1. Field of the Invention
The present invention is related to a printed wiring board and its manufacturing method.
2. Discussion of the Background
A printed wiring board and its manufacturing method are described in, for example, Japanese Patent 3795270. In such a printed wiring board, a high-density region in which conductive bumps are arranged densely, and a low-density region in which conductive bumps are arranged sparsely are both formed in a single substrate. The printed wiring board is structured by properly arranging those high-density regions and low-density regions. The contents of this publication are incorporated herein by reference in their entirety.
According to one aspect of the present invention, a printed wiring board includes a rigid multilayer board, a first substrate having multiple conductors, and a second substrate having multiple conductors electrically connected to the conductors of the first substrate. The conductors of the second substrate have an existing density which is set higher than an existing density of the conductors of the first substrate, and the first substrate and/or the second substrate is embedded in the rigid multilayer board.
According to another aspect of the present invention, a method for manufacturing a printed wiring board includes providing a first substrate having multiple conductors, forming from a single substrate multiple second substrates each having multiple conductors, forming an accommodation section which accommodates one or more of the second substrates in the first substrate, accommodating one or more of the second substrates in the accommodation section formed in the first substrate, electrically connecting the conductors of the first substrate and the conductors of one or more of the second substrates, and embedding one or more of the second substrates by laminating a predetermined material on the first substrate and one or more of the second substrates accommodated in the first substrate.
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
a)-(b) are photographs schematically showing a structure of the printed wiring board;
a)-(d) are cross-sectional views illustrating production steps of a first substrate according to the manufacturing method of the embodiment;
a)-(d) are cross-sectional views illustrating production steps of a first wiring layer of a second substrate according to the manufacturing method of the embodiment;
a)-(e) are cross-sectional views illustrating production steps of a second wiring layer of a second substrate according to the manufacturing method of the embodiment;
a)-(e) are cross-sectional views illustrating production steps of a third wiring layer of a second substrate according to the manufacturing method of the embodiment;
a)-(d) are cross-sectional views illustrating steps for manufacturing a printed wiring board after a second substrate has been accommodated in an accommodation section;
a)-(c) are cross-sectional views illustrating a modified example of a method for manufacturing a printed wiring board.
The embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings.
Printed wiring board 300 according to an embodiment of the present invention, for example, as its cross-sectional structure shows in
First substrate 10 has, for example, non-flexible base material (10a) (which corresponds to a core substrate of printed wiring board 300) containing inorganic material (such as glass cloth, silica filler or glass filler). As shown with broken lines in
Second substrate 20 has non-flexible base material (20a) containing inorganic material (such as glass cloth, silica filler or glass filler). Non-flexible base material (20a) corresponds to the core substrate of second substrate 20 and its thickness is made smaller (thinner) than the thickness of first substrate 10, and as shown with broken lines in
Resin 30 is filled between first substrate 10 and second substrate 20. Namely, first substrate 10 and second substrate 20 are physically connected and adhered (electrically insulated) to each other by means of resin 30. Resin 30 may be formed with the same material as the resin that makes upper-layer insulative materials 35, 36.
As described, by connecting first substrate 10 and second substrate 20 through resin 30, adhesiveness between first substrate 10 and second substrate 20 is enhanced. Also, filled resin 30 works as a shock absorber, and when an impact is exerted from the outside, the impact will not be passed along to second substrate 20. Thus, connection reliability of the wiring in second substrate 20, whose wiring density is higher than that of first substrate 10, may be enhanced. In addition, by embedding second substrate 20 which is separately produced, a complex build-up process may be simplified. Furthermore, since insulation layers of first substrate 10 have higher rigidity than insulation layers of second substrate 20, stress exerted on second substrate 20 may be eased.
First substrate 10 and second substrate 20 are set to have the same thickness as each other, and their uppermost layers, wiring layers 11, 12 and wiring layers 25, 26, are formed on the same layer. Namely, the number of wiring layers in a unit thickness of second substrate 20 (six: wiring layers 21-26) is set greater than the number of wiring layers in a unit thickness of first substrate 10 (two: wiring layers 11, 12). When the number of wiring layers is compared in a region having the same thickness in both substrates (a number of wiring layers within a given thickness (a certain thickness as a unit, “a unit thickness”)), second substrate 20 has a higher existing density of conductors than first substrate 10 (namely, in the end, substrate 300 containing both substrates). As such, in the printed wiring board, the number of wiring layers formed by the conductors in second substrate 20 is made greater than the number of wiring layers in a region of first substrate 10 that has the same thickness as second substrate 20. With such a structure, a high-density conductor region may be formed easily, and thus it may be easier to make part of the printed wiring board fine-pitched.
Also, the thickness of at least parts of the wiring layers (conductive circuits) of second substrate 20 is the same as the thickness of a conductive circuit of first substrate 10. However, the thickness of at least parts of the conductive circuits of second substrate 20 may be thinner than the thickness of a conductive circuit of first substrate 10.
Insulative materials 35, 36 are made with, for example, an RCF (Resin Coated Cupper foil) (or a prepreg may also be used). On their surfaces, wiring layers 41, 42 are formed respectively and are electrically connected to lower-layer wiring layers 11, 12, 25, 26 by means of interlayer connection portions (25b, 26a). Through wiring layers 41, 42, first substrate 10 and second substrate 20 are electrically connected.
When manufacturing such printed wiring boards, for example, as shown in
Specifically, when producing first substrate 10, as shown in
Also, when producing second substrate 20, as shown in
When forming second wiring layers, as shown in
Next, after trimming (edge cutting and marking), drilling a hole for alignment, soft etching and conducting a laser pre-treatment, vias 605 are formed using a laser, for example, as shown in
In the following, conductive films (606a, 606b) are each patterned through a predetermined photo-etching process (such as washing with acid, laminating a resist, direct drawing (exposing to light), developing, etching, removing the film and so forth), and wiring layers 23, 24 are formed, for example, as shown in
When forming third wiring layers, as shown
Next, after trimming (edge cutting and marking), drilling a hole for alignment, soft etching and conducting a laser pre-treatment, vias 608 are formed using a laser, for example, as shown in
In the following, conductive films (609a, 609b) are each patterned through a predetermined photo-etching process (such as washing with acid, laminating a resist, direct drawing (exposing to light), developing, etching, removing the film and so forth), and wiring layers 25, 26 are formed, for example, as shown in
After producing first substrate 10 and second substrate 20 as above, all the substrates 10, 20 formed on substrate 100 and substrate 200 are inspected for quality to determine which substrates are defect-free and which substrates are flawed (defective). Substrates 10, 20 determined as defective here are abandoned according to requirements. When inspecting substrates 10, 20, an inspection using, for example, an image checker or the like is conducted. Then, substrates 10, 20 are each further processed by a black-oxide treatment.
Next, as shown in
In the following, second substrate 20 determined as defect-free in the above inspection is cut out from single substrate 200 using a laser, for example, as a chip with a predetermined size as shown in
When filling resin 30 in gaps (D1, D2), an adhesive agent may be poured using, for example, a dispenser. Alternatively, an adhesive agent may be applied in accommodation section (100a) beforehand, and a chip of second substrate 20 may be accommodated in accommodation section (100a).
Next, on the top and bottom of the structure, insulative material 35 made with, for example, an RCF having copper foil (701a) on its surface and insulative material 36 made with, for example, an RCF having copper foil (701b) on its surface are disposed respectively, for example, as shown in
Next, after trimming (edge cutting and marking), drilling a hole for alignment, soft etching and conducting a laser pre-treatment, vias 702 are formed using a laser or the like, for example, as shown in
As shown in
The above embodiment may be practiced after being modified as follows.
At least either first substrate 10 or second substrate 20 may be connected to at least one electronic component. For example, as shown in
The second substrates, with a higher existing density of conductors than the first substrate, are not limited to those having a greater number of wiring layers per unit thickness than the first substrate. As shown in
In the above embodiment, first substrate 10 and second substrate 20 are electrically connected through upper-layer wiring layers. However, they are not limited to such; the method for connecting both substrates is optional. For example, as shown in
Multiple second substrates may be embedded in one first substrate. For example, as shown in
Furthermore, as shown in
The material for first substrate 10 and second substrate 20 is optional. Substrates 10, 20 may be made with the same material or with different materials.
The configuration, position and its posture at the position of second substrate 20 may also be optional. For example, as shown in
In the above embodiment, accommodation section (100a) is formed after inspecting first substrate 10 and second substrate 20. However, each substrate may be inspected after forming accommodation section (100a).
The configuration and size of accommodation section (100a) are optional. However, considering the alignment of second substrate 20, its configuration and size are preferred to correspond to second substrate 20.
Forming an accommodation section is not limited to a method in which a portion corresponding to its space is removed by a laser or the like. For example, accommodation section (312a) may also be formed as follows: sacrificial material 311 is formed on substrate 310 beforehand as shown in
A printed wiring board according to the first aspect of the present invention has a first substrate having conductors and one or more second substrates having conductors whose existing density is set higher than that of the first substrate. It includes the following: the conductors of the first substrate and the conductors of a second substrate are electrically connected; and at least either the first substrate or a second substrate is embedded in the printed wiring board.
The structure may also be formed in such a way that the number of wiring layers formed by the conductors in a second substrate is set greater than the number of wiring layers in a region of the first substrate that has the same thickness as a second substrate.
The structure may also be formed in such a way that the first substrate and a second substrate each have insulation layers; and the existing density of conductors on insulation layers of a second substrate is set higher than the existing density of conductors on insulation layers of the first substrate.
The structure may also be formed in such a way that the first substrate and a second substrate have a lower-layer wiring layer and an upper-layer wiring layer that are electrically connected through vias in an interlayer insulation layer; and the number of vias per interlayer insulation layer in a second substrate is set greater than the number of vias per interlayer insulation layer in the first substrate.
The structure may also be formed in such a way that the first substrate and a second substrate are positioned without touching each other; and resin is present in at least part of the gap between the first substrate and a second substrate.
The structure may also be formed in such a way that an insulative material is disposed on at least either the top or the bottom of the resin; and the resin that forms the insulative material and the resin in the gap between the first substrate and a second substrate are made of the same material.
The structure may also be formed in such a way that at least either the first substrate or a second substrate has an insulation layer containing inorganic material.
The structure may also be formed in such a way that at least either an insulation layer in the first substrate or an insulation layer in a second substrate has at least a cloth layer made with the inorganic material.
The structure may also be formed in such a way that the number of insulation layers containing inorganic material in the first substrate is set greater than the number of insulation layers containing inorganic material in a second substrate.
The structure may also be formed in such a way that the thickness of at least parts of conductors in a second substrate is set the same as or less than the thickness of the conductors in the first substrate.
The structure may also be formed in such a way that at least one electronic component is electrically connected to at least either the first substrate or a second substrate.
The structure may also be formed in such a way that at least one electronic component is electrically connected to a second substrate.
A method for manufacturing a printed wiring board according to the second aspect of the present invention may have a first step to produce a first substrate having conductors; a second step to produce on a single substrate a sufficient number of second substrates; a third step to form an accommodation section which is a space in the first substrate produced in the first step to accommodate a second substrate; a fourth step to accommodate one or more of the second substrates in the accommodation section formed in the third step; a fifth step to electrically connect the conductors of the first substrate and the conductors of a second substrate; and a sixth step to embed a second substrate by laminating a predetermined material on the second substrate accommodated in the fourth step and on the first substrate which accommodates the second substrate.
Prior to the fourth step, a substrate inspection step may be conducted to check the quality of the first substrate produced in the first step and the second substrates produced in the second step. Then, in the fourth step, one or more of the second substrates determined to be defect-free in the substrate inspection step may be accommodated in the accommodation section of the first substrate determined to be defect-free in the substrate inspection step.
In the third step, the accommodation section may be formed in such a way that it has sufficient space to allow alignment when accommodating a second substrate.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
The present application claims the benefits of priority to U.S. Application No. 61/071,790, filed May 19, 2008. The contents of that application are incorporated herein by reference in their entirety.
Number | Date | Country | |
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61071790 | May 2008 | US |