JP4116656B2 - High-strength circuit board and manufacturing method thereof - Google Patents

Description

The present invention relates to a high-strength circuit board using a silicon nitride (Si ₃ N ₄ ) sintered body as an insulator layer, a semiconductor device using the same, and a method for manufacturing the high-strength circuit board. In particular, the present invention relates to a high-strength circuit board having a single-layer wiring or a multilayer wiring in which an insulator layer and a conductor layer are integrally sintered.

  With the downsizing of electronic devices, how to efficiently dissipate heat generated from semiconductor elements mounted on a circuit board has become an important issue. Also, heat dissipation is an important issue when mounting power semiconductor elements.

Conventionally, Al ₂ O ₃ ceramic has been widely used as an insulating material for circuit boards. Here, since Al ₂ O ₃ has a low thermal conductivity of 20 W / mK at the maximum, there is a problem in heat dissipation.
Japanese Patent Application Laid-Open No. 60-178688 discusses the application of AlN ceramics having excellent electrical characteristics as an insulator such as electrical insulation and thermal conductivity to circuit boards.

However, AlN and Al ₂ O ₃ are weak against thermal stress caused by heat generation from the semiconductor element, and AlN ceramics have a four-point bending strength of about 300 MPa and the strength is low, and cracking occurs when thermal stress is concentrated. There is. This is not a phenomenon limited to AlN, and the same cracking phenomenon + is observed because Al ₂ O ₃ has a low sintered body strength. In addition, AlN ceramics have poor chemical resistance such as water resistance, acid resistance, and alkali resistance, and due to the stress caused by the difference in thermal expansion coefficient from the metal when the external terminals are joined with silver solder or solder, There is also a problem that a bonded portion with a pin, a lead or a ball which is a typical metal terminal is easily broken.

Japanese Unexamined Patent Publication No. 4-212441 discloses a ceramic substrate in which such problems are generally solved. This ceramic substrate is made of Si ₃ N ₄ , has higher heat dissipation than an alumina substrate, and is excellent in environmental resistance, mechanical strength, and electrical characteristics.

By the way, considering miniaturization and high density of electronic devices, high density wiring is required for wiring of circuit boards, and multilayering is an essential technology. However, the existing multilayer technology is to integrally sinter an AlO ₃ ceramic plate or an AlN ceramic plate and a conductor layer, and the multilayer technology of the Si ₃ N ₄ ceramic plate and the conductor layer has not yet been established. Further, in the existing multilayer technology, the circuit board or semiconductor device formed thereby has problems such as generation of warpage, disconnection of the conductor circuit, or peeling.

The present invention relates to a circuit board using Si ₃ N ₄ ceramics that has strong adhesion between a conductor layer and an insulator layer and is unlikely to cause warping or disconnection, a semiconductor device using the same, and a method for manufacturing the circuit board. An object of the present invention is to provide a high bonding strength circuit board having a single layer wiring or a multilayer wiring by simultaneous sintering.

The inventors have
In a circuit board including at least an insulator layer and at least a conductor layer,
At least one of all the insulator layers is a sintered body containing β-Si ₃ N ₄ as a main component and containing one or more elements selected from the group consisting of rare earth elements and alkaline earth elements, And at least one of all the conductor layers is selected from the group consisting of one or more elements selected from elements belonging to groups IVa, Va and VIa of the periodic table, and rare earth elements and alkaline earth elements. It has been found that a circuit board characterized by containing more than one kind of element and a semiconductor device using the same can solve the above problems.

In addition, the inventors added at least one compound containing an element selected from the group consisting of rare earth elements and alkaline earth elements as a sintering aid, and then sintered α-Si ₃ N ₄ . Forming an insulator layer;
A conductor layer is formed by adding one or more elements selected from the group consisting of rare earth elements and alkaline earth elements to one or more elements selected from elements belonging to groups IVa, Va and VIa of the periodic table. It has been found that a method of manufacturing a circuit board comprising the step of forming; and the step of simultaneously sintering the insulator layer and the conductor layer can solve the above-mentioned problems.

First, the insulator layer in the circuit board according to the present invention will be described.
The insulator layer is a polycrystalline sintered body containing β-Si ₃ N ₄ as a main component. This insulator layer has a high strength of 700 MPa or more. Here, the strength is preferably set to 1,000 MPa or more by optimizing the composition and sintering conditions.

The thermal conductivity is preferably 30 W / mK or higher, more preferably 70 W / mK or higher, than that of alumina. For example, as the insulator layer having a thermal conductivity of 70 W / mK, a material having a small amount of oxygen contained in the raw material powder of Si ₃ N ₄ is used. When Al ₂ O ₃ is added, the amount added is preferably 0.8% by weight or less, and more preferably 0.25% by weight or less. When optimized, an insulator layer having a thermal conductivity of 130 W / mK or higher is obtained.

Next, a method for manufacturing this insulator layer will be described. First, a Si ₃ N ₄ green sheet is prepared. This green sheet can be obtained by, for example, a doctor blade method or the like by sufficiently mixing Si ₃ N ₄ powder, a sintering aid, a binder (binder) and the like together with a solvent.

Relates _Si 3 _{N 4} powder to be used is not particularly limited, considering the thermal conductivity of the insulating layer, it is preferable that the oxygen content employed 3.0 wt% or less of _α-Si 3 _{N 4} powder. More preferably, the amount of oxygen is less than 2.0% by weight, and still more preferably less than 1.5% by weight.

The Si ₃ N ₄ powder to be used preferably has a small particle diameter, and the average particle diameter is preferably less than 2 μm. More preferably, it is less than 1 μm. More preferably, it is less than 0.8 μm. In particular, a powder containing 70% by volume or more of particles of less than 1 μm is optimal. Further, the Si ₃ N ₄ raw material powder preferably uses the α type crystal system, but can be used if the β type powder is 50% by volume or less. Also, the cation impurity is preferably less than 3,000 ppm. More preferably, it is 1,500 ppm, More preferably, it is less than 900 ppm. When a large amount of cationic impurities is contained, there is a disadvantage that the sintered body does not have high thermal conductivity. Anionic impurities other than oxygen are preferably less than 2,000 ppm. More preferably, it is 1,000 ppm, More preferably, it is less than 500 ppm. When a large amount of anionic impurities other than oxygen is contained, the sintered body does not have a high thermal conductivity. Further, the smaller the amount of oxygen in the sintered body, the higher the thermal conductivity, which is preferable.

Next, as the sintering aid to be added, at least one kind of rare earth elements such as Sc and Y and alkaline earth elements may be added in the form of a simple substance and / or a compound. For example, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Be, Mg, Ca, Sr, and Ba can be used. These rare earth elements and alkaline earth elements such as Y, Ce, La, Sc, Be, and Mg contribute to densification of the Si ₃ N ₄ ceramics, and oxygen in the Si ₃ N ₄ powder is a substructure of the grain boundary. It traps in the phase and greatly contributes to high thermal conductivity. Particularly preferable elements are Y, Ce, La, Yb, Sc, Be, and Mg elements having such a large effect.

  As a form of the compound containing these elements, an oxide form is particularly preferable, and a compound that becomes an oxide under sintering conditions may also be used. That is, carbonates, nitrates, oxalates, sulfates, hydroxides, and the like can also be used. Such sintering aids are added in the form of oxides, halides, acid halides, acetylide compounds, carbides, hydrides, nitrides, borides, silicides, sulfides and the like. For these rare earth elements and alkaline earth elements, the optimum amount should be determined in consideration of the amount of oxygen contained in the raw material powder, but it is 0.1 to 10% by weight in terms of oxide, preferably 1 Desirably, it is ˜8% by weight. Further, when both a compound containing rare earth elements and alkaline earth elements are added, or a complex compound containing both elements is added, sintering can be performed at a low temperature, and the sintering start temperature is reduced by 200 ° C. at the maximum. be able to.

Moreover, when a compound containing Si element is added as an auxiliary additive for sintering, the sinterability may be improved. If necessary, it is added. As a specific example, when a Si ₃ N ₄ raw material powder having a small amount of oxygen is used, a dense sintered body can be easily obtained by adding SiO ₂ for improving the sinterability. Further, when a compound containing Al element is added, a grain boundary component is crystallized, and a high strength Si ₃ N ₄ sintered body is obtained. The same effect can be obtained even when AlN is added.

  Furthermore, the circuit board is required to be colored, that is, light-shielding, depending on the application. In this case, light can be shielded from the near-ultraviolet region to the infrared region by adding group IVa, Va, VIa, VIIa, or Group VIII element alone or a compound in the periodic table. The addition amount may be 0.03 to 5% by weight in terms of element. More preferably, it may be added in an amount of 0.1 to 3% by weight, and more preferably 0.2 to 1% by weight.

  These additives such as sintering aids may be added to the raw material powder in advance. However, depending on the type of additive, it may be added later by a method such as impregnation.

Next, the binder used is preferably an organic polymer that decomposes at a temperature of 1,400 ° C. or lower.
Specifically, it is possible to use one or two or a mixture of three or more oxygen-containing organic polymers such as polymethyl methacrylate, polyvinyl butyral, polyacrylic acid ester, polyvinyl alcohol, cellulose acetate butyrate, and cellulose. it can.
Selection of the type and amount of the binder and the amount of the solvent is arbitrarily selected depending on the characteristics of the Si ₃ N ₄ raw material powder, the thickness of the sheet to be manufactured, and the like. The binder removal may be performed in a non-oxidizing atmosphere such as N ₂ , Ar, H ₂ or the like. Furthermore, H ₂ O may be included when it is desired to reduce the carbon after the binder removal. When a green sheet containing the above Si ₃ N ₄ powder, a sintering aid, a binder or the like is sintered, an insulating layer is formed. Preferred sintering conditions will be described later.

  Next, the conductor layer in the circuit board according to the present invention will be described.

The conductor in the conductor layer is not particularly limited as long as it can withstand the sintering temperature of the Si ₃ N ₄ ceramics. Preferably, IVa, Va, VIa group element simple substance of a periodic table, or a compound is included. More preferably, a single metal of Mo, W, Ti, Zr, Nb, and Ta or a compound containing these elements is used as the type of the conductor. More preferred are Mo, W, Ti, and Zr. Further, different elements of IVa, Va and VIa group elements of the periodic table may be mixed, or both a single metal and a compound may be used. Furthermore, you may contain a trace amount of low melting point noble metal elements (Au, Ag, Cu, Pt, Pd etc.).

  The conductor layer of the present invention further contains at least one element selected from alkaline earth elements and rare earth elements. Examples of rare earth elements and alkaline earth elements include Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Be, Mg, Ca, Sr and Ba are mentioned. In particular, Y, Ce, La, Yb, Sc, Be, and Mg are preferable industrially. In addition, compounds that become oxides under sintering conditions can be used, and carbonates, nitrates, oxalates, sulfates, hydroxides, and the like can also be used. Such additives are added in the form of halides, acid halides, acetylide compounds, carbides, hydrides, nitrides, borides, silicides, sulfides, etc. in addition to oxide forms.

  The content of the compound containing an element selected from rare earth elements and alkaline earth elements in the conductor layer is preferably 0.01 to 1.71% by weight in terms of oxide. This is because if the amount is too large, the conductivity of the conductor layer decreases, and if the amount is too small, effects such as prevention of peeling of the conductor layer and prevention of warping of the substrate cannot be obtained.

  When a simple substance or compound containing Si and / or Al element is further added to the conductor layer, a dense conductor layer having a larger relative density than that obtained without addition can be obtained. Effects such as improvement in strength and prevention of warping of the substrate can be obtained. Such additives form an aluminate liquid phase or a silicate liquid phase during simultaneous sintering. In addition, an aluminate liquid phase and a silicate liquid phase are also generated in the insulator layer during simultaneous sintering. As described above, the aluminate liquid phase and the silicate liquid phase are generated in the conductor layer, so that the liquid phase generated in the insulator layer is prevented from being sucked up by the conductor layer. Uniformity can be prevented and warping of the substrate can be prevented. This addition may be performed in the form of a mixture with a compound containing an element selected from rare earth elements and alkaline earth elements, or in the form of a complex compound with these elements. In this case, the amount of the compound containing an element selected from rare earth elements and alkaline earth elements, and a simple substance or a mixture of compounds containing Si and / or Al elements (or in the form of a composite compound containing these elements). ) Is preferably 0.05 to 20% by weight in terms of oxide.

  Next, the manufacturing method of the circuit board of this invention is demonstrated.

First, it is possible to maintain conductivity even after simultaneous sintering. Specifically, powders of group IVa, Va, and VIa elements or compounds in the periodic table are made into a paste, and a desired pattern is formed on the Si ₃ N ₄ green sheet. Print with. At this time, via holes are formed in the green sheet using a punching machine or the like, and a conductive paste to be a conductor after sintering is filled in advance by press filling or metal filling using a metal mask or the like. This via hole makes an electrical connection between the upper and lower conductors sandwiching the green sheet.

  To this conductor paste, a simple substance or a compound containing at least one of a rare earth element and an alkaline earth element, and further a simple substance or a compound containing Si and / or Al elements as necessary are added.

When this Si element or Al element is added in the form of a mixture together with a simple substance or a compound containing a rare earth element or the like, it is preferable to mix them at a ratio so as to form aluminate or silicate. For example, when alumina is added as a compound containing an Al element, the amount of alumina is preferably 0.03 to 10% by weight so that aluminate can be formed. More preferably, it is 0.05-5 weight%, More preferably, it is 0.1-1 weight%. Further, for example, when adding SiO ₂ as a compound containing a Si element, it is preferred that the amount of SiO ₂ is 0.03 to 10 wt% so as to form a silicate. More preferably, it is 0.05-5 weight%, More preferably, it is 0.1-1 weight%.

Further, the element selected from the rare earth elements and alkaline earth elements in the conductor layer is preferably the same type as the sintering aid for Si ₃ N ₄ ceramic. Even if different types are used, aluminate and silicate are generated in the insulating layer and in the conductor layer, but if the same type is used, the same aluminate and silicate are generated in the insulating layer and in the conductor layer. , Tissue non-uniformity is prevented and the suction is prevented. Therefore, the warpage of the substrate is further prevented.

  Note that even when the element is added in the form of a simple substance or a compound only to the via hole portion where the volume of the conductor is increased, the substrate may not be warped. That is, depending on the size of the substrate and the arrangement of the conductor layer determined by design, a circuit substrate with less warping may be obtained if it is added to at least a portion of the conductor layer.

The multilayer green molded body to which the conductive paste containing such components is applied is debindered and then subjected to a sintering process. This sintering step is not particularly limited, and a known sintering method performed with silicon nitride is employed as it is. The material of the setter when set in the sintering furnace can sinter the circuit board by using graphite, BN, AlN, etc., but the most preferable is a setter made of Si ₃ N _4. When used, even when sintered at high temperatures, the reaction that tends to occur in a part of the sintered body (reaction between the setter and non-sintered material) does not occur at all, and the surface roughness after sintering is very small and good. A simple circuit board is obtained. The surface roughness is 1.0 μm or less in terms of average surface roughness Ra. Those having a better surface are 0.5 μm or less, and those having a better surface are 0.3 μm or less. In general, sintering may be performed at a temperature of 1,500 ° C. to 1,950 ° C. in a non-oxidizing atmosphere under normal pressure, under pressure, or under reduced pressure, for example, under a nitrogen atmosphere or an argon atmosphere. When the sintering temperature is set to a high temperature, a portion of silicide is generated, but when the sintering temperature is set to 1850 ° C. or less, the generation of silicide is reduced. More preferably, it is 1,800 degrees C or less, More preferably, it is 1,750 degrees C or less. Although the time required for sintering varies depending on various conditions such as the thickness of the compact to be sintered and the sintering temperature, it is generally selected from the range of 0.5 to 100 hours. It is preferable that these conditions are carried out by determining an appropriate range in advance according to various conditions prior to implementation.

In order to make the resulting Si ₃ N ₄ circuit board dense with high heat conduction and further high strength, the average heating rate should be in the range of 1 to 40 ° C./min, particularly at a high temperature part of 1,000 ° C. or higher. Is preferred. More preferably, it is 5-30 degreeC / min, More preferably, it is preferable to set it as the range of 8-25 degreeC / min. By the sintering, a Si ₃ N ₄ insulating layer having a relative density of 95% or more is obtained. As a denser structure, an insulating layer of 98% or more, further 99% or more can be obtained.

  The circuit board manufactured in this way has the following characteristics.

First, the circuit board of the present invention has a very small value of parallelism between the front and back sides, and the warpage and undulation are very small, so that the number of external terminals is very large (for example, 1,000 terminals or more). Even on a board, solder connection can be easily performed during mounting. The degree of parallelism representing the presence or absence of warpage or undulation of the substrate was obtained by measuring the maximum value of warpage between the central portion and the peripheral portion with respect to 10 cm diagonal of the sintered multilayer circuit board. Very small value of 0.5mm or less.
In the case of a circuit board having a large area, mounting is possible by using a board having a parallelism of 0.3 mm or less.

  Further, the internal resistance of this circuit board was a good value with a surface resistance and an internal resistance of 200 μΩcm or less. In addition, when the conductor layer is formed by containing Si and / or Al element, a conductor having a high density and a low resistivity can be obtained, and at the same time, the formation of silicide can be suppressed and the resistance can be reduced. A conductor is formed. This optimization resulted in a circuit board having a resistivity of 50 μΩcm or less, and in some cases 20 μΩcm. As a method for suppressing the formation of silicide, AlN may be added as a feeler in the conductor layer.

Further, the bonding strength between the insulator layer and the conductor layer in the circuit board is a value of 5 kg / 2 mm × 2 mm or more. When the value is less than 5 kg / 2 mm × 2 mm, when a pin is used for the external terminal, the bonding strength is insufficient, and the pin is dropped between Si ₃ N ₄ and the conductor. In particular, in the case of BGA (ball grid array package), an organic material having a large thermal expansion coefficient such as a printed wiring board is required to have a higher bonding strength when performing surface mounting with a narrow pitch between balls. At that time, a conductor layer composition having a bonding strength of 6 kg / 2 mm × 2 mm or more may be selected. By further optimizing, it has a bonding strength of 7 kg / 2mm × 2mm or more.

  A suitable semiconductor device using the circuit board of the present invention will be described with reference to FIGS. In this semiconductor device, a semiconductor element 6 such as ECL is mounted on a substrate upper surface 12a, and the multilayer ceramic circuit board 12 having a wiring pattern electrically connected to the semiconductor element is electrically connected to the wiring pattern. In addition, an external terminal formed on the lower surface 12b of the multilayer ceramic circuit board 12 and a high thermal conductive sealing member 13 joined to the upper surface 12a of the multilayer ceramic circuit board so as to cover the semiconductor element 6 are provided. Yes. However, even if the external terminal and the semiconductor element are on the same main surface, they can be used without any particular problem. The external terminals are preferably lead pins 7 as shown in FIG. 2, or solder balls 15 (BGA ball grid array) as shown in FIG. The high thermal conductivity member is preferably composed of a silicon nitride or aluminum nitride sintered body having a thermal conductivity of 100 W / mK or more, or a metal including an alloy.

  According to the semiconductor device having the above configuration, heat generated in the semiconductor element is efficiently transmitted to a heat radiating fin or the like (the fin may not be used in some cases), and excellent heat dissipation can be exhibited.

  In addition, when a semiconductor element is mounted on the other main surface of the silicon nitride circuit board facing the bonding surface of the external terminal on the structure of the semiconductor device, the semiconductor device is reduced in size after being adapted to the increase in the number of pins. It is more preferable as a high-speed semiconductor device. Further, when the temperature changes between when the semiconductor is operating and when the semiconductor is stopped, the insulating layer of the circuit board is made of silicon nitride, so that stress is applied to the pins and solder ball portions of the external terminals. However, since the strength is high, defects such as cracks do not occur. Furthermore, when a semiconductor device is configured in the form of a multichip module (MCM) in which a large number of semiconductors are mounted on a single circuit board, external terminals must be bonded to the board over a wide area. In this respect, sufficient reliability can be obtained.

  In order to describe the present invention more specifically, examples will be described below, but the present invention is not limited to these examples.

Examples of the present invention will be described below.
(Example)
A sintering aid is added to Si ₃ N ₄ powder containing 95% α-Si ₃ N ₄ , the other being β phase, containing 1.4 wt% oxygen as an impurity, and having an average particle size of 0.6 μm. 5% by weight of Y ₂ O ₃ having an average particle diameter of 0.7 μm and 0.25% by weight of α-Al ₂ O ₃ having an average particle diameter of 0.8 μm are added, and WO ₃ is converted into W metal as a colorant. Was added at 0.3% by weight, and wet mixing was performed using Si ₃ N ₄ balls for 24 hours to prepare raw materials. Next, an organic binder was dispersed in this raw material together with an organic solvent to prepare a slurry. After the slurry was degassed, a uniform green sheet of about 100 to 800 μm was produced by the doctor blade method. Next, this sheet was cut into a size of about 130 mm × 130 mm, and a via hole for connecting an electric circuit between each layer was opened to a thickness of 100 to 300 μm φ by a punching machine.

On the other hand, 97.0% by weight of tungsten having an average particle diameter of 1.1 μm, 1.71% by weight of Y ₂ O ₃ having an average particle diameter of 0.7 μm, and 1.29% by weight of Al ₂ O ₃ having an average particle diameter of 0.8 μm. % Was mixed and dispersed together with an organic solvent to prepare a conductor paste with filler added. The green paste on which via holes were formed was filled with this inorganic filler-added tungsten paste using a press-fitting machine, and further a circuit in the same plane was printed using a screen printer. The lamination process was completed by heat-pressing these multiple sheets. This was cut to a size of 10 mm, and then the binder was removed in a N ₂ + H ₂ + H ₂ O atmosphere at a maximum temperature of 900 ° C., and then the molded body that had been removed from the binder was placed on a Si ₃ N ₄ setter, and nitrogen was removed. A multilayer ceramic substrate was obtained by pressure sintering at 1,850 ° C. for 3 hours in an atmosphere of 10 atmospheres. A disc (diameter 10 mm, thickness 3.5 mm) was cut out from the portion of the obtained substrate without the conductor portion, and the thermal conductivity was measured by a laser flash method using this as a test piece.

  Further, the front / back parallelism indicating the presence / absence of warpage of the substrate was determined by measuring the maximum value of the warpage between the central portion and the peripheral portion with reference to the diagonal line of the sintered multilayer substrate.

Next, the cross-sectional area of the conductor layer was calculated, and the conductor resistivity of the conductor layer was determined from the resistance value. However, the surface wiring was measured without conducting metal plating on the conductor layer, and the effect of adding an inorganic filler was observed. Furthermore, after Ni plating was performed on a 2 mm conductor portion of the obtained substrate, a wire was soldered, a tensile strength test was performed, and an adhesive strength between the Si ₃ N ₄ substrate and the conductor layer was measured. These results are shown in Tables 1 and 2.

Similar to Example 1 except that the type of Si ₃ N ₄ powder, the type of sintering aid powder of the Si ₃ N ₄ substrate, the type and amount of sintering aid filler, the conductor and the sintering conditions were variously changed. Then, a Si ₃ N ₄ multilayer ceramic substrate was produced, and the thermal conductivity, tensile strength, front / back parallelism, and surface resistance were measured for each. The results are shown in Tables 1 and 2. As is apparent from Table 2, it can be seen that the adhesion strength of the conductor layer is improved in the circuit board according to the present invention.

For example, in Example 1, the tensile strength was 6.8 kg / 2 mm × 2 mm, whereas in Comparative Example 1, the adhesion strength was insufficient, 3.5 kg / 2 mm × 2 mm.
In addition, it is understood that the simultaneous sintered body in the present invention has less warpage represented by the front and back sintered bodies, and the specific resistance is not improved at all compared to the additive-free one even though the amount added is included. .

(Example 48)
A circuit board was prepared using an insulating layer and a conductor layer having the same configuration as in Example 2. This circuit board is a 25 mm × 25 mm × 2.6 mm silicon nitride multilayer circuit board having an internal wiring layer. 240 lead pins were joined to the other side of the silicon nitride multilayer circuit board using 240 Ag solder. Thereafter, a silicon element with a power consumption of 10 W was bonded and mounted as a semiconductor element on the upper surface of the silicon nitride multilayer circuit board, and a bonding wire was attached to complete electrical connection.
Furthermore, a high thermal conductive sealing member that also serves as a heat radiating member was prepared by the silicon nitride sintered body having a thermal conductivity of 150 W / mK in the manner of manufacturing the insulator portion of Example 2. Then, the target semiconductor device was obtained by bonding the upper surface of the silicon nitride multilayer circuit board with Au—Sn solder, and disposing a heat radiation fin having a circular seven-stage structure with a diameter of 25 mm on the sealing member.
In order to evaluate the heat dissipation of this semiconductor device, the cooling air speed was set to 1.5 m / s and the thermal resistance was measured by the ΔVBE method. The heat resistance was as low as 2.7 ° C / W. It has been found that a semiconductor device having a high level can be obtained.

(Comparative Example 11)
Although it carried out like Example 48, when alumina was used for the insulating layer, the thermal resistance value was 8 ° C./W.

[The invention's effect]
As described above, in the Si ₃ N ₄ ceramic circuit board of the present invention, the insulator has high thermal conductivity, the adhesion of the conductor layer is strong, the deformation of the board during the sintering process is small, and the tensile strength Has various excellent properties such as exhibiting sufficiently practical characteristic values, and its industrial value is extremely large.

It is a partial notch perspective view which shows the multilayer ceramic circuit board of this invention. It is the figure which showed the semiconductor device (when an external terminal is a lead pin) using the multilayer ceramic circuit board of this invention. It is a fragmentary sectional view of the semiconductor device whose external terminal is a solder ball.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,12 Multilayer ceramic circuit board 2,14 Insulating layer 3 Conductor layer 4 Via hole 5 Radiation fin 6 Semiconductor element 7 Lead pin 8 Bonding wire 9 Conductor layer (internal wiring layer)
9a Via hole 10 Surface wiring layer 11 Wiring pattern 12a Substrate upper surface 12b Substrate lower surface 13 High thermal conductive sealing member 13a Convex outer edge portion 13b Concave portion 15 Solder ball A Bonding surface

Claims (4)

Forming an α-Si ₃ N ₄ green sheet to which at least one compound containing 0.1 to 10% by weight of a compound containing an element selected from the group consisting of rare earth elements and alkaline earth elements is added as a sintering aid ;
One or more elements selected from the group consisting of rare earth elements and alkaline earth elements are added to at least one element selected from elements belonging to groups IVa, Va and VIa of the periodic table from 0.01 to 1. Adding 71% by weight to form a conductor paste;
Printing the conductive paste on the α-Si ₃ N ₄ green sheet ;
A silicon nitride circuit substrate having a conductor layer with a resistivity of 50 μmΩcm or less is obtained by performing a step of simultaneously sintering the conductive paste on the α-Si ₃ N ₄ green sheet at 1500 to 1950 ° C. method of manufacturing a circuit board. The method for manufacturing a circuit board according to claim 1, wherein in the step of forming the conductor paste, at least one element selected from an Al element and an Si element is further added. 2. The circuit according to claim 1, wherein the one or more elements selected from elements belonging to groups IVa, Va and VIa of the periodic table are one or more selected from Mo, W, Ti, Zr, Nb and Ta. A method for manufacturing a substrate . The method for manufacturing a circuit board according to claim 1, wherein the warping of the circuit board is 0.5 mm or less per 10 cm diagonal of the circuit board .

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