JPH03159297A - Multilayer printed wiring board and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable full connection to inner layer patterns to be performed by a method wherein a through-hole is previously provided to a wiring base board in which an inner pattern has been formed, and two of the wiring base boards are bonded together with an adhesive agent. CONSTITUTION:Wiring base boards 12a and 12b in which a through-hole 11 has been previously bored respectively are bonded together with an adhesive agent 13 to form blind through-holes, resin such as epoxy resin or the like is filled into the blind through-holes, and then each of the blind through-holes is covered with a conductive land 14. By this method, a blind through-hole can be formed independent of the length and the size of a drill and the disper sion of a wiring base board in thickness. By this setup, a blind through-hole can be fully connected to an inner layer pattern provided inside a wiring base board. Thus, a multilayer printed wiring board can be obtained.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a high-density multilayer printed wiring board that is compatible with the increasing density of electronic components, particularly a multilayer printed wiring board in which blind through holes are formed from both the front and back sides. The present invention relates to a manufacturing method thereof.

[Prior Art] In recent years, as the mounting density of electronic components on wiring boards has increased, wiring patterns printed on wiring boards have become more multilayered.

Through holes are used as means for electrically connecting the wiring pattern on the front surface and the wiring pattern inside the board or the wiring pattern on the back surface.

Furthermore, when the wiring pattern becomes multilayered, through holes that do not penetrate the wiring board, ie, blind through holes, are provided.

A conventional multilayer printed wiring board provided with blind through holes and a method for manufacturing the same will be explained with reference to FIGS. 3(A) to 3(D).

A conventional multilayer printed wiring board is manufactured by drilling pilot holes 3, 3 for blind through holes from the front and back sides of a multilayer printed wiring board 1 (FIG. 3(A)), which has an internal layer pattern formed therein (FIG. 3(A)). FIG. 3(B)), Next, through-hole plating 4°4 is applied to electrically connect the copper foil layer 5 on the front side and the inner layer pattern 6, and the copper foil layer 7 on the back side and the inner layer pattern 8. Connect each electrically.

Finally, unnecessary portions are removed by etching to produce a multilayer printed wiring board having blind through holes 9.

[Problems to be Solved by the Invention] However, the multilayer printed wiring board manufactured by the above conventional manufacturing method has the following problems.

■ When drilling blind through holes, the depth of the blind through holes cannot be made uniformly for each wiring board due to variations in the length of the drill and variations in the thickness of the wiring board, so the depth of the blind through holes must be adjusted each time. In addition to this, there was a possibility that the connection with the inner layer pattern would be incomplete.

■ When drilling holes, since the holes are drilled from both the front and back sides of the wiring board, it is easy to make errors such as drilling in the wrong direction, resulting in slight dripping.

■ A blind hole is made by adding the drill tip (lip part) to the required depth of the complete hole, so in the area where the lip part bites, there is a gap between the deepest part of the blind through hole and the blind through hole. The insulation interval between inner layer patterns to which holes are not connected becomes narrower, and the inner layer patterns cannot be freely wired.

■ In the through-hole plating process, the plating thickness at the deepest part of the blind through-hole becomes thinner, so the overall plating thickness must be increased, which is uneconomical and increases the plating time.

- The surface treatment liquid does not flow sufficiently through the blind through hole, and the surface treatment liquid remains inside the blind through hole, causing corrosion.

■ If a protective film is not applied to the inner wall surface of the hole after forming the blind through hole, the copper-plated surface will oxidize.

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned circumstances.Through holes are formed in advance in a wiring board in which an inner layer pattern is formed, and two wiring boards are combined. , is characterized in that it is bonded with an adhesive.

[Function] Two wiring boards with through-holes formed in advance are pasted together with adhesive, and a blind through-hole is formed by the pasting, so the quality of the blind through-hole is greatly improved, and the quality of the blind through-hole is also improved. Patterns can be formed freely.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

The multilayer printed wiring board according to the present invention, as shown in FIG.
Wiring blank board 12a with through holes 11.11 formed in advance
, 12b are bonded with adhesive 13 to form a blind through hole, and after filling the inside of the blind through hole with a resin such as epoxy resin (the adhesive described above), the blind through hole is covered with a conductor land 14.14. This is what I did.

Next, the manufacturing process will be explained step by step with reference to FIGS. 2(A) to 2(H).

Components in the figure that are the same as those shown in FIGS. 3(A) to 3(D) are designated by the same reference numerals.

A wiring board 12 (FIG. 2(A)
(see FIG. 2(B)).

Next, a through-hole plating layer 17 is attached to the wiring board 12 to form through-holes 11 (FIG. 2(C)).
When the two wiring boards 12a and 12b are pasted together, a pattern 18 is formed on the inner layer side of each other (see Fig. 2(D)).
)).

An adhesive (epoxy resin) 13 is sandwiched between the wiring boards 12a and 12b on which the pattern 18 has been formed on the inner layer surface, and the wiring boards are bonded together by heating and pressing (Fig. 2 (E) and (F)).
.

During this bonding process, the molten adhesive is applied to the through hole 11.
and completely fills the through hole 11.

Further, since the through ball 11 is closed by another wiring board, it becomes a blind through hole for the multilayer printed wiring board 19 composed of the two wiring boards 12a and 12b.

Next, electroless copper is applied to the front and back surfaces of the multilayer printed wiring board 19.
Electrolytic copper plating is applied, and a plating layer 20 is applied over the entire front and back surfaces.
(Fig. 2 (G)).

Finally, patterns are formed on the front and back surfaces of the multilayer printed wiring board 19 by etching (FIG. 2(H)).

In addition, in order to prevent the copper plating layer of the blind through hole from being destroyed by the etching solution during pattern formation, a conductor land 14 covering the blind through hole and its surroundings is left, and the conductor land 14 is actually multilayer printed. This also serves to protect the blind through holes when the wiring board 19 is used.

[Effects of the Invention] As described above, according to the present invention, the following excellent effects are exhibited.

■ Since blind through holes can be formed regardless of variations in the length of the drill or the thickness of the wiring board, it can be perfectly connected to the inner layer pattern inside the wiring board.

■ When drilling holes for through-holes, you only need to work from one direction, so there are no mistakes in drilling.

■ Since blind through holes do not have a lip, patterns on the inner layer side of the wiring board can be formed freely, increasing the degree of freedom in wiring.

■ Since through-hole plating is done in the state of the through-hole, the plating thickness does not become thinner even at the deepest part of the hole, improving the quality of the through-hole and making it possible to reduce the overall plating thickness, which is economical. It is.

(2) Since the inside of the blind through hole is filled with resin, no etching solution remains inside the blind through hole, and corrosion of the through hole is prevented.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a multilayer printed wiring board according to the present invention, and FIG.
FIGS. 3A to 3H are explanatory views showing the manufacturing process according to the present invention, and FIGS. 3A to 3D are explanatory views showing the conventional manufacturing process. 11 is a through hole, 12, 12a and 12b are wiring boards, 13 is an adhesive, and 19 is a multilayer printed wiring board.

Claims (1)

[Scope of Claims] 1) A multilayer printed wiring board, characterized in that through-holes are formed in advance in a wiring board having an inner layer pattern formed therein, and two of the wiring boards are bonded together with an adhesive. 2) A through hole is formed in a wiring board with an inner layer pattern formed inside, a pattern is formed on the adhesive side of the wiring board, and the two wiring boards are sandwiched between the patterned surfaces with an adhesive. A method for manufacturing a multilayer printed circuit board, which involves bonding and forming patterns on both the front and back sides after bonding.