JP3615576B2 - Thin film wiring board - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a thin film wiring board, and more particularly to a thin film wiring board used for an electric circuit board having a high density of circuit wiring, a package for housing semiconductor elements, and the like.
[0002]
[Prior art]
Conventionally, wiring boards in electrical circuit boards, semiconductor element storage packages, and the like have been formed by thick film formation techniques such as the Mo-Mn method.
[0003]
In this Mo-Mn method, an organic solvent and a solvent are added to a metal powder composed of a refractory metal such as tungsten (W), molybdenum (Mo), manganese (Mn), etc. In this method, a predetermined pattern as circuit wiring is printed and applied to the outer surface of the sintered ceramic body by screen printing, and then fired in a reducing atmosphere to sinter and integrate the refractory metal and the ceramic body.
[0004]
However, when the circuit wiring is formed using this Mo-Mn method, the circuit wiring is formed by screen printing a metal paste, so that it is difficult to make the circuit wiring fine, and the circuit wiring has a high density. It had the disadvantage that it was not possible.
[0005]
Therefore, in order to eliminate the above-described drawbacks, tantalum nitride (on a thin film wiring substrate formed by using a thin film forming technique capable of miniaturization instead of forming a circuit wiring by a conventional thick film forming technique, that is, tantalum nitride ( An adhesive layer made of Ta ₂ N) or nickel-chromium alloy (NiCr), and an intermediate layer made of nickel-chromium alloy (NiCr), titanium-tungsten alloy (TiW), nickel (Ni), palladium (Pd), etc. The main conductor layers made of gold (Au) are sequentially laminated by thin film formation techniques such as ion plating, sputtering, vapor deposition, and plating, and then these layers are formed into a predetermined pattern by photolithography. There has been proposed a thin-film wiring board that is a circuit wiring.
In the thin film wiring board, the adhesive layer functions to firmly bond the circuit wiring to the insulating substrate, and the intermediate layer suppresses mutual diffusion of the adhesive layer and the main conductor layer and firmly fixes the main conductor layer to the adhesive layer. It works to adhere to.
[0006]
Further, if the thickness of the main conductor layer of the thin film wiring substrate is small, the conduction resistance of the circuit wiring increases, so that the thickness is 1.0 μm or more, preferably 4.0 μm or more. .
[0007]
[Problems to be solved by the invention]
However, the thin-film wiring board formed using this thin-film formation technique is such that the gold constituting the main conductor layer is easily absorbed by the solder (Pb-Sn), and the metal that is brittle by reacting with the solder (Pb-Sn). When an electronic component such as a semiconductor element or a capacitor is joined to the circuit wiring via solder and electrically connected to the circuit wiring, the gold thickness of the main conductor layer is less than 2.0 μm. A part of the main conductor layer is absorbed by the solder, resulting in an increase in the conduction resistance of the circuit wiring, and if it exceeds 2.0 μm, a large amount of fragile intermetallic compound is present at the connection between the circuit wiring and the electronic component. In other words, the reliability of the connection of the electronic component to the circuit wiring is low.
[0008]
OBJECT OF THE INVENTION
The present invention has been devised in view of the above-described drawbacks, and an object thereof is to provide a thin film wiring board capable of providing high density circuit wiring and capable of firmly electrically connecting electronic components to the circuit wiring.
[0009]
[Means for Solving the Problems]
The present invention has a three-layer structure in which an adhesive layer, an intermediate layer, and a main conductor layer are sequentially laminated on an insulating substrate by a thin film formation technique, and is formed by depositing circuit wiring to which electronic components are joined via solder. A thin-film wiring board, wherein the main conductor layer is a gold layer having a thickness of 4 μm or more, a nickel layer having a thickness of 0.4 μm to 5.0 μm, and a gold layer having a thickness of 0.05 μm to 2.0 μm on the surface of the circuit wiring. Are sequentially deposited.
[0010]
In the present invention, the adhesive layer is made of tantalum nitride or a nickel / chromium alloy, the intermediate layer is made of at least one of nickel / chromium alloy, titanium / tungsten alloy, nickel, palladium, and titanium, and the main conductor layer is made of gold or copper. It is characterized by doing.
[0011]
[Action]
According to the thin film wiring board of the present invention, a nickel layer having a thickness of 0.4 μm to 5.0 μm and a gold layer having a thickness of 0.05 μm to 2.0 μm are sequentially deposited on the surface of the circuit wiring. Even if an electronic component such as a semiconductor element or capacitor is joined to the circuit wiring through solder and electrically connected, the main conductor layer is absorbed by the solder and the conduction resistance increases. As a result, it is possible to increase the reliability of connection of electronic components to circuit wiring while maintaining a low conductive resistance of the circuit wiring. It becomes.
[0012]
Further, according to the thin film wiring substrate of the present invention, since the circuit wiring is formed by a thin film forming technique, the circuit wiring can be miniaturized and the circuit wiring can be densified.
[0013]
【Example】
Next, the thin film wiring board of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a sectional view showing an embodiment of a thin film wiring board according to the present invention, wherein 1 is an insulating substrate, and 2 is a circuit wiring.
[0014]
The insulating substrate 1 is made of an aluminum oxide sintered body, a mullite sintered body, a silicon carbide sintered body, an aluminum nitride sintered body, a glass ceramic sintered body, and the like. When it is composed of a knot, add a suitable organic solvent and solvent to the raw material powder such as alumina, magnesia, calcia, silica, etc. to make a slurry, and adopt the doctor blade method, calendar roll method, etc. A ceramic green sheet (ceramic green sheet) is formed by the above process, and then the ceramic green sheet is subjected to an appropriate punching process to obtain a predetermined shape and fired at a high temperature (about 1600 ° C.).
[0015]
A circuit wiring 2 is deposited on the upper surface of the insulating substrate 1 by a thin film formation technique, and the circuit wiring 2 has a three-layer structure of an adhesive layer 3, an intermediate layer 4, and a main conductor layer 5. ing.
[0016]
The adhesive layer 3 constituting the circuit wiring 2 is made of tantalum nitride (Ta ₂ N), nickel-chromium alloy (NiCr) or the like, and is deposited on the insulating substrate 1 by a thin film formation technique such as vapor deposition or ion plating. Is done.
[0017]
The adhesive layer 3 acts to increase the adhesive strength between the insulating substrate 1 and the circuit wiring 2. If the thickness is less than 100 angstroms, it is difficult to firmly bond the circuit wiring 2 to the insulating substrate 1. If the adhesive layer 3 exceeds 10,000 angstroms, the adhesive strength between the insulating substrate 1 and the adhesive layer 3 tends to decrease due to internal stress when the adhesive layer 3 is applied by the thin film formation technique. The thickness is preferably in the range of 300 to 2000 angstroms, and most preferably in the range of 500 to 1500 angstroms.
[0018]
Further, an intermediate layer 4 is deposited on the upper surface of the adhesive layer 3, and the intermediate layer 4 improves the adhesion between the adhesive layer 3 and the main conductor layer 5 and between the adhesive layer 3 and the main conductor layer 5. It works to prevent mutual diffusion.
[0019]
The intermediate layer 4 is made of nickel / chromium alloy (NiCr), titanium / tungsten alloy (TiW), nickel (Ni), palladium (Pd), titanium (Ti) or the like, and includes vapor deposition, ion plating, sputtering, and the like. The thin film is deposited on the upper surface of the adhesive layer 3 by the following thin film formation technique.
[0020]
If the thickness of the intermediate layer 4 is less than 500 angstroms, the adhesion between the adhesive layer 3 and the main conductor layer 5 is reduced and the mutual diffusion between the adhesive layer 3 and the main conductor layer 5 is effectively prevented. When the thickness exceeds 10,000 angstroms, the adhesive strength between the adhesive layer 3 and the intermediate layer 4 tends to decrease due to internal stress when the intermediate layer 4 is applied by the thin film formation technique. The range of angstroms is good, preferably 800 to 5000 angstroms, and most preferably 1000 to 3000 angstroms.
[0021]
A main conductor layer 5 is deposited on the upper surface of the intermediate layer 4 by a thin film forming technique such as a vapor deposition method, an ion plating method, a sputtering method or a plating method. Act as.
[0022]
The main conductor layer 5 is made of gold (Au) having a very low conduction resistance and has a thickness of 4 μm or more.
[0023]
The circuit wiring 2 formed on the insulating substrate 1 can be miniaturized because each of the adhesive layer 3, the intermediate layer 4 and the main conductor layer 5 constituting the circuit wiring 2 is formed by a thin film forming technique. As a result, the circuit wiring 2 can be densified.
[0024]
The circuit wiring 2 formed on the insulating substrate 1 by a thin film forming technique is further provided with a nickel layer 6 and a gold layer 7 sequentially deposited on the upper surface thereof.
[0025]
The nickel layer 6 firmly adheres the gold layer 7 to the circuit wiring 2 and when the electronic component is electrically connected to the circuit wiring 2 via solder, the solder absorbs the main conductor layer 5 of the circuit wiring 2. The solder and the main conductor layer 5 effectively prevent the formation of a brittle intermetallic compound.
[0026]
When the nickel layer 6 has a thickness of less than 0.4 μm, the adhesive strength between the circuit wiring 2 and the gold layer 7 decreases, and when the electronic component is electrically connected to the circuit wiring 2 via solder, When the solder absorbs the main conductor layer 5 of the circuit wiring 2 or a brittle intermetallic compound is formed between the solder and the main conductor layer 5, and the thickness exceeds 5.0 μm, the nickel layer 6 is formed on the circuit wiring 2. The circuit wiring 2 itself is peeled off from the insulating substrate 1 due to internal stress when depositing. Therefore, the thickness of the nickel layer 6 is specified in the range of 0.4 μm to 5.0 μm.
[0027]
The nickel layer 6 is deposited on the circuit wiring 2 to a predetermined thickness by, for example, nickel plating.
[0028]
Further, a gold layer 7 is deposited on the upper surface of the nickel layer 6, and the gold layer 7 strengthens the bonding strength when an electronic component is bonded to the circuit wiring 2 via solder and electrically connected thereto. By applying a plating method or the like on the upper surface of the nickel layer 6, it is deposited to a predetermined thickness.
[0029]
When the thickness of the gold layer 7 is less than 0.05 μm, when the electronic component is electrically connected to the circuit wiring 2 via solder, the bonding strength is weak, and when the thickness exceeds 2.0 μm, the gold layer 7 7 and a solder for connecting the electronic component, a large amount of fragile intermetallic compound is formed, and the reliability of the connection of the electronic component is deteriorated. Therefore, the thickness of the gold layer 7 is specified in the range of 0.05 μm to 2.0 μm.
[0030]
Thus, according to the thin film wiring board of the present invention, when electronic components such as semiconductor elements and capacitors are joined to the circuit wiring 2 on the insulating substrate 1 via solder, each electronic component is electrically connected via the circuit wiring 2. Will be.
[0031]
In the thin film wiring board of the present invention described above, the intermediate layer 4, the main conductor layer 5, the nickel layer 6, and the gold layer 7 in a partial region of the circuit wiring 2 are removed to form only the adhesive layer 3. The adhesive layer 3 acts as a resistor as an electronic component due to the high electric resistance value of tantalum nitride or nichrome constituting the adhesive layer 3. Therefore, when a resistor is connected to the circuit wiring 2, it is not necessary to separately prepare a resistor as an electronic component, but merely an intermediate layer 4, a main conductor layer 5, a nickel layer in a partial region of the circuit wiring 2. 6 and the gold layer 7 may be removed to form only the adhesive layer 3. In this case, the resistance value as the resistor is arbitrarily set according to the amount of removal of the intermediate layer 4, the main conductor layer 5, the nickel layer 6 and the gold layer 7 of the circuit wiring 2, that is, the size of the region of only the adhesive layer 3. Is done.
[0032]
【The invention's effect】
According to the thin film wiring board of the present invention, a nickel layer having a thickness of 0.4 μm to 5.0 μm and a gold layer having a thickness of 0.05 μm to 2.0 μm are sequentially deposited on the surface of the circuit wiring. Even if an electronic component such as a semiconductor element or capacitor is joined to the circuit wiring through solder and electrically connected, the main conductor layer is absorbed by the solder and the conduction resistance increases. As a result, it is possible to increase the reliability of connection of electronic components to circuit wiring while maintaining a low conductive resistance of the circuit wiring. It becomes.
[0033]
Further, according to the thin film wiring substrate of the present invention, since the circuit wiring is formed by a thin film forming technique, the circuit wiring can be miniaturized and the circuit wiring can be densified.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a thin film wiring board of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Insulating substrate 2 ... Circuit wiring 3 ... Adhesive layer 4 ... Intermediate layer 5 ... Main conductor layer 6 ... Nickel layer 7 ... Gold layer

Claims (4)

A thin-film wiring board having a three-layer structure in which an adhesive layer, an intermediate layer, and a main conductor layer are sequentially laminated on an insulating substrate by a thin-film forming technique, and a circuit wiring to which electronic components are joined via solder The main conductor layer is a gold layer having a thickness of 4 μm or more, a nickel layer having a thickness of 0.4 μm to 5.0 μm and a gold layer having a thickness of 0.05 μm to 2.0 μm on the surface of the circuit wiring. A thin film wiring board characterized by sequentially depositing layers. 2. The thin film wiring board according to claim 1, wherein the adhesive layer is made of tantalum nitride or nickel-chromium alloy. 2. The thin film wiring board according to claim 1, wherein the intermediate layer is made of at least one of nickel / chromium alloy, titanium / tungsten alloy, nickel, palladium, and titanium. 2. The thin film wiring board according to claim 1, wherein the main conductor layer is made of gold or copper.

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