid substrate, and has a concave portion formed by removing a rigid substrate in an upper layer in a region surrounded by the dam member. The multilayer printed wiring board according to claim 1. 4. The multilayer printed wiring board according to claim 1, further comprising an outermost layer. 5. An electronic component package having a multilayer printed wiring board partially having a reduced number of layers and a dam member provided around the reduced number of layers. 6. The multilayer printed wiring board according to claim 1, wherein the whole is formed by a rigid substrate, and has a concave portion formed by removing an upper layer rigid substrate surrounded by the dam member. The electronic component package according to claim 5. 7. A step of forming a cut in the rigid substrate for removing a portion to be removed, a step of forming a dam member for preventing resin flow corresponding to the cut, and preparing a flexible printed wiring board forming an inner layer. And preparing a prepreg from which a portion corresponding to the portion to be removed is removed; and laminating one of the rigid boards, the other of the prepreg, the flexible printed wiring board, the prepreg, and the rigid board. A method of manufacturing a multilayer printed wiring board, comprising: a step of: removing a portion of the rigid substrate to be removed. 8. The method according to claim 7, wherein the step of forming the dam member is a step of screen-printing a dam material.