JPS6135156B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a method for manufacturing a ceramic printed board, and more particularly to a method for manufacturing a ceramic printed board that concerns the selection of a conductive paste to serve as a circuit conductor.

(2) Conventional technology and problems For example, alumina ceramic has electrical insulation properties,
Because it has excellent heat resistance, thermal conductivity, and high mechanical strength, it is being used as a printed circuit board material for forming high-density three-dimensional conductor circuits. The main means for producing a desired three-dimensional conductor circuit from such a ceramic base material and the problems involved will be explained with reference to the drawings.

In the manufacturing process diagram of FIG. 1, A is the step of drilling holes in a ceramic substrate, so-called green sheet, before firing. That is, this is a drilling process for making through holes (or via holes) for making circuit connections between upper and lower layers when a large number of green sheets are stacked.

B is a step of filling the through hole with a paste consisting of powder of a noble metal such as gold having good conductivity, an inorganic binder, and some solvent.

C is a circuit (see 4 in Fig. 2) by printing a conductive paste having the same composition as the above in a predetermined circuit pattern on the surface of the green sheet following the through-hole conduction process, for example, by using a stencil screen printing method. This is the process of forming.

D is a step in which a three-dimensional circuit is assembled by stacking the green sheets on which the through-hole connections and circuit patterns have been formed in many layers.

Step E is a step in which the green sheets, which have been laminated in step D, are fired at, for example, 850.degree. C. for 10 minutes to form a multilayer ceramic board.

However, in the multilayer ceramic board 1 completed by such a manufacturing process, the filling paste for connection in the through-holes bulges 2 outward at the through-holes 3 that penetrate upward and downward, as illustrated in the cross-sectional view of FIG. Unsuitable for use as a raw product. For example, although not shown in the drawings, when mounting an element such as an LSI on the front surface (or back surface) of a substrate, it may cause problems such as not being able to perform proper mounting.

For this reason, we investigated the temperature characteristics of the through-hole filling conductor paste during ceramic firing, and the temperature (represented by the horizontal axis t) versus dimensional change characteristics (vertical axis, from 0 to The upper part shows a region of increasing size, and the lower part from 0 shows a region of decreasing size).

That is, as is clear from the figure, the conductive paste in the through-hole is in a shrinkage range up to temperature t ₁ (approximately 800° C.), but expands and increases in size at a steep gradient at temperatures higher than t ₁ . This is probably because the inorganic binder in the paste composition decomposes and generates a large amount of gas, which is clearly the main cause of the blistering.

(3) Purpose of the Invention The present invention eliminates the bulging of through-hole connections that occurs when firing a three-dimensional circuit type laminated ceramic board, and realizes a circuit forming method that is stable and has a high product yield using the manufacturing process shown in FIG. be.

(4) Structure of the invention In manufacturing a ceramic printed board by laminating and firing a plurality of unfired ceramic substrates on which circuit patterns have been generated, glass frit is inserted into interlayer connection holes formed in the unfired ceramic substrates. No conductive paste filling, including
Next, a circuit pattern is printed on the surface of the unfired ceramic substrate using a conductive paste containing no glass frit, and then the unfired ceramic substrates are laminated and fired.

(5) Embodiments of the Invention The glass frit having the above structure is a low contact point glass fine powder with a particle size of 1 or 1 micron or less, and is used as a base material for airtight bonding of metal and glass.

This is added to the conductive paste to be filled in step B of the manufacturing process in FIG. 1, and used by kneading.
That is, the electrically conductive paste used for interlayer circuit connection, which is filled in the sealing hole portion of the through hole or via hole, contains glass frit in an amount of approximately 1% by weight.

However, in step C of the manufacturing process in Figure 1,
A glass fritless conductive paste without added glass frit is used as the conductive paste for forming a circuit pattern by printing patterns on the surface of each green sheet.

Incidentally, the dimensional behavior of the glass frit-added conductive paste for through-hole connection according to the present invention as shown in FIG. 3 with respect to the ceramic firing temperature is shown by the dot-dashed line b characteristic.

When adding the glass frit, for example, a paste having a molybdenum-tungsten composition or a paste having a silver-palladium composition can be used as the pre-addition conductor paste. Of course, there is an optimal amount of frit to be added depending on the target paste, and care must be taken because if this amount is too large, the electrical connection resistance of the through holes will increase.

If the conductor circuit-forming green sheet bodies formed in steps B and C in Figure 1 are stacked and sintered at the same ceramic firing temperature t ₂ = 850 [°C] as in the past (step D), it will be stable. A ceramic substrate of high quality can be obtained.

(6) Effects of the Invention According to the method for manufacturing a ceramic printed board of the present invention as described above, it is stable and does not cause blisters (see 5 in Fig. 2) in the hole connecting portions 3 of a laminated ceramic printed board as in the conventional case. A printed board with a three-dimensional circuit is formed.
At the same time, the manufacturing capacity of the printed board is improved, so its practical value is great.

[Brief explanation of the drawing]

Figure 1 is a diagram of the manufacturing process for ceramic printed boards.
FIG. 2 is a sectional view of a ceramic printed board to which the present invention is applied, and FIG. 3 shows the characteristics of dimensional changes of through-hole conductor portions with respect to ceramic firing temperature t. In the figure, 1 is a ceramic printed board, 2 is a bulge in a through-hole portion 3 on the front (back) surface of 1, and 4 is a printed circuit conductor made of conductive paste.

Claims (1)

[Claims] 1. In manufacturing a ceramic printed board by laminating and firing a plurality of unfired ceramic substrates on which circuit patterns have been generated, conductive paste containing glass frit is filled into interlayer connection holes formed in the unfired ceramic substrate. Next, a circuit pattern is printed on the surface of the unfired ceramic substrate using a conductive paste that does not contain glass frit,
A method for manufacturing a ceramic printed board, comprising the step of laminating and firing the unfired ceramic substrates.