JPH04101489A - Thin film wiring substrate - Google Patents

Abstract

PURPOSE:To reduce the conducting resistance of circuit wiring, firmly bonding with a substrate and firmly bonding electronic components on the circuit wiring through brazing material by bonding the circuit wiring which has the three-layer structure which permits a bonding layer, a barrier layer and a main conducting layer, each of which is made of the prescribed metal, to be successively laminated on a ceramic substrate. CONSTITUTION:After cleaning a ceramic substrate 1, nickel/chrome as a bonding layer 3, at least one of the materials of Ni, Pd, Rh and platinum as a barrier layer 4 and gold as a main conducting layer 5 are successively laminated on the substrate 1 by vapor deposition for the prescribed thickness. Then, each layer is etched to be the prescribed pattern by photolithography andircuit wiring 2 which has three-layer structure is formed on the insulating substrate to be a product. When such thin film wiring substrate is used to bond electronic components on a circuit wiring 2, since the barrier layer 4 is between the bonding layer 3 and the main conducting layer 5, the alternate diffusion generated between the bonding layer 3 and the main conducting layer 5 caused by heat which melts the brazing material is prevented. The conducting resistance of the circuit wiring 2 is reduced, the bonding strength of the circuit wiring 2 on the substrate 1 is strengthened and high reliability is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thin film wiring board, and more specifically to improvements in ceramic wiring boards used for circuit wiring, high-density electric circuit boards, packages for housing semiconductor elements, etc. It is related to.

(Prior art and its problems) Conventionally, the circuit wiring of thin film wiring boards used in electric circuit boards, packages for storing semiconductor elements, etc. is M.

It is formed using a thick film forming technique such as the Mn method.

This Mo-Mn method involves adding an organic material and a solvent to a metal powder made of a high-melting point metal such as tungsten (W) or molybdenum-manganese (Mo-Mn), and then producing a metal paste in the form of a paste, either raw or sintered. This is a method in which a predetermined pattern of circuit wiring is coated on the outer surface of a ceramic body by screen printing, and then this is fired in a reducing atmosphere to sinter and integrate the high melting point metal and the ceramic body.

However, when circuit wiring is formed using this Mo-Mn method, it is difficult to miniaturize the circuit wiring because the circuit wiring is formed by screen printing a metal paste, and the high density of the circuit wiring is difficult to achieve. It had the disadvantage of not being able to be converted into

Therefore, in order to eliminate the above-mentioned drawbacks, instead of forming the circuit wiring using the conventional thick film forming technique, a thin film wiring board is formed using a thin film forming technique that allows for miniaturization.In other words, a titanium (Ti) ), chromium (Cr), nickel-chromium alloy (Ni-Cr), etc., and gold (
A main conductor layer consisting of Au) is sequentially deposited using a thin film forming technique such as an ion blasting method, a sputter link method, a plating method, or an evaporation method, and then these layers are formed into a predetermined pattern by photolithography. However, a thin film wiring board with circuit wiring has been proposed.

However, since the thin film wiring board formed using this thin film formation technique is a metal that easily interdiffuses with titanium, chromium, nickel-chromium alloy and gold, it is difficult to solder electronic components such as resistors and capacitors to the circuit wiring. When bonding and electrically connecting through a brazing material, the heat to melt the brazing material (approximately 2
When a temperature of 30 to 450°C is applied to the circuit wiring, it diffuses into the main conductor layer made of titanium, chromium, nickel-chromium alloy, or gold as an adhesive layer constituting the circuit wiring, and as a result, the ceramic substrate Another disadvantage is that the ceramic substrate comes into direct contact with the gold, which has poor adhesion, and the bonding strength of the circuit wiring to the ceramic substrate decreases, resulting in a significant deterioration of reliability as a thin film wiring substrate. had.

Another drawback is that titanium, chromium, nickel-chromium alloy, etc. used as an adhesive layer diffuse into the main conductor layer made of gold, resulting in extremely high conduction resistance of the circuit wiring.

(Object of the Invention) In view of the above-mentioned drawbacks, the present inventor has conducted various experiments and discovered that nickel, palladium, rhodium, platinum, etc. When a barrier layer made of at least one of nickel, palladium, etc. is interposed, interdiffusion between the barrier layer or adhesive layer and the main conductor layer is effectively prevented, and the circuit wiring is firmly bonded to the ceramic substrate. We found that it is possible to

Based on the above findings, the present invention lowers the conduction resistance of the circuit wiring, strengthens the adhesion between the circuit wiring and the ceramic substrate, and connects electronic components such as resistors and capacitors to the circuit wiring through brazing material such as solder. The object of the present invention is to provide a highly reliable thin film wiring board that can be firmly bonded by using a thin film wiring board.

(Means for Solving the Problems) The thin film wiring board of the present invention has an adhesive layer made of a nickel-chromium alloy and a barrier layer made of at least one of nickel, palladium, rhodium, and platinum formed on a ceramic substrate by thin film formation technology. The present invention is characterized in that a circuit wiring having a three-layer structure in which main conductor layers made of gold are sequentially laminated is formed.

(Example) Next, the thin film wiring board of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a cross-sectional view showing one embodiment of the thin film wiring board of the present invention, where 1 is a ceramic substrate and 2 is a circuit wiring.

The ceramic substrate 1 is made of aluminum oxide sintered body, mullite sintered body, aluminum nitride sintered body, barium titanate porcelain, lead zirconate titanate porcelain, etc.
When the ceramic substrate 1 is made of, for example, an aluminum oxide sintered body, a suitable organic solvent or solvent is added to and mixed with a raw material powder such as alumina, magnesia, or calcia to form a slurry, which is then subjected to a doctor blade method. A ceramic green sheet (ceramic raw sheet) is formed by employing the ceramic green sheet, and then the ceramic green sheet is punched in an appropriate manner, formed into a predetermined shape, and fired at a high temperature (about 1600°C). Ru.

Further, a circuit wiring 2 is formed on the upper surface of the ceramic substrate 1 by a thin film forming technique, and the circuit wiring 2 has a three-layer structure of an adhesive layer 3, a barrier layer 4, and a main conductor layer 5. ing.

The adhesive layer 3 of the circuit wiring 2 is made of a nickel-chromium alloy, and is deposited on the ceramic substrate l by a thin film forming technique such as vapor deposition, ion blasting, or sputtering.

The adhesive layer 3 serves to increase the bonding strength between the ceramic substrate l and the circuit wiring 2, and if its thickness is less than 500, it is difficult to firmly bond the circuit wiring 2 to the ceramic substrate l. In addition, if the number of people exceeds 5000, the bonding strength between the ceramic substrate 1 and the adhesive layer 3 tends to decrease due to internal stress when the adhesive layer 3 is deposited using a thin film formation technique. The number of people is preferably in the range of 1,000 to 3,000 people.

Further, a barrier layer 4 is layered on the upper surface of the connection layer 3, and the barrier layer 4 prevents mutual diffusion between the adhesive layer 3 and the main conductor layer 5, and also serves to separate the adhesive layer 3 and the main conductor layer 5. It works to make a strong bond.

The barrier layer 4 is made of nickel (Ni) and palladium (P).
d), rhodium (Rh), and platinum (Pt).
The adhesive layer 3 is formed of a seed and is deposited on the upper surface of the adhesive layer 3 by a thin film forming technique such as vapor deposition, ion blasting, or sputtering.

Note that if the thickness of the barrier layer 4 is less than 500 layers, mutual diffusion between the adhesive layer 3 and the main conductor layer 5 cannot be effectively prevented, and if the thickness exceeds 1000 layers, the barrier layer 4 tends to be Since the bonding strength between the adhesive layer 3 and the barrier layer 4 tends to decrease due to internal stress during layer deposition using a thin film forming technique, the number of participants is preferably in the range of 500 to 1,000 people, preferably 1,000 to 3,000 people. The range is good.

Further, a main conductor layer 5 is deposited on the upper surface of the barrier layer 4 by a thin film forming technique such as a vapor deposition method, an ion blating method, a sputtering method, or a plating method. It acts as.

The main conductor layer 5 is made of gold with very low conduction resistance,
If the thickness is less than 0.1 μm, the conduction resistance of the circuit wiring 2 tends to increase, making it unsuitable for use as a thin film wiring board. Therefore, it is preferable to set the thickness to 0.1 μm or more, taking into consideration the cost. Then, a range of 1.0 to 5.0 μm is suitable.

Next, a specific method for manufacturing the thin film wiring board of the present invention will be explained.

First, the ceramic substrate 1 is cleaned to remove dust and debris adhering to the outer surface of the ceramic substrate 1.

Next, nickel/chromium as an adhesive layer and nickel as a barrier layer are deposited on the ceramic substrate 1 by vapor deposition.
At least one of palladium, rhodium, and platinum and gold as a main conductor layer are sequentially deposited to a predetermined thickness.

Next, each of the adhesive layer, barrier layer, and main conductor layer is etched into a predetermined pattern by photolithography, and a circuit having a three-layer structure of the adhesive layer, barrier layer, and main conductor layer is formed on the ceramic substrate l. Wiring is deposited to form a thin film wiring board as a product.

When the thin film wiring board is used to bond electronic components such as resistors and capacitors to the circuit wiring 2 through a brazing material such as solder,
Since the barrier layer 4 is interposed between the adhesive layer 3 and the main conductor layer 5, heat for melting the brazing material is applied to the circuit wiring 2, and mutual diffusion occurs between the adhesive layer 3 and the main conductor layer 5. Even if such interdiffusion were to occur, the barrier layer 4 prevents such interdiffusion, thereby making the conduction resistance of the circuit wiring 2 extremely low, and strengthening the bonding strength of the circuit wiring 2 to the ceramic substrate l, resulting in extremely reliable thin film wiring. It becomes possible to use it as a substrate.

(Experimental Examples) Next, the effects of the present invention will be explained based on the following experimental examples.

(I) Preparation of sample A ceramic substrate made of an aluminum oxide sintered body is cleaned, and then an adhesive layer made of a nickel-chromium alloy (NiCr) with a thickness shown in Table 1 is placed on the top surface of the ceramic substrate, ), a barrier layer made of at least one of palladium (Pd), rhodium (Rh), and platinum (Pt) and a main conductor layer made of gold (Au) are sequentially deposited by an ion-blating method, and then photo-coated. It is processed into a dot shape of 1×1 mm by lithography and used as a circuit wiring sample.

Incidentally, sample number 183 is a comparative sample for comparison with the product of the present invention, and is a conventional sample in which a barrier layer is not layered between the adhesive layer and the main conductor layer.

(IF) Measurement of bonding strength The dot-shaped circuit wiring of each sample was heat treated at 420°C for 10 minutes.
After that, a tension fitting made of aluminum is bonded to the circuit wiring via epoxy resin, and then the tension fitting is pulled in a direction perpendicular to the circuit wiring to reduce the tensile force when the circuit wiring is peeled off from the ceramic substrate. This was evaluated as the bonding strength of the circuit wiring.

10- The above-mentioned bonding strength was measured for 20 pieces each, and the average value was calculated to evaluate the bonding strength.

The above results are shown in Table 1.

(Left below) As is clear from Table 1, conventional circuit wiring in which a main conductor layer made of gold is directly deposited on an adhesive layer made of a nickel-chromium alloy is not suitable for electronic devices such as resistors and capacitors on the circuit wiring. When parts are bonded using solder, etc., when heat is applied to the circuit wiring to melt the brazing material such as solder, mutual diffusion occurs between the adhesive layer and the main conductor layer, resulting in the bonding of the circuit wiring to the ceramic substrate. The strength decreased to 0.82K g/mm2 or less, and the reliability of the thin film wiring board was significantly deteriorated.

On the other hand, in the product of the present invention, a barrier layer made of at least one of nickel, palladium, rhodium, and platinum is interposed between the adhesive layer made of a nickel-chromium alloy and the main conductor layer made of gold. Mutual diffusion between the ceramic substrate and the main conductor layer is effectively prevented, and as a result, the bonding strength of the circuit wiring to the ceramic substrate can be increased to 2.28 K g/mm' or more, resulting in an extremely reliable thin film wiring board. .

(Effects of the Invention) As detailed above, according to the thin film wiring board of the present invention, the circuit wiring formed on the ceramic substrate is made of nickel.
Adhesive layer made of chromium alloy, nickel, palladium,
a barrier layer made of at least one of rhodium and platinum;
Because it has a three-layer structure with a main conductor layer made of gold, even if electronic components such as resistors and capacitors are bonded to the circuit wiring through a brazing material such as solder, the bonding strength of the circuit wiring to the ceramic substrate will decrease. There is no problem at all, and the bonding strength of the circuit wiring to the ceramic substrate is always strong, making it possible to create a highly reliable thin film wiring board.

At the same time, the conduction resistance of the circuit wiring can be made extremely low.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the thin film wiring board of the present invention. 1. Ceramic board 2. Circuit wiring 3. Adhesive layer
4. Barrier layer 5. Main conductor layer

Claims (1)

[Claims] It has a three-layer structure in which an adhesive layer made of a nickel-chromium alloy, a barrier layer made of at least one of nickel, palladium, rhodium, and platinum, and a main conductor layer made of gold are sequentially laminated on a ceramic substrate using a thin film formation technique. A thin film wiring board characterized by having circuit wiring formed thereon.