JPH0918152A - Low temperature fired circuit board - Google Patents

Abstract

PURPOSE: To obtain an integrally low temperature fired circuit board having a surface wiring conductor excellent in practicality, e.g. solder wettability, in which bonding reliability is enhanced while suppressing warpaqe of board. CONSTITUTION: An Ag based conductor film, serving as a surface wiring conductor 2, is formed on an unfired board made of a glass-ceramic material and then the conductor film is fired integrally with the unfired board thus producing a low temperature fired circuit board. The Ag based surface wiring conductor contains 0.2-1wt.% of Cu2 O for the metallic component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Low temperature, eg 800-105, using ceramic material
The present invention relates to a low temperature fired circuit board that can be fired at 0 ° C., and particularly to a low temperature fired circuit board having a highly reliable surface wiring conductor.

[0002]

2. Description of the Related Art Conventionally, the baking temperature of a substrate is 800 to 1
Materials that can be fired at temperatures as low as 050 ° C. have been investigated. This is because, for example, in a multilayer circuit board, the internal wiring conductor and the via-hole conductor are made of a low resistance material such as Ag-based, Cu-based, or Au-based to speed up the circuit. Since low-resistance materials such as Ag-based, Cu-based, and Au-based materials have relatively low melting points, substrate materials that can be fired at a temperature below the melting point have been studied.

[0003] Such substrate materials are generally glass-ceramic materials such as cordierite, mullite, anorthite, serdian, spinel, garnite, willemite, dolomite, petalite, osumilite and substituted derivatives thereof. It consisted of a low melting point glass component capable of precipitating at least one of them, and at least one kind of ceramic material (inorganic filler) among cristobalite, quartz and corundum (α-alumina). In particular, the mixing ratio of such a glass-ceramic substrate was such that the ceramic material was 10 to 60 wt%, the low melting glass component was 90 to 40 wt%, and the low melting glass component was large.

In fact, in order to construct a circuit board using such a board material, it is necessary to form a surface wiring conductor on the surface of the circuit board. Further, in the manufacturing process, it has been considered to simplify the manufacturing method by sharing the firing process of the substrate and the firing process of the surface wiring conductor.

[0005] Examples of the surface wiring conductor integrally fired with the substrate include an Ag-based conductor and a Cu-based conductor. However, in order to connect an IC chip or the like to the surface wiring conductor by a wire bonding fine wire, the conductor is limited to the Ag-based conductor.

Conventionally, an Ag-based surface wiring conductor that is integrally fired with a substrate is, for example, about 99 wt% Ag-based metal powder in the metal component, about 1 wt% Pt-based metal powder in the metal component, borosilicate low-melting glass, A conductive film of a predetermined shape is screen-printed on an unbaked substrate (a single plate or a multilayer substrate having a wiring conductive film formed therein) using an Ag-based conductive paste in which an organic binder and an organic solvent are homogeneously mixed. And was fired at a peak temperature of 800 to 1050 ° C. integrally with the substrate in an oxidizing atmosphere and an air atmosphere.

In particular, the addition amount of the borosilicate low melting point glass contained in the surface wiring Ag-based conductive paste for forming the surface wiring conductor is, for example, 1.0 with respect to the metal component.
It is about wt%, and the addition amount of the borosilicate low melting point glass contained in the Ag conductive paste for surface wiring when it is baked on the baked substrate later (3.0 to 5.0 wt% with respect to the metal component). %), Which is very small compared to This is because when the surface wiring conductor is integrally fired with the substrate, the glass component of the substrate material greatly affects the surface wiring conductor during the firing process, and a large amount of glass component is deposited even on the surface of the substrate. Is.

As a circuit board in which the surface wiring conductor and the substrate are integrally formed as described above, a thick film resistor film or an insulating protective film is adhered and formed on the surface wiring conductor, and further, This has been achieved by connecting various electronic components and the like via solder.

[0009]

However, the initial strength of the surface wiring conductor formed as described above is 1.5 kgf / 2.
mm □ or more, for example, 3.3 kgf / 2 mm □, which is extremely strong, but has a temperature cycle (−40 ° C. to 125 ° C.).
The strength after the test is 1.0 kgf / 2 mm □
The following results, for example, when the electronic component is mounted and then used in a harsh environment, the joint reliability between the substrate and the surface wiring conductor becomes low.

This is A constituting an Ag-based surface wiring conductor.
Anchor effect between g particles and glass component of substrate material (A
A spike structure is formed at the interface between the g particles and the glass component of the substrate material, and they are strongly bonded to each other.) However, if the spike structure is fragile, the spike structure is destroyed when thermally severe conditions are applied. It is thought that it will end up.

The present invention has been devised in view of the above-mentioned problems, and an object thereof is excellent in solder wettability on the surface and temperature cycle (-40 ° C to 125 ° C, 30 minutes each).
It is intended to provide a low-temperature fired circuit board which has a surface wiring conductor having a sufficient adhesive strength even after the test and is excellent in practicality.

[0012]

According to the present invention, a conductor film made of a metal powder containing Ag as a main component, which is a surface wiring conductor, is formed on an unfired substrate made of a glass-ceramic material, and then the conductor film is formed. And a low-temperature fired circuit board obtained by integrally sintering a non-fired board, the surface wiring conductor,
It is to contain Cu ₂ O.

Preferably, the Cu ₂ O is contained in an amount of 0.2 to 1 wt% with respect to 10 wt% of the metal powder.

[0014]

According to the present invention, the surface wiring conductor is formed by printing and drying an Ag-based conductive paste on an unfired substrate made of glass-ceramic and integrally firing it. At this time, by adding Cu ₂ O to the Ag-based conductive paste, in particular, the anchor effect of the glass component of the substrate material on the Ag particles forming the Ag-based conductive paste is promoted. Cycle (-4
Even if a test is performed at 0 ° C. to 125 ° C. for 30 minutes each, deterioration of the adhesive strength can be prevented. It is possible to delay the shrinkage reaction that occurs during the firing of the Ag powder, which allows
The warp of the substrate can also be effectively prevented.

In particular, the amount of Cu ₂ O added is 0.2 to 1 w.
When set to t%, the temperature cycle (-40 ℃ ~ 125
Even after the test, the adhesive strength is 1.0K.
The low-temperature fired circuit board has an excellent gf / 2 mm □ and also has excellent solder wettability on the surface.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A low temperature firing circuit board of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a low temperature firing circuit board according to the present invention. In the examples, a multi-layer circuit board formed by laminating five glass-ceramic layers will be described as the board.

In FIG. 1, reference numeral 10 is a low temperature fired circuit board, 1 is a laminate having internal wiring conductors forming a predetermined circuit therein, 2 is a surface wiring conductor formed on the surface of the laminate 1, and 3 is a surface wiring conductor. Internal wiring conductors, 4 are via-hole conductors, 5 is a thick film resistance film, and 6 is various electronic parts.

The laminated body 1 comprises a glass-ceramic layer 1a.
An internal wiring conductor 3 for achieving a predetermined circuit network and generating a capacitance component is arranged between each of the layers 1e and the glass-ceramic layers 1a to 1e. Further, via-hole conductors 4 are formed in the glass-ceramic layers 1a to 1e so as to extend through the thickness direction of the layers.

The glass-ceramic layers 1a to 1e are made of a glass-ceramic material that can be fired at a relatively low temperature, for example, around 850 to 1050 ° C. Specific examples of the ceramic material include cristobalite, quartz, corundum (α-alumina), mullite, and cordierite. In addition, by firing a glass frit containing a plurality of metal oxides as a glass material, at least one kind of crystal of cordierite, mullite, anorthite, Celsian, spinel, garnite, willemite, dolomite, petalite or a substituted derivative thereof is obtained. Is deposited. This glass-ceramic layer 1a-1
The thickness of e is, for example, about 100 to 300 μm.

The internal wiring conductor 3 and the via-hole conductor 4 are A
The internal wiring conductor 3 has a thickness of about 8 to 15 μm, and the diameter of the via-hole conductor 4 can be set to an arbitrary value, for example, although it is made of a conductor such as g-based (Ag simple substance, Ag alloy such as Ag-Pd). The diameter is 80 to 250 μm.

Surface wiring conductors 2 are formed on both main surfaces of the laminate 1. The surface wiring conductor 2 is composed of an Ag-based (Ag simple substance, Ag alloy such as Ag-Pd) conductor containing a metal oxide Cu ₂ O.

The Ag-based conductor of the surface wiring conductor 2 is formed by firing at the same time as the firing of the laminate 1, and when the electronic component 6 is soldered onto the Ag-based surface wiring conductor 2. , Pt or the like is slightly added to the Ag-based conductor so that solder erosion does not occur in the Ag-based surface wiring conductor 2.

The surface wiring conductor 2 includes an input / output terminal portion and an electronic component mounting pad. If necessary, a thick film resistor film 5 and an insulating protective film are formed on the surface wiring conductor 2, and a chip-shaped capacitor and a chip-shaped capacitor. Various electronic components 6 such as resistors, transistors, and ICs are mounted by soldering, wire bonding, or the like.

A method of manufacturing the above low temperature firing circuit will be described.

The method for manufacturing the laminated ceramic circuit board 1 is as follows.
First, glass-ceramic layers 1a to 1e
A green sheet made of a ceramic material is formed. Specifically, a ceramic powder, a frit of a low-melting glass component, an organic binder, and a slurry obtained by homogeneously kneading an organic solvent are tape-formed to a predetermined thickness by a doctor blade method, and cut into a predetermined size to form a sheet. .

The ceramic powder is an insulating ceramic material such as cristobalite, quartz, corundum (α-alumina), mullite or cordierite, BaTiO ₃ , Pb ₄ F.
e ₂ Nb ₂ O _12, the dielectric ceramic material, such as TiO _2, Ni-Zn ferrite, (referred to ceramic in a broad sense) Mn-Zn ferrite Do to as magnetic ceramic material can be mentioned, its average particle size 1 0.0-6.0μ
m, preferably 1.5 to 4.0 μm. Note that two or more ceramic materials may be used in combination. In particular, the use of corundum is advantageous in terms of cost.

The low-melting-point glass component frit is subjected to firing treatment to precipitate crystals of cordierite, mullite, anorthite, sergian, spinel, garnite, willemite, dolomite, petalite or a derivative thereof or a spinel structure. Any material such as glass frit containing B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , ZnO, or an alkaline earth oxide can be used. Such a glass frit has a wide vitrification range and a yield point of about 600 to 800 ° C.
Suitable for firing at a low temperature of about 0 ° C, Ag-based internal wiring conductor 3, A
The sintering behavior with the conductor film serving as the g-based surface wiring conductor 2 is similar. The average particle size of the glass frit is 1.0
６6.0 μm, preferably 1.5-3.5 μm.

The composition ratio of the above-mentioned ceramic material and glass material is such that when firing at a relatively low temperature of 850 to 1050 ° C., the ceramic material is 10 to 60 wt%, preferably 30 to 50 wt%. Is 90-40
wt%, preferably 70 to 50 wt%.

It is necessary to give importance to the wettability of the organic binder with the solid content (ceramic powder, frit of a low melting point glass component), and the organic binder is thermally decomposable so that it can be burned out at a relatively low temperature and in a short firing process. An excellent one is preferable, and an ethylenically unsaturated compound having a carboxyl group or an alcoholic hydroxyl group such as an acrylic acid or methacrylic acid polymer is preferable.

As the solvent, an organic solvent or an aqueous solvent can be used. For example, in the case of an organic solvent, 2.
For example, 2.4-trimethyl-1.3-pentadiol monoisoventilate is used. In the case of an aqueous solvent, it must be water-soluble, and a hydrophilic functional group such as carboxyl is contained in the monomer and the binder. A group has been added.

The amount of addition is 2 to 300, preferably 5 to 100, when expressed as an acid value. If the added amount is small, the solubility in water, the dispersibility of the powder of the fixed component becomes poor,
When the amount is large, the thermal decomposability deteriorates. Therefore, the addition amount is appropriately added in the above range in consideration of solubility in water, dispersibility, and thermal decomposability.

Next, the via-hole conductor 4 of each layer is formed on each of the green sheets to be the glass-ceramic layers 1a to 1e.
A through hole having a predetermined diameter is formed by punching at the forming position.

Next, the conductor of the via-hole conductor 4 is printed and filled with Ag-based conductive paste in the through hole of the green sheet, and each internal wiring conductor 3 is formed on the green sheet to be the glass-ceramic layers 1b to 1e. A conductive film to be used is printed and dried.

Here, the Ag-based conductive paste for internal wiring is Ag-based (Ag simple substance, Ag alloy such as Ag-Pd).
A conductive powder, a predetermined amount of a borosilicate low-melting glass frit, an organic binder such as ethyl cellulose, and a solvent in which a solvent is homogeneously mixed are used as necessary.

On the green sheet which becomes the glass-ceramic layer 1a, a conductor film which becomes the surface wiring conductor 2 is printed by using Ag-based conductive paste for surface wiring, and dried.

Here, the Ag-based conductive paste for surface wiring is Ag-based (Ag simple substance, Ag alloy such as Ag-Pd).
Powder, Pt powder, a predetermined amount of Cu ₂ O powder, an organic binder, and a homogeneous mixture of a solvent are used. Cu ₂
A trace amount of metal oxide other than O may be contained.

In this way, the conductor that becomes the via-hole conductor 4,
The green sheet on which the conductor film serving as the internal wiring conductor 3 and the conductor film serving as the surface wiring conductor 2 are formed is laminated and integrated in accordance with the lamination order of the glass-ceramic layers 1 a to 1 e of the laminate 1.

Next, the unfired laminate is fired in an oxidizing atmosphere or an air atmosphere. The firing process includes a binder removal process and a sintering process.

In the binder removal process, the organic components contained in the green sheets to be the glass-ceramic layers 1a to 1e, the conductor film to be the internal wiring conductor 3, the conductor to be the via-hole conductor 4 and the conductor film to be the surface wiring conductor 2 will be described. It is for burning out, and is performed, for example, in a temperature range of 600 ° C. or lower.

In the sintering process, the glass component of the glass-ceramic green sheet is crystallized, and at the same time, it is uniformly dispersed in the grain boundaries of the ceramic powder to give the laminated body a certain strength to form the internal wiring conductor 3. A conductor film, a conductor to be the via-hole conductor 4, and a conductive material of the conductor film to be the surface wiring conductor 2, for example, Ag-based powder is grain-grown to reduce the resistance and be integrated with the glass-ceramic layers 1a to 1e. Is. This is done until a peak temperature of 850-1050 <0> C is reached.

As a result, a laminated body in which the surface wiring conductor 2 is formed is achieved, and thereafter, if necessary, a thick film resistance element 5 and an insulating protective film connected to the surface wiring conductor 2 are formed, and various electronic components are formed. The parts 6 are joined and mounted by soldering or the like.

As a result, a low temperature firing circuit board in which the surface wiring conductor 2 is fired integrally with the laminate 1 is achieved.

In the present invention, the surface wiring conductor 2 that is integrally fired with the laminate 1 is, for example, an Ag-based conductive paste for surface wiring.
m Ag powder, Pt powder with an average particle size of 0.5 μm, and Cu
It is formed by homogeneously mixing a metal oxide of ₂ O powder, an organic binder such as ethyl cellulose, and an organic solvent such as pentanediol isobrate.

Here, the Ag powder is a main conductive material that gives conductivity, and is added in a ratio of about 99 wt% in the metal component.

Here, the Pt powder is added to prevent the Ag component from being eaten by the solder when the electronic component 7 or the like is joined onto the surface wiring conductor 2 through the solder, and the Pt powder is contained in the metal component. , For example, about 1 wt.

The Cu ₂ O metal oxide powder further strengthens the spike structure of the anchor effect between the Ag-based powder and the glass component of the glass-ceramic material of the laminated body 1, for example. 0 for (Ag, Pt).
It is added in the range of 1 to 2 wt%.

As described above, Ag which becomes the surface wiring conductor 2
Since Cu ₂ O powder is added to the system conductive paste, the spike structure due to the anchor effect can be further promoted as described above. This allows the glass component of the glass-ceramic material to be stably adhered to the uneven surface of the Ag-based particles, whereby the anchor effect can be maintained and maintained for a long time, and the laminate 1 and the surface wiring can be maintained. The adhesive strength with the conductor 2 can be stabilized for a long time. Furthermore, since Cu ₂ O acts mainly on the interface between the laminate 1 and the surface wiring conductor 2,
Since it is less likely to be deposited on the surface of the surface wiring conductor 2,
The wettability of the solder is not hindered on the surface of the surface wiring conductor 2.

[Experimental Example] The inventor of the present invention has found that the surface wiring conductor 2 integrally fired with the laminated body 1 is made of Cu ₂ O.
The effect of was investigated.

As an Ag-based conductive paste for surface wiring,
The solid component pastes shown in Table 1 were prepared. The organic binder and organic solvent are omitted.

In forming the laminated body of the sample, the glass-ceramic material which is the substrate material is composed of the glass component capable of precipitating anorthite type crystals and the aluna powder.
Five green sheets with a thickness of 00 μm were prepared, and a conductive film having a predetermined pattern was formed on the lower green sheet of the laminated body with an Ag-based conductive paste for internal wiring. After forming conductive films of a predetermined shape with the Ag-based conductive paste for surface wiring shown in the drawing, lamination and pressure bonding were performed, and baking treatment was performed at 950 ° C. in the air atmosphere.

[Evaluation of Solder Wettability] After dipping the sample thus obtained in a rosin-based flux solution, 23
Immerse in a Sn-Pb eutectic solder bath containing 0% 2% Ag,
The solder wettability of the surface of the surface wiring conductor 2 was examined. Regarding the solder wettability, a solder having 90% or more of the total surface area on which solder was adhered was defined as "excellent", and a solder wettability thereof was defined as "poor".

[Evaluation of Adhesive Strength] A lead-plated conductive wire of 0.6 mmφ is soldered to the surface wiring conductor 2 having an adhesive strength of 2 mm □, and the adhesive strength in the initial state is −40 by the peel method.
The adhesive strength after a temperature cycle test (cycle) in which 100 cycles of 30 ° C. to 125 ° C. and 30 minutes each, respectively, was examined.

In the present invention, the initial state is 2.0 kgf / 2.
More than mm □, 1.0kgf / 2mm □ after cycle test
The above is a highly reliable surface conductor.

[Evaluation of Warp of Substrate] Further, the surface wiring conductor 2 having a size of 8.5 mm square was formed after firing, and the state of warpage of the laminate 1 was measured and the appearance of the laminate was discolored. The situation was measured.

In the present invention, a circuit board having a warp of more than 0.03 mm is considered to be inferior in practicality.

The results are also shown in Table 1.

[0057]

[Table 1]

As is clear from Table 1 above, by adding a predetermined amount of Cu ₂ O powder as a metal oxide to the Ag wiring type conductive paste for surface wiring (Samples 1 and 2),
The initial adhesive strength of 2.0 Kgf / 2 mm □ was achieved, and the adhesive strength was also 1.0 Kgf / 2 mm □ after the temperature cycle test (cycle) in which 100 cycles were performed at -40 ° C to 125 ° C for 30 minutes each. Above 1.5-1.6 Kgf
/ 2mm □ has been achieved.

That is, it can be seen that even when exposed to harsh conditions, a low-temperature fired circuit board having a high adhesive strength between the surface wiring conductor 2 and the laminated body 1 and stable for a long period of time can be achieved.

On the other hand, as the metal oxide, SiO
_{When 2} was added (Sample 4) and the usual borosilicate low melting point glass frit was added (Sample 5), the adhesive strength in the initial state was 2.6 Kgf / 2 mm □ and 3.
Although it shows a very high value of 3 Kgf / 2 mm □, it rapidly decreases to 0.7 Kgf / 2 mm □ after the temperature cycle test, and it cannot maintain a strong adhesive strength for a long period of time, and is laminated with the surface wiring conductor. This results in a low-temperature fired circuit board with low reliability of adhesion to the body.

Next, the amount of the metal oxide Cu ₂ O powder added to the Ag wiring conductive paste for surface wiring was examined.
As shown in, the addition amount is 1.5 wt% with respect to the metal component.
In that case, the warp of the substrate rapidly increases to 0.21 mm, and it cannot be practically used as a circuit substrate.

As shown in sample 6, when the added amount of Cu ₂ O was 0, the adhesive strength in the initial state was 2.6 Kgf / 2 mm □ and 3.3 Kgf, respectively, as in samples 4 and 5.
Although it shows a very high value of / 2 mm □, it drops sharply to 0.7 Kgf / 2 mm □ after the temperature cycle test, and it cannot maintain a strong adhesive strength for a long period of time, and the surface wiring conductor and the laminated body It becomes a low temperature firing circuit board having low adhesion reliability with, and the warp of the board is as large as 0.05 mm, so that it cannot be practically used as a circuit board.

From this, as shown in the second invention,
As the surface wiring conductor 2, it is important to add Cu ₂ O to the metal component, specifically 0.2 wt% or more, and the upper limit is less than 1.5 wt%, specifically, If the addition amount is 1.2 wt% or less, the solder wettability is excellent, the warp of the substrate is small, and the surface wiring conductor has high adhesive strength even under severe conditions such as initial conditions and cycle tests, It will be a low temperature firing circuit board with high adhesion reliability for a long time.

In the above embodiment, the substrate is
Although the description has been given of the laminated circuit board in which the plurality of glass-ceramic layers 1a to 1e are laminated and the internal wiring conductor 3 is provided therebetween, a single plate made of an unfired glass-ceramic material may be used.

Further, although the method of forming the laminated body has been described by the method of laminating the green sheets, the laminated body may be formed by a printing multilayer in which the paste of the glass-ceramic material is sequentially printed. A method of forming a laminated body including a method of adding a photocurable monomer to a slip-up material made of, and forming a through hole to be a via-hole conductor by exposure and development may be used. In the case of a low-temperature fired circuit board in which a conductor film to be a surface wiring conductor is formed on the surface of (1) by using an Ag-based conductive paste for surface wiring and then fired at the same time as the board (laminated body), The structure and forming method of the body can be arbitrarily changed.

The above-mentioned Ag-based conductive paste for surface wiring may be the one to which a small amount of pt powder has been added as described above, the main component of which is Ag-based (Ag simple substance or Ag alloy). The above-mentioned Ag powder may be used as the Ag-based material, and Ag-P may be used.
Like the d alloy, it may be an Ag-based alloy powder.

Further, Cu ₂ O was added as a metal oxide to a metal material containing an Ag-based material as a main component, but the solder wettability of the surface wiring conductor 2 was not impaired.
Minor amounts of other metal oxides may be included.

[0068]

As described above, according to the present invention, the surface wiring conductor is printed and dried on the unfired substrate made of glass-ceramic by using the Ag-based conductive paste containing Cu ₂ O. Is a low temperature firing circuit board formed by integrally firing.

As described above, Cu is added to the Ag-based surface wiring conductor.
By containing ₂ O, the anchor effect from the glass component of the substrate material to the Ag particles of the surface wiring conductor is promoted, and stable and strong adhesive strength can be maintained for a long period of time.
It becomes a low temperature firing circuit board with excellent adhesion reliability. Further, the warp of the substrate can be effectively prevented, and the low temperature firing circuit substrate is excellent in practicality.

The amount of Cu ₂ O added is 0.2 to 1 wt.
When set to%, in addition to the adhesion reliability and the warpage of the board, the low temperature firing circuit board has excellent solder wettability on the surface.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a low temperature firing circuit board according to the present invention.

[Explanation of symbols]

 10-Layered ceramic circuit board 1-Layered body 1a to 1e-Ceramic layer 3-Internal wiring conductor 4-Via-hole conductor 2 ... Surface wiring conductor

Claims (2)

[Claims] 1. A non-fired substrate made of a glass-ceramic material is formed with a conductor film made of a metal powder containing Ag as a main component, which is a surface wiring conductor, and then the conductor film and the non-fired substrate are integrally formed. A low-temperature fired circuit board obtained by sintering to, wherein the surface wiring conductor contains Cu ₂ O. 2. The low temperature firing circuit board according to claim 1, wherein Cu ₂ O of the surface wiring conductor is contained in an amount of 0.2 to 1 wt% with respect to 100 wt% of the metal powder.