JPS5843919B2 - How to form via holes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a via hole (1), and more specifically, a method for forming a via hole by removing the deflection of the metal mask so as to accurately align metal balls in the holes in the metal mask. Regarding method 1.

When manufacturing ceramic printed boards for various electronic devices, when modifying the printed board due to design changes such as wiring changes, the wiring is changed and via holes are provided in the ceramic printed board.

In forming this via hole, it is required to make the via hole smaller, and for this reason, it is necessary to accurately fill the insulating layer such as ceramic with metal balls by applying pressure.

Conventionally, a method using a metal mask has been used to form via holes.

That is, a metal mask 1' having a large number of small holes as shown in FIG. 1 was placed on a green sheet 2', and metal balls were arranged.

However, the thickness of the metal mask 1 is approximately 0.05 m.
Since the metal mask 1' is very thin, warping occurs before the balls are arranged, resulting in insufficient adhesion between the metal mask 1' and the raw sheet 2'.

For this reason, the arrangement of the balls was inaccurate, such as a plurality of metal balls being arranged in the holes provided in the metal mask 1'.

Further, since the hole diameter of the metal mask 1' is not appropriate for the diameter of the metal balls, there is a drawback that the percentage of balls that are accurately arranged is low.

The present invention has been made in order to eliminate such drawbacks, and involves placing a metal mask on an insulating layer, pressing the entire peripheral edge of the metal mask onto the insulating layer, and then inserting metal balls into holes in the metal mask. The metal balls are arranged in the insulating layer and then filled with the metal balls by applying pressure.

Furthermore, in the present invention), by adopting a ratio of the diameter of the metal balls to be arranged to the hole diameter of the metal mask of 0.5 to 0.81ζ, the optimum arrangement rate of the metal balls could be obtained. It is something.

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

FIG. 2 is a perspective view of the metal ball arrangement jig A.

The ball arrangement jig A is manufactured by fixing the circumference am of a metal frame 31ζ metal mask 1 made of aluminum or the like using, for example, an adhesive or the like.

Furthermore, four corners 1 (guide holes 4 are provided) of the metal ball arrangement jig A.

Furthermore, regarding the hole diameters of the plurality of holes in the metal mask 1,
The ratio of the diameters of the arranged metal balls to the diameters of the holes in the metal mask (hole diameter ratio) is set to 0.5 to 0.8.

For example, if metal balls with a diameter of 0.1 mm are to be arranged, and the hole diameter ratio is set to 0.71, a metal mask with a hole diameter of 0.14 mm will be used.

In order to fill the insulating layer (green sheet of ceramic printed board) 2 with metal balls, first the insulating layer 2 is placed on the mold 5 tζ.

Next, the metal ball arranging jig A is placed on the insulating layer 2, such as a raw sheet, and the L1 guide pin 6 is pushed through the guide hole 41 to align the position and set on the insulating layer 2.

As mentioned above, as an example of the present invention, the metal frame 3t and the metal mask 1 are bonded together and fixed, so the metal mask 1 does not bend.In this case, the metal frame 3 itself becomes a kind of weight, and the insulating layer The adhesion between the metal mask 2 and the metal mask 1 is improved.

Then, for example, the pore size is 0. When there is one metal mask of L4 mrn and the hole diameter ratio is 0.7, for example, 1600 metal balls each having a diameter of 0.1 am are arranged in tζ on the metal mask 1.

Next, pressure is applied using a mold 5 (a press mold having a corresponding predetermined shape) to fill the insulating layer 2 with metal balls 7 (made of gold paste, for example) to form via holes.

As described above, a pattern is formed with a thick film on the insulating layer with via holes formed thereon to create a circuit board.L1 The circuit boards are laminated, C-pressed, and fired to create a multilayer circuit board. .

In the above example (hole diameter ratio 0.7), the arrangement ratio of metal balls was 98.

Here, the arrangement rate is the rate at which metal balls are arranged on the insulating layer and only one metal ball is arranged at a predetermined position (ζ).

In the measurement, the entire area of the insulating layer was observed using a microscope, and the number of metal balls at a predetermined position was counted.

In addition, when using the conventional method, the alignment rate was 65.2.

FIG. 4 shows the arrangement ratio of metal balls when the ratio of metal ball diameter to metal mask hole diameter is changed.

From the same figure, the metal ball diameter/metal mask hole diameter is 0.5.
It has been found that a preferable alignment ratio can be obtained when the ratio is 0.8.

It has also been found that the above results can be obtained regardless of the diameter of the metal ball (1ζ).

In the present invention, as described above, the entire peripheral edge of the metal mask is suppressed onto the insulating layer and the metal balls are arranged in one hole of the metal mask, so that the bending of the metal mask is completely eliminated. This has the effect of significantly improving the adhesion between the metal mask and the insulating layer.

Therefore, there is an effect that the arrangement of the metal balls becomes accurate.

Furthermore, by setting the ratio of the metal ball diameter to the metal mask hole diameter within a predetermined range, the arrangement rate of the metal balls can be improved.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a metal mask simply placed on an insulating layer, Fig. 2 is a perspective view of a jig for arranging metal balls, and Fig. 3 is a perspective view showing a metal mask simply placed on an insulating layer. FIG. 4, which is a partially cross-sectional perspective view showing a state in which it is pressed upward, is a graph showing the relationship between the arrangement ratio and the metal ball diameter/metal mask hole diameter. 1...Metal mask, 2...Insulating layer,
7...Metal ball.

Claims (1)

[Claims] 1. A metal mask in which the metal balls to be arranged have a diameter-to-hole diameter ratio of 0.5 to 0.8 is placed on the raw sheet of the ceramic printed board, and the entire periphery of the metal mask is covered with the raw sheet of the ceramic printed board. A method for forming a via hole, which comprises pressing onto a sheet, then arranging metal balls in the holes of a metal mask, and then filling the raw sheet of the ceramic printed board with metal balls by applying pressure.