JP3202840B2 - 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 multilayer printed wiring board suitable for high-density mounting, and more particularly to a multilayer printed wiring board having a blind via hole and a through via hole having excellent physical and electrical characteristics and a method of manufacturing the same. It is.

[0002]

2. Description of the Related Art With the miniaturization and multifunctionalization of electric equipment,
Currently, printed wiring boards are moving toward higher densities. For example, thinner conductor circuits, higher multi-layers, smaller through holes including interstitial via holes such as through via holes, blind via holes, and buried via holes, and high-density mounting by surface mounting of small chip components. There is.

In order to explain a conventional method for manufacturing a multilayer wiring board having blind via holes, FIGS. 11 to 19 show schematic cross sections of respective steps. As shown in FIG. 11, an inner layer panel 7 in which a copper wiring pattern 6 has been formed in advance by an etching method is prepared, and one or two prepregs 5 are laminated between the outer layer copper foil 1 and the inner layer panel 7 and laid. Up,
By hot pressing, a copper clad laminate panel having an inner wiring pattern shown in FIG. 12 is obtained.

[0004] Next, holes are formed sequentially at predetermined positions by a drill machine to form blind via hole holes 13, as shown in FIG. 13. Subsequently, when a conventional through-hole via hole 10 is provided, the result is as shown in FIG.

Hereinafter, conventional electroless copper plating and electrolytic copper plating are performed to form plated through holes 11 as shown in FIG.
After the etching resist 12 is formed (FIG. 16), the etching is continued, as shown in FIG. 17, and finally the etching resist film is stripped to have a blind via hole as shown in FIG. A multilayer printed wiring board is obtained. FIG. 19 shows the result when the solder resist 16 is further formed.

However, in order to form a blind via hole with a drill as described above, it is not possible to open a plurality of panels one by one as in a normal through hole, and it is necessary to make holes one by one. There is a disadvantage that it takes a very long time and production efficiency is poor. Further, in drilling, in order to control the depth of the tip of the drill, it is necessary to match the moving distance in the drilling direction, generally the Z-axis direction, with the depth of the copper wiring pattern on the surface of the inner layer panel. . However, as described above, 0.1 to 0.
Drills with a small diameter of about 5 mm have large runout, and there are variations in the position of the copper wiring pattern in the Z-axis direction. Therefore, it is difficult to control with high accuracy. If the drilling is shallow, it will not reach the lower copper wiring pattern. However, it is not connected by plating in a later process and causes a blind via hole defect. Conversely, if the drilling is too deep, it may further contact with a copper foil pattern therebelow, resulting in a short circuit defect.

As the prepreg, those obtained by impregnating resin into glass fibers are mainly used. However, when electricity is supplied to a conductor circuit of a printed wiring board in which the glass fibers and the conductor are in contact with or in proximity to each other, the glass fibers are converted into glass fibers. CAF (Conductive Anodic) where conductors grow along
It is known that a phenomenon called “filament” occurs and causes insulation deterioration. A major problem has been how to prevent insulation deterioration due to CAF of a printed circuit board when the conductor gap and the through-hole gap are extremely small in high-density wiring.

In order to solve these disadvantages of the conventional method, the present inventors have already completed a method of manufacturing a multilayer printed wiring board which is completely different from the conventional method (Japanese Patent Application No. 4-56347).
issue). The present invention relates to a method for heating and laminating an insulating layer side of a copper-clad insulating sheet comprising an insulating layer and an outer layer conductor on an inner layer panel having a conductor pattern such as a copper foil, forming a conductor pattern on the outer layer conductor, and forming a blind via. After the copper foil at the position where the hole is to be formed is removed by etching, the exposed resin layer is dissolved in alkali to expose the conductor pattern of the inner layer panel and form a blind via hole or an access hole-shaped through via hole. This is a method for manufacturing a multilayer printed wiring board in which conductive patterns of an inner layer panel panel and conductive patterns of an outer layer are electrically connected by conductive paste or plating.

[0009]

However, in the above manufacturing method, in order to form an access hole-shaped through via hole using an inner layer panel having no through hole, a copper-clad insulating sheet is laminated on the inner layer panel. Thereafter, a blind via hole is provided, and a through hole is subsequently formed by a drill. In this case, even if a drilling plate such as aluminum or an insulating substrate is used, a space is generated in the drill hole portion, and burrs of the copper foil are generated. Since it is difficult to remove the burrs, stress is concentrated on the burrs at the time of imparting conductivity to the through-holes with a conductive paste or plating, and cracks are generated.

As an improvement, a method of laminating the above-mentioned copper-clad insulating sheet using an inner layer panel provided with through holes in advance has been considered. However, in that case, the resin of the copper-clad insulating sheet flowed into the through-hole, and the through-hole was completely filled with the resin, and was exposed after etching and removing the surface copper foil at the position where the blind via hole was to be formed. When the resin layer is alkali-dissolved under optimal conditions, the resin flowing into the through-hole of the access hole shape is incompletely dissolved, and conversely, if the resin in the through-hole is completely dissolved, the The resin around the blind via hole that forms the layer between the conductive pattern of the panel and the outer layer conductor is excessively dissolved, undercut progresses, and the resin dissolves more than the land part of the inner layer conductor pattern, and the outer layer There is a disadvantage that insulation between the conductor and the conductor on the inner layer panel cannot be obtained.

The present invention provides a multilayer printed wiring board having blind via holes and through via holes which eliminates the drawbacks of the above method, is excellent in physical and electrical characteristics, is stable in quality, and is excellent in mass productivity, and its manufacture. Is what you do.

The blind via hole is a hole for electrically connecting two layers of conductive patterns, and the access hole-like through via hole is a hole for electrically connecting three or more layers of conductive patterns. The reason for forming an access hole in order to connect multiple layers is to increase the contact area between the conductive paste and the conductive pattern of plating and to secure electrical connection reliability.

[0013]

A multilayer printed wiring board according to the present invention is a printed wiring board for an inner layer in which a required printed wiring circuit is formed on both sides by subjecting a double-sided copper-clad laminate to drilling and etching. A copper foil sheet in which a copper foil is stretched on an insulating substrate comprising a chemically dissolvable first and second insulating layers laminated on both sides of the printed wiring board for an inner layer; and the copper foil Etching the copper foil of the copper foil sheet corresponding to each through-hole of the printed wiring circuit for the outer layer formed by etching the copper foil of the sheet and the printed wiring circuit of the printed wiring board for the inner layer;
And the second insulating layer is chemically dissolved to open through holes corresponding to the respective through holes of the printed wiring circuit of the inner printed wiring board, and the printed wiring circuit of the inner printed wiring board and Etching the copper foil of the copper foil sheet corresponding to the via hole portion with the printed wiring circuit for the outer layer and chemically dissolving the first and second insulating layers to open the via hole; And a conductive portion of the inner and outer layer printed wiring circuit formed by filling the via hole with a conductive material, and the method of manufacturing the inner layer printed wiring board with a double-sided copper-clad laminate, First and second chemically dissolvable on both sides of the printed wiring board for the inner layer.
Laminating a copper foil sheet in which a copper foil is stretched on an insulating substrate composed of two insulating layers, and etching the copper foil of the copper foil sheet to form a printed wiring circuit for an outer layer; Etching the copper foil of the sheet and dissolving the insulating layer to form through holes and via holes for conduction with the printed wiring circuit of the inner layer printed wiring board; anda conductive material in the through holes and the via holes. Filling and conducting the inner and outer layer printed wiring circuits.

[0014]

Embodiment 1 FIG. 1 is a schematic sectional view of a copper-clad insulating sheet used in the present invention, and FIGS. 2 to 10 are schematic sectional views for explaining a manufacturing process and a structure of a multilayer printed wiring board. A through hole 10 of 0.5 mmφ is formed by drilling a 0.6 mm thick glass epoxy double-sided copper clad board having a 35 μm thick copper foil as an inner layer panel, and then a copper wiring pattern 6 is formed at a predetermined position by selective etching. Is prepared, and the surface of the copper wiring pattern 6 of the inner layer panel 7 is coated with 37 g / l of sodium chlorite, 10 g / l of sodium hydroxide, and 20 g / l of trisodium phosphate dodecahydrate. A solution consisting of 9
The mixture was treated at 5 ° C. for 5 minutes, washed well with water, dried, and subjected to blackening treatment.

Next, the copper-clad insulating sheet 1 for forming the outer layer panel 18 is placed on both sides of the inner layer panel 7 (FIG. 2), and the inner layer panel is laminated at 75 ° C. by a metal roll. A built-in copper clad laminate panel was prepared. Here, the second resin composition layer 3 flows between the copper wiring patterns 6 and into the through holes 10 because of its high fluidity, and the first resin composition layer 2 Since there was almost no resin flow, the copper-clad laminate panel 19 shown in FIG.

On the surface of the copper foil 4 of the copper clad laminate panel 19, except for the portions where the via holes 8 of the copper foil of 0.3 to 0.5 mmφ and the via holes 17 for the access holes of 0.8 mmφ are formed. To form an alkali-soluble etching resist 12 by screen printing,
Copper in the via holes 8 and 17 of the copper foil 4 was etched with a copper solution. Subsequently, a 1 wt% sodium carbonate solution at 40 ° C. was sprayed at a spray pressure of 1.5 kg / cm ² , and the first and second resin composition layers 2 and 3 below the copper foil via holes 8 were formed. At the same time to expose the lower copper wiring pattern 6 to form a blind via hole 9 as shown in FIG. 6 and to completely dissolve the second resin composition flowing into the through hole 10. An access hole via hole 17 was formed.

Subsequently, after washing with water and a 10% sulfuric acid aqueous solution, the portion of the blind via hole where the resin was exposed was irradiated with an electron beam to cure the surface of the resin. First
After curing the layer 2 of the resin composition and the layer 3 of the second resin composition, the silver paste 14 is simultaneously printed on the blind via holes and the through holes as shown in FIG. Baking for 45 minutes, an etching resist 15 is formed as shown in FIGS. 8 and 9, etching and stripping are performed, and a solder resist 16 which is an overcoat of silver paste is formed as shown in FIG. A multilayer printed wiring board having blind via holes for connecting two layers and through-hole holes for connecting conductive patterns to four layers was obtained.

The peel strength between the copper foil and the resin layer of the printed wiring board prepared as described above was 1.4 kg / cm. The solder heat resistance was normal at 280 ° C. for 3 minutes in a 25 mm square pattern. The surface insulation resistance was 10 ¹⁴ Ω at the initial stage and 10 ¹² Ω after moisture resistance (C-96 / 40/95). The interlayer insulation resistance is initially 10 ¹² Ω and after moisture resistance (C-96 / 40/9)
5) 10 ¹¹ Ω was obtained. The dielectric breakdown withstand voltage was 3,000 V DC or more in the initial stage and after moisture resistance (C-96 / 40/95). Interlayer dielectric strength is measured by pressure cooker test (13
0 ° C, 85% RH, 100 hours, DC20V bias)
There was no abnormality. The conduction resistance of the blind via hole showed almost no change as a result of a 100-cycle test in which the temperature cycle was 125 ° C. for 30 minutes and −65 ° C. for 30 minutes as one cycle.

[0019]

Embodiment 2 A 0.5 mmφ through hole 10 is formed by drilling a 1.0 mm thick glass epoxy double-sided copper clad board having a 35 μm thick copper foil as an inner layer panel, and copper is selectively etched to a predetermined position. An inner layer panel 7 on which a wiring pattern 6 is formed is prepared, and the surface of the copper wiring pattern 6 of the inner layer panel 7 is coated with 37 g / liter of sodium chlorite, 10 g / liter of sodium hydroxide, and 20 g of trisodium phosphate dodecahydrate. Per liter of solution, 9
The mixture was treated at 5 ° C. for 5 minutes, washed well with water, dried, and subjected to blackening treatment.

Next, the copper-clad insulating sheets 1 are stacked on both sides of the inner-layer panel 7 (FIG. 2), and laminated by a metal roll at 75 ° C. to produce a copper-clad laminate panel having the inner-layer panel built therein. did. Here, the layer 3 of the second resin composition has a large fluidity, so that the layers 3 between the copper wiring patterns 6 and the through holes 1
0, the layer 2 of the first resin composition has almost no resin flow, so that the copper clad laminate panel shown in FIG.

The portions of the surface of the copper foil 4 of the copper-clad laminate panel other than those where the via holes 8 of the copper foil of 0.3 to 0.5 mmφ and the via holes 17 for the access holes of 0.8 mmφ are formed, An etching resist of an alkali-soluble type was formed by a photo method, and copper in a via hole of a copper foil was etched with a cupric chloride solution. Then 40
1.5 kg / cm 1% by weight sodium carbonate solution
^At a spray pressure of ² , the lower layer 1 of the first resin composition at the location of the via hole 8 of the copper foil is simultaneously dissolved and removed to expose the lower layer copper wiring pattern 6, and the blind as shown in FIG. At the same time as the formation of the via hole,
Was completely dissolved to form via holes 17 for access holes.

Subsequently, after washing with water and a 10% sulfuric acid aqueous solution, the portion of the blind via hole where the resin was exposed was irradiated with an electron beam to cure the surface of the resin. First
After curing the layer 2 of the resin composition and the layer of the second resin composition, the conductive paste 14 is simultaneously printed on the blind via holes and the through holes as shown in FIG. 7, and then at 150 ° C. for 45 minutes. After baking, an etching resist 15 is formed as shown in FIGS. 8 and 9, etching and stripping are performed, and a solder resist 16 which is an overcoat of a conductive paste is formed as shown in FIG. A multilayer printed wiring board having blind via holes to be connected and access-hole-shaped through via holes to connect four layers of conductor patterns was obtained.

The peel strength between the copper foil and the resin layer of the printed wiring board prepared as described above was 1.4 kg / cm. Solder heat resistance is 280 ℃ with 25mm square pattern
There was no abnormality in 3 minutes. Surface insulation resistance is initial 10
¹⁴ Ω and 10 ¹² Ω after moisture resistance (C-96 / 40/95) were obtained. The interlayer insulation resistance is initially 10 ¹² Ω, after moisture resistance (C-96
/ 40/95) 10 ¹¹ Ω was obtained. The breakdown withstand voltage was 3,000 V DC or more in the initial stage and after moisture resistance (C-96 / 40/95). No abnormalities were found in the interlayer dielectric strength in the pressure cooker test (130 ° C., 85% RH, 100 hours, DC 20 V bias). In addition, the conduction resistance of the blind via hole is a temperature cycle of 125 ° C. for 30 minutes and −65 ° C.
As a result of a 100-cycle test with 30 minutes as one cycle, there was almost no change.

The copper-clad insulating sheet used in the first and second embodiments has the structure shown in FIG. 1 and is soluble in an alkaline aqueous solution and has a low fluidity when heated. Layer is formed on the lower surface of the rough surface of the copper foil, and the second resin composition having high solubility in an alkaline aqueous solution and high fluidity during heating is formed on the first insulating layer. Is formed by forming the above layer. Here, that the fluidity at the time of heating is large means that the resin composition side of the copper-clad insulating sheet is superimposed on the surface of the inner layer panel, and the heating in the step of laminating the whole by pressing or laminating, that is, approximately 60 to 80 ° C. In the range of
It means that the resin composition melts and easily flows into the conductive pattern of the inner layer panel, and can fill the concave portions of the pattern.

The difference between the solubility of the first and second resin compositions in the aqueous alkali solution in the copper-clad insulating sheet is attributed to the difference in the conditions of the step of dissolving these resin compositions to form blind via holes. It is expressed by a relative evaluation of the melting time of each of the first resin composition and the second resin composition. That is, when dissolving the layer of the first resin composition and the layer of the second resin composition under the same conditions, for example, at about 30 to 40 ° C. and using 1% by weight of sodium carbonate, the conditions are as follows. In the above, the second resin composition must have higher solubility in an aqueous alkaline solution than the first resin composition.

When the dissolution conditions of the respective layers are different, for example, under the condition that the first resin composition and the second resin composition are dissolved in alkaline aqueous solutions having different concentrations or temperatures, the respective concentrations or temperatures are different. The second resin composition needs to have higher solubility than the first resin composition, as compared with the solubility of each resin composition in the aqueous alkali solution. More specifically, as compared with the solubility of the first resin composition in an alkaline aqueous solution at a certain liquid temperature, the second resin composition exhibits greater solubility in a lower-temperature alkaline aqueous solution at a lower temperature. If you have it, that's fine. Thus, the relative solubility of the first resin composition and the second resin composition changes according to the dissolution conditions.

Further, the copper-clad insulating sheet can be manufactured by applying a first resin composition to a copper foil and forming a second resin composition thereon. The above copper-clad insulating sheet is laminated on one or both sides of the insulating layer for the inner layer in which the conductive pattern has been formed in advance by a hot roll, an etching resist is formed on the copper foil and selectively etched to specify the insulating panel for the inner layer. After forming fine holes corresponding to the conductive pattern of the above, the resin layer under the fine holes etched and removed is removed with an alkaline aqueous solution, and the resin layer is cured. And the outer layer copper foil are electrically connected to each other, and then the outermost layer copper foil is selectively etched to form a predetermined pattern, whereby a multilayer printed wiring board having blind via holes can be manufactured.

Further, in the production of a multilayer printed wiring board having blind via holes and through via holes using a copper-clad insulating sheet, fine holes are formed by etching a copper foil, and a resin layer of the fine holes is formed with an alkaline aqueous solution. As a method for electrically connecting the conductor pattern of the inner insulating panel exposed by melting and the copper foil of the outer layer, electroless plating and / or electrolytic plating, a conductive paste such as gold, silver, copper, solder, etc. are screened. A method of applying by printing, dispenser, pin printing and the like and drying and curing can be used.

If a copper-clad insulating sheet is used, the layer of the first resin composition exposed by etching is dissolved in an alkali in the access via-shaped through via hole under the alkali dissolving condition of a brand via hole. After the flowing second resin composition is dissolved in the layer of the first resin composition,
Since the resin layer is melted in a short time, the undercut of the resin layer between the conductor pattern of the inner layer plate and the outer layer conductor can be suppressed as much as possible. Thus, if a copper-clad insulating sheet is used, the above-described brand hole and through-hole in the form of an access hole can be simultaneously and favorably formed. In addition, because a thin copper-clad insulating sheet is used instead of the conventional prepreg in which resin is impregnated into thick glass fiber, CAF does not occur in this insulating layer, reliability is obtained, and thin multilayer printed circuit boards are manufactured. Is possible.

[0030]

According to the present invention, physical properties, electrical properties,
A multilayer printed wiring board having highly reliable blind via holes and access hole-like through via holes can be obtained. In addition, since blind via holes and through via holes can be easily and collectively formed by etching copper foil and dissolving the resin with an alkaline aqueous solution, productivity is higher than conventional drilling, which has been drilled one hole at a time. Is greatly improved. Also, regardless of the variation in the depth of the inner layer copper foil pattern, the blind hole can be reliably provided by dissolving the resin layer up to the inner layer copper foil pattern. The connection failure is eliminated, and there is no short-circuit failure erroneously connected to the copper foil pattern of another layer for the inner layer.

Further, for insulation between the inner layer panel and the outer copper foil, a thin copper-clad insulating sheet is used instead of the conventional prepreg in which a thick glass fiber is impregnated with a resin.
Since no CAF is generated in the insulating layer and the thickness of the printed wiring board can be reduced, a highly reliable high-density multilayer printed wiring board can be obtained. Therefore, it is very useful because it enables the manufacture of a multilayer printed wiring board requiring blind via holes and through via holes used for high-density mounting in various electronic devices.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the configuration of a copper-clad insulating sheet.

FIG. 2 is a schematic cross-sectional view showing a configuration before a thermocompression bonding of an inner layer panel having a copper wiring pattern on its surface and a copper-clad insulating sheet in a manufacturing process of the multilayer printed wiring board of the present invention.

FIG. 3 is a schematic cross-sectional view showing a configuration of an inner layer panel after lamination in the same manufacturing process.

FIG. 4 is a schematic sectional view showing the inner layer panel after an etching resist is formed on a copper foil on the surface in the same manufacturing process.

FIG. 5 is a schematic cross-sectional view showing the inner layer panel after forming a blind via hole in a surface copper foil by etching in the same manufacturing process.

FIG. 6 is a schematic cross-sectional view of the inner layer panel after dissolving a resin layer below a copper foil blind via hole and dissolving a resin in a through hole to form an access hole-like through via hole in the same manufacturing process. .

FIG. 7 is a schematic sectional view after a conductive paste is formed in the same manufacturing process.

FIG. 8 is a schematic cross-sectional view after forming an etching resist for etching the outer layer copper foil pattern in the same manufacturing process.

FIG. 9 is a schematic cross-sectional view after the unnecessary copper foil of the outer layer is etched and the etching resist is removed in the same manufacturing process.

FIG. 10 is a schematic sectional view after a solder resist is formed in the same manufacturing process.

FIG. 11 is a schematic cross-sectional view showing a configuration of a conventional multilayer printed wiring board having a blind via hole, in which a pattern for an inner layer having a copper wiring pattern on its surface and a copper foil are not press-bonded through a prepreg; .

FIG. 12 is a schematic cross-sectional view showing a configuration of the copper-clad laminate panel after the thermocompression bonding in the manufacturing process.

FIG. 13 is a schematic sectional view showing the copper clad laminate panel after forming blind via hole holes by drilling in the same manufacturing process.

FIG. 14 is a schematic cross-sectional view showing the copper-clad laminate panel after forming through holes by drilling in the same manufacturing process.

FIG. 15 is a schematic cross-sectional view after a plating process in the same manufacturing process.

FIG. 16 is a schematic sectional view after an etching resist is formed in the same manufacturing process.

FIG. 17 is a schematic sectional view after unnecessary copper foil is removed by etching in the same manufacturing process.

FIG. 18 is a schematic cross-sectional view after the etching resist is removed in the same manufacturing process.

FIG. 19 is a schematic sectional view after a solder resist is formed in the same manufacturing process.

[Explanation of symbols]

 Reference Signs List 1 copper foil 2 layer of first resin composition 3 layer of second resin composition 4 copper-clad insulating sheet 5 prepreg 6 copper wiring pattern 7 panel for inner layer 8 via hole of copper foil 9 blind via hole 10 through hole ( (Through via hole) 11 Plating through hole 12 Etching resist 13 Via hole hole 14 Conductive paste 15 Etching resist 16 Solder resist 17 Access hole

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenya Matsumoto 1 at Funami-cho, Minato-ku, Nagoya-shi, Aichi Prefecture Toagosei Chemical Industry Co., Ltd. Nagoya Research Institute (72) Inventor Tomio Kambayashi Port of Nagoya City, Aichi Prefecture Nagoya Research Institute, Toagosei Chemical Industry Co., Ltd. (72) Inventor Jin Hitoshi Kato 1 Nagoya Research Institute, Minato-ku, Nagoya City, Aichi Prefecture ) Inventor Takehisa Hattori 1-1, Funami-cho, Minato-ku, Nagoya-shi, Aichi, Japan Nagoya Research Institute, Toagosei Chemical Industry Co., Ltd. (56) References JP-A-4-338695 (JP, A) JP-A-59-86290 (JP, A) JP-A-62-222697 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05K 3/46

Claims (1)

(57) [Claims] A double-sided copper-clad laminate is subjected to a drilling process and an etching process to form a required printed wiring circuit on both sides, and an inner-layer printed wiring board is laminated on both sides of the inner-layer printed wiring board. Copper foil sheet in which copper foil is stretched on an insulating substrate comprising first and second two-layer insulating layers which can be dissolved in a flexible manner, and a printed wiring circuit for an outer layer formed by etching the copper foil of the copper foil sheet Etching the copper foil of the copper foil sheet corresponding to each through hole of the printed wiring circuit of the printed wiring board for the inner layer, and chemically dissolving the first and second insulating layers, A through hole corresponding to each through hole of the printed wiring circuit of the printed wiring board is opened, and a via hole portion between the printed wiring circuit of the printed wiring board for the inner layer and the printed wiring circuit for the outer layer. Etching the copper foil of the copper foil sheet corresponding to the above, chemically dissolving the first and second insulating layers to open via holes, and further filling each of the through holes and the via holes with a conductive material. A multilayer printed wiring board comprising conductive portions of inner and outer printed wiring circuits formed as described above.