JP3287285B2 - Manufacturing method of glass ceramic wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a glass-ceramic wiring board, and more particularly, to a method of manufacturing a glass-ceramic wiring board having a fine wiring pattern and capable of forming a surface wiring having high adhesion strength. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, a general method of forming a wiring pattern on a substrate is a screen printing method using a metal paste (conductor paste). The wiring width and the wiring interval of the wiring pattern formed by the screen printing method are limited to about 60 μm, and further miniaturization of the wiring pattern by this method is practically impossible.

[0003] Vapor deposition and sputtering are known as methods for forming fine wiring, but these methods have a problem in terms of cost because the process is complicated and equipment costs are high. From such a background, a technique of forming a fine wiring pattern, which cannot be formed by the screen printing method, by using a photolithography technique has attracted attention.

Japanese Patent Application Laid-Open No. 5-315754 discloses that a copper paste screen is printed on the surface of a low-temperature fired ceramic multilayer wiring board having an Ag-based internal conductor (eg, a glass ceramic multilayer wiring board), and the Cu paste is printed at 600 to 750 ° C. After baking, a method of forming a surface Cu wiring by patterning the obtained Cu layer using a photolithography technique is disclosed. It is described that according to this method, it is possible to form a surface wiring having a wiring interval of up to about 30 μm on a ceramic substrate.

However, according to this method, a conductor layer (Cu) necessary for forming a Cu wiring by photolithography after firing is used.
Since a corrosive aqueous solution such as an alkaline or acidic solution is used for etching the layer and removing the resist, there is a problem in that the joint between the surface wiring and the substrate is eroded from the surroundings, and the adhesion strength of the surface wiring is reduced. Also, with this method,
Since Ag is used for internal wiring and Cu for surface wiring,
An Ag-Cu intermetallic compound is generated, and the adhesive strength is reduced even inside the wiring joint.

[0006]

SUMMARY OF THE INVENTION The present invention provides a method for manufacturing a glass-ceramic wiring substrate, which can form a fine wiring pattern and a surface wiring having high adhesion strength, which cannot be formed by screen printing. Is the subject.

[0007]

Means for Solving the Problems The present inventors disclosed in Japanese Patent Laid-Open No.
In the method of forming fine surface wiring on a glass ceramic wiring substrate by a method combining screen printing and photolithography technology as described in -315754, a metal paste containing glass powder is used during screen printing Then, the metal layer generated by firing is patterned using photolithography technology and the like, and after forming a surface wiring, firing is performed again to diffuse the glass components in the surface wiring and the substrate to each other. It has been found that a decrease in adhesion strength can be prevented and the above problem can be solved.

Here, the present invention relates to a method for manufacturing a glass-ceramic wiring substrate having a surface wiring, comprising: (1) applying or printing a metal paste containing glass powder on a glass-ceramic substrate; Form a metal layer on the substrate by pre-firing at a temperature of ℃ or more, (3) pattern this metal layer, and (4) perform a main firing at a temperature of 600 ℃ or more to adhere to the substrate
This method comprises a step of obtaining a glass-ceramic multilayer wiring board on which a surface wiring having a strength of 2 kgf / 2 mm square or more is formed.

The patterning of the metal layer in the above step (4) can be performed by a method utilizing photolithography or a laser processing method. A pattern formed by photolithography generally comprises the following steps.

(A) forming a photoresist layer on the metal layer, (b) exposing the photoresist layer through a photomask having a pattern shape corresponding to the surface wiring, and (c) exposing the photoresist layer After development, (d) the metal layer exposed at the portion where the photoresist layer has been removed by the development is removed by etching, and (e) the photoresist layer remaining on the metal layer is removed.

In a preferred embodiment, the glass ceramic substrate is a multilayer wiring board having internal wiring, the metal of the internal wiring and the metal in the metal paste are both Cu, Perform at temperatures of ~ 1000 ° C. In this case, the main firing temperature is more preferably 850 to 1000 ° C.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a process chart in the case of performing patterning of a metal layer using photolithography technology in the method of the present invention.

As shown in FIG. 1, a glass paste containing glass powder is first applied or printed on a glass-ceramic multilayer wiring board 10 having internal wirings 12 (internal wirings also include vias) and then pre-baked. Then, a metal layer 14 containing glass powder is formed on the substrate 10 [FIG. 1 (a), step (1),
(2)].

The substrate on which the surface wiring is formed in accordance with the present invention may be a single-layer glass-ceramic substrate having no internal wiring. In this case, the substrate has only through-holes, and Is filled or coated with a conductive metal. The structure, material, and the like of the glass-ceramic multilayer wiring board having the internal wiring used in the present invention are not particularly limited.

As glass components of the glass ceramic material, in addition to amorphous glass such as borosilicate glass which contains SiO ₂ and B ₂ O ₃ as main components and hardly crystallizes during firing, cordierite glass Glasses that partially crystallize during firing, such as anorthite glass, can also be used. The ceramic component of the glass-ceramic material is usually alumina, but is not limited thereto. Mullite, aluminum nitride, silicon carbide,
Other ceramic materials, such as quartz or other silicon oxide crystals, can be used in addition to or in place of alumina.

The metal material of the internal wiring is not particularly limited either, but metal species generally used for low-temperature fired substrates such as glass ceramics, for example, Cu, Pd, Ag, A
Precious metals such as u and Pt and their alloys (eg, Ag / Pd, Ag
/ Pt) is preferable, and as described later, it is particularly preferable that the metal is the same as the surface wiring or does not form an intermetallic compound therewith.

Although there is no particular limitation on the method of manufacturing the glass ceramic multilayer wiring board having internal wiring, it is usually manufactured by a green sheet multilayer laminating method. However,
The glass ceramic multilayer wiring board can be manufactured by other methods such as a thick film multilayer printing method. In any case, before forming the surface wiring according to the method of the present invention, the substrate and the internal wiring are fired. As previously mentioned,
The substrate may be a single-layer glass-ceramic substrate having through-holes, in which case, the firing and metal coating (eg, plating) or filling of the through-holes has been completed.

For example, in the green sheet multilayer laminating method,
The screen-printed surface wiring can be fired at the same time as the green sheet of the substrate, but the method of the present invention utilizes photolithography technology when forming the surface wiring to perform relatively severe chemical treatment such as etching. Is applied to the substrate, so that the laminated green sheet and the internal wiring are baked before forming the surface layer wiring so as to withstand such processing, and the state of the baked substrate (that is, the glass ceramic multilayer wiring substrate) Keep it. The firing temperature may be selected according to the material of the glass ceramic substrate and the internal wiring, but will usually be in the range of 850 to 1000 ° C. The firing atmosphere must be a non-oxidizing atmosphere (e.g., vacuum or inert gas atmosphere) to prevent oxidation of the wiring when the internal wiring is Cu, but in the case of noble metal Can be fired.

A surface wiring is formed on the surface (one or both surfaces) of the glass ceramic substrate according to the method of the present invention. First, a metal paste is applied or printed on a substrate according to a screen printing technique.

The metal paste to be used contains glass powder in addition to the metal powder to be the conductor. By the inclusion of the glass powder, high adhesion of the surface wiring is ensured in the final main firing as described later. The type of glass powder to be contained in the metal paste is not particularly limited, but is preferably one that is not easily eroded by a chemical for etching or resist removal used when forming wiring by photolithography. A metal paste containing glass powder is commercially available and may be used.

The metal species in the metal paste preferably does not form an intermetallic compound during firing with the metal used for the internal wiring. When the above-mentioned intermetallic compound is generated during firing, since the intermetallic compound is generally brittle, the strength of the joint of the surface wiring is significantly reduced, the adhesion of the surface wiring is reduced, and a crack is formed in the joint. In addition, there arises a problem that the conduction resistance increases. In order to surely prevent the generation of an intermetallic compound, the metal type of the internal wiring and the surface wiring may be the same. For example, if the surface wiring is to be made of Cu, the internal wiring is also made of Cu. However, when the surface wiring is made of a noble metal such as Ag, Ag / Pt, or Ag / Pd, the internal wiring may be made of another noble metal if the noble metal is used. A preferred metal type is Cu because of its cost and ease of removal by etching in a later step. Therefore, it is preferable to use Cu paste for forming both the internal wiring and the surface wiring.

The mixing ratio of the glass powder in the metal paste is such that the weight ratio of the metal to the glass is generally 99.5: 0.5 to 90:90.
A ratio falling within the range of 10 is preferred. The metal paste contains, in addition to the metal powder and the glass powder, an organic resin and an organic solvent which are usually used as a binder.

In the present invention, since the wiring pattern is formed by photolithography or laser processing, the printing of the metal paste on the glass ceramic substrate may be solid printing (that is, coating) on the entire surface, or the use of a conductive paste. In order to save the amount, a coarse wiring pattern corresponding to a target wiring pattern may be screen-printed. That is, the metal paste does not necessarily need to be screen-printed, but may be simply applied by a simple method such as a doctor blade method.

Preliminary baking is performed after application or printing of the metal paste containing glass powder to form a metal layer 14 containing glass powder on the glass ceramic substrate 10. The thickness of the metal layer substantially matches the thickness of the surface wiring. The preferred thickness is about 5 to 30 μm.

In the method of the present invention, the necessary adhesion strength is obtained by performing the main baking after the formation of the surface layer wiring pattern. Therefore, in the pre-baking, the adhesion strength between the metal layer and the substrate is reduced by the patterning step of the metal layer (photo (Lithography processing or laser processing). Such a measure of the adhesion strength is, for example, such that the adhesion strength between the metal layer and the substrate measured by the peel strength method is 1.0 kgf / 2 mm square or more. Naturally, the pre-baking temperature is not so high as to cause dripping of the metal paste on the substrate, deformation of the substrate, adhesion to the setter, and the like. If the temperature of the pre-baking is high, the adhesion strength becomes too high, and the metal diffuses to the substrate surface, so that it may be difficult to remove an unnecessary portion of the metal layer by etching in the photolithography process. In this sense, the lower the pre-firing temperature, the better, as long as the minimum necessary adhesion strength is secured.

The preferable pre-firing temperature depends on the type of metal in the metal paste, but in any case, it is preferable that the pre-firing temperature is not higher than the main firing temperature, that is, the same as or lower than the main firing temperature. . Metal paste
For Cu paste, the preferred pre-firing temperature is 600-1000
° C, more preferably from 600 to 900 ° C, particularly preferably from 650 to 750 ° C.

When the metal paste is a noble metal based paste such as Ag or Ag alloy, the preferable pre-baking temperature is 600 to
The temperature is 950 ° C, more preferably 600 to 750 ° C. If the pre-baking temperature is lower than 600 ° C., the yield point of the glass is not reached, so that it becomes difficult to secure the above minimum adhesion strength between the surface wiring and the substrate. If the pre-baking temperature exceeds 1000 ° C., substrate deformation or the like may occur.

As described above, the firing atmosphere is a non-oxidizing atmosphere in the case of the Cu paste, and the atmospheric atmosphere is sufficient in the case of the noble metal-based paste. Since only the surface metal paste is pre-fired, a short time of about 5 to 30 minutes is sufficient.

The metal layer 14 formed on the substrate 10 is patterned by a suitable means. This patterning can be performed using photolithography technology or laser processing, but other methods capable of patterning the metal layer may be employed. The patterning by the photolithography technique may be performed in the same manner as in the related art, but will be briefly described below with reference to FIG.

First, a photoresist layer 16 is formed on the metal layer 14 on the substrate 10 [FIG. 1 (b), step (3)]. The formation of the photoresist layer 16 is not particularly limited as long as the photoresist layer 16 that is in close contact with the metal layer 14 can be formed. For example, liquid photoresist (resist ink)
May be applied on the metal layer and the coating film dried to form a solid photoresist film. The solid photoresist film may be thermocompression-bonded to the metal layer. The photoresist layer may be positive or negative.

Thereafter, the photoresist layer 16 is exposed through a photomask having a pattern shape corresponding to the surface wiring, and then developed to form a concave portion 18 of the same fine wiring pattern as the surface wiring in the photoresist layer. [FIG. 1 (c), Steps (4) and (5)]. Exposure is usually performed with ultraviolet light.

The photomask is prepared according to whether the photoresist is a positive type or a negative type, and a developing solution is used in accordance with the photoresist. The developer is generally an acidic or alkaline aqueous solution. By development, the photoresist of the exposed part in the positive type and the photoresist of the non-exposed part in the negative type are removed,
In the concave portion 18 of the photoresist layer formed by removing the photoresist, the lower metal layer 14 is exposed.

Next, the metal layer in the exposed portion is removed by etching, and a recess 20 of the metal layer is formed so that the same fine wiring pattern as the surface wiring remains in the metal layer.
[FIG. 1 (d), step (6)]. This etching can be performed using an etching solution containing a component capable of solubilizing the metal by chemically reacting with the metal constituting the metal layer. For example, an etching solution suitable for removing Cu is a concentrated aqueous solution of ferric chloride (30 to 50% concentration), an aqueous solution of ammonium persulfate, an aqueous solution of cupric chloride, or chromic acid.
For example, a sulfuric acid mixture. Etching is performed so that the concentration of the etching solution, the temperature,
This is performed by setting an etching time and the like.

Thereafter, the photoresist layer remaining on the metal layer which has not been removed by the etching is removed by an appropriate method to obtain the glass ceramic substrate 10 having the surface wiring 22 [FIG. 1 (e)]. Step (7)].

When the photoresist layer is a positive type, the remaining photoresist layer is an unexposed portion, so that the entire surface is exposed to make the photoresist layer soluble in a developing solution, and then processed with a developing solution. This makes it possible to easily remove the remaining photoresist layer. This overall exposure may be performed before etching.

When the photoresist layer is a negative type, the remaining photoresist layer is an exposed portion and is insoluble in a developing solution. Therefore, a stronger solution is used, or plasma or heat is used. More severe removal means such as decomposition are generally required. In the case of thermal decomposition, it is necessary to set conditions so that the glass ceramics substrate and the wiring layer are not deteriorated by deformation or oxidation. A preferred method for removing the photoresist layer is plasma irradiation. Plasma such as oxygen can be used as the plasma. Since the plasma is at a very high temperature, the irradiation time can be very short, so that the influence on the glass ceramic substrate and the surface wiring is small.

As described above, when the metal layer 14 is patterned by the photolithography technique to form the surface wiring 22, the unnecessary removal of the metal layer by etching and, in some cases, the removal of the photoresist layer may be corrosive. Since the aqueous solution is used, the adhesion strength between the surface layer wiring and the substrate is inevitably reduced as compared with the same adhesion strength immediately after the preliminary firing.

Therefore, in the present invention, finally, in order to increase the adhesion strength between the surface wiring and the substrate, the glass ceramic substrate is finally fired [Step (8)]. As a result of the main baking, as shown in FIG. 2, the glass component remaining in the surface wiring (metal layer) and not eluted during the etching and the glass component contained in the glass ceramic substrate are mutually diffused. Therefore, the adhesion strength between the surface wiring and the substrate is significantly increased. That is, the fact that the metal paste used for forming the surface wiring contains glass powder effectively acts to improve the adhesion strength.

When the metal layer is patterned by laser processing, the adhesion between the surface layer wiring and the substrate hardly decreases due to the patterning, but also in this case, the adhesion is insufficient due to the preliminary firing alone. Because of this, the final baking improves the adhesion strength by mutual diffusion of the glass components.

The main firing temperature may be in the same temperature range as that of the preliminary firing, preferably at the same temperature as the preliminary firing or at a higher temperature, and particularly preferably, the main firing temperature is higher than the preliminary firing temperature. Unless the wiring metal is high enough to cause drooling, board deformation, or sticking to the setter, etc.
The higher the firing temperature, the better. When the surface wiring is made of Cu, the firing temperature is particularly preferably set to 850 to 1000 ° C. The firing atmosphere for the main firing is also selected according to the metal type of the surface wiring. The firing time is preferably, for example, about 10 to 120 minutes so that the above-mentioned diffusion occurs sufficiently.

However, as in the case of the glass ceramic multilayer wiring board described in JP-A-5-315754, the internal wiring is noble metal (eg, Ag or Ag / Pd) and the surface wiring is Cu.
If different from the above, it is preferable that both the preliminary firing and the main firing be performed at a relatively low temperature (for example, 750 ° C. or lower) at which generation of an intermetallic compound at the joint is suppressed. Even if the firing temperature is low, the final firing reduces the adhesion between the surface wiring and the substrate due to etching or the like to some extent, so that the adhesion is improved as compared with the method described in the above publication. Is done.

[0042]

[Example] Alumina and cordierite glass (Al ₂ O ₃
-MgO-SiO ₂ ) glass ceramic multilayer wiring board (internal wiring and vias both formed from Cu paste) formed by a green sheet method from a glass ceramic material containing a mixed powder of 50:50 by weight as a main component ( In a nitrogen atmosphere
(Baked at 950 ° C. for 30 minutes) to form a surface wiring according to the method of the present invention.

First, a commercially available Cu paste (manufactured by DuPont: QP-153) containing glass powder was applied to the entire surface of one surface of the glass ceramic substrate by screen printing.
Preliminary baking was performed at 700 to 900 ° C. for 10 minutes in a nitrogen atmosphere to form a glass powder-containing metal layer having a thickness of 10 μm.

Next, a negative type liquid photoresist (OMR-83, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied on the metal layer by a spin coater, and the film was formed in a hot air drying oven at 85 ° C. for 30 minutes. Drying was performed to form a photoresist layer. Thereafter, the photoresist layer was irradiated with ultraviolet rays through a photomask having a surface wiring negative pattern with a wiring width of 30 μm and a line interval of 30 μm (irradiation amount: 1000 mJ / cm ² ). Next, a developer for the above photoresist (OMR- manufactured by Tokyo Ohka Kogyo Co., Ltd.)
By developing with a developing solution SG), a concave portion corresponding to the surface wiring pattern was formed in the photoresist layer.

After the developed photoresist layer was dried at 145 ° C. for 30 minutes, a portion of the metal layer exposed in the concave portion of the photoresist layer was removed by etching with a 40 wt% aqueous solution of cupric chloride. This etching is performed at a temperature of about 25 ° C. for about 0.5 until the metal layer in this part is substantially completely removed.
Performed for ~ 10 minutes. Thereafter, the photoresist layer remaining on the remaining metal layer was removed by irradiating with oxygen plasma for 2 to 3 minutes to form a surface wiring pattern on the substrate. Finally, main firing was performed at 750 to 900 ° C. for 30 minutes in a nitrogen atmosphere to obtain a glass-ceramic multilayer wiring substrate having a surface wiring.

For comparison, the temperature of the preliminary firing or the main firing is as low as 500 ° C. (the firing time is the same), the case of not performing the main firing, the Cu paste used for forming the surface wiring contains glass powder. No paste (copper powder with average particle size of 1.2 μm
100 parts by weight, prepared by mixing an appropriate amount of 25 parts by weight of ethylcellulose and terpineol as a solvent) in the same manner as above, except that the surface layer wiring was formed on a glass ceramic multilayer wiring board. Formed.

The surface wirings on the glass-ceramic multilayer wiring substrates of the above Examples and Comparative Examples were observed with an optical microscope, and the shape of the surface wirings was evaluated based on the presence or absence of disconnection. When there was any disconnection, it was evaluated as x, and when there was no disconnection, it was evaluated as ○.

Separately, the same glass ceramic substrate as above
(However, a single-layer substrate having no internal wiring) was used to form a 2 mm square Cu pad for peel strength measurement by using the same Cu paste and performing a series of operations similar to the above. this
Parallel to the surface of the Cu pad (that is, parallel to the substrate surface),
A 0.6 mm diameter Sn-plated copper wire (TA wire, Sumitomo Electric) was joined by Pb-63Sn solder using a soldering iron having a tip temperature of 300 ° C. The copper wire was bent perpendicularly to the substrate at the edge of the Cu pad, and the edge was pulled upward to measure the peel strength of the Cu pad and the adhesion strength between the substrate and the surface wiring.

For reference, the adhesion strength between the substrate and the metal layer after the preliminary firing was also measured by the same method as above. Table 1 summarizes the above test results.

[0050]

[Table 1]

From Table 1, according to the method of the present invention, using a metal paste containing glass powder, pre-baking after screen printing to form a metal layer, and forming a surface wiring pattern on the metal layer by photolithography. Finally, when the final baking is performed, even if the wiring width is as fine as 30 μm, there is no shape defect (disconnection), and a surface wiring having a substrate-surface wiring adhesion strength as high as at least 2 kgf / 2 mm square or more can be formed. I understand. In particular, when the main firing temperature was as high as 900 ° C., the adhesion strength was remarkably improved to about twice as compared with when the firing temperature was 750 ° C.

On the other hand, if the pre-firing temperature is lower than 600 ° C., the pre-firing does not provide sufficient adhesion between the substrate and the metal layer to withstand the photolithography process, so that the wiring shape is broken and the adhesion strength is measured. It was impossible. On the other hand, even if the pre-baking was performed at 600 ° C. or higher, if the main firing was not performed or the main firing temperature was lower than 600 ° C., the wiring shape was good, but the adhesion strength between the substrate and the surface wiring was reduced by the pre-baking. It was lower than the adhesion strength at the time, and did not reach 1.5 kgf / 2 mm square. It is clear that when the adhesion strength is low, the reliability of the surface wiring greatly decreases. When the conductor paste did not contain glass powder, the adhesion strength after pre-firing was low, and after main firing, the adhesion strength was further reduced, making measurement impossible.

[0053]

As described above, according to the method of the present invention, a glass-ceramic multilayer wiring board having a surface wiring having a fine pattern having a wiring width and a line interval of about 30 μm and having high adhesion strength to a substrate is manufactured. It is possible to do.
Therefore, the method of the present invention contributes to downsizing and improving the reliability of the glass ceramic multilayer wiring board.

[Brief description of the drawings]

FIG. 1 shows a manufacturing process diagram of the method of the present invention.

FIG. 2 is an explanatory diagram showing mutual diffusion of glass particles in a main firing step.

[Explanation of symbols]

 10: Glass ceramic multilayer wiring board 12: Internal wiring 14: Metal layer 16: Photoresist layer 18: Depression of photoresist layer 20: Depression of metal layer 22: Surface wiring

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Ichiro Uchiyama 4-33 Kitahama, Chuo-ku, Osaka-shi Inside Sumitomo Metal Industries, Ltd. (56) References JP-A-6-204645 (JP, A) JP-A Sho 50-97865 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05K 3/46

Claims (3)

(57) [Claims] 1. A method for manufacturing a glass-ceramic wiring board having surface wiring, comprising: (1) applying or printing a metal paste containing glass powder on a glass-ceramic substrate; (3) This metal layer is patterned, and (4) Main firing is performed at a temperature of 600 ° C or more to adhere to the substrate.
Obtaining a glass-ceramic multilayer wiring board having a surface wiring having a strength of 2 kgf / 2 mm square or more . 2. The glass ceramic substrate is a multilayer wiring board having internal wiring, wherein the metal of the internal wiring and the metal in the metal paste are both Cu, and the pre-firing and main firing are performed at a temperature of 600 to 1000 ° C. The method according to claim 1, wherein the method is performed. 3. The method according to claim 2, wherein the main sintering temperature is 850 to 1000 ° C.