JPH0268807A - Paste for forming electrode of thick film hybrid in and thick film hybrid ic - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a paste for forming electrodes of a thick film hybrid IC and a thick film hybrid IC.

[Prior art] In forming a thick-film hybrid IC, an electrode-forming paste is printed on a substrate and baked to form an electrode, and the electrode and IC chip are wire-bonded using a gold wire. Connected.

Organic gold paste (IIIetal) is used as a material for forming electrodes in such thick-film hybrid ICs.
organic gold paste) is known.

This is a material in which Au is combined with the edges of organic matter. When this organic gold paste is silk screen printed on a substrate to form a pattern and then fired, the organic matter scatters and Au atoms precipitate and accumulate. This forms a thin, smooth film, forming an electrode. The electrode obtained using the organic gold paste has the following advantages when used as a gold electrode for a thermal head, for example. That is, since the etching pattern accuracy is good, there is little variation in resistance value, and the printing quality is good. Furthermore, since a thin film can be obtained, heat from the heating resistor is difficult to escape, resulting in good heat generation efficiency. Furthermore, the thin film thickness eliminates unevenness on the base of the resistor.

[Problems to be solved by the invention] Although electrodes obtained using organic gold paste have the above-mentioned advantages, they have low bonding properties, and sufficient bonding strength cannot be obtained when gold wire is bonded. There were drawbacks. In order to solve this drawback and improve the bondability, impurities are added. If impurities are added, the impurities will form a film on the surface after printing and baking the paste, which will deteriorate the bonding properties. However, there are problems in that the addition of impurities reduces etching properties, making it impossible to form an electrode pattern accurately, and that the resistance value increases, resulting in a deterioration in the quality of the electrode.

The present invention solves the problems of the prior art, has sufficient bonding strength, and has a low etching property.
It is an object of the present invention to provide an electrode for a thick film hybrid IC and a paste for forming the electrode without increasing the resistance value.

[Means for Solving the Problems] According to the present invention, a paste for forming electrodes of a thick film hybrid IC containing organic gold as a main component is a paste made of a mixture of organic gold and powdered gold. .

According to one feature of the present invention, the proportion of gold powder in the mixture is 0.02% by volume or more and 0.3% by volume or less.

Further, according to the present invention, there is provided a substrate, an IC chip disposed on the surface of the substrate, and a thick film electrode disposed on the surface of the substrate, and the IC chip and the thick film electrode are connected by wire bonding. In the thick film hybrid IC, the thick film electrode is formed by applying a paste made of a mixture containing organic gold as a main component and powdered gold to the surface of the substrate and baking it.

[Function] According to the present invention, the paste for forming electrodes of a thick film hybrid IC is a paste made of a mixture of organic gold and powdered gold. Therefore, when an electrode pattern is printed on a substrate using this paste and fired, the formed electrode contains powder gold in a thin organic gold film, so the surface of the electrode has irregularities due to the powder gold. occurs. This electrode is
When wire bonding is performed with a gold wire between the C-chip and the electrode, the unevenness of the electrode surface improves the bite of the gold wire, resulting in a large bonding strength.

Furthermore, since it does not contain any impurities, the etching properties will not deteriorate and the resistance will not increase.

According to the present invention, the electrodes of the thick film hybrid IC are made of a paste made of organic gold mixed with powdered gold. Therefore, since the surface of the electrode has irregularities due to the gold powder, the strength of wire bonding between the electrode and the IC chip is high. Furthermore, since the electrode does not contain impurities, it can be kneaded accurately and there is no increase in resistance value.

[Example] Next, an example of a paste for forming electrodes of a thick film hybrid IC according to the present invention will be described.

The paste for forming electrodes of a thick film hybrid IC according to the present invention is made into a paste by adding a vehicle to a mixture of organic gold and powdered gold. The powdered gold to be mixed preferably has a particle size of about 1 gm, and the mixing ratio of the powdered gold is 0.02 to 0°3 in volume percentage.
%, that is, the gold component consisting of organic gold and powdered gold is composed of 0.02 to 0.3% by volume of powdered gold and 99.7 to 99.98% of organic gold.

When forming the electrodes of a thick film thermal head using the above paste, for example, as shown in FIG. 3A,
The above paste is passed through the gaps between the meshes of the silk screen and printed on the alumina substrate 24 to form a pattern of the electrode 20 having a thickness of, for example, 10 pm. The pattern of the printed electrode 20 is as shown in the figure.
Powdered gold 20a is uniformly dispersed in organic gold paste 20b. It is desirable that the organic gold and powdered gold have a size that allows them to pass through the mesh of the silk screen. Further, in order to uniformly disperse the gold powder 20a in the organic gold paste 20b, it is preferable that the gold powder 20a be spherical and have the size described above.

After printing the paste on the substrate 24 as described above, when it is fired at a predetermined temperature, as shown in FIG. The electrode 20 is formed by dispersing gold powder 20a having a particle size of about 1 km in a thin film 20c having a thickness of less than 1 pm. As shown in FIG. 3B, since the gold powder 20a is included in the thin film 20c formed by precipitation of Au atoms, the surface of the electrode 20 is uneven due to the gold powder 20a.

The electrode 20 of such a thick film thermal head has a surface roughness that improves the bite of the wire during wire bonding, so that the bonding strength is high. Furthermore, since it does not contain impurities, etching properties do not deteriorate, and resistance does not increase.

Next, embodiments of the thick film hybrid IC according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a thick film thermal head, and FIG. 2 shows a sectional view taken along the line II--II in FIG. As shown in FIG. 2, the thick film thermal head has a substrate 24 of alumina (A1203). A heat insulating underglaze layer 22 is provided on the main surface of the substrate 24, and an electrode 20 formed by printing and baking the electrode forming paste according to the present invention is arranged on the upper surface of the underglaze layer 22. has been done. electrode 20
A resistor 1B is provided on the surface of the resistor 16, and the resistor 16 is covered with an overcoat layer 10.

As shown in FIG. 1, the electrode 20 includes a plurality of common electrodes 201, 203, . A plurality of signal electrodes 202, 204 are arranged to
,... are arranged. The IC chip 12 is provided on the substrate 24, and the signal electrodes 202, 204, . . .
* are each connected to the IC chip 12 by a bonding wire 26, and a common electrode is also connected to the IC chip 12 by a bonding wire (not shown).

External terminals 14 are provided at the ends of the substrate 24, and the IC chip 12 and the external terminals 14 are similarly connected by bonding wires 28.

The signal electrodes 202 , 204 , . . . are the IC chip 12
Similarly, the common electrodes 201 , 203 , . . . are energized during printing in response to a control signal sent from the IC chip 12 . The resistor 16 is in contact with a portion of the tips of the common electrodes 201 , 203 , . . . and the signal electrodes 202 , 204 , . Therefore, for example, when the signal electrodes 202, 204, . The current-carrying portion of the resistor 16 generates heat. Heat from the current-carrying portion of the resistor 1B is transmitted to thermal recording paper (not shown) through the overcoat layer 10, and thermal recording is performed. Alternatively, heat a thermal transfer ribbon and transfer it to recording paper.

According to the thick film hybrid IC of this embodiment, the electrode 20 is formed by printing and firing an electrode forming paste in which powdered gold 20a is mixed with an organic gold paste 20b. Therefore, as described above, the surface of the electrode 20 has irregularities caused by the powdered gold 20a, and the surface roughness increases, so that the bonding has good bite and the bonding strength is high. Moreover, since no impurities are added to the electrode forming paste, there is no increase in resistance value and it has good characteristics as an electrode. Furthermore, since it does not contain impurities, the etching accuracy during processing is good and there is little variation in resistance value, so the amount of current flowing through the resistor can be accurately controlled and the quality of the printed image is high.

Furthermore, since the electrode 20 is formed of a paste containing organic gold as a main component, it is a thin film, which can reduce the amount of heat from the resistor 16 escaping through the electrode 20, and improve the heat generation efficiency of the resistor 16. be able to. Therefore, it is possible to save energy without causing excessive current to flow due to heat generation. In addition, the fired electrode 2
Since the film thickness of 0 is thin, there is no unevenness on the base of the resistor 16,
Since no unevenness occurs on the surface of the resistor 18, the thermal recording paper or the transfer ribbon can be heated accurately, and the printing quality can be improved.

Next, a specific example of the bonding strength of an electrode formed using the paste for forming an electrode of a thick film hybrid IC according to the present invention will be described in comparison with that of a conventional electrode.

A paste according to the invention was made with the following ingredients.

Engelhard organic gold paste (low impurity type) 140 parts by weight Au powder (particle size 1 μm)! , 9i parts were dispersed and mixed at the above ratio (Au powder was mixed at a ratio of 0.1 volume % to the organic gold paste) to prepare a sample paste. This paste was printed on a glazed alumina substrate and fired to form electrodes. Two types of electrodes were created: one in which the substrate was printed and fired only once (single layer) and one in which printing and firing were performed twice (two layer).

On the other hand, as a conventional example for comparison, only the organic gold paste manufactured by Engelhard was printed on a glazed alumina substrate and fired to form an electrode. Two types of electrodes, one layer and two layers, were also created for this conventional example.

Figures 5A to 5D show micrographs of the surfaces of electrodes made using the paste according to the invention, respectively, at a magnification of 400 times;
The images are shown at magnifications of 5000x, 20000x, and 50000x. Further, FIG. 5E shows a micrograph at a magnification of 1000 times of an electrode formed on an alumina substrate using the paste according to the present invention, and a cut section thereof viewed obliquely. In the figure, the upper part is an oblique view of the surface of the electrode, and the lower part is a cross section of the substrate.

On the other hand, FIGS. 6A to 6D show micrographs of the surface of the conventional electrode at magnifications of 400x, 5000x, and 200x, respectively.
00x and 50000x magnification. Moreover, in FIG. 6E, a conventional electrode is formed on an alumina substrate,
A microscopic photograph of the cut section viewed from an angle at a magnification of 1000
Shown in doubles. Similar to FIG. 5E, the upper part is an oblique view of the surface of the electrode.

The lower part is a cross section of the substrate.

As can be seen by comparing FIGS. 5A to 5E and FIGS. 6A to 6E, the electrodes made of the paste of the present invention shown in FIGS. 5A to 5E are superior to the conventional electrodes shown in FIGS. 6A to BE. There are irregularities on the surface. Therefore, this increases the strength of pounding, which will be described later.

Gold wires with diameters of 25 gm and 30 μm were bonded to the electrode made of the paste of the present invention and the electrode of the conventional example under predetermined conditions, respectively. FIG. 5F shows a gold wire bonded to an electrode made of the paste of the present invention. Further, FIG. 6F shows a state in which a gold wire is bonded to a conventional electrode.

Further, as shown in FIG. 4, these bonded gold wires are pulled by a hook-shaped tensioning member 30, and the gold wire 2B is peeled off from the electrode 20.
5G and 6G respectively.
The electrode made of the paste of the present invention shown in Figure G has a rough electrode surface after being peeled off compared to the conventional electrode shown in Figure 6G, indicating that the electrode has stronger strength. There is.

FIG. 7 shows the results of measuring the tensile strength of the electrode using the paste of the present invention and the electrode of the conventional example. The figure shows that a gold wire with a diameter of 25 μm is vibrated for the same period of time using ultrasonic waves of the same output for the electrode made of the paste of the present invention and the conventional electrode with one layer and two layers, respectively. The force required to peel off the gold wire was measured using the same pounding force. As can be seen from the figure, in both cases of one layer and two layers, the electrode made of the paste of the present invention has a higher tensile strength during bonding than the conventional electrode.

FIGS. 8A to 8D show the results of multiple measurements of the tensile strength of bonding for electrodes made of the paste of the present invention and conventional electrodes. In these figures, the black circle indicates the average value of the measured tensile strength of the punch ink, the bar-shaped parts that overlap with the black circle indicate the maximum and minimum values of the measured tensile strength of the punching, and the other bar-shaped parts indicate the tensile strength of the punching. The range of 3σ (σ is the standard deviation) of intensity is shown. These figures show cases in which the electrodes have one layer and two layers, and the direction in which the bonded wire is pulled is vertical and horizontal, respectively.

As can be seen from FIGS. 8A to 8D, in any case, the electrode made of the paste of the present invention has a greater tensile strength and less variation in bonding than the conventional electrode.

[Effects of the Invention] According to the present invention, since the paste for forming an electrode of a thick film hybrid IC is a mixture of organic gold and powdered gold, the electrode formed using this paste has irregularities on its surface. Therefore, these irregularities improve the bite of the gold wire and provide greater bonding strength. Furthermore, since it does not contain any impurities, the etching properties will not deteriorate and the resistance will not increase.

Further, according to the present invention, since the electrodes of the thick-film hybrid IC are formed from a paste made of organic gold mixed with powdered gold, the surface of the electrodes is uneven. The strength of wire bonding is high, and since the electrode does not contain impurities, it can be etched accurately and there is no increase in resistance.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view showing an embodiment in which the present invention is applied to a thick film thermal head, and FIG. 2 is a section II of FIG. 1.
-II line sectional view and FIG. 3A are sectional views of an electrode pattern printed on a substrate with the paste according to the present invention. FIG. 3B is a cross-sectional view of an electrode formed by firing the electrode pattern shown in FIG. 3A, FIG. 4 is a diagram showing an example of a bonding strength measurement method, and FIGS. 5A to 5E are according to the present invention. A microscopic photograph of the surface of an electrode made using the paste, Figure 5F is a microscopic photograph showing a state in which a gold wire is bonded to the electrode made of the paste of the present invention, and Figure 5G is a micrograph showing the gold wire of Figure 5F being pulled from the electrode. Micrographs showing the surface of the electrode after peeling off, Figures 6A to 6E
The figure shows a microscopic photograph of the surface of a conventional electrode. Figure 6F shows a conventional electrode with a gold wire bonded to it. Figure 6G shows the gold wire shown in Figure 6F being peeled off from the electrode. Figure 7 is a diagram showing the measurement results of the tensile strength of the electrode using the paste of the present invention and the conventional electrode, Figures 8A to 8D are FIG. 3 is a diagram showing comparative data obtained by measuring the tensile strength of bonding many times for an electrode made of the paste of the invention and a conventional electrode. 12. 16. 20. 0a 0b 24. 28.28 - IC chip resistor electrode powder gold-organic gold paste substrate wire Figure 5"E Figure !"F Figure 6A Figure 6A;・Labor 2. The first time after the threat "1 Hankomon No. 61': 1 Fig. 8A Fig. 1, Myou,, 1-Double 1chi Sashikariba:] - Male No. 813 fi heat 1 'tA 沫い 連本 R1 Akira

Claims (4)

[Claims] 1. A thick film hybrid IC electrode forming paste containing organic gold as a main component, wherein the paste is a paste made of a mixture of the organic gold and powdered gold. Paste for electrode formation. 2. The proportion of the powdered gold in the mixture is 0.02.
2. The paste for forming electrodes of a thick film hybrid IC according to claim 1, wherein the paste has a content of at least 0.3% by volume and not more than 0.3% by volume. 3. A thick film hybrid IC comprising: a substrate; an IC chip disposed on the surface of the substrate; and a thick film electrode disposed on the surface of the substrate, the IC chip and the thick film electrode being connected by wire bonding. In the thick film electrode, the thick film electrode is formed by applying a paste made of a mixture containing organic gold as a main component and powdered gold to the surface of the substrate and baking it. Hybrid IC. 4. 4. The thick film hybrid IC according to claim 3, wherein the thick film electrode is connected to a resistor and selectively energizes the resistor.