JP3274971B2 - Wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board used for a package for housing a semiconductor element for housing a semiconductor element or a hybrid integrated circuit board.

[0002]

2. Description of the Related Art Conventionally, a wiring board, for example, a wiring board used for a semiconductor element housing package for housing a semiconductor element is made of ceramics such as an aluminum oxide sintered body, and the semiconductor element is housed in the center of the upper surface thereof. And a wiring conductor made of a refractory metal powder such as tungsten or molybdenum which is led out from the periphery to the lower surface of the concave portion of the insulating substrate, and a semiconductor element is formed on the bottom surface of the concave portion of the insulating substrate. Glass, resin, adhesively fixed via an adhesive such as a brazing material, and electrically connecting each electrode of the semiconductor element to a wiring conductor through an electrical connection means such as a bonding wire, and thereafter,
On the upper surface of the insulating substrate, a cover made of a metal, ceramics, or the like, so as to cover a concave portion of the insulating substrate, glass, resin,
A semiconductor device as a product is obtained by joining the semiconductor element in a concave portion of the insulating base in an airtight manner by joining through a sealing material such as a brazing material. The semiconductor element to be accommodated is electrically connected to the external electric circuit board by connecting to the wiring conductor of the board via an electrical connection means such as solder.

This conventional wiring board is manufactured by a ceramic green sheet laminating method. Specifically, an organic binder suitable for a ceramic raw material powder such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, etc.
A plurality of ceramic green sheets are obtained by adding a solvent or the like to form a slurry and forming the sheet into a sheet shape by employing a conventionally known doctor blade method. Thereafter, a suitable punching process is performed on the ceramic green sheet. And a metal paste serving as a wiring conductor is printed and applied in a predetermined pattern. Finally, the ceramic green sheets are laminated vertically in a predetermined order to form a green ceramic molded body. It is manufactured by firing at a high temperature of ° C.
However, in this conventional wiring board, since the ceramics such as an aluminum oxide sintered body constituting the insulating base have a hard and brittle property, the wiring boards are not connected to each other in the transfer process or an automatic line for manufacturing semiconductor devices. If the substrate violently collides with a part of the semiconductor device manufacturing line, the insulating substrate may be chipped, cracked, cracked, etc. As a result, the semiconductor element cannot be housed in an airtight manner and the semiconductor element can be normally used for a long time. And it cannot be operated stably.

According to the method of manufacturing a wiring board,
When firing the green ceramic molded body, uneven firing shrinkage occurs in the green ceramic molded body, resulting in deformation and dimensional variation such as warpage of the obtained wiring board, and as a result, the semiconductor element and the wiring conductor are separated from each other. It has a drawback that it is difficult to electrically and accurately connect.

Accordingly, the applicant of the present application has previously filed Japanese Patent Application No.
In 3407, the insulating base of the wiring board is formed of a material obtained by bonding inorganic insulating powder with a thermosetting resin instead of the conventional ceramics, and the wiring conductor attached to the insulating base is formed of a conventional conductor. A wiring board formed of a material obtained by bonding a metal powder such as copper with a thermosetting resin instead of a metal having a high melting point such as tungsten or molybdenum, and a method of manufacturing the same have been proposed.

According to a wiring board in which a wiring conductor formed by bonding a metal powder with a thermosetting resin is adhered to an insulating base formed by bonding the inorganic insulating powder with a thermosetting resin, Insulation is achieved even if the wiring boards or the wiring board and a part of the automatic semiconductor device manufacturing line violently collide with each other because the inorganic insulating powder and the metal powder to be the wiring conductor are bonded by a thermosetting resin with excellent toughness. Chips, cracks, cracks, and the like hardly occur in the base.

Further, a wiring board in which a wiring conductor formed by bonding a metal powder with a thermosetting resin is adhered to an insulating substrate formed by bonding the inorganic insulating powder with a thermosetting resin, for example, comprises a plurality of insulating substrates. In the case where the substrates are laminated, first, a plurality of semi-cured precursor sheets prepared by mixing a thermosetting resin precursor and an inorganic insulating powder are prepared, and then the semi-cured precursor sheet is prepared. A metal paste obtained by mixing a thermosetting resin precursor and a metal powder in each is printed and applied in a predetermined pattern as necessary and heated to semi-harden the metal paste, and finally, the precursor sheet The precursor sheet and the metal paste are manufactured by completely laminating and pressing the precursor sheet and the metal paste and thermally curing the precursor sheet and the metal paste, and thermally curing the precursor sheet and the metal paste. From being produced, variation of deformation and dimensions due to non-uniform shrinkage due to sintering does not occur.

According to this wiring board, the wiring conductor is
A metal powder such as copper, silver, or gold is bonded by a thermosetting resin such as an epoxy resin, and the thermosetting resin contained in the wiring conductor is directly joined to an electrical connection means such as a bonding wire. Is not possible, and when the metal powder contained in the wiring conductor is made of copper or silver, the metal powder made of copper or silver is easily oxidized. In order to make the connection with the conductor easy and strong, and to prevent the metal powder contained in the wiring conductor from being oxidized and corroded, the surface of the wiring conductor is excellent in corrosion resistance of gold and the like, and the bonding wire and the like. It is preferable that a metal having excellent connectivity with the electrical connection means is applied by a plating method such as an electrolytic plating method.

In order to apply a plating metal layer to each wiring conductor of the wiring board by electrolytic plating, a lead-out conductor for plating leading out from each of the wiring conductors to the side surface of the insulating substrate is provided on the insulating substrate in advance. At the same time, a common conductor for plating for electrically connecting the respective lead-out conductors for plating is commonly applied to the side surfaces, and the common conductor for plating is immersed in a plating bath of an electrolytic plating apparatus. Electrically connecting the cathodes of the above and supplying electric charges for electrolytic plating to the respective wiring conductors via the common electrode for plating and the lead-out electrode for plating, thereby depositing a plating metal layer on each of the wiring conductors. It is conceivable to adopt a method in which the common conductor for plating is removed from the side surface of the insulating substrate to make each wiring conductor electrically independent.

In this case, the lead-out conductor for plating is formed by printing a metal paste to be a wiring conductor on a precursor sheet to be an insulating substrate in a predetermined pattern, and simultaneously applying the same metal paste as the metal paste to the metal paste to be a wiring conductor. Is printed and applied so as to be led out to the edge of the precursor sheet from the pattern, and the precursor sheet and the metal paste serving as the wiring conductor are cured at the same time as the precursor is cured, so that the edge of the insulating substrate is separated from each wiring conductor. The common electrode for plating is formed so as to be led out to the end, and the common electrode for plating is substantially the same as the metal paste for forming the wiring conductor and the lead-out conductor for plating. It is applied to the side surface of the insulating substrate by printing and applying on the side surface of the insulating substrate thus formed, and by thermosetting this.

However, when the wiring board is composed of a plurality of insulating substrates stacked and the lead-out conductor for plating is disposed between the insulating substrate and the insulating substrate, the lead-out conductor for plating is placed in the upper and lower insulating substrates. It is necessary to be laminated in a state of being completely embedded, otherwise, a gap is formed between the laminated insulating substrates, or it becomes impossible to hermetically seal the semiconductor element housed therein, Alternatively, a drawback is caused in that the moisture in the atmosphere enters the gap to cause corrosion of the wiring conductor, so that the semiconductor element cannot be operated normally and stably for a long period of time.

In order to laminate the insulating substrates with the lead-out conductors for plating disposed between the insulating substrates completely embedded in the upper and lower insulating substrates, it is necessary to form a precursor for each of the insulating substrates. The portions of the sheets that are in contact with the metal paste printed and applied thereto are compressed and deformed by an amount corresponding to the thickness of the metal paste by the pressure at the time of laminating and pressing the precursor sheet up and down, thereby forming a wiring conductor and plating. A method of completely embedding the metal paste to be the lead conductor in the upper and lower precursor sheets and thermally curing the upper and lower precursor sheets in that state is adopted.

[0013]

However, as semiconductor devices and hybrid integrated circuit boards have recently become smaller and denser, the wiring boards used in these devices have a higher wiring density of wiring conductors. With the increase in the wiring density of the wiring conductors and the increase in the number of the laminated insulating substrates as described above, the wiring conductors formed on the respective insulating substrates are increased. As the number of lead-out conductors for plating led out to the side of the insulating substrate from between the insulating substrates has increased, the number of lead-out conductors for plating has also been increased between the insulating substrates. For example, the lead conductors are arranged at positions where the lead conductors vertically overlap each other.

For this reason, this wiring board is formed on the same portion of the precursor sheet as the insulating substrate, particularly in the portion where the lead-out conductors for plating arranged on the upper and lower surfaces of each insulating substrate overlap each other. It is necessary to cause compressive deformation enough to simultaneously embed both the metal pastes serving as the lead conductors for plating, and as a result, this portion cannot be sufficiently compressed and deformed by the laminating pressure, and a gap is formed between the laminated insulating substrates. The semiconductor element formed and accommodated therein cannot be normally and stably operated for a long period of time.

[0015]

According to the present invention, there is provided a wiring board comprising:
5 to 40% by weight of inorganic insulating powder of 0 to 95% by weight
An insulating base formed by vertically stacking at least three insulating substrates joined by a thermosetting resin; and a plurality of wirings formed by applying a metal powder by a thermosetting resin and formed on the surface of the insulating substrate. A conductor, a plating metal layer applied to the surface of the wiring conductor by an electrolytic plating method, and a plating drawer arranged to pass from the wiring conductor to the insulating substrate and to be led out to the side surface of the insulating substrate. A wiring board having a conductor, wherein the lead-out conductor for plating is arranged at a position not to vertically overlap each other on both upper and lower surfaces of each insulating substrate, and the conductor for plating is Since the upper and lower surfaces of the respective insulating substrates are arranged so as not to overlap each other vertically, lamination failure does not occur in the insulating base.

[0016]

Next, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment in which the wiring board of the present invention is applied to a package for housing a semiconductor element for housing a semiconductor element, wherein 1 is an insulating base, and 2 is a wiring conductor.

The insulating substrate 1 is made of an inorganic insulating powder such as silicon oxide, aluminum oxide, aluminum nitride, silicon carbide, barium titanate, zeolite, etc., made of epoxy resin, polyimide resin, bismaleimide resin, thermosetting polyphenylene ether resin. And five insulating substrates 1a to 1e made of a material bonded by a thermosetting resin, etc., and have a recess A which is recessed in a stepped shape at the center of the upper surface thereof. 3 is bonded and fixed via an adhesive such as a resin.

The insulating base 1 has a portion of the insulating substrate 1e on the bottom surface of the concave portion A, and the insulating substrates 1b to 1
A part of d is exposed.

The inorganic insulating powder contained in the insulating bases 1a to 1e has a particle size of about 0.1 to 100 μm, and the coefficient of thermal expansion of the insulating substrates 1a to 1e is reduced to the coefficient of thermal expansion of the semiconductor element 3. In addition to acting to make the insulating substrates 1a to 1e good thermal conductivity and water resistance, or to impart a predetermined relative dielectric constant, etc., the heat contained in the insulating bases 1a to 1e is obtained. The curable resin functions to bind the inorganic insulating powders together and hold the insulating base 1 in a predetermined shape.

Since the insulating substrates 1a to 1e are formed by bonding inorganic insulating powder with a thermosetting resin having excellent toughness, the insulating substrate 1 may be chipped, broken, cracked or the like when the wiring substrates collide with each other. Hardly occurs.

If the content of the inorganic insulating powder contained in the insulating substrates 1a to 1e is less than 60% by weight, the thermal expansion coefficient of the insulating base 1 is lower than that of the semiconductor element 3. In comparison with the semiconductor device 3
When heat generated during the operation of the semiconductor element 3 is applied to the semiconductor element 3 and the insulating substrate 1, a large thermal stress is generated due to a difference in thermal expansion coefficient between the semiconductor element 3 and the insulating element 1. When the content of the inorganic insulating powder exceeds 95% by weight, it becomes difficult to firmly bond the inorganic insulating powder with a thermosetting resin. Therefore, the content of the inorganic insulating powder contained in the insulating substrates 1a to 1e is specified in the range of 60 to 95% by weight.

Further, the insulating substrate 1 formed by laminating the insulating substrates 1a to 1e is characterized in that the inorganic insulating powder contained in the insulating substrates 1a to 1e is made of silicon oxide and the thermosetting resin is made of epoxy resin. Epoxy resin such as bisphenol A type epoxy resin, novolak type epoxy resin, glycidyl ester type epoxy resin and amine type curing agent, imidazole type curing agent, acid anhydride type curing on silicon oxide powder with particle size of about 0.1-100 μm A curing agent such as an agent is added and mixed to form a paste, and this is formed into a sheet by employing a conventionally known doctor blade method, thereby obtaining a precursor sheet in a semi-cured state to become the insulating substrates 1a to 1e. ,
Thereafter, the precursor sheets in the semi-cured state to be the insulating substrates 1a to 1e are subjected to appropriate punching and stacked up and down to obtain a precursor sheet laminate in the semi-cured state to be the insulating substrate 1. Finally, the precursor sheet laminate in the semi-cured state is heated at a temperature of about 80 to 300 ° C. for about 10 seconds to 24 hours.
Manufactured by heating and curing completely for a period of time.

The insulating substrate 1 is further provided on the insulating substrate 1b from the upper surface of the insulating substrate 1b to 1d exposed on each step of the concave portion A.
A large number of wiring conductors 2 penetrating through to 1e and leading out to the lower surface of the insulating substrate 1e are formed by bonding metal powder of, for example, copper, silver, gold or the like with a thermosetting resin such as an epoxy resin.

The wiring conductor 2 serves to electrically connect the semiconductor element 3 housed therein to an external electric circuit.
Each electrode of the semiconductor element 3 is electrically connected to each upper portion of the recess A through a bonding wire 4, and a portion extending to the lower surface of the insulating base 1 is electrically connected to an external electric circuit board. You.

The metal powder contained in the wiring conductor 2 is as follows:
The wiring conductor 2 acts to impart conductivity to the wiring conductor 2.
If the content in the wiring conductor 2 is less than 70% by weight, the conductivity of the wiring conductor 2 tends to be deteriorated. If the content in the wiring conductor 2 exceeds 95% by weight, the metal powder may be strongly bonded with the thermosetting resin. It tends to be difficult. Therefore, the content of the metal powder contained in the wiring conductor 2 in the wiring conductor 2 is preferably in the range of 70 to 95% by weight.

If the average particle size of the metal powder contained in the wiring conductor 2 is less than 0.5 μm, the contact resistance between the metal powders increases and the electric resistance of the wiring conductor 2 becomes high. When the thickness exceeds 50 μm, the wiring conductor 2 having a predetermined pattern is generally required on the insulating substrate 1.
It tends to be difficult to form a line width of about 200 μm to 200 μm. Therefore, it is preferable that the metal powder contained in the wiring conductor 2 has an average particle size of 0.5 to 50 μm.

The thermosetting resin contained in the wiring conductor 2 functions to bond the metal powders in contact with each other and to attach the wiring conductor 2 to the insulating base 1, and to provide bisphenol. It is made of an epoxy resin such as an A-type epoxy resin, a novolak-type epoxy resin, and a glycidyl ester-type epoxy resin, and a thermosetting resin such as a phenol resin, a polyimide resin, a bismaleimide resin, and a thermosetting polyphenylene ether resin.

If the content of the thermosetting resin in the wiring conductor 2 is less than 5% by weight, the metal powder cannot be firmly bonded to each other, and it becomes difficult to firmly adhere the wiring conductor 2 to the insulating base 1. When the content in the wiring conductor 2 exceeds 30% by weight, it is difficult to bring the metal powders into sufficient contact with each other, and the electric resistance of the wiring conductor 2 tends to be large. Therefore, the content of the thermosetting resin contained in the wiring conductor 2 in the wiring conductor 2 is preferably in the range of 5 to 30% by weight.

For example, when the metal powder and the thermosetting resin contained in the wiring conductor 2 are made of copper and epoxy resin, respectively, the powder of copper or the like having a particle size of about 0.1 to 20 μm is added to bisphenol A. Epoxy resin, novolak type epoxy resin, glycidyl ester type epoxy resin and other epoxy resin and amine paste curing agent, imidazole curing agent, acid anhydride curing agent, etc. The semi-cured precursor sheet to be the substrates 1b to 1e is printed and applied in a predetermined pattern with a predetermined thickness by using a conventionally well-known screen printing method, and is thermally cured together with the semi-cured precursor sheet laminate. Thereby, it is adhered and formed so as to be led out from above each step of the concave portion A of the insulating base 1 to the lower surface of the insulating base 1.

The wiring conductor 2 is provided with a plating metal layer 5 made of nickel and gold on an exposed surface to a predetermined thickness by employing a conventionally known electrolytic plating method.
This effectively prevents the wiring conductor 2 from being oxidized and corroded, and makes it possible to easily and firmly connect the wiring conductor 2 to the bonding wires 4 and the wiring conductor of the external electric circuit board. .

The plating metal layer 5 applied to the wiring conductor 2 is immersed in a plating bath of a conventionally well-known electrolytic plating apparatus, and the wiring metal adhered to the insulating substrate 1 is formed. The conductor 2 is applied to the exposed surface of the wiring conductor 2 by supplying a charge for electrolytic plating via a lead-out conductor 6 for plating, which will be described later. A gold plating layer having a thickness of about 5 μm is sequentially applied. The nickel plating layer functions as a base plating layer, and the gold plating layer functions as a finish plating layer.

Further, each of the insulating substrates 1 is
b to 1d, between the insulating substrates 1a and 1b, between 1b and 1c, 1c and 1d, respectively.
And a large number of lead-out conductors 6 for plating that are led out to the side surface of the insulating base 1 through the space between them.

The lead-out conductor 6 for plating is formed by
Acts as a conductive path for applying a charge for electrolytic plating from the side surface of the insulating base 1, as described above.
Is immersed in a plating bath of an electrolytic plating apparatus, and a charge for electrolytic plating is supplied to each wiring conductor 2 via the lead-out conductor 6 for plating, so that a plating metal layer 5 is formed on an exposed surface of each wiring conductor 2. Is formed.

The lead-out conductor 6 for plating is made of the same material as that of the wiring conductor 2, and the same metal paste as the metal paste forming the wiring conductor 2 is applied to the insulating substrates 1 b-1.
On the semi-cured precursor sheet 1d, the metal paste for the wiring conductor 2 is printed and applied at the same time as the metal paste is printed, and this is thermally cured together with the precursor sheet laminate for the insulating substrate 1 to form the insulating substrate 1 It is disposed so as to be led out to the side surface of the insulating base 1 from each wiring conductor 2 through the space between the insulating substrates 1a and 1b, between 1b and 1c, and between 1c and 1d.

As shown in FIG. 2, the lead-out conductor 6 for plating is formed on the upper and lower surfaces of the insulating substrate 1b and the upper and lower surfaces of 1c.
They are arranged at positions that do not overlap each other.

In the wiring board, since the lead-out conductors 6 for plating are arranged on the upper and lower surfaces of the insulating substrate 1b and the upper and lower surfaces of the insulating substrate 1b so as not to be vertically overlapped with each other, the precursor to be the insulating base 1 is formed. When the sheets are stacked one on top of the other, the metal paste that becomes the lead-out conductor 6 for plating is not simultaneously buried from above and below in the same part of each precursor sheet. The metal paste can be completely compressed and deformed by the pressure of the laminating pressure to completely embed the metal paste in each of the precursor sheets. As a result, each of the insulating substrates 1a to 1e becomes
The semiconductor elements 3 are air-tightly stacked without generating a gap between 1e, and the semiconductor elements 3 housed therein can operate normally and stably for a long period of time.

In order to apply a charge for electrolytic plating to each wiring conductor 2 via the lead-out conductor 6 for plating, as shown in FIG. A common conductor for plating 7 that electrically connects the lead conductors 6 in common is adhered thereto, and the common conductor for plating 7 is brought into contact with a cathode of an electrolytic plating apparatus to thereby form a common conductor for plating 7 and a lead conductor for plating. 6, a method of applying a charge for electrolytic plating to each wiring conductor 2 through the wiring conductor 6 is adopted, and the plating common conductor 7 attached to the side surface of the insulating base 1 is plated on the exposed surface of each wiring conductor 2. After the metal layer 5 is applied, the metal layer 5 is removed together with a part of the insulating base 1 by, for example, a mechanical polishing method or a mechanical cutting method, so that each wiring conductor 2 as shown in FIG. Completed wiring board .

Thus, according to the wiring board of the present invention, the semiconductor element 3 is bonded and fixed to the bottom surface of the recess A of the insulating base 1 and each electrode of the semiconductor element 3 is electrically connected to the wiring conductor 2 via the bonding wire 4. Finally, the lid 8 is joined to the upper surface of the insulating base 1 via a sealing material, thereby obtaining a semiconductor device as a product.

It should be noted that the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the gist of the present invention. Although the case where the wiring board of the present invention is applied to a package for housing a semiconductor element for housing a semiconductor element has been described as an example, this may be applied to a wiring board used for a hybrid integrated circuit board or the like.

In the above-described embodiment, the wiring substrate is formed by laminating five insulating substrates. However, the wiring substrate is formed by laminating three, four, or six or more insulating substrates. It may be formed by performing.

Further, in the above-described embodiment, the wiring conductor and the lead-out conductor for plating are formed by bonding metal powder with a thermosetting resin. It may be formed by bonding with a resin. In this case, an appropriate amount of a low-melting metal such as solder is contained in the metal paste to be the wiring conductor and the lead for plating, and the metal paste to be the wiring conductor and the lead for plating is thermally cured or heated. A method of bonding the metal powder with the low melting point metal by melting the low melting point metal contained in the metal paste at the same time as the curing is performed.

[0043]

According to the wiring board of the present invention, since the insulating base is formed by bonding the inorganic insulating powder with the thermosetting resin having excellent toughness, the wiring boards are connected to each other or the wiring board and the semiconductor device manufacturing line. Even when a part of the insulating substrate collides violently, the insulating substrate is not chipped, broken or cracked.

Further, according to the wiring board of the present invention, since the lead-out conductors for plating are arranged so as not to vertically overlap each other on the upper and lower surfaces of each of the insulating substrates constituting the insulating base, the lead to be the insulating base is formed. When the body sheets are stacked on top of each other, the metal paste to be the lead conductor for plating is not simultaneously embedded from the top and bottom in the same portion of each precursor sheet, and therefore, the precursor sheets to be the insulating base are stacked. The metal paste can be fully compressed and deformed by the pressure of the pressurization, and the metal paste can be completely embedded in each of the precursor sheets. As a result, each of the insulating substrates can be hermetically sealed without generating a gap therebetween. The semiconductor elements stacked and housed therein can operate normally and stably for a long period of time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment in which a wiring board of the present invention is applied to a package for housing a semiconductor element.

FIG. 2 is a side view of an insulating base of the package for housing a semiconductor element shown in FIG. 1;

FIGS. 3A and 3B are cross-sectional views for each process for explaining a method of applying a plating metal layer to a wiring conductor of a wiring board according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulating base 1a-1e ... Insulating board 2 ... Wiring conductor 3 ... Semiconductor element 5 ... Plating metal layer 6 ...・ Lead conductor for plating

Claims (1)

(57) [Claims] 1. An inorganic insulating powder of 60 to 95% by weight is mixed with 5
An insulating base formed by vertically stacking at least three insulating substrates joined by a thermosetting resin of about 40% by weight;
A plurality of wiring conductors formed on the surface of the insulating substrate by bonding a metal powder with a thermosetting resin; a plating metal layer formed on the surface of the wiring conductor by an electrolytic plating method; And a lead-out conductor for plating disposed so as to pass from the conductor to between the insulating substrates and to be led out to the side surface of the insulating base, wherein the lead-out conductors for plating are vertically arranged on both upper and lower surfaces of each insulating substrate. A wiring board, wherein the wiring board is arranged so as not to overlap with the wiring board.