JP2006324526A - Wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board having via holes without occurrences of an exfoliation at an interface between the board and a conductive member, and also without a trouble caused by a thermal stress of the board crack or the like, and also to provide its manufacturing method. <P>SOLUTION: The wiring board has a via hole 4 formed through between one surface 1a and the other surface 1b of the board 1 comprising a hourglass-shaped through hole 2 with its inside diameter at the central part in a thickness direction of the board 1 smaller than the diameter of the openings at the surfaces 1a, 1b; and a layer of a conductive member 3 covering whole inside face of the through hole 2 with its ends of the both end openings of the through hole 2 exposed and with the central part of the through hole 2 blocked up. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wiring board having a via hole which is electrically conductive between both surfaces of a substrate made of a silicon wafer or a glass wafer and has a sealed via hole, and a method for manufacturing the wiring board.

2. Description of the Related Art In recent years, research has been actively conducted to ensure sealing performance and form conductive wiring for electrical conduction in a through-hole inside a silicon wafer or glass wafer. For example, as shown in FIG. 5, there is provided a wiring board having via holes 4 formed by filling a through-hole 2 penetrating both side surfaces of the board 1 with a conductive member 3 such as copper by plating (for example, Patent Document 1).
JP 2002-185140 A (FIG. 1, paragraph number 0014)

  By the way, in the via hole structure as shown in Patent Document 1, the coefficient of thermal expansion between the silicon wafer or glass wafer to be the substrate 1 and the conductive member 3 such as copper is significantly different. There is a problem that troubles such as peeling on the surface of the conductive member 3 and substrate cracks occur.

  On the other hand, in order to solve such heat stress troubles, it has been studied to reduce the hole diameter, but it has sufficient effects such as difficulty in forming the hole and filling the conductive member in the hole. The current situation is that it is not possible.

  The present invention has been made in view of the above-mentioned points, and its purpose is to eliminate the occurrence of troubles due to thermal stress such as peeling at the interface between the substrate and the conductive member and substrate cracks. An object of the present invention is to provide a wiring board having a via hole and a manufacturing method thereof.

  In order to achieve the above-mentioned object, in the invention of the wiring board according to claim 1, the central portion in the thickness direction of the substrate is located on the one surface side and the other surface between one surface and the other surface of the substrate. A through-hole that is narrower than the side, and a conductive member layer that is formed along the inner surface of the through-hole, exposes both end portions at both end openings of the through-hole, and closes only the central portion of the through-hole. It has the via hole which consists of.

  According to the invention of the wiring board of claim 1, the conductive member layers formed on the inner surfaces of both end portions of the through-hole having the greatest thermal stress are thinned, so that the thermal stress generated due to the difference in thermal expansion is small, and therefore the through-hole It is possible to prevent interfacial delamination from the hole, substrate cracking, and the like, and since the central part of the through hole is narrow, the thermal stress generated by the difference in thermal expansion can be reduced. Even if interface peeling or substrate cracking occurs, troubles such as conduction and airtightness can be mitigated because it is inside the through hole.

  The wiring board manufacturing method according to claim 2 is the wiring board manufacturing method according to claim 1, wherein the taper-shaped first narrows from one surface of the substrate toward a central portion in the thickness direction of the substrate. Forming a concave portion of the first concave portion, plating a conductive member layer on the inner surface of the first concave portion, reaching the bottom of the first concave portion from the other surface of the substrate, and narrowing toward the bottom. The method includes a step of forming a tapered second recess, and a step of plating a conductive member layer on the inner surface of the first recess.

  According to the invention of the method for manufacturing a wiring board of claim 2, the wiring board of the invention of claim 1 can be easily manufactured.

  According to a third aspect of the present invention, there is provided a method of manufacturing a wiring board according to the first aspect, in which the taper-shaped first narrows from one surface of the board toward the center in the thickness direction of the board. Forming a first recess, forming a tapered second recess that communicates from the other surface of the substrate to the bottom of the first recess and narrows toward the bottom, and A conductive member layer is formed by plating on the inner surface of the first recess and the inner surface of the second recess from each of the front surface side and the other surface side, and the communicating portion of both recesses is closed with the conductive member layer. It consists of a process.

  According to the invention of the method for manufacturing a wiring board of claim 3, the wiring process according to the invention of claim 1 can be simplified by simplifying the plating process once and reducing the breakage of the conductive member when forming the recess. A substrate can be manufactured.

  According to a fourth aspect of the present invention, there is provided a method for manufacturing a wiring board according to the third or fourth aspect, wherein the conductive member layer is plated on the inner surface of the first recess or the inner surface of the second recess. It is characterized in that it is performed simultaneously with the step of plating the wiring pattern on one surface or the other surface.

  According to the invention of the method for manufacturing a wiring board according to claim 4, it is not necessary to newly form the wiring pattern by plating.

  According to the present invention, the conductive member layers formed on the inner surfaces of both end portions of the through-hole having the largest thermal stress are thinned, so that the thermal stress generated due to the difference in thermal expansion is small, so that the interface peeling from the through-hole or In addition, since the central part of the through-hole can be narrowed, the thermal stress generated due to the difference in thermal expansion can be reduced, and the interface peeling at the central part and the substrate can be prevented. Even if a crack occurs, since it is inside the through-hole, it is possible to provide a wiring board that can alleviate troubles such as conduction and airtightness, and to produce the wiring board easily.

  The present invention will be described below with reference to an embodiment.

  FIG. 1 shows a cross section of the main part of the wiring board of the present embodiment, and a via hole 4 is formed between one surface 1a and the other surface 1b of the substrate 1. The via hole 4 includes a drum-shaped through hole 2 in which the inner diameter of the central portion in the thickness direction of the substrate 1 is smaller than the diameter of the opening in the surfaces 1 a and 1 b, and the entire inner surface of the through hole 2. It is composed of a layer of the conductive member 3 whose end portions are exposed at both end openings and the central portion of the through hole 2 is closed.

  Here, in this embodiment, a silicon wafer having a thickness of about 300 to 1000 μm, a glass wafer, an alumina substrate, or the like is used as the substrate 1, and the through hole 2 has a circular cross section and an inner diameter of both end openings of 50 to 500 μm. The inner diameter of the part is formed with a dimension of about 10 to 100 μm. Here, when the inner diameter dimension of the through hole 2 is larger than the above-mentioned dimension due to the relationship with the thickness of the substrate 1, the thermal stress increases. It becomes difficult to close the hole by the member 3.

  A method for forming the through-hole 2 is not particularly limited, but a method such as wet etching with chemicals, dry etching, laser processing, drilling, or sandblasting is used. The thickness of the layer of the conductive member 3 formed on the inner surface of the through hole 2 is about 3 to 20 μm at both ends of the through hole 2. That is, when the thickness is increased, the thermal stress increases and the influence on the substrate 1 increases. The thickness of the layer closing the central portion is about 10 to 100 μm. That is, if the thickness is less than this, the airtightness is insufficient, and conversely, if the thickness is increased, the thermal stress increases.

  The method for forming the conductive member 3 is not particularly limited, but a method in which conductive paste, electrolytic plating, or the like is generally used may be used.

  In electrolytic plating, a sputtered film, an electroless plated film, or a CVD film is used as a conductive seed layer for energization formed inside the through hole 2.

  Next, an example of the method for manufacturing the wiring board according to the present embodiment will be described.

Example 1
The steps of the manufacturing method of this embodiment will be described with reference to FIG.

  First, the substrate 1 having the above-mentioned predetermined thickness is prepared (FIG. 2A), and in the first step (FIG. 2B), the thickness direction of the substrate 1 is formed by counterbored holes on one surface 1a side of the substrate 1. A tapered first concave portion 2a having an inner diameter narrowing toward the central portion is formed. The counterbore hole processing method here is not particularly limited, but as described above, an appropriate method such as wet etching, dry etching, laser processing, drilling, or sandblasting is used.

  After the completion of the first step, a conductive seed thin film is formed on the entire inner surface of the recess 2a and the surface of the substrate 1 in the second step (FIG. 2C). This conductive seed thin film is usually 0.05 to 0.2 μm thick and is formed by sputtering, electroless plating, CVD, or the like. The metal species used for the film formation may be copper, gold, nickel, chromium, titanium, or the like, and a plurality of metals may be used as a multilayer. After the conductive seed thin film is formed, a conductive metal film is formed over the entire inner surface of the recess 2a by electrolytic plating. Although the metal seed | species of this metal film is not specifically limited, A metal with high electrical conductivity, such as copper, gold | metal | money, nickel, is used. That is, the conductive member 3 is composed of a conductive metal film (including a conductive seed thin film).

  Now, after the end of the second step, in the next third step (FIG. 2 (d)), the depth reaches the layer of the conductive member 3 at the bottom of the recess 2a from the other surface 1b side of the substrate 1 again. A tapered second recess 2b similar to the recess 2a is formed by counterboring. This forming method is the same as the first step, but is carefully and accurately processed so that the layer of the conductive member 3 at the bottom of the recess 2a is not damaged during the processing. By forming the recess 2b and the recess 2a, the through hole 2 whose center is closed with the layer of the conductive member 3 is formed.

  After the formation of the second recess 2b, in the next fourth step (FIG. 2 (e)), the conductive seed thin film is formed and the entire inner surface of the recess 2b is made conductive by electrolytic plating after the formation of the conductive seed thin film. The layer of member 3 is formed. As a result, the conductive members 3 on the inner surfaces of the recesses 2a and 2b are integrated, and electrical conduction between the end portions of the conductive member 3 exposed at the opening portions at both ends of the through hole 2 can be obtained.

  Then, if necessary, the unnecessary layer of the conductive member 3 formed on both surfaces 1a and 1b of the substrate 1 is removed by polishing or etching, as shown in FIG. 2 (f). A wiring board is obtained.

Example 2
In the first embodiment, the concave portion 2a is formed on one surface 1a of the substrate 1 and then the concave portion 2a is plated. Thereafter, the concave portion 2b is formed on the other surface 1b and then the concave portion 2b is plated. However, in this embodiment, a wiring board is manufactured by the process shown in FIG.

  First, the substrate preparation in FIG. 3 (a) and the hole formation by counterboring the recess 2a in the substrate 1 in FIG. 3 (b) are the same as in Example 1, but in this example, after the formation of the recess 2a, In the second step, the recesses 2b are formed from the other surface 1b of the substrate 1 in the same manner, and the through holes 2 penetrating the side surfaces 1a and 1b of the substrate 1 are recessed as shown in FIG. 2a and 2b. At this time, it is desirable to form the inner diameter of the central portion of the through hole 2 in the thickness direction of the substrate 1 as small as possible, that is, when the diameter becomes large, it becomes difficult to block in the subsequent electrolytic plating process.

  In the next second step (FIG. 3D), a conductive seed layer is first formed on the entire inner surface of the through hole 2 from both side surfaces 1a and 1b of the substrate 1 in the same manner as in the first embodiment, and then the first embodiment. Similarly to the above, electrolytic plating is performed on the entire inner surface of the through-hole 2 from both side surfaces 1a and 1b of the substrate 1, and the entire inner surface of the through-hole 2 is made of a conductive member 3 made of a metal having a high conductivity such as copper, gold or nickel. Forming a layer. At this time, the thickness of the conductive member 3 on the inner surface of the opening portions at both ends of the through hole 2 close to the surfaces 1a and 1b of the substrate 1 is made as thin as possible, and the thickness of the conductive member 3 covering the center of the through hole 2 is reduced. In order to form a thick film, the plating solution and the plating conditions are optimized.

  Thereafter, if necessary, the layer of unnecessary conductive member 3 formed on both surfaces 1a and 1b of substrate 1 is removed by polishing or etching, so that a desired wiring as shown in FIG. A substrate is obtained. It is necessary to make the conductive member 3.

Example 3
In this embodiment, the wiring pattern is simultaneously formed in the step of forming the inner surface conductive member 3 of the through hole 2 by electrolytic plating.

  FIG. 4 shows a subdivided process in the case where this embodiment is adopted in the process of electrolytic plating the inner surface of the recess 2a formed on the one surface 1a side in the first embodiment.

  First, as shown in FIG. 4 (a), after forming a recess 2a on the surface 1a of the substrate 1, first, the conductive seed layer 3a is extended to the inner surface of the recess 2a and the surface 1a of the substrate 1 as shown in FIG. Then, as shown in FIG. 4C, the surface of the conductive seed layer 3a other than the recess 2a and the wiring pattern formation position is covered with a resist 6, and then electroplating is performed on the inner surface of the through hole 2 At the same time when the conductive member 3 is formed, the wiring pattern 7 electrically connected to the conductive member 3 is plated on the surface 1a of the substrate 1 as shown in FIG. Similarly, the wiring pattern 7 is formed through the same process as that shown in FIGS. 4A to 4D in the plating process after the recess 2b is formed on the other surface 1b of the substrate 1.

  The resist is a sheet resist or a liquid resist, and the wiring pattern 7 is formed by photolithography or the like.

  After the formation of the wiring pattern 7 by electrolytic plating, the resist 6 is peeled off as shown in FIG. 4E, and the conductive seed layer is removed by etching or the like.

  FIG. 4 shows the flow when the present embodiment is adopted in the plating process in the first embodiment. After forming the through holes 2 penetrating the both side surfaces 1a and 1b as in the second embodiment, When electrolytic plating is performed simultaneously from both side surfaces 1a and 1b of the substrate 1, the processes shown in FIGS. 4A to 4D may be performed simultaneously on both sides.

It is sectional drawing of the principal part of the wiring board of one Embodiment. It is process explanatory drawing of Example 1 of the method of manufacturing the wiring board of one Embodiment. It is process explanatory drawing of Example 2 of the method of manufacturing the wiring board of one Embodiment. It is explanatory drawing of the plating process of Example 4 of the method of manufacturing the wiring board of one Embodiment. It is sectional drawing of the principal part of the wiring board of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 1a, 1b Surface 2 Through-hole 3 Conductive member 4 Via hole

Claims (4)

Between the one surface and the other surface of the substrate, a central portion in the thickness direction of the substrate is formed so as to be along the inner surface of the through hole and the through hole in which the central portion is narrower than the one surface side and the other surface side. And a via hole comprising a conductive member layer having both end portions exposed at both end openings of the through hole and having only the center portion of the through hole closed. 2. The method of manufacturing a wiring board according to claim 1, wherein a step of forming a tapered first concave portion that narrows from one surface of the substrate toward a central portion in the thickness direction of the substrate, and the first concave portion. Forming a conductive member layer on the inner surface of the substrate, forming a tapered second recess that reaches the bottom of the first recess from the other surface of the substrate and narrows in the bottom direction; and And a step of plating a conductive member layer on the inner surface of the first recess. 2. The method of manufacturing a wiring board according to claim 1, wherein a step of forming a tapered first concave portion that narrows from one surface of the substrate toward a central portion in the thickness direction of the substrate; Forming a tapered second recess that communicates with the bottom of the first recess from the surface of the substrate and narrows in the direction of the bottom, and from each of the one surface side and the other surface side of the substrate, And a step of forming a conductive member layer on the inner surface of the first concave portion and the inner surface of the second concave portion, and closing the communicating portion of both concave portions with the conductive member layer. Method. The plating of the conductive member layer on the inner surface of the first recess or the inner surface of the second recess is performed simultaneously with the step of plating the wiring pattern on one surface or the other surface of the substrate. A method for manufacturing a wiring board according to claim 2 or 3.

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