JP2006339350A - Printed wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board which can attain thinning and high-density arrangement, and high connection reliability of conductor patterns, and also to provide its manufacturing method. <P>SOLUTION: The printed wiring board comprises an insulation substrate 1, conductor patterns 2 formed on the front and rear faces 1A and 1B of the insulation substrate 1, a through-hole 4 formed in the insulation substrate 1, a penetration-direction plating portion 41 in the penetrating direction which is deposited on the inner wall of the through-hole 4, a lateral plating portion 42 which is extended along the insulation substrate 1 from both ends of the plating portion 41 in the penetration direction and is connected to the conductor patterns 2, a resin layer 5 which fills up the through-hole 4 and is formed with concave portions 5a on the front and rear faces thereof, and lid plating portions 43 which are formed on both front and rear faces of the resin layer 5 and are connected to the plating portion 41 in the penetration direction and the lateral plating portion 42. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printed wiring board in which conductor patterns formed on both front and back surfaces of an insulating substrate are interlayer-connected at appropriate positions, and a method for manufacturing the same.

Printed wiring boards are used in all types of electronic equipment, from mass production equipment such as televisions to equipment that requires high reliability such as rockets, for the purpose of improving productivity, ensuring mass production quality, and improving reliability. Yes. In recent years, electronic devices have been miniaturized, and accordingly, there has been a demand for higher precision and higher density of printed wiring boards.
This type of printed wiring board generally has a configuration in which conductor patterns formed on both front and back surfaces of an insulating substrate are electrically connected at appropriate positions via plated through holes.

Depending on the use of the printed wiring board, it may be preferable to fill the plated through hole. As the hole filling method, the copper foil on the insulating substrate is overlaid by plating the entire through hole to fill the hole, so-called filled plating method (for example, refer to Patent Document 1), or after the primary plating over the copper foil, So-called lid plating that fills through holes with conductive paste, etc., polishes both ends of this conductive paste body to make it flush with the primary plating layer, and then applies plating on these primary plating layer and conductive paste body The law (see, for example, Patent Document 2) is known.
JP 2003-046248 A JP 2003-069228 A

  However, in the case of these conventional filled plating methods and lid plating methods, the through hole is filled and a plating layer is further formed thereon, so that the plated portion applied to the inner wall of the through hole and both the front and back surfaces Although it is possible to ensure the connection reliability between the conductor patterns formed on the copper foil, since the plating layer is laminated on the copper foil, the thickness of the conductor layer (copper foil and plating layer) for forming the conductor pattern is There is a problem that pattern formation becomes difficult. In particular, in the conventional lid plating method, since two plating layers are laminated on the copper foil, the tendency becomes remarkable.

  Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a printed wiring board having both thinning and high density of a conductor pattern and connection reliability, and a manufacturing method thereof. There is.

  In order to solve the above problems, a printed wiring board according to claim 1 of the present invention includes an insulating substrate, a conductor layer provided on both front and back surfaces of the insulating substrate, a through hole formed in the insulating substrate, A first plated portion deposited on an inner wall of the through hole; and a second plated portion extending from both ends of the first plated portion along the insulating substrate and connected to the conductor layer. A resin layer in which the through hole is filled and recesses are formed on both front and back surfaces thereof, and formed on both the front and back surfaces of the resin layer and connected to at least one of the first plating portion and the second plating portion. And a third plating part.

  According to this invention, since the concave portions are formed on both the front and back surfaces of the resin layer that fills the through hole, the third plating portion can be provided so as to be accommodated in the concave portion. An increase in the thickness of the conductor layer (copper foil and plating layer) for pattern formation can be suppressed, and pattern formation can be easily performed. And since the said 3rd plating part is connected to at least any one of the said 1st plating part or the said 2nd plating part, the 1st plating part given to the inner wall of a through hole, and both front and back surfaces Connection reliability between the formed conductor patterns can be ensured.

A printed wiring board according to a second aspect of the present invention is the printed wiring board according to the first aspect, wherein the third plating portion is flush with the conductive layer and the second plating portion. It is formed so that it may become.
According to this invention, since it can prevent that the said 3rd plating part protrudes with respect to the said conductor layer and the said 2nd plating part, the increase in the thickness of the said printed wiring board can be suppressed. Moreover, the convenience at the time of performing a post process increases by making it flush.

A printed wiring board according to a third aspect of the present invention is the printed wiring board according to the first or second aspect, wherein the resin layer is formed of a conductive resin.
According to this invention, when the third plating portion is formed, the power supplied to the conductor layer can be transmitted to the resin layer, so that the deposition of plating on the front and back surfaces of the resin layer is easy. Thus, the third plating portion can be easily formed.

  According to a fourth aspect of the present invention, there is provided a printed wiring board manufacturing method comprising: a masking step of forming a plating resist layer on both front and back surfaces of a copper-clad laminate having through holes, leaving an opening peripheral edge of the through holes; Etching process for etching copper foil exposed at the peripheral edge of the opening of the through hole in the thickness direction, and a first plating process for depositing plating layers on both the inner wall of the through hole and the front and back surfaces of the laminate exposed by the etching A hole filling step of filling a hollow portion of the plated through hole formed by the first plating step with a resin, a concave portion forming step of forming concave portions on both the front and back surfaces of the resin, and a layer under the plating resist layer A second plating step is provided, in which a plating layer is deposited on both the front and back surfaces of the resin by electroplating using copper foil as a power feeding part.

  According to this invention, since the thickness of the conductor layer etched at the time of pattern formation becomes the thickness of the copper foil originally laminated on the copper-clad laminate, the formation of the conductor pattern is facilitated, the thinning and Densification can be easily realized. Further, by forming recesses on both the front and back sides of the resin, the third plating part can be provided so as to be accommodated in the recesses, whereby a conductor layer (copper foil and copper foil) for forming a conductor pattern can be provided. An increase in the thickness of the plating layer) can be suppressed, and pattern formation can be easily performed.

The manufacturing method of the printed wiring board concerning Claim 5 of this invention is a thing of Claim 4, Comprising: The plating layer formed by the said 2nd plating process is said copper foil and said 1st plating. It is characterized by comprising a polishing step of polishing so as to be flush with the plating layer formed by the step and both the front and back sides.
According to this invention, since the plating layer formed by the second plating step can be prevented from protruding with respect to the copper foil and the plating layer formed by the first step, the printed wiring board. The increase in thickness can be suppressed. Moreover, the convenience at the time of performing a post process increases by making it flush.

  According to the printed wiring board of the present invention, it is possible to suppress an increase in the thickness of a conductor layer (copper foil and plating layer) for forming a conductor pattern, and it is possible to easily perform pattern formation. And the connection reliability between the 1st plating part given to the inner wall of a through hole, and the conductor pattern formed in front and back both surfaces can be ensured.

  According to the method for manufacturing a printed wiring board of the present invention, it is easy to form a conductor pattern, and it is also possible to easily realize thinning and high density. An increase in the thickness of the conductor layer (copper foil and plating layer) for forming the conductor pattern can be suppressed, and the pattern can be easily formed.

The best mode for carrying out the present invention will be described below with reference to FIGS.
First, an example of a printed wiring board will be described with reference to FIG.
In this printed wiring board P, a conductive pattern (conductor layer) 2 cut out from, for example, a copper foil (conductor layer) of a copper-clad laminate is provided on both the front and back surfaces 1A and 1B of the insulating substrate 1. Of the conductor pattern 2, the conductor pattern 2 a formed at the periphery of the opening of the through hole 3 filled in the hole is flush with the surface-direction plating portion (second plating portion) 42 of the plating through hole 4. It is configured. And the conductor pattern 2a and the surface direction plating part 42 are contacting with respect to the thickness direction, respectively.

The plated through hole 4 extends along the insulating substrate 1 from a cylindrical through direction plated portion (first plated portion) 41 formed on the inner wall of the through hole 3 and from both axial ends of the through direction plated portion 41. It is composed of a ring-shaped surface direction plating part 42 (extruding), and the inner space surrounded by the penetration direction plating part 41 is filled with a hole filling part 5 made of a conductive resin such as polyacetylene. .
The thickness of the conductor patterns 2 and 2a is the same as or slightly smaller than the thickness of the copper foil previously laminated on the copper-clad laminate, and is set to 12 μm or less, for example. Moreover, the thickness T of the surface direction plating part 42 is the same as the thickness of the conductor patterns 2 and 2a, and the overhanging dimension L in the surface direction of the surface direction plating part 42 is, for example, L = 0.1 to 0.2 mm. Is set to

In addition, on both the front and back surfaces of the hole filling portion 5, concave portions 5 a that are curved from the peripheral portion to the center portion are formed. A lid plating part (third plating part) 43 is formed on the hole filling part 5 so as to be accommodated in the recess 5a.
Further, the lid plating portion 43 is formed so that both the front and back surfaces thereof are flush with the conductor pattern 2 a and the plated through hole 4.

  As described above, according to the printed wiring board P of the present embodiment, the lid plating part 43 formed on the hole filling part 5 is connected to the penetration direction plating part 41 and the surface direction plating part 42. The connection reliability between the plated through hole 4 formed on the inner wall of the through hole 3 and the conductor pattern 2 formed on both the front and back surfaces of the insulating substrate 1 can be ensured. Therefore, the reliability of interlayer connection is high even when the conductor pattern 2 is miniaturized and densified.

Next, an example of a method for manufacturing the printed wiring board P will be described with reference to FIGS.
First, a copper-clad laminate Q having copper foils 12 for forming the conductor pattern 2 on both the front and back surfaces of the insulating substrate 1 is prepared (FIG. 1) and insulated from one surface to the other surface. Through-holes 3 are formed for interlayer connection of conductor patterns 2 formed on both the front and back surfaces of the substrate 1 at appropriate positions (FIG. 2).
Next, surface preparation and desmearing are performed, and a catalyst for improving the adhesion of electroless copper plating, for example, palladium (Pd), is adsorbed on the surface of the copper foil 12 and the inner wall of the through hole 3.

  Next, the plating resist layer 13 is formed so that the copper foil 12 is exposed at the opening periphery of the through hole 3 leaving (excluding) the opening periphery of the through hole 3 (FIG. 3, masking process). ). And the copper foil 12a exposed to this opening peripheral part is etched in the thickness direction (FIG. 4, an etching process).

  The thickness of the copper foil 12a removed by this etching is set to be the same as the initial thickness 12 μm of the copper foil 12, for example. In the etching, an alkaline type etchant is used so that the Pd catalyst adsorbed in the previous step remains on the surface of the copper foil 12 and the inner wall of the through hole 3 while only the copper foil 12a. Is selectively etched.

Next, as a result of the etching, electroless copper plating is applied to the insulating substrate exposed surface 21 on the inner peripheral side of the copper foil 12 directly below the plating resist layer 13 and the inner wall of the through hole 3 to deposit copper plating.
Then, a cylindrical penetration direction plating portion 41 extending in the penetration direction is deposited on the inner wall of the through hole 3 and protrudes in the surface direction of the insulating substrate 1, in other words, protrudes along the radially outer side of the through hole 3. A ring-shaped surface direction plating portion 42 is deposited (FIG. 5, first plating step).

Since the through-direction plated portion 41 and the surface-direction plated portion 42 are deposited together, the through-hole 3 is electrically connected between the conductor patterns 2 and 2 formed on both surfaces of the insulating substrate 1 in a later step. The plated through hole 4 is formed.
Next, a filling process for filling the inner space 14 of the plated through hole 4 with a conductive resin is performed (FIG. 6, filling process).

  And the process which forms the recessed part 5a in the front and back both surfaces of the hole-filling part 5 formed by the hole-filling process is performed (FIG. 7, recessed part formation process). As the processing for forming the concave portion, for example, it is preferable to form the concave portion 5a by shrinking by performing an annealing process because the concave portion 5a can be formed while increasing the rigidity of the hole filling portion 5.

  Next, electrolytic copper plating is performed using the copper foil 12 immediately below the plating resist layer 13 as a power feeding portion, and plated copper is deposited on both the front and back surfaces of the hole filling portion 5 to form a lid plating portion 43 (FIG. 8, first). 2 plating step). The lid plating portion 43 is formed until it bulges from the outer surface 12A of the copper foil 12. In the present embodiment, since the hole filling portion 5 is formed of a conductive resin, the power supplied to the copper foil 12 can be transmitted to the hole filling portion 5, so that plating is deposited on both the front and back surfaces of the hole filling portion 5. Thus, the third plating portion can be easily formed.

Next, the plating resist layer 13 is removed, and the front and back surfaces of the copper-clad laminate Q are polished. At the time of polishing, not only the bulging portion of the hole filling portion 15 is polished, but a polishing margin is set such that the copper foil 12 is polished by 0.1 to 0.2 μm from its outer surface. 12, the outer surface is polished so that the surface direction plating portion 42 of the plated through hole 4 and the lid plating portion 43 are flush with each other (FIG. 9).
At this time, an external force acts on the plated through hole 4 in the polishing direction, that is, in the direction along the insulating substrate 1. However, since the plated through hole 4 is filled, the surface direction plated portion 42 is dragged in the polishing direction. However, even if it may be dragged, the contact state between the planar plating portion 42 and the copper foil 12 is maintained as it is, so that interlayer connection is ensured.

Thereafter, when the copper foil 12 is etched in a predetermined pattern by the subtractive method, conductor patterns (circuit patterns) 2 are formed on the front and back surfaces 1A and 1B of the insulating substrate 1, and the conductor patterns 2 are plated through holes. A printed wiring board P electrically connected to each other through 4 is formed (FIG. 8).
At this time, since the thickness of the conductor layer to be etched is the thickness obtained by subtracting the polishing margin from the copper foil 12 originally laminated on the copper-clad laminate Q, the formation of the conductor pattern 2 is facilitated. Thinning and high density can be easily realized.

In addition, this invention is not limited to the said Example, A various design change is possible in the range which does not deviate from the summary.
For example, although the conductive resin is used as the material of the hole filling portion 5, the present invention is not limited to this, and a nonconductive resin such as an epoxy resin may be used.

It is sectional drawing which shows the copper clad laminated board used for manufacture of the printed wiring board by one Example of this invention. It is sectional drawing which shows the state which formed the through hole in the copper clad laminated board shown in FIG. FIG. 3 is a cross-sectional view illustrating a state in which a plating resist layer is formed on the copper foil, leaving the opening peripheral edge of the through hole, following FIG. 2. FIG. 4 is a cross-sectional view illustrating a state where the copper foil exposed at the peripheral edge of the opening is etched following FIG. 3. FIG. 5 is a cross-sectional view showing a state in which electroless plating is applied to the inner wall of the through hole and the etched copper foil portion following FIG. 4. FIG. 6 is a cross-sectional view illustrating a state where the through hole is filled with a conductive resin following FIG. 5. FIG. 7 is a cross-sectional view showing a state in which concave portions are formed on both the front and back surfaces of the conductive resin following FIG. 6. FIG. 8 is a cross-sectional view showing a state in which concave portions are formed on both the front and back surfaces of the conductive resin with the copper foil under the plating resist layer as a power feeding portion following FIG. 7. FIG. 9 is a cross-sectional view illustrating a state in which, after removing the plating resist layer, the substrate surface is polished and the hole filling portion and the copper foil are flush with each other after FIG. 8. FIG. 10 is a cross-sectional view illustrating a state in which the copper foil is etched into a predetermined conductor pattern to obtain a printed wiring board following FIG. 9.

Explanation of symbols

1 ... Insulating substrate 1A, 1B ... Both sides
2 ... Conductor pattern (conductor layer)
3 through hole 5 hole filling portion 5a concave portion 12 copper foil (conductor layer)
13 ... Plating resist layer
14 ... The inner space
41 ... Plating direction plating part (first plating part)
42 ... plane direction plating part (second plating part)
43 ... Lid plating part (third plating part)
P ... Printed wiring board
Q ... Copper-clad laminate

Claims (5)

An insulating substrate;
A conductor layer provided on both front and back surfaces of the insulating substrate;
A through hole formed in the insulating substrate;
A first plating portion deposited on the inner wall of the through hole;
A second plating portion extending from both ends of the first plating portion along the insulating substrate and connected to the conductor layer;
A resin layer in which the through hole is filled, and recesses are formed on both front and back surfaces;
A printed wiring board comprising: a third plating portion formed on both front and back surfaces of the resin layer and connected to at least one of the first plating portion and the second plating portion.   The printed wiring board according to claim 1, wherein the third plating portion is formed so that both front and back surfaces thereof are flush with the conductor layer and the second plating portion.   The printed wiring board according to claim 1, wherein the resin layer is made of a conductive resin. A mask process for forming a plating resist layer on both the front and back surfaces of the copper-clad laminate having a through hole, leaving an opening peripheral edge of the through hole; and
Etching process for etching the copper foil exposed at the opening peripheral edge of the through hole in the thickness direction;
A first plating step of depositing plating layers on both the inner wall of the through-hole and the front and back surfaces of the laminate exposed by the etching;
A hole filling step of filling the inner space of the plated through hole formed by the first plating step with a resin;
A recess forming step of forming recesses on both the front and back surfaces of the resin;
A printed wiring board manufacturing method comprising a second plating step of depositing a plating layer on both front and back surfaces of the resin by electroplating using the copper foil under the plating resist layer as a power feeding portion. It comprises a polishing step of polishing the plating layer formed by the second plating step so as to be flush with the copper foil and the plating layer formed by the first plating step. The manufacturing method of the printed wiring board of Claim 4.

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