JP4471730B2 - Double-sided wiring board and manufacturing method thereof - Google Patents

Description

  The present invention is a double-sided wiring board in which wiring layers provided on both sides (front and back surfaces) of the board are connectable by through wirings that pass through both sides of the board, and in particular, the inside of fine through holes. The present invention relates to a double-sided wiring board and a method of manufacturing the same.

  For example, in the technical fields such as electronic devices and optical devices applying recent MEMS (micro electro mechanical system) technology, miniaturization and high functionality have been promoted. There is a demand for miniaturization and high density of the wiring pattern of the double-sided wiring board. In this double-sided wiring board, wiring layers provided on both sides (front and back surfaces) of the board are connectable by through wirings that are wired through both sides of the board. As the through wiring, a fine through hole is formed in a substrate, and a conductor is formed in the inside to form a conductive connection between the wiring layers on both sides. In order to realize a finer and higher density wiring pattern on the double-sided wiring board, it is essential to refine the through wiring in which a conductor is formed in the through hole. That is, it is essential to reduce the diameter of the through hole. Further, for example, in the case of providing a double-sided wiring board of this type that requires airtightness such as a microswitch, high heat resistance for sealing and bonding is also required.

Here, conventionally, the following methods are known as methods for obtaining a through wiring in which a conductor is formed inside a through hole penetrating both surfaces (front and back surfaces) of a double-sided wiring board and the wiring layers on both surfaces can be connected to each other. It has been.
(1) A method of filling a resin in a through hole after forming a conductor layer on the side wall of the through hole by a plating method (see Patent Document 1).
(2) A method of filling the through hole with a metal material by a plating method (see Patent Document 2).
(3) A method of sucking and filling molten metal using differential pressure into a through hole (see Patent Document 3).
JP 2001-44639 A JP-A-11-177200 JP 2003-133410 A

However, when the through-holes are filled with resin, the heat resistance and airtightness of the double-sided wiring board are problematic because the resin has low heat resistance and the resin has high gas permeability. In addition, the method of filling the through hole with a metal using a plating method is not problematic in terms of heat resistance and air tightness, but it is difficult to suppress the generation of voids in the through hole, and the inside of the voids. In this case, the plating solution remains, which impairs the reliability of the double-sided wiring board. This problem is particularly apparent in the case of through holes with a high aspect ratio. Furthermore, the method of sucking and filling the molten metal into the through-hole is limited to a metal having a relatively low melting point from the viewpoint of workability and the like, so the heat resistance as a double-sided wiring board becomes a problem.
The present invention has been made under the above-mentioned background, and can be used for miniaturization of a double-sided wiring board, has excellent heat resistance, airtightness and reliability, and has high mass productivity. The object is to provide a manufacturing method.

As a means for solving the above-mentioned problem, the first means is:
A board, a wiring layer provided on both sides of the board, a through-hole penetrating both sides of the board, and a conductive material filled in the through-hole to electrically connect the wiring layers on both sides A double-sided wiring board, wherein the conductive material has an average composition of Cu _x Sn _y M _{100- (x + y)} .
However, x and y are weight fractions of 100, 30 ≦ x ≦ 99, and 1 ≦ y ≦ 70, and M is at least one metal selected from Au, Ag, and Ni.

The second means is
The Cu concentration of the conductive material is not uniform in the radial direction of the through hole, and decreases from the vicinity of the side wall portion of the through hole toward the vicinity of the center line of the through hole. It is the double-sided wiring board concerning a means.

The third means is
The Cu concentration of the conductive material is not uniform in the radial direction of the through hole, is maximum near the side wall portion of the through hole, and is minimum near the center line of the through hole. This is a double-sided wiring board according to the first or second means.

The fourth means is
A method for manufacturing a double-sided wiring board, comprising: a conductive part forming step for electrically connecting wiring layers formed on both sides of the substrate by filling a through hole penetrating both sides of the substrate with a conductive material. And
The conductive portion forming step includes a first step of attaching Cu or an alloy containing Cu to the side wall portion of the through hole, leaving a void portion communicating with both surfaces of the substrate at the center portion of the through hole,
A second step of attaching Sn or an alloy containing Sn to the surface of Cu or an alloy containing Cu attached to the side wall portion of the through hole and filling the void portion;
A third step in which the Cu or Cu-containing alloy deposited in the first step and the Sn or Sn-containing alloy deposited / filled in the second step are formed into a diffusion alloy with each other by heat treatment; It is a manufacturing method of the double-sided wiring board characterized by having.

The fifth means is
The method for producing a double-sided wiring board according to the fourth means, wherein the first step is a step of attaching Cu or an alloy containing Cu to the side wall portion of the through hole by a plating method.

The sixth means is
In the second step, the substrate obtained through the first step is brought into contact with the molten metal obtained by heating and melting Sn or an alloy containing Sn, and the void portion is filled with the alloy containing Sn or Sn by capillary action. It is a manufacturing method of the double-sided wiring board concerning the 4th or 5th means characterized by the above-mentioned.

The seventh means is
Controlling the average Cu concentration in the CuSn alloy filled in the through-hole or an alloy containing at least Cu and Sn by the volume of Cu or the alloy containing Cu deposited in the first step. A method for manufacturing a double-sided wiring board according to any one of the fourth to sixth features.

  In the above-described means, the “average composition of the conductive material” means a value obtained by averaging the composition value of each part of the conductive material over the entire through hole. If the composition of the conductive material is uniform inside the through hole, the composition of any part is the same, so it is sufficient to simply use the concept of “composition”, but the composition of the conductive material depends on the location inside the through hole. Are different from each other, the concept of “average composition” is used to represent the composition of the entire through-hole.

By setting the average composition of the conductive material filled in the through holes to the above composition by the first to third means described above, sufficient heat resistance is ensured, and from the physical and mechanical properties of the material. The confidentiality and reliability of the double-sided wiring board can be made sufficient. That is, by using the alloy having the above composition, heat resistance and airtightness do not become a problem as compared with the case where the through hole is filled with a resin or a low melting point metal. Furthermore, since the alloy having the above composition can be easily formed in the through hole with a high yield, it is excellent in mass productivity. Further, if the composition distribution is provided as in the second and third means, the vicinity of the through hole center line is a low melting point alloy within a range having sufficient heat resistance and the vicinity of the side wall of the through hole. Is filled with a high melting point alloy. Generally, in a metal material, there is a correlation between the melting point and the rigidity, and the low melting point metal tends to have a lower rigidity than the high melting point metal. Thus, the vicinity of the through hole center line is filled with an alloy having a low melting point and a low rigidity, and the vicinity of the side wall of the through hole is filled with an alloy having a high melting point and a high rigidity. As a result, the low melting point alloy filled in the vicinity of the center line of the through hole, that is, the alloy having a low rigidity has a buffering action against the stress in the vicinity of the through hole generated by the subsequent process, and the generation of cracks due to the stress, etc. Can be prevented.
The composition distribution of the alloy filled in the through holes can be controlled by the heat treatment conditions described later.

  According to the fourth to seventh means described above, the double-sided wiring board according to the first to third means can be reliably manufactured. That is, unlike the case where the plating method is used, there is no fear that voids are generated in the through holes or the plating solution remains in the voids, and the high melting point alloy can be filled and formed in the through holes. It becomes possible. Moreover, Cu is plated on the side wall of the through hole first, and then the low melting point metal is filled in the through hole by utilizing the capillary phenomenon, so that even a through hole with a very small diameter and a high aspect ratio is used. Can be packed closely. In addition, since the Cu on the side wall of the through hole is alloyed by heat treatment after that, by selecting the heat treatment conditions, the filled metal can be made into a desired high melting point alloy and the alloy composition in the through hole. Can also have a distribution. Moreover, the average composition of the alloy with which a through-hole is filled can also be controlled by controlling the film thickness of Cu or Cu alloy formed in the through-hole side wall. As a result, it is possible to deal with the miniaturization of the double-sided wiring board and to mass-produce the double-sided wiring board excellent in heat resistance, airtightness and reliability with a high yield.

  FIG. 1 is a sectional view of a double-sided wiring board according to an embodiment of the present invention. As shown in FIG. 1, a double-sided wiring board 10 according to an embodiment has wiring layers 2a and 2b formed on both sides (front and back) 1a and 1b of a substrate 1, respectively. The conductive material 4 filled in the through hole 3 is conductively connected. In this case, a wiring pattern is formed on the wiring layers 2a and 2b, and the wiring layers 2a and 2b are firmly attached to the surface of the substrate 1 and the conductive material 4 by the conductive adhesive layers 2c and 2d. It is fixed to.

The conductive material 4 has an average composition of Cu _x Sn _y M _{100- (x + y)} . However, x and y are weight fractions of 100, 30 ≦ x ≦ 99, and 1 ≦ y ≦ 70, and M is at least one metal selected from Au, Ag, and Ni. Further, the Cu concentration of the conductive material 4 is not uniform in the radial direction of the through-hole 3, and decreases from the vicinity of the side wall portion of the through-hole 3 toward the vicinity of the center line of the through-hole 3. It is the maximum in the vicinity of the side wall portion and the minimum in the vicinity of the center line of the through hole 3.
As described above, the Cu concentration distribution of the conductive material has an effect of relaxing the stress generated in the vicinity of the through hole, but is not indispensable for the present invention. Further, it is possible to make the alloy composition in the through hole uniform by sufficiently performing heat treatment for diffusion alloying described later.

The substrate 1 may be any of a photosensitive glass substrate, a glass substrate, a ceramic substrate, or a silicon substrate that is an insulating substrate. In the case of a silicon substrate, a thermal oxide film is grown on the entire surface after the through hole is formed, or an insulating film is formed. Of these, a photosensitive glass substrate is most desirable. This is because the photosensitive glass substrate has sufficient heat resistance, is excellent in smoothness and rigidity, and can easily form fine wiring, and can form fine and high aspect ratio through-holes at once. As this photosensitive glass substrate, for example, by weight, SiO ₂ : 55 to 85%, Al ₂ O ₃ : 2 to 20%, Li ₂ O: 5 to 15%, SiO ₂ + Al ₂ O ₃ + Li ₂ O> 85% as a basic component, Au: 0.001 to 0.05%, Ag: 0.001 to 0.5%, Cu ₂ O: 0.001 to 1% as a photosensitive metal component, and CeO ₂ : It is particularly preferable to use a photosensitive glass containing 0.001 to 0.2% as a photosensitizer.

  The wiring layers 2a and 2b may be a thin film made of a conductive material, but a Cu thin film is preferably used. The adhesive layers 2c and 2d may be any conductive material that can ensure adhesion or adhesion between the substrate 1 and the wiring layers 2a and 2b, but a Cr or titanium thin film is preferably used.

  2-4 is explanatory drawing of the manufacturing method of the double-sided wiring board concerning embodiment of this invention. Hereinafter, a method for manufacturing a double-sided wiring board according to the embodiment will be described with reference to FIGS. The method for manufacturing a double-sided wiring board according to the embodiment roughly includes a through-hole forming step and a conductive material forming step.

(Through hole forming process)
FIG. 2 is an explanatory diagram of the through hole forming step. First, a photosensitive glass substrate 1 is prepared (FIG. 2-1). Next, as shown in FIG. 2-2, light passes through a portion where a through hole (through hole) is formed on the photosensitive glass 1. A mask on which a pattern to be a part is formed is brought into close contact, and the through hole forming part 3a is irradiated with ultraviolet light through the mask to form a latent image corresponding to the exposed part. Next, heat treatment is applied to the exposed substrate 1 to crystallize only the exposed portion 3a (see FIG. 2-3). Next, the crystallized portion is removed with a solvent such as an etching solution (see FIG. 2-4) to form the through hole 3. After forming the through holes, heat treatment is performed to crystallize the entire substrate. And after heat processing, in order to ensure the uniformity of the through-hole diameter of the thickness direction of the board | substrate 1, while removing the part where the same diameter near the board | substrate front and back surface was expanded, the thickness of a board | substrate was made into predetermined thickness. To do.

(Conductive material formation process)
Next, a conductive material is formed in the through hole 3 of the substrate 1. 3-4 is explanatory drawing of an electroconductive material formation process. The conductive material forming step includes a first step of attaching Cu or an alloy containing Cu to the side wall portion of the through hole 3 while leaving a gap portion communicating with both surfaces of the substrate at the center portion of the through hole; A second step of attaching Sn or an alloy containing Sn to the surface of the alloy containing Cu or Cu attached to the side wall portion of the through hole 3 and filling the void portion, and Cu attached in the first step Alternatively, there is a third step in which the alloy containing Cu and the alloy containing Sn or Sn deposited and filled in the second step are formed into a diffusion alloy with each other by heat treatment.

  First, a pretreatment for forming plating layers on both surfaces of the substrate 1 is performed. In this pretreatment, an adhesive layer film 6a such as a Cr film is formed on both surfaces (front and back surfaces) by sputtering or the like, and a power feeding layer 6b such as a Cu film is sequentially formed on the adhesive layer 6a (FIG. 3). 1). As a method for forming the film, any method such as a CVD method, a vapor deposition method, and an ion beam sputtering method may be used regardless of the sputtering method.

  Next, an electroless copper plating thin film 7a is formed on the side wall portion of the through hole 3 and both surfaces of the substrate 1 by a known through hole plating method. A Cu film 7b is grown on the side wall and both sides of the hole so that the film thickness of the Cu film 7b on the side wall of the through hole 3 becomes a desired value (see FIG. 3-2). Next, the surface of the Cu film is activated by applying flux solvent 8 to at least one or both surfaces of the substrate and the inside of the through-hole 3 to perform flux treatment (see FIG. 3-3). . At this time, an active rosin-based flux is desirable, although it is not limited as long as it improves the wettability of the Cu surface.

  On the other hand, Sn, which is a low melting point metal as a conductive material filled in the through hole 3, is dissolved and prepared. At this time, the reason for selecting Sn is that it is easy to form a diffusion alloy with Cu. However, the present invention is not limited to this, and commercially available Sn—Au, Sn—Ag, Sn—Cu. , Sn-Ag-Cu, Sn-Cu-Ni, Sn-Pb and other low melting point eutectic solders are also available. Preferably, those containing Sn are desirable, but similar results can be obtained if the melting point is low, diffusion with Cu is easy, and the alloy formed by diffusion has sufficient heat resistance. Since Cu or Cu alloy is generally selected as the front and back wiring layers for reasons such as low resistance, it is preferable that the conductor layer grown on the side wall portion of the through hole be the same kind of Cu or Cu alloy.

Next, by bringing the dissolved Sn and the activated Cu surface into contact with each other, the inside of the through hole is filled with Sn using a capillary phenomenon (see FIG. 3-4). In this state, the central portion of the through hole 3 remains Sn, and the necessary high heat resistance cannot be obtained. Therefore, by performing heat treatment at a predetermined temperature, Cu alloy formed on the side wall of the through hole and Sn filled in the central part of the through hole are promoted to form a Cu-Sn compound having high heat resistance. Obtain (see FIG. 4-1). In this case, when sufficient heat treatment is performed, the alloy composition inside the through-hole is almost uniform regardless of the site, otherwise, the Cu concentration is maximum in the vicinity of the side wall of the through-hole, and the through-hole A concentration distribution is minimized in the vicinity of the center line. In any case, the concentration of each part can be controlled by the heat treatment temperature and time, and these heat treatment conditions can be selected in consideration of the required heat resistance of the double-sided wiring board. In selecting heat treatment conditions, it is needless to mention again that the heat treatment temperature and the heat treatment time are complementary to each other as taught by diffusion theory.
Finally, the front and back surfaces of the substrate are subjected to mechanical polishing or the like to remove the Cr film, the Cu film, and the Cu-Sn diffusion mixed layer on the Sn-filled surface side, and the substrate is planarized (see FIG. 4-2). Then, wiring conductors, for example, an adhesive layer 2c such as a Cr film and a wiring layer 2b such as a Cu film are sequentially formed on the front and back surfaces of the through wiring substrate by sputtering or the like (FIG. 4). 3), patterning is performed by a normal photolithography technique to obtain a double-sided wiring board 10 as shown in FIG.

Hereinafter, the present invention will be described in more detail based on examples.
Example 1
In this example, photosensitive glass (trade name: PEG3 manufactured by HOYA Corporation) having the following composition was used as the glass substrate. Glass _{composition, SiO 2: 78.0wt%, Li} 2 O: 10.0wt%, Al 2 O 3: 6.0wt%, K 2 O: 4.0wt%, Na 2 O: 1.0wt%, ZnO : 1.0wt%, Au: 0.003wt% , Ag: 0.08wt%, CeO 2: 0.08wt%. The substrate thickness is 0.5 mm and the size is 5 inch square.

(Through hole forming process)
A mask was brought into close contact with the photosensitive glass, and the through hole portion was irradiated with ultraviolet light through the mask to form a latent image corresponding to the exposed portion (see FIG. 2-2). As the mask, quartz glass patterned with Cr / Cr oxide was used. Thereafter, heat treatment was performed at 400 ° C. for 3 hours to crystallize only the exposed portion (see FIG. 2-3). The light source used was a deep UV lamp, and the irradiation energy was 800 mJ / cm ² . Next, thin hydrofluoric acid (10% solution) was sprayed on the front and back of the photosensitive glass to dissolve and remove the crystallized through-hole glass, thereby forming a through-hole having a diameter of 0.04 mm (40 μm) ( (See Figure 2-4). After forming the through holes, the entire substrate was crystallized by performing a heat treatment temperature of 800 ° C. and a holding time of 3 hours. After the heat treatment, in order to ensure the uniformity of the through-hole diameter in the substrate thickness direction, the portion with the same diameter enlarged in the vicinity of the front and back surfaces of the substrate was ground and removed, so that the substrate thickness was 0.3 mm.

(Through hole filling process)
For a 5-inch square glass substrate with a plate thickness of 0.3 mm and a through-hole with a diameter of 40 μm on the entire surface, the Cu film is 2 μm thick so that the Cr film as the adhesion layer at the same time on the front and back surfaces is 0.05 μm thick. Thus, the films were continuously formed in the same vacuum by the DC magnetron sputtering method. Next, an electroless copper plating film is formed to a thickness of 0.3 μm on the front and back surfaces and the side wall of the through hole, and the electroless copper plating layer is used as a power feeding layer (cathode). A thick Cu layer was deposited. At this time, the hole diameter of the air gap communicating with the front and back surfaces of the substrate remaining in the central portion of the through hole is 20 μm (see FIG. 3-2).

Next, a rosin flux (manufactured by Nippon Superior Co., Ltd .: NS-828A: activation temperature 200-300 ° C.) diluted to 50 vol% with alcohol (C ₂ H ₅ OH) was added to the through hole side wall at a thickness of 10 μm. After the crystallized glass substrate on which the Cu layer was deposited was immersed for 30 minutes, the diluted solvent was sufficiently dried in a clean oven at 90 ° C. for 10 minutes. Thus, the activation was completed by the flux treatment of the front and back surfaces and the Cu surface in the through hole (see FIG. 3-3).

  Separately, granular Sn (manufactured by Mitsuwa Chemical Co., Ltd .: purity 4N) was melted in a SiC heat-resistant boat at a liquidus temperature (melting point: 232 ° C.) or higher at 250 ° C. However, because there was a part that did not reach the liquidus temperature due to the effect of thermal convection in the oven, the temperature was raised to 250 ° C, but 232 ° C is sufficient if the oven has good temperature uniformity. . Next, the substrate subjected to the flux treatment is preheated in an oven at 200 ° C. for about 5 minutes, and then is flowed onto the liquid phase Sn from which the surface layer oxide is removed. From this point of time, it was confirmed that Sn was filled in the through hole voids after 2 minutes due to capillary action (see FIG. 3-4). This is because preheating of the glass substrate causes damage to the substrate due to a temperature difference when a substrate at room temperature is flowed onto the liquid phase Sn. For example, preheating is not necessary. Further, it may be added immediately after the flux dilution solvent drying 90 ° C., and is not limited to 200 ° C. However, the flux used in this example rapidly oxidizes at a temperature higher than 300 ° C., and does not make sense for activation. In the absence of preheating, we confirmed about 10% (about once in 10 times) of substrate breakage, but because the initial substrate had a defect and it was a defect-free substrate, it was intentionally reserved There is no need for heating.

After the completion of filling, the substrate was taken out from the liquid phase Sn, and the alloy layer adhering to the front and back surfaces of the substrate was removed by a known and usual polishing technique.
Next, heat treatment was performed on the substrate filled with Sn and the glass surfaces exposed on the front and back surfaces. The heat treatment was performed in a clean oven in a nitrogen stream at 300 ° C., 400 ° C., 500 ° C., and 600 ° C. for 10 minutes. Interdiffusion of the state of through-holes before and after heat treatment, and the distribution of the alloy composition by mapping the Sn and Cu concentrations by cross-sectional SEM image analysis and characteristic X-ray analysis by EPMA (electron beam microanalyzer) It was confirmed. At this time, the electron beam acceleration voltage is 15 kV, the irradiation current is 100 nA, and the electron beam diameter is 1 μm. 5 to 7 show Cu and Sn concentration distributions when heat treatment is performed at 500 ° C. for 10 minutes and at 600 ° C. for 10 minutes before heat treatment. In the figure, the horizontal axis indicates the position in the direction crossing the through hole, and the vertical axis indicates the concentration in arbitrary units.
Prior to the heat treatment, the Cu concentration in the vicinity of the through-hole center line and the Sn concentration at the end of the through-hole were almost at the noise level, and almost no alloying proceeded.
When heat treatment was performed at 500 ° C. for 10 minutes, remarkable alloying was observed in the vicinity of the center line of the through hole, but alloying hardly progressed at the end of the through hole, and at the end of the through hole. A Cu concentration distribution was observed with high Cu concentration and low near the center line. At this time, the alloy composition in the vicinity of the central portion of the through hole was Cu: 65 wt% and Sn: 35 wt%. In this case, Cu-Sn2 ternary equilibrium diagram (e.g., the literature: TB Massalski al ^{Binary Alloy Phase Diagrams (2 nd edition} ) P.1482 (ASM , published 1990) refer) melting point of the alloy to be predicted from, about It was confirmed that sufficient heat resistance was obtained at 750 ° C.
In addition, when heat treatment was performed at 600 ° C. for 10 minutes, the composition distribution inside the through-hole was not recognized and was almost uniform, and the alloy composition was Cu: 79 wt% and Sn: 21 wt%. It was. In this case, the melting point of the alloy predicted from the Cu—Sn binary system equilibrium diagram is 910 ° C., and higher heat resistance is obtained compared to the case where heat treatment is performed at 500 ° C. for 10 minutes. Was confirmed.
When the heat treatment temperature was 300 ° C. or 400 ° C., significant alloying was not observed.
Finally, in order to obtain the smoothness and flatness of the substrate (exposed glass) surface, a through wiring insulating substrate was obtained by a CMP method using well-known colloidal silica (see FIG. 4-2).

(Formation of conductor pattern for wiring)
Using a sputtering apparatus, a Cr film having a thickness of 0.05 μm was formed on the front and back of the glass substrate. Next, a Cu film having a thickness of 2 μm was formed using a sputtering apparatus. Next, a positive liquid resist (positive resist TGMR-1000 manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied with a spinner to a thickness of about 4 μm, and then exposed to 400 mJ / cm ² with a parallel light exposure machine using a glass mask. went. Subsequently, dip development was performed for 2 minutes at room temperature with a developer (developer NMD-3 manufactured by Tokyo Ohka Kogyo Co., Ltd.) to form a resist pattern. After the Cu layer was sprayed by spraying a 40 Baume ferric chloride solution onto the wiring layer on which the resist pattern was formed, the resist was removed with acetone. Subsequently, the Cr layer was etched using the Cu pattern as a metal resist to form a wiring pattern having a line width of 10 μm, a gap of 10 μm, and a through-hole land width of 120 μm. This obtained the double-sided wiring board. In addition, the chemical | medical agent which has potassium ferricyanide as a main component was used as Cr etching liquid.

(Example 2)
Since this embodiment has many configurations such as through-hole formation in common with the first embodiment, the following description will mainly focus on differences from the first embodiment. For a 5-inch square glass substrate with through-holes with a plate thickness of 0.3 mm and a diameter of 40 μm on the entire surface, the Cr film as the adhesion layer at the same time on the front and back surfaces is 0.05 μm thick, and the Cu film is 2 μm thick. Films were continuously formed in a vacuum by a DC magnetron sputtering method. Next, an electroless copper plating film is formed to a thickness of 0.3 μm on the front and back surfaces and the side wall of the through hole, and the electroless copper plating layer is used as a power feeding layer (cathode). A C5 μm thick Cu layer was deposited. At this time, the hole diameter of the gap communicating with the front and back surfaces of the substrate remaining in the central portion of the through hole is 30 μm.

  In the same manner as in Example 1, flux treatment was performed, and then the substrate was flowed onto liquid phase Sn at 250 ° C., and Sn filling was performed by capillary action for 2 minutes. Next, after removing the double-sided thick film, diffusion heat treatment was performed in a clean oven at 600 ° C. for 10 minutes in a nitrogen stream. The alloy composition after the heat treatment was uniform inside the through hole, and was Cu: 49 wt% and Sn: 51 wt%. In this case, it was confirmed that the melting point of the alloy predicted from the Cu—Sn binary system equilibrium diagram is 700 ° C. and high heat resistance is obtained.

(Example 3)
Since this embodiment also has many configurations such as the formation of through-holes in common with the first embodiment, the following description will mainly focus on differences from the first embodiment. For a 5-inch square glass substrate with through-holes with a plate thickness of 0.3 mm and a diameter of 40 μm on the entire surface, the Cr film is continuously 0.05 μm thick and the Cu film is 2 μm thick at the same time in the same vacuum. Specifically, the film was formed by DC magnetron sputtering. Next, an electroless copper plating film is formed to a thickness of 0.3 μm on the front and back surfaces and the side wall of the through hole, and the electroless copper plating layer is used as a power feeding layer (cathode). The layer was deposited to a thickness of 10 μm. At this time, the hole diameter of the air gap communicating with the front and back surfaces of the substrate remaining in the central portion of the through hole is 20 μm.

Commercially available low melting point solder (Nippon Superior Co., Ltd .: Model No. SN96Cl), Ag: 3.8 wt%, Cu: 1.0 wt%, Sn: bal. (Melting point: 217 ° C.) formed a liquid phase in a clean oven (liquid temperature: 230 ° C.). As in Example 1, the flux-treated substrate was flowed onto a 230 ° C. liquid phase low melting point solder and filled with solder by capillary action for 2 minutes. Next, after removing the double-sided thick film, diffusion heat treatment was performed in a clean oven at 600 ° C. for 10 minutes in a nitrogen stream. The alloy composition after the heat treatment was uniform inside the through hole, and was Cu: 85 wt%, Sn: 14 wt%, and Ag: 1 wt%.
In order to evaluate the heat resistance of the double-sided wiring board according to this example, the substrate was left in a clean oven at a temperature of 600 ° C. for 3 hours. As a result, no change in shape or the like was observed in the vicinity of the filled through hole, and it was confirmed that the film had good heat resistance.

Example 4
Since this embodiment also has many configurations such as the formation of through-holes in common with the first embodiment, the following description will mainly focus on differences from the first embodiment. For a 5-inch square glass substrate with a plate thickness of 0.3 mm and a through-hole with a diameter of 40 μm on the entire surface, the Cr film has a thickness of 0.05 μm and the Cu film has a thickness of 2 μm at the same time in the same vacuum. Films were continuously formed by DC magnetron sputtering. Next, an electroless copper plating film is formed to a thickness of 0.3 μm on the front and back surfaces and the side wall of the through hole, and the electroless copper plating layer is used as a power feeding layer (cathode). A 5 μm thick Cu layer was deposited. At this time, the hole diameter of the gap communicating with the front and back surfaces of the substrate remaining in the central portion of the through hole is 30 μm.

Commercially available low melting point solder (Nippon Superior Co., Ltd .: Model No. SN100C), Cu: 0.7 wt%, Ni: 0.1 wt%, Sn: bal (melting point: 227 ° C) in a clean oven (liquid temperature: 250 ° C) A liquid phase was formed. As in Example 1, the flux-treated substrate was flowed onto a 250 ° C. liquid phase low melting point solder and filled with solder by capillary action for 2 minutes. Next, after removing the double-sided thick film, diffusion heat treatment was performed in a clean oven at 600 ° C. for 10 minutes in a nitrogen stream. The alloy composition after the heat treatment was uniform inside the through hole, and was Cu: 85 wt%, Sn: 46.7 wt%, and Ni: 0.3 wt%.
In order to evaluate the heat resistance of the double-sided wiring board according to this example, the substrate was left in a clean oven at a temperature of 600 ° C. for 3 hours. As a result, no change in shape or the like was observed in the vicinity of the filled through hole, and it was confirmed that the film had good heat resistance.

(Comparative example)
In this comparative example, a conductive material of 100% Sn is filled in the through hole by the method described in Patent Document 3 described above. In this comparative example, only heat resistance of 230 ° C. was obtained.
As mentioned above, although this invention was demonstrated in detail using the Example, the conditions of the heat processing performed after through-hole filling are not limited to the conditions described in the present Example. That is, considering the complementarity between temperature and time in the diffusion process, the results obtained in this example are not obtained only with the temperature and time conditions described in this example, but different heat treatment temperatures and heat treatments. It is also realized in time. Therefore, in this example, when the heat treatment temperatures were 300 ° C. and 400 ° C., remarkable progress of alloying was not recognized, but the alloying can be made obvious by sufficiently increasing the heat treatment time. It is.

  The present invention provides a double-sided wiring board that can cope with the miniaturization of a double-sided wiring board, is excellent in heat resistance, airtightness, reliability, and mass production, and a manufacturing method thereof. (Electro-mechanical system) It can be used in technical fields such as electronic devices and optical devices applying technology.

It is sectional drawing of the double-sided wiring board concerning embodiment of this invention. It is explanatory drawing of a through-hole formation process. It is explanatory drawing of the formation process of an electroconductive material. It is explanatory drawing of the formation process of an electroconductive material. It is a figure which shows the density | concentration distribution of Cu and Sn in the through-hole after Sn filling. It is a figure which shows Cu and Sn density | concentration distribution in the through-hole after heat-processing for 10 minutes at 500 degreeC. It is a figure which shows the density | concentration distribution of Cu and Sn in the through-hole after heat-processing for 10 minutes at 600 degreeC.

Explanation of symbols

1 ... Substrate 1a, 1b ... Both sides of substrate (front and back)
2a. 2b ... wiring layer 2c. 2d ... adhesive layer 3 ... through hole 4 ... conductive material

Claims (6)

A board, a wiring layer provided on both sides of the board, a through-hole penetrating both sides of the board, and a conductive material filled in the through-hole to electrically connect the wiring layers on both sides The conductive material is made of Cu, Sn, and M, and the composition ratio of Cu, Sn, and M is wt% (wt%), and 49% ≦ Cu ≦ 85%, 14%. ≦ Sn ≦ 51%, 0% ≦ M <1%,
The double-sided wiring board , wherein the Cu concentration of the conductive material is not uniform in the radial direction of the through hole, and decreases from the vicinity of the side wall portion of the through hole toward the vicinity of the center line of the through hole .
Here, M is at least one metal selected from Au, Ag, and Ni. Claims Cu concentration of the conductive material is not uniform in the radial direction of the through hole is greatest side wall portion near the through hole, and characterized in that it is a minimum at the center line near the through hole Item 2. The double-sided wiring board according to item 1 . A method for manufacturing a double-sided wiring board, comprising: a conductive part forming step for electrically connecting wiring layers formed on both sides of the substrate by filling a through hole penetrating both sides of the substrate with a conductive material. And
The conductive portion forming step is a first step of attaching Cu or an alloy containing Cu to the side wall portion of the through hole, leaving a gap portion communicating with both surfaces of the substrate at the central portion of the through hole;
A second step of attaching Sn or an alloy containing Sn to the surface of Cu or an alloy containing Cu attached to the side wall portion of the through hole and filling the void portion;
A third step of forming a diffusion alloy with each other by heat treatment of Cu or an alloy containing Cu deposited in the first step and an alloy containing Sn or Sn deposited and filled in the second step; A method for producing a double-sided wiring board, comprising: 4. The method for manufacturing a double-sided wiring board according to claim 3 , wherein the first step is a step of attaching Cu or an alloy containing Cu to the side wall portion of the through hole by a plating method. In the second step, the first metal is added to the molten metal obtained by heating and melting Sn or an alloy containing Sn.
5. The method for manufacturing a double-sided wiring board according to claim 3 , wherein the substrate having undergone the step is brought into contact, and the gap or the alloy containing Sn is filled into the gap portion by capillary action. An average Cu concentration in the CuSn alloy filled in the through-hole or an alloy containing at least Cu and Sn is controlled by the volume of Cu or Cu-containing alloy deposited in the first step. A method for manufacturing a double-sided wiring board according to any one of claims 3 to 5 .

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