JP2616572B2 - Method for manufacturing multilayer printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board, and more particularly to a method for manufacturing a multilayer printed wiring board having blind via holes suitable for surface mounting.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become lighter, thinner, smaller and more sophisticated, multi-layer printed wiring has been supported by high-density mounting in which an outer-layer mounting pattern of an electronic component and an inner-layer wiring pattern are conducted through blind via holes. doing. The method of manufacturing the multilayer printed wiring board of Conventional Example 1 having such blind via holes is performed as follows. That is, as shown in FIG. 5A, a through hole 3b is first formed in an insulating substrate 2 having copper foils 1 on both sides by drilling or punching. Next, as shown in FIG. 5B, a copper panel plating layer 4 and a through blind via hole 13b are formed on the surface of the insulating substrate 2 including the inner wall of the through hole 3b, and the front and back of the insulating substrate 2 are conducted. After this, FIG.
5C, the etching resist layer 5 is formed, and as shown in FIG. 5D, the panel plating layer 4 is etched.
Then, as shown in FIG. 5E, the etching resist layer 5 is peeled off to form a wiring pattern 6. After that, as shown in FIG. 6A, the surface of the copper foil 1 on which the wiring pattern 6 of the insulating substrate 2 is not formed is set as the outermost layer surface, and the insulating substrate 2 and a thermosetting adhesive resin sheet (hereinafter, referred to as “the resin”). Prepreg 7
6B) to form a multilayer printed wiring board 8 shown in FIG. 6B.

As another method of manufacturing a multilayer printed wiring board of Conventional Example 2, as shown in FIG. 7A, first, as shown in FIG. After the formation of the through holes 3b, as shown in FIG. 7B, the conductive paste 9 is filled in the through holes 3b to form the through blind via holes 13b, thereby ensuring conduction between the front and back copper foils 1. Thereafter, the etching resist layer 5 shown in FIG. 7C is formed in the same manner as in the manufacturing method shown in FIG.
The wiring pattern 6 is formed by etching in (D) and peeling of the etching resist layer 5 in FIG. Thereafter, as shown in FIG. 8A, a prepreg 7 is combined with the insulating substrate 2 and is heated and pressed to form
As shown in FIG. 8B, the intended multi-layered board 8 is obtained.

[0004] As a method of manufacturing the multilayer wiring board of the prior art example 3, as shown in FIG. 9A, as shown in FIG.
The non-through hole 3a is formed up to this point. Thereafter, as shown in FIG. 9 (B), by filling the non-through holes 3a with the conductive paste 9, a multilayer printed wiring board having blind via holes for conducting the outermost layer pattern and the wiring pattern 6 adjacent thereto is formed. It has gained.

[0005]

The above-mentioned conventional method for manufacturing a multilayer printed wiring board has the following problems. That is, in the construction method in which the through-hole blind via hole is subjected to copper panel plating to form a panel plating layer, as shown in FIG. 6B, the resin 11 in the prepreg 7 flows into the through-hole blind via hole 13b after the lamination. Then, the resin 11 is ejected from the surface of the laminate 8, and the ejected resin 11 causes a large variation in the thickness of the laminate 8. In addition, the ejected resin 11 hinders the subsequent processing, and therefore must be removed mainly by polishing the surface of the laminate 8. However, as described above, since the thickness of the laminated plate 8 varies greatly, a difference occurs in the polished thickness. Accordingly, the thickness of the conductor layer on the polished surface of the laminate 8 also varies, making it difficult to perform fine processing by etching the laminate 8 in the next step.

Further, in the main body of the laminated plate 8, copper panel plating is performed again to form through holes for the purpose of conducting between the front and back surfaces and conducting between the outermost layer and other wiring patterns 6. That is, the conductor layer forming the outermost layer of the laminated plate 8 is subjected to copper panel plating twice for the blind via hole and for the through hole, so that the conductor layer becomes thick and the fine wiring pattern is formed. Was not suitable for the formation of

In the method of laminating the conductive paste 9 after filling it into the through blind via hole 13b shown in FIG. 8, the resin 11 of the prepreg 7 is suppressed from the through blind via hole 13b after the lamination. In addition, since the copper panel plating for energizing the through blind via hole 13b is not required, the thickness of the outermost conductor layer of the laminated board 8 can be reduced. However, since the volume of the conductive paste 9 is usually reduced by curing, dents occur on the surface of the through blind via hole 13b after filling and curing the conductive paste 9. Due to the dent due to the volume decrease when the conductive paste 9 is hardened, it is difficult to secure the electrical connection reliability between the conductive foil 1 and the conductive paste 9 of the insulating substrate 2 and between the wiring pattern 6 and the conductive paste 9.

In particular, when an electronic component mounting pad of the laminated board 8 is formed on the through blind via hole 13b, the dent of the through blind via hole 13b becomes a dent on the surface of the component mounting pad. This causes a decrease in solder wettability of the mounting pad, which also affects the connection reliability of component mounting.

Also, in the method shown in FIG. 9, it is possible to suppress the ejection of the prepreg resin 11 and the thickness of the outermost conductor layer at the time of lamination. There is a problem that the same trouble as the manufacturing method occurs.

An object of the present invention is to solve the problems of the conventional method by electrically connecting the outermost electronic component mounting pattern and the inner layer pattern of a multilayer printed wiring board through blind via holes filled with a conductive paste. Improves the connection reliability between the inner layer pattern and the conductive paste in the blind via hole, smoothes the surface of the mounting pattern formed on the blind via hole of the multilayer printed wiring board, and improves the solder wettability during component mounting. To provide a method of manufacturing a multilayer printed wiring having high connection reliability.

[0011]

According to the method of manufacturing a multilayer printed wiring board of the present invention, an etching resist layer is formed on both sides of an insulating substrate having copper foil on at least a pair of both sides, exposed, developed, and laminated. A step of forming a wiring pattern only on the side of the inner layer while leaving the copper foil to be the outermost layer surface, a step of applying a thermosetting insulating resin over the entire surface only on the wiring pattern forming surface, drying by thermosetting, and laser processing Forming a non-through hole in a state where only the outermost copper foil is held at a position to be a blind via hole of the insulating substrate, and filling the non-through hole with a conductive paste, drying and curing the non-through hole. Forming a through blind via hole, and laminating at least a pair of insulating substrates via a prepreg with the surface on which the wiring pattern and the thermosetting insulating resin are formed as an inner layer surface; And heating and pressurizing with a pressing device to completely cure and integrate the prepreg with the prepreg adhered to the insulating substrate to form a laminate, and forming a through-hole in the laminate to form a copper panel. Forming a through-hole formed by a plating layer or filled with a conductive paste.

[0012]

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1A to 1F and FIGS.
3 (B) and FIGS. 3 (A) and 3 (B) are cross-sectional views shown in the order of steps for explaining the first embodiment of the present invention. In the first embodiment of the present invention, a step of forming a wiring pattern of an insulating substrate constituting an outermost layer among insulating substrates constituting each layer of a laminated board, and laminating and integrating these insulating substrates Process. As the insulating substrate, an epoxy resin is used as an insulating layer.
The thickness of the copper foil is 0.1 to
A 0.2 mm thin plate substrate can be used.

In the step of forming a wiring pattern on an insulating substrate, first, as shown in FIG. 1A, an etching resist layer 5 is formed by exposure and development. At this time, the etching resist layer 5 is left on the entire surface of the copper foil 1, which is the outermost layer surface when the layers are laminated, and the etching resist layer in a portion where a blind via hole is to be formed later is removed. Next, as shown in FIG. 1B, etching is performed by spraying an etching solution on the surface of the insulating substrate 2, and the exposed copper foil 1 is removed. At this time, the portion of the copper foil 1 that will become the blind via hole is also removed at the same time. Next, as shown in FIG. 1C, the etched insulating substrate 2
To the etching resist layer 5
Is peeled off. Thus, the formation of the wiring pattern 6 on only one surface of the insulating substrate 2 is completed.

Next, as shown in FIG. 1D, a thermosetting insulating resin 12 is applied to the entire surface on which the wiring pattern 6 is formed. It is assumed that the heat resistance of the thermosetting insulating resin 12 withstands at least the melting point of the solder. Specifically, a material that can withstand temporary heating at about 230 to 260 ° C. is preferable. In this embodiment, an epoxy resin mainly containing a brominated bisphenol A type epoxy resin as a thermosetting insulating resin 12, a dicyandiamide and benzyldimethylamine as a curing agent, and methyl ethyl ketone as a diluent is used. As the other epoxy-based thermosetting insulating resin 12, a bisphenol A type epoxy resin is used as a main component, and a phenol novolak type, a cresol novolak type, a brominated phenol novolak type, and a bisphenol phenol novolak which have high heat resistance and cure as a flame retardant are used. Novolak type epoxy resin such as novolak type,
A polyfunctional epoxy resin such as N, N, N ', N'-tetraglycidylmetaxylenediamine, and a naphthalene skeleton epoxy resin or the like as a single substance or a mixture of two or more kinds.
Examples of the curing agent include catalyst-type curing agents such as phenylimidazole and BF ₃ monoethylamine; aromatic polyamine curing agents such as metaphenylenediamine, diphenyldiaminosulfone and diphenyldiaminomethane; and resinous polyamines such as diethylenetriamine and triethylenetetraamine. An acid-based curing agent, such as chlorendic anhydride, methylnadic anhydride, etc., as a simple substance or a mixture of two or more kinds thereof, hexane, methyl ethyl ketone, xylene, methyl alcohol, ethyl alcohol, propyl One or a mixture of two or more organic solvents such as alcohol, butyl alcohol, ethyl acetate and butyl acetate can be used. It is also effective to mix tertiary amines, imidazoles and BF ₃ amine complex compounds as curing accelerators. Further, as the thermosetting insulating resin 12 other than the epoxy resin, a phenol resin, a polyester resin, a melamine resin, a urea resin, a polyimide resin, and a polybutadiene resin can also be used.

In the present embodiment, the thermosetting resin 12 is applied by a screen printing method using a solid mesh screen on the entire surface. And the thickness of the thermosetting insulating resin 12 is adjusted to be 30 to 70 μm thicker than the thickness of the wiring pattern. As will be described later, in the next manufacturing process, a blind via hole is formed, a conductive paste is filled in the blind via hole, and conduction between the multilayer copper foil 1 and the wiring pattern 6 is obtained. However, as described in the above-mentioned problem in the prior art, since the conductive paste involves a volume decrease due to curing, the conductive paste slightly changes depending on the diameter of the bridging via hole.
A dent of ２０20 μm occurs on the surface of the blind via hole. 30-70 μm thickness of thermosetting insulating resin 12
Covers the dents of the conductive paste and covers the insulating substrate 2
The thickness is sufficient to obtain a connection surface between the wiring pattern 6 and the conductive paste.

Next, after the thermosetting insulating resin 12 is applied, it is cured by heating at 120 to 150 ° C. for 30 to 50 minutes. Next, as shown in FIG. 1 (E), only the thermosetting insulating resin 12 and the insulating resin of the insulating substrate 2 are selectively removed by laser processing, and the copper foil on the side opposite to the surface on which the wiring pattern 6 is formed is formed. The non-through hole 3a is formed in a state where 1 is held. Examples of the processing laser include an ultraviolet laser such as an excimer laser and an infrared laser such as a carbon dioxide gas laser. However, the laser irradiation part is partially decomposed and scattered, and no thermal influence is generated around the processing part. In particular, an ultraviolet laser is optimal because the generation of carbonized resin in the through-hole 3a is extremely small. In this example, a krypton fluorine laser having an oscillation wavelength of 248 nm was used as an excimer laser, and the non-through hole 3a was processed under the condition that the irradiation energy density was 1 to ² J / cm ² . continue,
The inner wall of the non-through hole 3a is cleaned. Next, as shown in FIG. 1 (F), the non-through hole 3a is filled with the conductive paste 9 by a screen printing method, a dispenser method or the like to form a non-through blind via hole 13a. The outer layer copper foil 1 is electrically connected. Examples of the conductive paste 9 include a copper paste, a silver paste, a cream solder paste, and other conductive pastes. The copper paste and the cream solder paste are most suitable because of low resistance, extremely little migration, and low cost.
An example of the above-mentioned conductive paste 9 is shown below. Epoxy resin, phenol resin, and polyester resin can be used as the thermosetting resin serving as the binder. When an epoxy resin is used, an imidazole compound or an acid anhydride is added alone or as a mixture thereof as a curing agent. As powder metal, the average particle diameter is 5 to 20 μm
And a copper powder having a specific gravity of 1 g / cm ³ can be used.
As the antioxidant, unsaturated fatty acids such as linoleic acid and linolenic acid can be used. As the organic solvent for adjusting the viscosity of the conductive paste, methyl alcohol,
Ethyl alcohol, butyl alcohol, hexane, xylene, ethyl acetate, butyl acetate, methyl carbitol,
Organic solvents such as ethyl carbitol can be used alone or as a mixture of two or more. The viscosity of the conductive paste 9 is 100 to 30000 cpc (25
° C). The screen printing conditions are 100 to 22 mesh, and the conductive paste 9 is printed using a screen specification of an emulsion: diazo system or acrylic system. Resin curing conditions are 140-1
60 ° C., 30 to 60 min. In the case of a cream solder paste, a metal mask screen is used as a printing condition, and preheating is performed at 140 to 160 ° C.
~ 80 sec, main heating 240 ~ 260 ° C, 10 ~ 20s
ec is performed by a reflow furnace in which a temperature profile is set.

The formation of all the wiring patterns 6 on the insulating substrate 2 for electrically connecting the wiring pattern 6 and the outermost copper foil 1 is completed, and then the laminating is performed by laminating and integrating the insulating substrate and the prepreg. The steps will be described. The insulating substrate 2
In the formation of the wiring pattern 6, there is an insulating substrate 2 serving as an outer layer and an insulating substrate 2 serving as an inner layer when laminating. The steps up to this point show the manufacturing steps of the insulating substrate 2 serving as the outer layer. Can be manufactured by the same method. In the step of forming a panel plating layer, the insulating substrate 2 serving as the outer layer is formed by plating the inner wall surface of a through hole formed through the laminate after the lamination with copper panel plating.
One surface that will be the outermost layer of the laminate will be plated. Therefore, the wiring pattern 6 is formed on one of the outermost layer sides of the insulating substrate 2 after the lamination. Next, FIG.
As shown in (A), in the laminating press step of the insulating substrate 2, the prepreg 7 composed of the insulating substrate 2 and a resin in an insulative semi-cured B-stage state and a base material such as glass cloth or paper is interposed therebetween. After stacking in a sandwiched state, FIG. 2 (B)
As shown in (1), the prepreg 7 is completely cured in a state where the prepreg 7 is adhered to the insulating substrate 2 by applying heat and pressure by a press device, and the insulating substrate 2 is integrated to form a laminated plate 8. At the time of this laminating press, since the non-penetrating blind via holes 13a formed in each insulating substrate 2 are still filled with the conductive paste 9, the non-penetrating blind via holes 13a Through blind via hole 13
The resin of the prepreg 7 does not blow out from a. As an example, an experiment was conducted in which three insulating substrates 2 having a thickness of 0.1 mm and a non-penetrating blind via hole diameter of 0.1 mm were subjected to a wiring pattern 6 forming process, and then these insulating substrates 2 were stacked. In addition, the resin of the prepreg 7 was not ejected from the non-penetrating blind via holes 13a, and the conventional process of polishing the surface of the laminate 8 was unnecessary. This makes it possible to omit the step of polishing the surface of the laminated plate 8 and, conventionally, ± 100 μm (per 100 mm of laminated plate)
The dimensional accuracy of the existing laminated plate 8 can be reduced to a variation of ± 75 μm. The thickness of the thermosetting insulating resin 12 applied 30 to 70 μm thicker than the thickness of the wiring pattern 6 of the insulating substrate 2 also reduces the volume of the conductive paste 9 filled in the non-penetrating blind via holes 13a during curing. A sufficient connection surface can be obtained between the cover and the wiring pattern 6 of the insulating substrate 2. Also in the thermal shock test of the test laminate of the present example, the same connection reliability as in the case where the conventional through-hole blind via hole 13b was plated with a copper panel to form the panel plating layer 4 was obtained. Further, in the conventional method of forming the through blind via hole 13b by filling the conductive paste 9 in the through hole 3b, the maximum volume of the conductive paste 9 is reduced by 10 to 20 μm due to the volume reduction accompanying the curing of the conductive paste 9.
Depression of about m occurs in the outer conductor layer. This dent of the outer conductor layer reduces the solder wettability on the surface of this wiring pattern when an electronic component mounting pattern is formed later on this portion, which in turn causes a reduction in connection reliability when mounting the electronic component. I was In the test laminate of this example, dents were smaller than in the conventional manufacturing method, and the solder wettability of the component mounting pattern was improved by 20%.

Next, as shown in FIG. 3A, through holes 23 are formed in the laminated plate 8 after the laminating press step by drilling or the like. Subsequently, as shown in FIG.
In order to make the substrate conductive, a copper panel plating is performed to form a panel plating layer 4 and a through-hole 33. Thereafter, through the steps of forming a wiring pattern on the outermost layer surface of the laminate 8, forming a solder resist layer, printing symbol characters, processing an outer shape, and inspecting, a multilayer printed wiring board is completed. The formation of the through-holes 33 and the outer layer wiring patterns and the like is manufactured by a known method.

As described above, according to the first embodiment of the present invention, it is possible to prevent the resin 11 of the prepreg 7 from being ejected from the non-penetrating blind via holes 13a at the time of lamination. Therefore, the dimensional variation of the laminated plate 8 is reduced, and the variation of the thickness of the outermost conductor is similarly reduced. Thereby, the positional accuracy of the outermost wiring pattern is improved, and the etching accuracy of the outer wiring pattern is also improved. In addition, the thermosetting insulating resin 12 applied on the surface of the insulating substrate 2 allows the conductive paste 9 to be filled in consideration of the volume reduction at the time of thermosetting. Since the bonding surface between the wiring pattern 6 and the conductive paste 9 is sufficiently ensured, the connection reliability of the wiring pattern 6 of the insulating substrate 2 via the non-penetrating blind via holes 13a is improved. Furthermore, in the outermost layer, a non-penetrating blind via hole 1
When the electronic component mounting pattern is formed on the conductor layer including the outermost copper foil 1, the surface of the component mounting pattern becomes smooth because the copper foil 1 on 3a remains held. By improving the solder wettability on the top,
The connection reliability of electronic components is also improved.

FIGS. 4A to 4C are sectional views showing a second embodiment of the present invention in the order of steps for explaining the same. In the second embodiment of the present invention, as shown in FIG. 4A, the first embodiment combines the insulating substrate 2 in which the non-penetrating blind via holes 13a are filled with the conductive paste 9 and the prepreg 7. After forming the laminated plate 8 and forming the through-holes 33, when forming the through-holes 33, copper panel plating is performed to form the panel plating layer 4, whereas the through-holes 23 are formed in the laminated plate 8 by drilling or the like. Form. Thereafter, as shown in FIG. 4B, the conductive paste 9 used in the first embodiment is filled in the through-hole 23 and cured by heating in the same manner as in the first embodiment. Next, as shown in FIG. 4C, in order to improve the connection reliability between the conductive paste 9 and the outermost conductor layer,
A panel plating of copper is performed to form a panel plating layer 4.
According to the second embodiment described above, the same effect as that of the first embodiment is obtained, and the wiring pattern 6 in which the conductive paste 9 filled in the through holes 23 is formed on the outermost layer surface of the laminated plate 8 is provided.
Therefore, there is no need to plate the inner wall of the through-hole 33 in order to ensure necessary conductivity, and the outermost conductor layer of the laminate 8 does not become thick. Therefore, it is possible to easily form the fine wiring pattern 6 on the outermost conductor layer of the laminate 8.

The method for manufacturing a multilayer printed wiring board according to the first and second embodiments of the present invention is an example of a method for manufacturing a multilayer printed wiring board. It goes without saying that a modified method may be used. For example, the resist layer can be formed by any known method such as a photographic method and a screen printing method.

[0023]

As described above, according to the method for manufacturing a multilayer printed wiring board of the present invention, the outermost layer surface in the blind via hole prevents the prepreg resin from being blown out during lamination, thereby providing the outermost layer conductor. Variations in the thickness of the layer and in the dimensions of the insulating substrate itself can also be reduced. In addition, when filling the conductive paste into the blind via holes, the conductive layer of the insulating substrate and the conductive paste are applied by applying a thermosetting insulating resin in advance in consideration of the volume reduction when the conductive paste is cured. The bonding area can be secured, and the reliability of the conductive connection of the blind via hole can be improved. In addition, by forming non-penetrating blind via holes while holding the copper foil of the insulating substrate, which is the outermost layer of the laminate, the wiring pattern of the multilayer printed wiring board can be smoothed, and electronic components can be mounted. Connection reliability is likewise improved.

[Brief description of the drawings]

FIGS. 1A to 1F are cross-sectional views illustrating a first embodiment of the present invention in the order of steps for explaining the same.

FIGS. 2A and 2B are cross-sectional views showing a first embodiment of the present invention in the order of steps for explaining the first embodiment.

FIGS. 3A and 3B are cross-sectional views illustrating a first embodiment of the present invention in the order of steps for explaining the first embodiment.

FIGS. 4A to 4C are cross-sectional views shown in the order of steps for explaining a second embodiment of the present invention.

FIGS. 5A to 5E are cross-sectional views illustrating a method of manufacturing a multilayer printed wiring board of Conventional Example 1 in the order of steps.

FIGS. 6A and 6B are cross-sectional views illustrating a method of manufacturing a multilayer printed wiring board according to Conventional Example 1 in the order of steps.

FIGS. 7A to 7E are cross-sectional views illustrating a method of manufacturing a multilayer printed wiring board according to Conventional Example 2 in the order of steps.

FIGS. 8A and 8B are cross-sectional views illustrating a method of manufacturing a multilayer printed wiring board according to Conventional Example 2 in a process order.

FIGS. 9A and 9B are cross-sectional views illustrating a method of manufacturing a multilayer printed wiring board according to Conventional Example 3 in a process order.

[Explanation of symbols]

 Reference Signs List 1 copper foil 2 insulating substrate 3a non-through hole 3b, 23 through hole 4 panel plating layer 5 etching resist layer 6 wiring pattern 7 prepreg 8 laminated board 9 conductive paste 10 drilling 11 resin 12 thermosetting insulating resin 13a non-through blind via Hole 13b Through blind via hole 33 Through through hole

Claims (3)

(57) [Claims] 1. An etching resist layer is formed on both sides of an insulating substrate having copper foil on at least one pair of both sides, exposed and developed, and the copper foil to be the outermost layer surface when laminated is left on the inner layer side. A step of forming only a wiring pattern, a step of applying a thermosetting insulating resin over the entire surface only on the wiring pattern forming surface and drying by thermosetting, and the outermost layer surface at a position to be a blind via hole of the insulating substrate by laser processing. Forming a non-through hole while holding only the copper foil to be formed, filling the non-through hole with a conductive paste, drying and curing to form a non-through blind via hole, A step of laminating at least a pair of insulating substrates via a prepreg with the surface on which the curable insulating resin is formed as an inner layer surface; A step of forming a laminated board by completely curing and integrating the laminated board while bonding the same to the insulating substrate; and forming a through-hole in the laminated board to form a through-hole. Manufacturing method of printed wiring board. 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein said through-holes are formed by a copper panel plating layer. 3. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein said through-holes are formed by filling a conductive paste.