JP4540500B2 - Wiring board - Google Patents

Description

  The present invention relates to an electronic component storage package for mounting an electronic component, a wiring substrate used for a hybrid integrated circuit substrate, and the like.

  Conventionally, for example, a wiring substrate used for an electronic component storage package or a hybrid integrated circuit substrate for storing an electronic component such as a semiconductor element, a ceramic material such as an aluminum oxide sintered body, a resin material such as an epoxy resin, An insulating substrate made of an electrically insulating material such as a composite material of a resin material and a ceramic material, and having a mounting portion on which an electronic component is mounted at the center of the upper surface, and a high melting point metal powder such as tungsten or molybdenum. And a wiring conductor formed on the upper surface.

  Then, the electronic component is mounted on the mounting portion, and the electrode of the electronic component is electrically connected to the wiring conductor via a conductive connecting material such as solder or bonding wire, and a lid or a sealing resin as necessary. Thus, an electronic device is obtained by hermetically sealing the electronic component.

  In this case, a metal plating layer such as nickel or gold is deposited on the exposed surface of the wiring conductor to make the connection of the conductive connecting material easy and strong.

  Such a wiring board is manufactured by a ceramic green sheet lamination method or the like. For example, when the insulating substrate is made of an aluminum oxide sintered body, an appropriate organic binder, solvent, etc. are added to and mixed with ceramic raw material powder such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, etc. A ceramic green sheet is produced by adopting a doctor blade method to form a sheet. Thereafter, a metal paste serving as a wiring conductor is printed on a ceramic green sheet in a predetermined pattern and fired at a high temperature of about 1600 ° C. in a reducing atmosphere.

Note that parts of the wiring conductor other than the part to which the conductive connecting material is connected are insulating layers made of an insulating material similar to the insulating base in order to prevent the conductive connecting material such as solder from flowing too much. It is covered.
Japanese Patent Laid-Open No. 2002-16179 JP 2001-77499 A

  However, in the conventional wiring board, there are a portion of the wiring conductor covered with the insulating layer and a portion exposed from the insulating layer. Since the exposed portion is coated with a metal plating layer, the line width is larger than that of the portion covered with the insulating layer.

  Recently, with the miniaturization of electronic components, wiring boards are also required to be miniaturized and densified, and the spacing between adjacent wiring conductors has become narrower, so that the metal plating layer is deposited and the wire is deposited. There has been a problem that the wiring conductors are electrically short-circuited in the exposed portion having a large width. In order to deal with this problem, the line width has to be set narrow by subtracting the line width of the wiring conductor by the width of the metal plating layer on each side of each wiring conductor.

However, if the line width of the wiring conductor narrowly set, the higher the electrical resistance of the wiring conductors (exchange of electrical signals, the signal oscillating etc.) electrical operation of the electronic component problem that you to put the problem occurs End up. In particular, with the recent increase in functionality and multifunction of electronic components, problems such as the above-described malfunctions due to the high electrical resistance of wiring conductors have become prominent.

  The present invention has been completed in view of the above problems in the prior art, and an object of the present invention is to provide a wiring conductor in which a part of the wiring conductor is exposed and the other part is covered with an insulating layer. An object of the present invention is to provide a wiring board that is effectively prevented from being electrically short-circuited with each other and that has excellent electrical characteristics without increasing the electrical resistance of the wiring conductor.

  The wiring board of the present invention includes an insulating base having an electronic component mounting portion on an upper surface, a wiring conductor formed on the upper surface of the insulating base and electrically connected to the electrodes of the electronic component, and the wiring conductor And an insulating layer covering the wiring conductor so that a portion to which the electronic component is electrically connected is exposed, and the width of the exposed portion of the wiring conductor is covered with the insulating layer. It is narrower than the width of the portion, and a metal plating layer is deposited on the exposed portion.

  Furthermore, the wiring board of the present invention is characterized in that the metal plating layer is deposited with the same width as that of the portion covered with the insulating layer of the wiring conductor.

  The wiring board of the present invention includes an insulating base having an electronic component mounting portion on the upper surface, a wiring conductor formed on the upper surface of the insulating base and electrically connected to the electrode of the electronic component, and the electronic component of the wiring conductor being electrically connected. And an insulating layer that covers the wiring conductor so that the portion to be connected is exposed, and the wiring conductor is narrower than the width of the portion covered with the insulating layer, In addition, since the metal plating layer is applied to the exposed part, even if the line width is widened by the metal plating layer in the exposed part of the wiring conductor, it is between the adjacent wiring conductors. A sufficient interval can be ensured, and an electrical short circuit between the wiring conductors can be effectively prevented.

  In addition, in the exposed part where the width of the wiring conductor is narrow, a metal plating layer is deposited, and since, for example, low resistance gold can be used as the metal plating layer, electric resistance is kept low. Can do. In addition, in the portion of the wiring conductor covered with the insulating layer, the metal plating layer is not deposited on the surface and the line width does not increase, so the width of the wiring conductor can be set large, and the low resistance. can do. As a result, the resistance can be reduced over the entire length of the wiring conductor formed on the upper surface of the insulating base, and the electrical characteristics (conduction resistance) as the wiring board can be improved.

  In addition, the exposed part of the wiring conductor to which the electrode of the electronic component is connected is coated with a metal plating layer, so the conductive connection material has good connectivity (solder wettability, bonding wire bonding, etc.) It can be.

  Furthermore, according to the wiring board of the present invention, adjacent metal conductors are electrically short-circuited by depositing the metal plating layer with the same width as that of the portion covered with the insulating layer of the wiring conductor. In addition, it is possible to effectively prevent problems such as an increase in the electric resistance of the wiring conductor and to make the electric resistance uniform with the same line width over the entire length of the wiring conductor on the upper surface of the insulating base. The wiring board has excellent electrical characteristics.

(Embodiment 1)
First, the wiring board according to claim 1 and claim 2 will be described with reference to FIG.

  FIG. 1 is a plan view showing an example of a wiring board according to Embodiment 1 of the present invention. In FIG. 1, 1 is an insulating substrate, 2 is a wiring conductor, and 3 is an insulating layer. The insulating substrate 1, the wiring conductor 2, and the insulating layer 3 basically constitute a wiring substrate 9 on which electronic components (not shown) are mounted.

  The insulating substrate 1 includes an aluminum oxide sintered body (alumina ceramic), an aluminum nitride sintered body, a mullite sintered body, a silicon nitride sintered body, a silicon carbide sintered body, a glass ceramic sintered body, and the like. It is made of an electrically insulating material and has a mounting portion 1a for mounting an electronic component at the center of the upper surface.

  When the insulating base 1 is made of, for example, an aluminum oxide sintered body, it is manufactured as follows. First, an appropriate organic binder and solvent are added to and mixed with raw material powders such as aluminum oxide, silicon oxide, calcium oxide, and magnesium oxide to produce a slurry ceramic slurry. A ceramic green sheet (ceramic green sheet) is obtained by adopting the sheet forming technique of the above and forming a sheet. Thereafter, ceramic green sheets are laminated in the predetermined order in the vertical direction to form a green ceramic molded body. The green ceramic body is fired at a high temperature of about 1600 ° C. in a reducing atmosphere, whereby the insulating substrate 1 is manufactured.

  A wiring conductor 2 is formed on the upper surface of the insulating substrate 1. The wiring conductor 2 is electrically connected to an electrode (not shown) of an electronic component mounted on the mounting portion 1a. A part of the wiring conductor 2 is led out to the surface outside the mounting portion 1a such as the outer peripheral portion, the side surface, and the lower surface of the upper surface of the insulating base 1, and functions as a conductive path for leading the electrode of the connected electronic component to the outside. To do. That is, an electrode (not shown) of an electronic component is electrically connected to the mounting portion 1a of the wiring conductor 2 via a conductive connecting material (not shown) such as solder or a bonding wire, and the wiring conductor 2 Of these, the part led out to the surface outside the mounting portion 1a is electrically connected to an external electric circuit via solder or the like, whereby the electrodes of the electronic component are electrically connected to the external electric circuit.

  The wiring conductor 2 is made of a metal material such as tungsten, molybdenum, manganese, copper, silver, palladium, or gold. For example, in the case of tungsten, a metal paste obtained by adding and mixing an appropriate organic binder and solvent to tungsten powder. In addition, it is formed by previously printing and applying a predetermined pattern on the upper surface of the ceramic green sheet to be the insulating substrate 1 by a screen printing method or the like.

  The wiring conductor 2 may extend on the surface other than the upper surface of the insulating base 1 or inside the insulating base 1.

  Further, the wiring conductor 2 is covered with an insulating layer 3 so that a portion to which an electrode of an electronic component is connected is exposed. Thereby, an electronic component can be reliably and firmly electrically connected to the exposed part of the wiring conductor 2. In this case, for example, even if the electrode of the electronic component is connected to the wiring conductor 2 with a conductive connecting material such as solder, an unnecessary flow of the conductive connecting material can be suppressed by the insulating layer 3. The electronic component can be connected to the wiring conductor 2 with a sufficient amount of the conductive connecting material.

  The metal plating layer 4 functions to prevent oxidative corrosion of the wiring conductor 2 and to make connection of a connecting material such as solder easy and reliable. The metal plating layer 4 is made of a metal such as nickel, gold, copper, cobalt, platinum, palladium, or an alloy thereof, and is also a metal or alloy containing a component other than a metal such as nickel-phosphorus, nickel-boron, etc. Is included.

  The metal plating layer 4 can be deposited and formed by a plating method such as an electrolytic plating method or an electroless plating method. For example, an organic acid (salt) such as potassium citrate or potassium phosphate is added to a gold cyanide compound. The wiring substrate 2 is immersed in an electrolytic gold plating bath to which additives such as phosphates are added, and a predetermined plating current is supplied to the wiring conductor 2 via a plating jig or the like. It is applied to the exposed part.

  In the wiring board 9 of the present invention, the width of the exposed portion of the wiring conductor 2 is narrower than the width of the portion covered with the insulating layer 4, and the metal plating layer 4 is deposited on the exposed portion. Has been. With this configuration, even when the line width is increased by the metal plating layer 4 in the exposed portion of the wiring conductor 2, a sufficient space can be secured between the adjacent wiring conductors 2, and the wiring conductor It is possible to effectively prevent an electrical short circuit between the two. Further, since the metal plating layer 4 is deposited on the exposed portion where the width of the wiring conductor 2 is narrow, and, for example, low resistance gold can be used as the metal plating layer 4, the electric resistance is lowered. Can be suppressed. In addition, in the portion of the wiring conductor 2 that is covered with the insulating layer 3, the metal plating layer 4 is not deposited on the surface of the wiring conductor 2 and the line width does not increase, so the width of the wiring conductor 2 can be set large. Low resistance can be achieved. As a result, the resistance can be reduced over the entire length of the wiring conductor 2 formed on the upper surface of the insulating base 1, and the electrical characteristics (conduction resistance) as the wiring substrate 9 can be improved.

  Further, as described above, since the metal plating layer 4 is deposited on the exposed portion of the wiring conductor 2 where the electrodes of the electronic components are connected, the connectivity of the conductive connecting material (solder wettability and bonding wire) And the like can be improved.

  In order to firmly connect the conductive connecting material to the exposed portion of the wiring conductor 2, the thickness of the metal plating layer 4 is preferably 3 μm or more. In this case, for example, a nickel plating layer having a thickness of 2 μm or more and a gold plating layer having a thickness of 1 μm or more are sequentially deposited.

  The insulating layer 3 is made of the same material as the insulating material forming the insulating substrate 1 (electrical insulation such as ceramic material such as aluminum oxide sintered body, resin material such as epoxy resin, composite material of resin material and ceramic material, etc. Material).

  For example, when the insulating layer 3 is made of an aluminum oxide sintered body, an appropriate organic binder and solvent are added to and mixed with raw material powders such as aluminum oxide, silicon oxide, calcium oxide, and magnesium oxide to produce a ceramic paste, The ceramic paste is formed by printing and coating so as to cover the ceramic green sheet to be the insulating substrate 1 and the metal paste printed on the upper surface thereof.

  The insulating layer 3 preferably has a thickness of 10 μm or more in order to reliably cover the wiring conductor 2. For example, when it consists of a ceramic material, it is more preferable to set it as the range of 10-40 micrometers considering also ensuring the joining strength with respect to the insulation base | substrate 1. FIG.

  The insulating layer 3 is preferably formed so as to cover not only the wiring conductor 2 but also the upper surface of the insulating base 1 around the wiring conductor 2 as described above. In this case, the insulating layer 3 can be firmly bonded to the upper surfaces of the wiring conductor 2 and the insulating base 1. In addition, for example, it is easier to print and apply a ceramic paste to be the insulating layer 3, and productivity can be improved. Further, as shown in FIG. 1, the insulating layer 3 may be formed so as to cover the entire upper surface of the insulating substrate 1 except for a portion where the wiring conductor 2 needs to be exposed.

  In the wiring board 9 of the present invention, the metal plating layer 4 is preferably applied with the same width as that of the portion covered with the insulating layer 3 of the wiring conductor 2. Accordingly, it is possible to effectively prevent problems such as an electrical short circuit between the adjacent wiring conductors 2 and an increase in the electrical resistance of the wiring conductor 2, and a wiring conductor on the upper surface of the insulating base 1. The electric resistance can be made uniform with the same line width over the entire length of 2, and the wiring board 9 can be further improved in electrical characteristics.

In the following, the wiring board of the present invention will be described with reference to FIG. In addition, about the structure which is common in Embodiment 1 described previously, the same referential mark is attached | subjected and the overlapping description shall be abbreviate | omitted.

Figure 2 is a plan view showing a reference example of wiring substrate of the present invention.

  In the wiring substrate shown in the figure, the insulating base 1, the wiring conductor 2, and the insulating layer 3 are formed by the same material and the same manufacturing method as those of the first embodiment.

In FIG. 2, the wiring conductor 2 has a portion covered with the insulating layer 3 having a thickness larger than that of the exposed portion, and the exposed portion of the wiring conductor 2 is metal-plated. Layer 4 is deposited.

  This metal plating layer 4 is also made of the same metal material as that of the first embodiment described above, and is deposited and formed by the same method.

  According to the wiring board of this embodiment, the wiring conductor 2 is thicker in the portion covered with the insulating layer 3 than the exposed portion, and the metal plating layer 4 is exposed in the exposed portion. Even if the width of the wiring conductor 2 is partially narrowed so that adjacent wiring conductors are not short-circuited with the formation of the metal plating layer 4, the thickness is compensated by the thickness, and the insulating layer 3 covers it. Thus, it is possible to effectively prevent the electrical resistance from being increased in the portion that is provided.

  Also in this case, the metal conductor 4 is deposited on the exposed portion where the thickness of the wiring conductor 2 is thin, and the metal plating layer 4 can be made of, for example, low resistance gold. Electrical resistance can be kept low.

  Thereby, it can be set as low resistance over the full length of the wiring conductor 2 formed in the upper surface of the insulation base | substrate 1, and the electrical characteristic (conducting resistance) as the wiring board 9 can be made favorable.

  In addition, in order to make the thickness of the wiring conductor 2 thicker than the thickness of the exposed portion at the portion covered with the insulating layer 3, a metal paste is screen printed on the upper surface of the ceramic green sheet to be the insulating base 1. When printing and applying to a predetermined pattern by a method or the like, the screen that becomes the exposed portion of the wiring conductor 2 and the screen that becomes the portion of the wiring conductor 2 that is covered with the insulating layer 3 are separately prepared, and the insulating layer 3 It is formed by increasing the film thickness of the screen that will be the wiring conductor 2 that is to be covered with.

  In this case, the insulating layer 3 preferably has a thickness of 20 μm or more in order to reliably cover the wiring conductor 2. For example, when it is made of a ceramic material, it is more preferable that the thickness be in the range of 20 to 50 μm in consideration of securing the bonding strength to the insulating substrate 1.

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

  For example, in Embodiment 1 described above, the exposed end portion of the wiring conductor 2 with a narrow line width that is not covered with the insulating layer 3 is slightly extended to the portion covered with the insulating layer 3 and is covered with the insulating layer 3. Alternatively, the metal plating layer 4 may be deposited on a wide line width portion to reliably prevent an electrical short circuit between the wiring conductors 2.

  Further, since the exposed portion of the wiring conductor 2 may be thicker than the portion covered with the insulating layer 3 by the amount of the metal plating layer 4 deposited, in that case, the wiring conductor 2 including the metal plating layer 4 is used. The width of the exposed portion is preferably slightly narrower than the portion covered with the insulating layer 3. Then, the cross-sectional area including the metal plating layer 4 at the exposed portion of the wiring conductor 2 and the cross-sectional area of the portion covered with the insulating layer 3 are more approximate, and the electrical characteristics (conductivity) of the exposed portion of the wiring conductor 2 Resistance) and the electrical characteristics (conduction resistance) of the portion covered with the insulating layer 3 can be made substantially the same. Moreover, the space | interval of the exposed parts of the wiring conductor 2 spreads, and it becomes difficult to produce a short circuit.

Furthermore, in FIG. 2 described above, the boundary between the thin portion and the thick portion of the wiring conductor 2 does not have to coincide with the edge of the insulating layer 3 in plan view, and is slightly shifted to the insulating layer side or the opposite side. It doesn't matter.

  Furthermore, since the exposed portion of the wiring conductor 2 may be wider than the portion covered with the insulating layer 3 by the amount of the metal plating layer 4 deposited, in that case, the wiring including the metal plating layer 4 is included. The thickness of the exposed portion of the conductor 2 is preferably slightly smaller than the portion covered with the insulating layer 3. Then, the cross-sectional area including the metal plating layer 4 at the exposed portion of the wiring conductor 2 and the cross-sectional area of the portion covered with the insulating layer 3 are more approximate, and the electrical characteristics (conductivity) of the exposed portion of the wiring conductor 2 Resistance) and the electrical characteristics (conduction resistance) of the portion covered with the insulating layer 3 can be made substantially the same.

It is a top view which shows an example of the wiring board concerning Embodiment 1 of this invention. Reference Example of wiring substrate of the present invention is a plan view showing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulating board 1a ... Mounting part 2 ... Wiring conductor 3 ... Insulating layer 4 ... Metal plating layer 9 ... Wiring board

Claims (2)

  An insulating base having an electronic component mounting portion on the upper surface, a wiring conductor formed on the upper surface of the insulating base and electrically connected to the electrode of the electronic component, and the electronic component of the wiring conductor being electrically connected An insulating layer covering the wiring conductor so that a portion to be exposed is exposed, the wiring conductor is narrower than the width of the portion covered by the insulating layer, the width of the exposed portion, The wiring board is characterized in that a metal plating layer is deposited on the exposed portion.   The wiring board according to claim 1, wherein the metal plating layer is deposited with the same width as that of a portion covered with the insulating layer of the wiring conductor.

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