JPH0656913B2 - Circuit board - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention provides a circuit board having a metal substrate coated with an enamel layer, and particularly a substrate having a fine wiring pattern formed on the substrate by a thick film printing method. A circuit board that can be used.

2. Description of the Related Art Conventionally, alumina substrates and glass epoxy substrates have been used for thick film hybrid ICs and printed circuit boards. The disadvantage of the alumina substrate is that it has low mechanical strength and it is difficult to manufacture a large substrate. On the other hand, the glass epoxy substrate is inexpensive and suitable for mass production, but has poor heat resistance and is a material used for circuit formation (a thick film paste has a firing temperature of 800 to 9).
However, there are restrictions that the use environment of the product is 400 ° C or less.

As a method for solving these problems, a so-called enamel substrate in which a glass substrate is coated on a metal substrate has been proposed. The first proposal is the alkali metal oxide (Na
It is a substrate coated with amorphous glass having a relatively small amount of ₂ O, K ₂ , Li ₂ O). The disadvantages of this type of board are (a)
When repeatedly fired, the enamel layer re-softens,
(b) Inferior in electrical insulation at high temperature compared to alumina substrate, (c) When voltage is applied for a long time at high temperature, migration of alkali ions adversely affects the network, (d) paste The size of the printed circuit shrinks before and after firing due to the cohesive force during firing. There are problems with resoftening of the insulating layer, electrical insulation, reliability, and circuit accuracy.

On the other hand, the second proposal is an attempt to use crystallized glass as the enamel layer. For example, as disclosed in JP-A-56-73643, 6 to 25 mol% of BaO, 3
0-60 mol% of metal oxides (MgO, ZnO, CaO
1 or 2 or more mixtures selected from the group
A enamel substrate in which a crystallized glass having a composition of 5 mol% B ₂ O ₃ and 10 to 25 mol% SiO ₂ is coated on a steel plate is a enamel layer even if paste is printed at 800 to 900 ° C. and repeatedly fired. Since it does not re-soften, and it is an alkali-free glass, it has excellent electrical insulation and reliability.
It completely exceeded the first proposal.

When the range expressed in mol% of the second proposal is expressed in weight% with reference to the examples, BaO = 16 to 50%, M
gO = 16 to 42%, CaO = 0 to 11%, ZnO = 0
~11%, CaO + ZnO = 0~11 %, B 2 O 3 = 12
_{~34%, SiO 2 = 10~23%} , ZrO 2 = 0~5
%, Al ₂ O ₃ = 0 to 5%, SnO ₂ = 0 to 5%, ZrO ₂
+ Al ₂ O ₃ + SnO ₂ = 0 to 5%. Hereinafter, the present specification is unified by weight%.

Problems to be Solved by the Invention The problems of the second proposal are (a) poor heat resistance, (b) poor acid resistance, (c) large surface roughness, and unsuitable as a fine wiring substrate. There is, and so on.

Regarding these drawbacks (a) and (b), attempts have been made to improve the glass composition as disclosed in JP-A-58-104042 and JP-A-60-172102. However, it has not been put to practical use yet. The reason is that the surface roughness becomes extremely larger than that of the second proposal and it cannot be used as a circuit board for thick film printing. Because, when such _{MgO-BaO-B 2 O 3} -SiO 2 system glass is fired at 800 to 900 ° C., BaO · 2M
This is because the crystal phases of gO · 2SiO ₂ and 2MgO · B ₂ O ₃ are precipitated and the crystal grains are enlarged, so that the surface roughness of the substrate is increased. FIG. 2 shows the situation.

An object of the present invention is to provide an enamel substrate that solves the above problems.

Means for Solving the Problems In order to solve the above problems, the present invention comprises, as an enamel layer, at least a main component of La ₂ O ₃ = 0.5.
~ 3%, MgO = 20-50%, CaO = 1-25%,
BaO = 0 to 15%, B ₂ O ₃ = 10 to 30%, SiO ₂
= 8 to 20% Mo ₂ (M is Ti, Zr, at least one of Sn) to = 0 to 5%, characterized in that used as the P ₂ O ₅ = 0-5%.

Desirably La ₂ O ₃ = 0.5-3%, MgO = 20-40
%, CaO = 1-20%, BaO = 0-15%, B ₂ O _{3
= 15~25%, SiO 2 = 10~20} %, ZrO 2 = 0
˜5%, P ₂ O ₅ = 0 to 5%.

More preferably, La ₂ O ₃ = 0.5 to 3%, MgO = 20
~40%, CaO = 1~20%, B 2 O 3 = 15~25
%, SiO ₂ = 10-20%, ZrO ₂ = 0-5%, P ₂
It is characterized in that O ₅ = 0 to 5%.

Effects According to the present invention, as shown in FIG. 1, a circuit board having improved surface smoothness and excellent in acid resistance and heat resistance can be obtained.
As a result, it can be applied as a substrate on which a high-density wiring pattern can be formed.

Example Crystallized glass used in the enamel layer of the present invention, oxides, carbonates, nitrates, phosphates and the like corresponding to each component as a raw material, in platinum or platinum rhodium crucible,
After being melted at 1400-1500 ° C. for 30 minutes to 1 hour, it was manufactured by quenching in water or quenching with twin rollers.

Table 1 shows the composition of the glass for the enamel substrate coated with the enamel layer of the present invention, and the glass powder was dispersed in propanol with a ball mill to obtain a stainless steel substrate (SUS430, size).
100μm thick electrodeposited on the entire surface of 50 × 50 × 1), 10 at 900 ℃
The results of examining the surface roughness, waviness, heat resistance, acid resistance, etc. of the substrate that has been partially fired are shown.

Here, the surface roughness is represented by the center line average roughness Ra, and the waviness is represented by the maximum height R _max as a guide. Heat resistance of the substrate is 920 ℃
The cycle of putting in the electric furnace for 10 minutes, taking out, and leaving at room temperature for 30 minutes was repeated to examine the occurrence of cracks and peeling. Crack red board After soaking in the ink, it was taken out and the excess ink was removed with an air gun and observed. In the table, ◯ Δx indicates that cracks and peeling did not occur even after 10 cycles or more, Δ indicates that it survived 5 to 9 cycles, and x indicates that it occurred after 4 cycles. The acid resistance was examined by immersing the substrate in a 5% citric acid aqueous solution at 60 ° C. for 30 minutes, and ○ means 1
0 mg / cm ² to less weight loss, it △ is 11~20mg / cm ^2, × is 20 mg / cm ² or more indicates it shows enough that acid resistance is good small.

The printing accuracy was evaluated by using a printing method and a photoresist method on the substrate, and 6 gold electrodes each having a width of 30 μm were formed in a stripe pattern / m.
m at a rate of 300 μm, and a ruthenium oxide resistor having a width of 300 μm is further formed thereon to make a thermal head as a prototype.
The resistance value between the electrodes was measured. At that time, the variation in resistance between the electrodes was within 10%, and the variation was 10 to 20%, and the variation was 20% or more.

The resistance change in the table refers to the change in resistance value of the gold electrode, which was obtained by examining the reactivity between the electrode and the enamel layer, and the thickness was 0.5 μm.
The change in resistance value when a gold electrode having a size of 1 × 20 mm is formed on a substrate is expressed by a change when compared with the resistance value when an electrode having the same shape is formed on a quartz substrate. In the table, ◯ indicates a change within one digit, Δ indicates a change within two digits, and x indicates a change of three digits or more. The smaller the change, the less the reactivity.

Based on the above evaluations, the overall evaluation is shown in the bottom column as ◯ Δ ×.

No. 1 to 7 are SiO ₂ / B ₂ with other components being constant.
That the O ₃ is varied, No. 8 to 13 are SiO ₂ / B ₂
The O ₃ is substantially constant, that changing the MgO, No.
Nos. 14 to 18 have the same CaO, No. 1
Nos. 9 to 24 have the same La ₂ O ₃ content, No. Two
5 to 27 are BaO, No. 28 to 33 are ZrO ₂ , T
This is the effect of adding iO ₂ , SnO ₂ , P ₂ O ₅ , and Al ₂ O ₃ . As a comparative example, No. 34 is JP-A-56-7
No. 3643, No. 35 is Japanese Patent Laid-Open No. 58-104042, N
o. No. 36 shows the evaluation results of those disclosed in JP-A-60-172102.

As is clear from the table, if the SiO ₂ content is increased, the heat resistance and the acid resistance are improved, but the surface roughness deteriorates, making it unsuitable for fine printing. Conversely, if B ₂ O ₃ is increased, the opposite is true. Therefore, it is preferable that SiO ₂ is 8 to 20%, B ₂ O ₃ is 10 to 30%, and the ratio SiO ₂ / B ₂ O ₃ is 0.25 to 1.0.

If MgO is less than 20%, crystal precipitation is insufficient and heat resistance is poor. When it is more than 50%, it is difficult to melt, it is difficult to obtain a homogeneous glass, the surface roughness becomes large, and the printability of a fine pattern becomes poor.

If CaO is less than 1%, there is no effect of improving the smoothness and acid resistance of the surface, and if it is more than 25%, printing accuracy deteriorates. Figure 3 shows BaO / (BaO + C) contained in glass.
aO) changed glass (its composition is No. 1 in Table 2)
5 shows the acid resistance to the above-mentioned citric acid of the substrate. BaO / (BaO + Ca
As O) becomes smaller, the weight loss is smaller and the acid resistance is excellent. Means that Further, FIG. The results are obtained by examining the weight loss of the substrates made of glass 1 and 5 immersed in 5% aqua regia at room temperature. No. 1 means that the weight loss is small and the acid resistance is excellent. From the above, CaO has the function of improving the acid resistance of glass,
It can be seen that O does not have such a function.

Further, FIG. Substrates made of glass Nos. 1 and 5 had a firing temperature and a center line average roughness Ra as a measure of surface smoothness.
No. In the case of 5, Ra becomes extremely large by firing at 820 ° C. or higher. Since the firing temperature of commercially available thick film pastes is often 810 to 850 ° C., it is generally necessary to keep the firing temperature of the substrate higher than this. For example, when the baking temperature of the substrate is 900 ° C, Ra is 0.35 μm
Therefore, if a thick film paste is printed on this to a thickness of 0.3 μm, a circuit break will occur. On the other hand, No. In the case of No. 1, Ra was 0.08 μm even if it was baked at 900 ° C., and even if a thick film paste was printed on it, circuit breakage was unlikely to occur. The reason is No. 5 glass is 2MgO ・ B ₂ O ₃ , BaO ・ 2
While two types of crystals of MgO · 2SiO ₂ are generated and Ra is increased, No. 2M because 1 glass does not contain BaO
This is because only gO · B ₂ O ₃ is generated and such a situation does not occur.

La ₂ O ₃ improves the surface smoothness of the substrate and greatly contributes to the improvement of heat resistance. The reason why the heat resistance is improved seems to be that the adhesion between the substrate and the holo layer is improved. According to the PEI test method developed by the American Enamel Society, No. ₂ containing no La ₂ O ₃ was used when nickel-treated SUS430 was used as the base material. The adhesion of the substrate using 6 glass is 26%, and No. 6 containing La ₂ O ₃ is used. In case of 1, it was 100%. The reason why the adhesion between the substrate and the holo layer is improved is not clear, but La ₂ O ₃ and F contained in the base material
This is considered to be due to the mutual reaction with e ₂ O ₃ and NiO. Although this does not directly support this, Binary Phas
e Diagrams Handbook (1981 GE Co) 3/81 has La and F
Although it is described that e and Ni form a solid solution,
It is considered that some reaction is occurring even in the case of oxide. For the above reasons, La ₂ O ₃ is at least 0.
It is desirable to contain 5 wt% or more.

Further, if it exceeds 3%, the acid resistance is lowered and the change in the resistance value of the gold electrode is increased. For the latter reason, see
It has been shown that Au and La form a solid solution.
In e Diagrams for Ceramists P46 (1969 Am Ceram Soc), it is shown that PdO, an oxide of Pd, which is the same precious metal as Au, forms a compound with La ₂ O ₃ . From this, it is speculated that the gold electrode reacted with La ₂ O ₃ in the enamel layer to cause a change in resistance value.

BaO is not an essential component in the present invention, but may be added if it is 15 wt% or less. The reason is that the acid resistance and the surface smoothness are lowered as described above.

Other components that can be added are ZrO ₂ , TiO ₂ , Sn
O ₂ , P ₂ O ₅ , Al ₂ O ₃ , ZnO, etc.
Up to 5% can be added. The reason is that the surface smoothness deteriorates if there are many.

In addition to the above-mentioned components, alkali metal oxides; iron, manganese,
It is possible to add oxides such as nickel, cobalt, vanadium, lead, molybdenum, tungsten, bismuth, cadmium and strontium, but alkali metal oxides are 2% or less in consideration of electric insulation, and other oxides. Is also preferably 5% or less.

EFFECTS OF THE INVENTION As described in detail above, the substrate of the present invention is excellent in surface smoothness, heat resistance, acid resistance, fine printing accuracy, and stability of gold electrodes, and is particularly useful as an electric circuit board. Applications include motor bearings, mechanical seals, chemical devices such as pipes and tanks, automobile parts such as engine covers, and household appliances such as enamel pots.

Is.

[Brief description of drawings]

FIG. 1 is a shape diagram showing the surface roughness of a circuit board according to an embodiment of the present invention, and FIG. 2 is a shape diagram showing the surface roughness of a conventional circuit board. 3 and 4 are diagrams showing the acid resistance of the circuit board, and FIG. 5 is a diagram showing the relationship between the firing temperature and the surface roughness of the circuit board.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Hiraga 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-63-89435 (JP, A) JP-A-2- 40990 (JP, A)

Claims (4)

[Claims] 1. La ₂ O ₃ = 0.5-3% by weight, MgO
= 20 to 50%, CaO = 1 to 25%, BaO = 0 to 1
_{5%, B 2 O 3 =} 10~30%, SiO 2 = 8~20%,
Mo ₂ (M is at least one of Ti, Zr and Sn) = 0
5%, the circuit board, characterized in that a gold electrode was formed on the enamel layer mainly composed of P ₂ O ₅ = 0~5%. 2. The main component of the enamel layer is at least% by weight.
And La ₂ O ₃ = 0.5-3%, MgO = 20-40%, C
aO = 1-20%, BaO = 0-15%, B ₂ O ₃ = 15
_{~25%, SiO 2 = 10~20%} , ZrO 2 = 0~5
%, Claim 1, characterized in that the P ₂ O ₅ = 0~5%
The described circuit board. 3. The main component of the enamel layer is at least% by weight.
And La ₂ O ₃ = 0.5-3%, MgO = 20-40%, C
aO = 1 to 20%, B ₂ O ₃ = 15 to 25%, SiO ₂ =
10-20%, ZrO ₂ = 0-5%, P ₂ O ₅ = 0-5%
The circuit board according to claim 2, wherein 4. The circuit board according to claim 1, 2 or 3, wherein SiO ₂ / B ₂ O ₃ is 0.25 to 1.0.