JP2006066658A - Manufacturing method of circuit substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit substrate with a penetrating conductor formed for conduction between upper and lower surfaces of an insulating substrate and high in connective reliability. <P>SOLUTION: A recess 3 is formed by applying blast process on one main surface of the insulating substrate 1 consisting of ceramics, then, base layers 4, 5 are formed on the inner surface of the recess 3, and, subsequently, the recess 3 is filled with a conductor 7 and thereafter both of the main surfaces of insulating substrate 1 are polished whereby the conductor 7 on the bottom 3b side of the recess 3 is exposed to form the penetrating conductor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a circuit board, and more particularly to a circuit board having a through conductor for conducting upper and lower surfaces and a method for manufacturing a multilayer circuit board.

  Along with the recent remarkable miniaturization and high-density mounting of electronic components, circuit boards on which electronic components are mounted are also required to have high performance. As the method, a method of reducing the size by miniaturizing a patterned circuit conductor, a method of multilayering the circuit conductor three-dimensionally, or the like is adopted.

  As a method of multilayering circuit conductors three-dimensionally, a method of laminating a plurality of circuit boards in which the upper and lower surfaces are electrically connected by penetrating conductors is adopted, and desired conduction between each layer is ensured. As a result, circuit design has been performed to cope with downsizing, high integration, and the like.

  A circuit board having such a three-dimensional high-density wiring is widely put into practical use in the field of printed wiring boards using a resin-made substrate having good workability, but a ceramic substrate having excellent insulation characteristics and heat dissipation characteristics ( There is also an increasing demand for alumina sintered bodies, aluminum nitride sintered bodies, silicon carbide sintered bodies, and the like. As a circuit board manufacturing method used in the multilayer circuit board manufacturing method using such a ceramic substrate, a so-called cofire method and a postfire method are known.

  The cofire method is a paste-like substance in which a through hole is drilled in a ceramic precursor before sintering called a ceramic green sheet (hereinafter also referred to as a green sheet), and then metal powder is dispersed in the organic binder in the through hole. (Hereinafter, also referred to as a metal paste), followed by degreasing and firing.

On the other hand, the post-fire method is a method of filling a ceramic paste in which a through hole is formed with a metal paste and refiring, and as a through hole forming method, a general-purpose method is used to drill a green sheet, A method of degreasing and firing, and a method of directly processing a ceramic sintered body using a drill are known. Further, a post-fire method using a laser method and a Cu plating method as described in Patent Document 1 is considered. In any method, after penetrating the ceramic precursor or the ceramic substrate, the through conductors for conduction on the upper and lower surfaces are formed.
JP 2003-218518 A

  However, according to the post-fire method as described in Patent Document 1, the conductor of the through hole is formed by drilling the ceramic precursor or the ceramic substrate and forming a conductive film on the surface of the inner wall of the formed through hole. In order to further reduce the electrical resistance of the through-hole, the conductor film formed as described above is further filled with a metal conductor using a plating method or the like, but the ceramic precursor or the ceramic substrate is perforated. Therefore, in the process of metal deposition from the conductor film of the plating method, metal deposition is only on the inner wall surface of the through hole, and metal deposition from the bottom is not performed. There is a problem that poor filling (dents, pinholes, voids, etc.) occurs due to variations in the metal deposition rate.

  The present invention has been completed in view of the problems of the prior art, and an object of the present invention is to provide a circuit board with high connection reliability in which through conductors for conducting the upper and lower surfaces of an insulating board are formed. is there.

  In the method of manufacturing a circuit board according to the present invention, a concave portion is formed by blasting one main surface of an insulating substrate made of ceramics, and then a base layer is formed on the inner surface of the concave portion, and then the concave portion is formed into a conductor. Then, both the main surfaces of the insulating substrate are polished to expose the conductor on the bottom surface side of the recess, thereby forming a through conductor.

  The method for manufacturing a circuit board according to the present invention is preferably characterized in that, in the manufacturing method, the underlayer is made of at least one of titanium, chromium, aluminum, molybdenum, tungsten, copper, and a nickel-chromium alloy. And

  The circuit board manufacturing method of the present invention is preferably characterized in that, in the above manufacturing method, the conductor is made of at least one of copper, silver, and titanium.

  The method for manufacturing a circuit board according to the present invention is preferably characterized in that, in the above manufacturing method, the conductor is formed on the base layer by a plating method and is filled in the recess.

  The method for manufacturing a circuit board according to the present invention is preferably characterized in that, in the above manufacturing method, the insulating substrate has an arithmetic average roughness Ra of the surface after polishing of both main surfaces of 0.3 μm or less.

  The circuit board manufacturing method of the present invention is preferably characterized in that a plurality of circuit boards manufactured by the above manufacturing method are stacked.

  According to the method for manufacturing a circuit board of the present invention, the insulating substrate is formed with a recess in the insulating substrate using a blasting method using blast, so that a blasting projection material is sprayed onto the insulating substrate. The insulation substrate is physically cut, the surface roughness of the inner wall of the recess is rough and uniform, and heat is not applied to the insulation substrate as in the laser method. Therefore, it is possible to supply a highly reliable circuit board having high adhesion strength between the inner wall surface of the recess and the base layer in close contact with the wall surface.

  Furthermore, according to the present invention, since the concave portion is processed by blasting after firing the ceramic green sheet, heat treatment at a high temperature is not applied at the time of processing the concave portion or after processing, thereby effectively preventing thermal contraction of the insulating substrate. In addition, a substrate on which fine through conductors are arranged in a complicated manner can be manufactured with high accuracy.

  According to the circuit board manufacturing method of the present invention, the underlayer is made of at least one of titanium, chromium, aluminum, molybdenum, tungsten, copper, and nickel-chromium alloy. Since high adhesion strength can be obtained between the base layer and the conductor, a highly reliable circuit board can be obtained.

  Further, according to the method for manufacturing a circuit board of the present invention, the conductor is made of at least one of copper, silver, and titanium, so that the thermal conductivity and electrical conductivity between the upper and lower surfaces of the insulating substrate are good. The circuit board can be electrically connected by a through conductor made of a simple conductor, and can easily and efficiently produce a circuit board having a low electrical resistance and an excellent heat drawing characteristic.

  In addition, according to the method for manufacturing a circuit board of the present invention, the conductor is formed on the underlayer by plating and filled in the concave portion, so that there is no subsequent thermal history. Cracks in the underlying layer and conductor due to impact do not occur, and high reliability can be obtained in the conduction resistance on the upper and lower surfaces.

  In addition, according to the circuit board manufacturing method of the present invention, the flatness of the circuit board surface is improved because the insulating board has an arithmetic average roughness Ra of 0.3 μm or less of the polished surfaces of both main surfaces. In addition, since the processing accuracy of photolithography is improved, highly accurate and fine wiring can be formed on the surface of the circuit board.

  In addition, according to the method for manufacturing a circuit board of the present invention, by laminating a plurality of circuit boards manufactured by the above-described manufacturing method of the present invention, there is no thermal shrinkage on the board, so that the position accuracy is not affected by the board shrinkage. A multilayer circuit board having excellent connection reliability can be obtained.

  A method of manufacturing a circuit board according to the present invention will be described in detail with reference to FIG.

1 (a) to 1 (g) are cross-sectional views of a circuit board for each step for explaining a representative example of an embodiment of a method for manufacturing a circuit board of the present invention. Is the insulating substrate, 2 is the dry film resist (primary), 3 is the recess, 3a is the depth of the recess, 3b is the size of the bottom of the recess, 4 is the first underlayer, 5 is the second underlayer, and 6 is the dry film resist. (Secondary), 7 is a conductor, 8 is a circuit board, 8a and 8b are opening dimensions of the circuit board 8.

  The manufacturing method of the circuit board 8 of the present invention is performed by the following steps.

First, an insulating substrate 1 as shown in the sectional view of FIG. Such an insulating substrate 1 is made of a ceramic insulating material such as an aluminum oxide (alumina: Al ₂ O ₃ ) sintered body or an aluminum nitride (AlN) sintered body. In the case of a composite, first, a suitable organic solvent or solvent is added to and mixed with raw material powders such as alumina (Al ₂ O ₃ ), silica (SiO ₂ ), calcia (CaO), and magnesia (MgO) to form a slurry. Then, this is formed into a sheet shape by a conventionally known doctor blade method, calendar roll method or the like to obtain a ceramic green sheet (hereinafter also referred to as a green sheet). Thereafter, the green sheet is punched into a predetermined shape, and a plurality of sheets are laminated as necessary, and the green sheet is fired at a temperature of about 1600 ° C. Thereafter, the main surface of the insulating substrate 1 may be polished as necessary.

  In particular, when an aluminum oxide sintered body or an aluminum nitride sintered body is used as the material of the insulating substrate 1, the thermal conductivity of these materials is as high as 40 W / m · K or higher, so that high heat dissipation. From the viewpoint of performance, it can be suitably used for a wiring board on which various semiconductor elements having a large calorific value such as LD (laser diode), LED (Light Emitting Diode), and high-speed CPU (Central Processing Unit) are mounted.

  Next, as shown in the cross-sectional view of FIG. 1 (b), a dry film resist (primary) 2 is attached to the surface of the insulating substrate 1 by thermocompression bonding and becomes a recess 3 of the insulating substrate 1 by a conventionally known photolithography method. The upper dry film resist (primary) 2 is opened.

  Next, as shown in the sectional view of FIG. 1C, a blast projection material such as SiC (for example, GP manufactured by Shinano Random Co., Ltd.) is formed from the surface of the dry film resist (primary) 2 opened in FIG. The concave portion 3 is formed by projecting # 320) and physically scraping the portion of the insulating substrate 1 where the dry film resist (primary) 2 is opened. At this time, the blast condition is adjusted, the recess depth 3a is managed, and the recess 3 holding the recess bottom surface dimension 3b is formed. The recess depth 3a is preferably about -0.1 mm of the substrate thickness, that is, the thickness of the insulating substrate 1 at the bottom of the recess is about 0.1 mm. Further, the dimensions of the recess 3 are preferably such that the opening is 100 to 500 μm, the depth is 300 to 650 μm, and the angle between the opening surface of the recess 3 and the side surface of the recess 3 is about 60 to 80 °. When deviating from this, it becomes difficult to completely fill the through hole in the subsequent step of filling the conductor 7 by electrolytic Cu plating, or a void is likely to be generated inside the conductor 7.

  Next, as shown in the sectional view of FIG. 1 (d), after removing the dry film resist (primary) 2 on the insulating substrate 1, the inner wall surface of the recess 3 and the insulating substrate 1 formed by using the blast method. An underlayer made of Ti, for example, is laminated on the surface by sputtering. This example shows an example in which a first underlayer 4 made of Ti, for example, and a second underlayer 5 made of Cu, for example, are sequentially deposited. The first underlayer 4 and the second underlayer 5 are used as an adhesion metal with the second underlayer 5 and a plating conductive film, respectively, and the thickness of the first underlayer 4 is preferably 0.05 to 0.15 μm. . If the thickness is less than this, the adhesion to the inner wall surface of the recess 3 is likely to be reduced, and if it is greater, Ti or the like as the first base layer 4 diffuses into the conductor 7 and the conduction resistance is likely to vary. .

  The thickness of the second underlayer 5 is preferably about 0.5 to 1.5 μm. If the thickness is less than this, the adhesiveness with the conductor 7 is likely to be lowered, and if it is greater, the thickness of the underlying layer on the surface of the insulating substrate 1 is increased, and hence the workability in the subsequent polishing step is likely to be lowered.

  Next, as shown in the sectional view of FIG. 1E, a dry film resist (secondary) 6 for plating is formed on the surface on which the first underlayer 4 and the second underlayer 5 are formed on the insulating substrate 1. Is attached by thermocompression bonding, and a dry film resist (secondary) 6 on the recess 3 of the insulating substrate 1 is opened by a conventionally known photolithography method.

  Next, as shown in the cross-sectional view of FIG. 1 (f), Cu plating or the like is applied to the recess 3 in which the first underlayer 4 and the second underlayer 5 are sequentially formed by electrolytic plating, and the conductor 7 is partially formed. Form. At this time, the plating is finished when the conductor 7 is completely buried in the recess 3.

  Next, as shown in the sectional view of FIG. 1 (g), after removing the dry film resist (secondary) 6 on the insulating substrate 1 to which the conductor 7 is applied in FIG. Then, polishing using a polishing method is performed to form the circuit board 8. At this time, the opening size 8a on the lower surface side of the insulating substrate 1 and the opening diameter 8b on the upper surface side of the insulating substrate 1 are managed. As a polishing procedure at that time, first, only the conductor 7 protruding convexly on the upper surface of the insulating substrate 1 is removed by rough polishing, and then the polishing is performed from the lower surface side of the insulating substrate 1 and the conductor 7 embedded in the concave portion 3 is then removed. Is exposed to the lower surface of the insulating substrate 1, and polishing is performed until the opening size of the exposed conductor 7 reaches a specified size, and further polishing is performed from the upper surface of the insulating substrate 1 to the specified thickness of the insulating substrate 1. Do.

  The circuit board 8 of the present invention can be obtained through the above steps. In the circuit board 8 of the present invention, a dry film resist (primary) 2 is attached to the insulating substrate 1 by thermocompression bonding, and the dry film resist (primary) on the portion that becomes the concave portion 3 of the insulating substrate 1 by a conventionally known photolithography method. ) 2 is opened, and the blast projection material is projected from the opened surface of the dry film resist (primary) 2, thereby controlling the depth 3 a of the substrate and forming the recess 3 that holds the size 3 b of the bottom of the recess. Then, the first underlayer 4 and the second underlayer 5 are formed on the inner wall surface, and further, a dry film resist (secondary) 6 is attached by thermocompression bonding, and the recess 3 of the insulating substrate 1 is formed by a conventionally well-known photolithography method. The upper dry film resist (secondary) 6 is opened, the conductor 7 is partially formed in the recess 3 by electrolytic plating, and the upper and lower surfaces of the insulating substrate 1 are polished to form the circuit board 8. Therefore, as compared with the post-fire method as described in Patent Document 1, the conductor 7 is deposited also from the bottom of the recess, so that the conductor 7 can be embedded in a short time, and the conductor 7 deposition time can be reduced. It is possible to provide a circuit board 8 that does not cause filling defects (dents, pinholes) due to variations or the like.

  In addition, when the recess 3 is drilled using blasting, the modified layer by laser (as the glass component is sintered by the influence of the laser heat source is very brittle and peeled off), as in the case of drilling using laser. There is no generation of an easy layer, and there is also an anchor effect, the adhesion strength between the conductor 7 and the insulating substrate 1 is increased, and a gap is generated at the interface between the inner wall of the recess 3 formed in the insulating substrate 1 and the conductive film. It is possible to provide the circuit board 8 that is not allowed to occur.

  Furthermore, because of the piercing process by blasting using the photolithography method, the circuit board 8 is provided that has extremely high positional accuracy of the through hole and has a low electrical resistance on the upper and lower surfaces because the conductor 7 is embedded in the Cu plating. can do.

  Examples of the circuit board manufacturing method of the present invention will be described below. First, a dry film resist (primary) 2 was attached to the surface of an insulating substrate 1 made of an aluminum oxide sintered body having a thickness of 500 μm, and an opening having a diameter of 300 μm for forming the recess 3 was formed.

  Next, a recess 3 having a depth of 400 μm was formed on the insulating substrate 1 by a blasting method using a blast projection material (GP # 320 manufactured by Shinano Random Co.).

  Then, after removing the dry film resist (primary) 2, the inner wall surface of the recess 3 and the surface of the insulating substrate 1 are made of the first underlayer 4 made of Ti having a thickness of 0.1 μm and the Cu having a thickness of 1.0 μm. The second underlayer 5 thus formed was sequentially formed by a sputtering method.

  Furthermore, a dry film resist (secondary) 6 was formed on the surface of the insulating substrate 1 excluding the recesses 3, Cu plating was performed in the recesses 3, and the conductors 7 were filled.

  Next, after removing the dry film resist (secondary) 6, the upper and lower surfaces of the insulating substrate 1 were polished. At this time, the arithmetic average roughness Ra of the surface of the insulating substrate 1 is set to various values of 0.02 μm to 0.50 μm, a thin circuit conductor is formed on the surface of the circuit substrate 8, and the adhesion of the circuit conductor Then, the presence or absence of resistance variation of the circuit conductor and the presence or absence of the residue of the dry film resist on the surface of the circuit board 8 were evaluated.

  Each evaluation method will be described below. The adhesion of the circuit conductor is such that NiCr alloy and Au are sequentially formed on the upper and lower surfaces of the circuit board 8 by vapor deposition, and a patterned circuit conductor is formed by a conventionally well-known photolithography method, followed by tape (manufactured by NITTO, cello tape , No. 29) was applied to the circuit conductor, and then the tape peel test was performed to peel off the tape. The case where the circuit conductor was not peeled off was evaluated as good (◯), and the case where the circuit conductor was peeled off was rated as poor (×).

  As for the resistance variation of the circuit conductor, a film of Ta is formed on the surface of the circuit board 8 by sputtering, a resistor as a part of the circuit conductor is formed by a well-known photolithography method, and the heat resistance is 5 minutes on the 420 ° C. heater block. Those having a subsequent resistance increase rate of 10% or less were evaluated as non-defective (◯), and those exceeding 10% were determined as defective (×).

The dry film resist residue on the surface of the circuit board 8 is applied to the entire surface of the circuit board 8 with an organic dry film resist, dried at 130 ° C. for 60 minutes, and then immersed in a phenolic solvent. Then, after removing the dry film resist, by a visual inspection using a stereomicroscope, if the dry film resist residue does not remain on the surface of the circuit board 8, it is a non-defective product (○), and if the dry film resist residue remains, it is defective ( X). These evaluation results are shown in Table 1.

  From the evaluation results, it was found that the surface roughness (Ra) was 0.3 μm or less.

  The present invention is not limited to the above-described embodiment and examples, and various modifications can be made without departing from the scope of the present invention.

It is sectional drawing of the circuit board for every process for demonstrating the manufacturing method of the circuit board of this invention.

Explanation of symbols

1: Insulating substrate 3: Concave parts 4 and 5: Underlayer 7: Conductor 8: Circuit board

Claims (6)

A concave surface is formed by blasting one main surface of an insulating substrate made of ceramics, then a base layer is formed on the inner surface of the concave portion, and then the concave portion is filled with a conductor, and then the insulating substrate is formed. A method of manufacturing a circuit board, comprising: forming a through conductor by polishing both main surfaces of the first and second surfaces to expose the conductor on the bottom surface side of the recess. 2. The method of manufacturing a circuit board according to claim 1, wherein the underlayer is made of at least one of titanium, chromium, aluminum, molybdenum, tungsten, copper, and nickel-chromium alloy. 3. The circuit board manufacturing method according to claim 1, wherein the conductor is made of at least one of copper, silver, and titanium. 4. The method for manufacturing a circuit board according to claim 1, wherein the conductor is formed on the base layer by a plating method and is filled in the recess. 5. The method of manufacturing a circuit board according to claim 1, wherein the insulating substrate has an arithmetic average roughness Ra of 0.3 μm or less of the polished surfaces of both main surfaces. A method for manufacturing a laminated circuit board, comprising stacking a plurality of circuit boards manufactured by the manufacturing method according to claim 1.

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