JPH04188689A - Printed wiring board - Google Patents

Abstract

PURPOSE:To enable electronic components to be surely electrically connected at mounting so as to obtain a mounted circuit device of high reliability by a method wherein conductor of comparatively high melting point is filled into a through-hole connection. CONSTITUTION:The inner wall of a connecting through-hole 2 used for the connection between circuit pattern layers is coated with a chemical plating layer 3, and a conductor 4 of comparatively high melting point metal such as electroplating copper is deposited thick to fill the through-hole. Therefore, even if a printed board reaches up to a melting point of solder in a process where the mounted electronic components are soldered, the comparatively high melting point conductor 4 filled into the through-hole 2 is prevented from melting to flow out of the through-hole 2. By this setup, a mounted circuit device of high reliability which always retains and displays a required electrical connection function can be constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a printed wiring board, and particularly to a printed wiring board in which circuit pattern layers are electrically connected via through holes.

(Prior Art) For example, in response to the miniaturization of electronic devices and the improvement of circuit functions, printed wiring boards on which electronic components are mounted and mounted have multilayered circuit patterns. In other words, in the configuration of a printed wiring board for mounting, a required circuit pattern is installed in multiple layers within an insulating substrate layer, and the required circuit pattern layers are electrically connected via so-called through holes or via holes. Printed wiring boards are widely used in practical applications. Note that the electrical connection of the through hole or via hole is made by using, for example, chemical plating on the inner wall of the through hole or via hole.
The conductive metal layer is deposited and grown by electroplating and resist solder plating. In particular, when forming a circuit pattern, a resist solder plating layer that functions as an etching resist is deposited (adhered and grown) thickly to improve the reliability of through-hole connections.

(Problems to be Solved by the Invention) However, the printed wiring board having the above structure has the following problems in terms of reliability. That is, at the stage of mounting and mounting required electronic components on the printed wiring board configured as described above, that is, when soldering the electronic components, the printed wiring board on which the electronic components are mounted is exposed to high temperatures due to melting of the solder. . However, when exposed to this high temperature, the resist solder attached to the inner wall surface of the through hole tends to melt and flow out. Melting and leaking of the resist solder that was adhered to the inner wall surface of the through hole not only impairs the functionality and reliability of the through hole connection that electrically connects circuit pattern layers, but sometimes the resist solder that has leaked onto the surface side This may cause a short circuit between circuit patterns. This phenomenon becomes a serious problem when this type of printed wiring board is used for, for example, a mounted circuit. In other words, the process of locating and mounting required electronic components through complicated operations is often completely wasted.

The present invention has been made in response to the above-mentioned circumstances, and an object of the present invention is to provide a printed wiring board that can be used to construct a mounted circuit device with high reliability at all times.

[Structure of the Invention] (Means for Solving the Problems) A printed wiring board according to the present invention is a printed wiring board in which required circuit pattern layers are electrically connected via through holes, and the through holes It is characterized in that the connection is made by a conductor with a relatively high melting point that fills the through hole.

(Function) In the printed wiring board according to the present invention, when electrically connecting circuit pattern layers via through holes, the through holes are filled with a conductive material having a relatively high melting point, so that the required circuit Connects pattern layers. For this reason, during the soldering process of mounted electronic components, even if the solder reaches the melting temperature, there is a risk that the conductor with a relatively high melting point that fills the through-hole will melt and flow out of the through-hole. will be suppressed and prevented.

In other words, the through hole is densely filled with a conductor having a relatively high melting point, and melting and leakage are suppressed or prevented, so that the required electrical connection function is always maintained and exhibited.

(Example) The present invention will be described in detail below with reference to FIG. 1 and FIGS. 2(a) to 2(p).

FIG. 1 is a cross-sectional view of a main part of a configuration example of a printed wiring board according to the present invention, where 1 is a printed wiring board main body incorporating a required circuit pattern layer, and 1a is the printed wiring board main body. 1 a surface circuit pattern; 2 a through hole region for connection between circuit pattern layers; 3 a chemical plating layer deposited on the inner wall surface of the through hole 2; and 4 a chemical plating layer 3 deposited on the inner wall surface. This is electrolytic copper plating (conductor) deposited thickly so as to fill (fill) the inside of the through hole 2.

The printed wiring board having the above configuration is, for example, shown in FIGS.
It can be manufactured through a process as shown schematically in the embodiment shown in (d). That is, a copper-clad laminate 5 with a thickness of 1.6 mm is prepared, and a hole (through-hole) with a diameter of about 1.3 mm is inserted through the copper layer on the other side at a predetermined location on the copper-clad laminate 5.
5a (FIG. 2(a)).

Next, chemical copper plating and electrolytic copper plating are sequentially applied to the entire surface including the inner wall surface of the formed through hole 5a to form a copper layer 3 having a thickness of about 20 to 30 microns. A photosensitive dry film 6 is laminated on the surface of the copper-clad laminate 5 on which the copper layer 3 is formed, and exposed and developed to selectively expose the through holes 5a (FIG. 2(b)). After that,
The copper plating 4 is applied to the exposed inner wall surface of the through hole 5a by electroplating using a plating solution similar to the one used in the electrolytic copper plating for a long time at a relatively low current density. It is grown to fill the inside of the through hole 5a (FIG. 2(C)).

After completing the copper plating in the through holes 5a, the dry film 6 is removed, and the portions of the copper plating 4 that are built up in the through holes 5a and protrude from the surface of the copper-clad laminate 5 are cut by polishing. Next, after patterning the 5th side of this copper-clad laminate using an etching resist, the unnecessary portions of the copper plating layer and the copper foil are selectively removed by etching (Fig. 2(d)), and then the etching resist pattern 7 is removed. By removing , a printed wiring board having the main part configuration shown in FIG. 1 can be obtained.

In the above manufacturing process, the through-holes 5a in the copper-clad laminate 5 are formed so that they do not penetrate to the extent that they reach the copper layer on the other side, as shown in cross-section in FIG. It may also function as a sealing part.

In the above example, the conductor 4 that contributes to the electrical connection between the circuit pattern layers in the through-hole region 2 is made of copper plating. It may be replaced with. That is, in the manufacturing process of the printed wiring board, the conductor 4 in the through hole for electrical connection between the circuit pattern layers is filled with a conductive paste using heat-resistant resin as a binder, or by filling the conductor 4 with a heat-resistant resin as a binder, instead of using electrolytic copper plating. This may also be done by inserting and arranging a rod of a highly conductive metal such as copper.

Therefore, in any case, the conductor 4 embedded in the connection through-hole is mounted in the mounting 1. A material with a melting point higher than that of the solder used for soldering electronic components is selected.

[Effects of the Invention] As described above, according to the printed wiring board according to the present invention,
The through-hole connections are filled with a conductor with a relatively high melting point and are constructed using this material, so they are prevented from melting or flowing out even when exposed to high temperatures when electronic components are mounted, thereby preventing electrical leakage between circuit pattern layers. connections are maintained reliably. In other words, the configuration of a highly reliable mounted circuit device can be easily achieved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of the main part configuration of a printed wiring board according to the present invention, and FIGS. FIG. 1...Printed wiring board body la...Surface circuit pattern 2...Through hole area 3...Chemical-electroplating layer 4... Conductor 5 filling the through hole...
... Copper-clad laminate 5a ... Through hole 6 ... Photosensitive dry film 7 ... Etching resist pattern applicant
Toshiba Corporation Representative Patent Attorney Sasa Suyama - Figure 1%1fqki14LnL (a)
5Figure 2

Claims (1)

[Claims] A printed wiring board in which required circuit pattern layers are electrically connected via through-holes, and the through-hole connection is performed by a conductor with a relatively high melting point filling the through-holes. printed wiring board.