JP4422453B2 - Wiring board - Google Patents

Description

The present invention relates to a wiring board having a thin-film wiring conductor layer formed on the surface of an insulating board, and in particular, includes an insulating board that can be fired simultaneously with silver, copper, and gold, which are low resistance conductors, and has high strength characteristics. those related to the wiring board to be.

  A wiring board used in various electronic devices has, for example, an insulating substrate formed of alumina ceramics and the like, and a surface of the insulating substrate and / or a metallized wiring layer co-fired on the surface. Yes. In addition, as a method of forming a thin-film wiring conductor layer capable of wiring with a low resistance and a fine pattern on the surface of the insulating substrate, for example, after polishing the surface of the insulating substrate to be smooth, A method of laminating a thin film wiring conductor layer made of a metal such as Ti, Cr, W, Cu and an insulating film made of an organic polymer material such as polyimide by a thin film forming method is employed.

  The insulating substrate made of alumina ceramic that constitutes the above wiring board has a high firing temperature of about 1600 ° C., so that the metallized wiring layer formed inside the insulating substrate is made of a high material such as W or Mo. A melting point metal is used. This is because if a low melting point Ag, Cu, Au or the like is used, the wiring pattern is destroyed during firing.

  By the way, alumina ceramics have a high dielectric constant. For this reason, a wiring board provided with an insulating substrate made of alumina ceramic has a drawback that a signal delay time is long and signals cannot be propagated at high speed. Furthermore, since the refractory metal constituting the metallized wiring layer has a high electric resistance, it cannot similarly propagate signals at high speed.

Therefore, it has been proposed to use glass ceramics having a low dielectric constant and a firing temperature of 1000 ° C. or lower that can be fired at a low temperature as an insulating substrate, and Cu, Ag, Au, or the like having a low electrical resistance as a conductor. For example, the present applicant forms a wiring substrate of Cu by forming a Cu conductive wiring layer on the surface of a green sheet containing a mixture of lithium silicate-based glass and SiO ₂ -based filler, and firing it at 1000 ° C. or lower. (See Patent Document 1).
JP-A-10-212136

However, as in Patent Document 1, in the case where the insulating substrate is made of glass ceramics containing the above lithium silicate glass or the like and SiO ₂ filler, a large amount of voids are present in the insulating substrate. As a result, the positional accuracy of the thin-film wiring conductor layer formed on the surface is lowered, making it difficult to make fine wiring, and it is difficult to form a thin-film wiring conductor layer having a uniform thickness. Has caused a problem that the adhesive strength of the thin-film wiring conductor layer is lowered.

  In addition, the above glass ceramic insulating substrate has a thermal conductivity as low as 2 W / mK or less and a bending strength of about 200 MPa, which is greatly inferior in thermal and mechanical characteristics compared to conventional alumina. Met.

  Furthermore, the smoothness of the surface of the insulating substrate is impaired by voids. As a result, the unevenness at the interface of the thin film wiring conductor layer through which high-frequency signals mainly pass increases, increasing the wiring resistance in the high-frequency band and increasing the conductor loss. As a result, there is a problem that the transmission characteristics of the high-frequency signal are deteriorated.

  Accordingly, an object of the present invention is to form a thin wiring conductor layer having a fine and uniform thickness and having a high adhesive strength on the surface of the insulating substrate, which has a high strength and further a high thermal conductivity, and its manufacture. It is to provide a method.

According to the present invention, in a wiring board comprising an insulating substrate and a thin-film wiring conductor layer formed on the surface thereof,
The insulating substrate contains SiO ₂ , Al ₂ O ₃ , MgO, BaO, and RE ₂ O ₃ (RE is a rare earth element), 50 to 60% by mass of silicate glass powder not containing ZnO, and alumina powder 35 to 50 An organic binder and a solvent are mixed into a mixed powder composed of 0% by mass and at least one ceramic powder selected from the group consisting of forsterite, enstatite, mullite, zirconia, aluminum nitride and silicon nitride. It is obtained by firing a green sheet, contains Si, Al, Mg, Ba , RE and O as constituent elements , does not contain Zn, contains a forsterite crystal phase as a crystal phase , containing hexagonal celsian crystal phase and the alumina crystal phase as a large crystal phases of the peak intensity than stellite crystalline phase And, it does not contain gahnite crystal phase and the spinel crystal phase is formed of a sintered body having an open porosity of 0.3% or less,
Before SL thin film wiring conductor layer, Cu, Ag, the wiring board, characterized by containing at least one conductor selected from the group of Au and Al is provided.

Preferred embodiments of the wiring board of the present invention are as follows.
(1) Before Symbol sintered body, the respective elements, in terms of oxide, _S iO 2: 5 to 36 _{wt%, Al} 2 O 3: _11~65 wt%, MgO: 2 to 22 wt%, BaO: 5 to 36% by mass and RE ₂ O ₃ : 0.5 to 18 % by mass, and selected from the group consisting of B ₂ O ₃ , CaO, SrO, ZrO ₂ , SnO ₂ and TiO _2. At least one kind is contained in a total amount of 18% by mass or less .
(2) The R E ₂ O ₃ is Y ₂ O ₃ .
(3) the sintered body, as a crystal phase, further, et Nsutataito, mullite, zirconia, contains at least one member selected from the group consisting of aluminum nitride 及 beauty silicon nitride.
(4) the silicate-based glass powder, a SiO ₂ 10 to 40 wt%, _Al 2 _{O 3} 1 to 30 wt%, the MgO 6 to 25 wt%, a BaO 10 to 40% by weight and _RE 2 _{O 3} 2-20 mass%, does not contain ZnO, and further contains at least one selected from the group of B ₂ O ₃ , CaO, SrO, ZrO ₂ , SnO ₂ and TiO _{2 in} a total amount of 20 mass% or less. is doing.
( 5 ) The insulating substrate is made of a sintered body having a thermal conductivity of 3.5 W / mK or more and a bending strength of 400 MPa or more.
( 6 ) The insulating substrate is formed of a plurality of insulating layers, and an internal wiring layer containing at least one selected from the group consisting of Cu, Ag, Au, Pd and Pt is formed between the insulating layers. .

In the wiring board provided by the present invention , Si , Al, Mg, Ba , rare earth elements RE and O are contained as constituent elements , Zn is not contained, and the forsterite crystal phase (2MgO.SiO ₂ ) is used as the crystal phase. And a hexagonal serdian crystal phase and an alumina crystal phase as crystal phases having higher peak intensity than the forsterite crystal phase, and an insulating substrate is formed by a sintered body containing no garnite crystal phase and spinel crystal phase. Therefore, the bending strength is increased to 400 MPa or more, the thermal conductivity is also increased, and the thermal properties are improved.

  Moreover, since the open porosity of the sintered body is 0.3% or less, a thin and thin thin-film wiring conductor layer can be formed on the surface of the insulating substrate with few voids, and the wiring resistance in the high frequency band can be reduced. The increase can be avoided, the deterioration of the transmission characteristic of the high frequency signal due to the increase of the conductor loss can be suppressed, and the adhesive strength between the thin film wiring conductor layer and the insulating substrate can be increased.

  Hereinafter, the present invention will be described in detail based on specific examples shown in the accompanying drawings.

  FIG. 1 is a view showing a cross-sectional structure of a package for housing a semiconductor element, which is one of preferred applications using the wiring board of the present invention, together with a semiconductor element mounted thereon, and FIG. It is a schematic sectional drawing which shows the mounting structure to the external circuit board of a package.

  In FIG. 1, a package indicated by A as a whole is composed of an insulating substrate X and a multilayer wiring layer Y formed on the surface thereof.

  The multilayer wiring layer Y has a laminated structure of thin film wiring conductor layers 1 and insulating films 2 and has a structure in which thin film wiring conductor layers 1 and insulating films 2 are alternately laminated. That is, the thin film wiring conductor layer 1 includes a lower layer 1a formed on the surface of the insulating substrate X, an intermediate layer 1b formed between the films of the insulating film 2, and a surface layer formed on the surface of the upper insulating film 2. 1c, and the lower layer 1a, the intermediate layer 1b, and the surface layer 1c are electrically connected to each other by a conductor layer. The electrode terminal 5 of the semiconductor element 4 is mounted (primary mounted) and connected to the thin-film wiring conductor layer 1c on the outermost surface of the multilayer wiring layer Y.

  Further, the insulating substrate X has a structure in which a plurality of insulating layers 3 are laminated, and an internal wiring layer 6 is formed between the insulating layers 3. The internal wiring layer 6 normally contains at least one low-resistance metal selected from the group of Cu, Ag, and Au as a main component. That is, it is possible to increase the density of wiring by multilayering the insulating substrate X and forming the internal wiring layer 6, and by forming the internal wiring layer with a low-resistance metal such as Cu, Ag, or Au, high speed is achieved. Simple signals can be transmitted with low loss.

  Further, a metallized pad 7 is formed on the back surface of the package A (that is, the back surface of the insulating substrate X), and this metallized pad 7 is internally connected via a via-hole conductor 8 extending through the insulating layer 3. The wiring layer 6 and the thin-film wiring conductor layer 1a below the multilayer wiring layer Y are electrically connected. Further, as shown in FIG. 2, the metallized pad 7 is provided with a connection terminal 9 for electrical connection to the external circuit board B. By this connection terminal 9, the external circuit board B is provided. The package A is mounted on the external circuit board B by being electrically connected to the wiring conductor 10 on the surface. Accordingly, in such a mounting structure, the semiconductor element 4 mounted on the surface of the package A includes the multilayer wiring layer Y (surface layer, intermediate layer and lower thin film wiring conductor layers 1c, 1b, 1a) and the via-hole conductor 8. It will be electrically connected through.

  In general, the electrode terminals 5 and the connection terminals 9 are preferably formed of a brazing material such as solder. When the package A is a BGA type package as shown in FIG. 1, the connection terminals 9 are solder balls. Formed by.

The external circuit board B is made of, for example, an insulating material containing at least an organic resin (specifically, a glass-epoxy composite material), and generally has a linear thermal expansion coefficient of 13 to 20 × at 0 to 150 ° C. An insulating printed board of 10 ⁻⁶ / ° C. is used, and the wiring layer 10 formed on the surface of the printed board is made of a metal conductor such as Cu, Au, Al, Ni, Pb—Sn. .

In the present invention, each insulating layer 3 forming the insulating substrate X is made of a sintered body containing at least Si, Al, Mg, Ba, RE (rare earth element) and O as constituent elements and not containing Zn. This sintered body contains a forsterite crystal phase (2MgO.SiO ₂ ), a Serdian crystal phase (BaAl ₂ Si ₂ O ₈ ), and an alumina crystal phase as crystal phases, and a Serdian crystal phase. Are present as anisotropic crystals (for example, needle-like crystals or plate-like crystals) having an aspect ratio of 3 or more.

That is, the Serdian crystal phase, which is an anisotropic crystal having an aspect ratio of 3 or more, exhibits a remarkable bending strength improvement effect, and the forsterite crystal phase also contributes to the improvement of the bending strength. Further, among the constituent elements, Si, Al, Mg, Ba and O are elements necessary for the formation of each of the above crystal phases, but the rare earth element RE is, for example, in the residual glass after the above crystal phases are precipitated. Present in the form of an oxide (RE ₂ O ₃ ) and exhibits an effect of increasing the bending strength of the sintered body by improving the Young's modulus of the residual glass phase in the sintered body.

Therefore, according to the present invention, the bending strength of the insulating substrate X can be increased to 400 MPa or more. For example, when the above-mentioned Celsian crystal phase or forsterite crystal phase is not contained in the sintered body, the bending strength cannot be increased to 400 MPa or more, and the rare earth element component is not contained. In addition, the bending strength is reduced.

In the present invention, the above celsian crystalline phase, that contain hexagonal. Celsian crystals six-cubic, since it can be grown as highly anisotropic crystal aspect ratio, because it is advantageous in enhancing the bending strength.

Further, the rare earth element RE is not particularly limited, but yttrium (Y) is preferable in that it is particularly effective for improving the Young's modulus of the residual glass phase, and Y ₂ O ₃ is used in the sintered body. It is preferable that it exists in.

  The sintered body forming the insulating layer 3 has an open porosity of 0.3% or less, particularly 0.25% or less, and optimally 0.2% or less. That is, by forming the insulating layer 3 with such a dense sintered body having few voids, the surface of the insulating substrate X can be smoothed, and the thin and thin thin-film wiring conductor layer 1 having a low resistance can be formed on the surface. It can be formed, an increase in wiring resistance in the high frequency band is avoided, a deterioration in transmission characteristics of the high frequency signal due to an increase in conductor loss is suppressed, and an adhesive strength between the thin film wiring conductor layer 1 and the insulating substrate X is also reduced. Can be increased.

  For example, a fine thin-film wiring conductor layer 1 (particularly, the lower thin-film wiring conductor layer 1a) having a wiring width of 75 μm or less, particularly 50 μm or less, and a distance between wirings of 75 μm or less, particularly 50 μm or less can be formed with a uniform thickness and high accuracy. If the open porosity of the insulating substrate X exceeds the above range, the position accuracy of the thin film wiring conductor layer 1 is lowered and it becomes difficult to form fine wiring, and the thin film wiring conductor formed on the surface of the insulating substrate X Variations in the thickness of the layer 1 (lower layer a) and the wiring width are increased, and the impedance characteristics of signals transmitted through the wiring layer are deteriorated. In the worst case, this causes an open or short circuit failure.

In the present invention, the sintered body forming the insulating layer 3 may also be celsian crystal and forsterite crystal phase described above, in addition to the alumina crystal phase containing the other crystal phases, e.g., beam light (3Al ₂ O ₃ · 2SiO _2), enstatite (MgSiO _3), di zirconia _(ZrO 2), preferably contains at least one selected from the group consisting of aluminum nitride and silicon nitride, containing such other crystal As a result, various characteristics can be improved.

That is, those exemplified above as other crystal phases, Ru der contributes to an improvement in the flexural strength.

  Alumina, aluminum nitride, and silicon nitride have the effect of improving thermal conductivity.

  Furthermore, alumina has particularly high wettability with glass powder, and is effective in reducing the open porosity of the sintered body and reducing the area ratio of pores present on the polished surface, which will be described later.

Mullite, Ensutatai DOO has an effect of lowering the dielectric constant of the sintered body, and has the effect of reducing even dielectric constant forsterite described above.

Alumina and ZrO ₂ have the effect of improving the chemical resistance of the sintered body, and the effect of alumina is particularly great. Such an effect of improving chemical resistance is effective in that deterioration due to a chemical used for forming the thin film wiring conductor layer 1 described later can be effectively avoided.

The sintered body forming the insulating layer 3 may contain a metal oxide crystal phase other than the above-mentioned various crystal phases as long as the object of the present invention is not impaired. Examples of such metal oxide crystal _{phases, SiO 2, CaMgSi 2 O 6} , Sr 2 MgSi 2 O 7, Ba 2 MgSi 2 O 7, ZnO, Zn 2 SiO 4, Zn 2 Al 4 Si 5 O 18 and the like What is necessary is just to contain suitably according to a use.

In the present invention, a dense sintered body with few voids is obtained, and at the same time, the hexagonal serdian crystal phase, forsterite crystal phase , alumina crystal phase and other crystal phases are effectively present in the sintered body, In terms of ensuring high bending strength and further improving thermal conductivity, the composition ratio in terms of oxide of the sintered body is:
SiO ₂ : 5 to 36% by mass, particularly 8 to 31% by mass,
Al ₂ O ₃ : 11 to 65% by mass, in particular 13 to 32% by mass,
MgO: 2 to 22% by mass, particularly 3 to 18% by mass,
BaO: 5-36% by mass, in particular 8-36% by mass,
RE ₂ O ₃ (in particular _Y 2 _O 3): _0.5~18% by weight, in particular 1.5 to 13% by weight,
It is preferable to contain in the range.

If necessary, it contains at least one selected from the group of B ₂ O ₃ , CaO, SrO, ZrO ₂ , SnO ₂ and TiO _{2 in} a total amount of 18% by mass or less, particularly 13% by mass or less. It is desirable. Among these optional components, B ₂ O ₃ has a property of lowering the softening point of glass, and by being present in the raw material powder for producing a sintered body, the ceramic powder in the raw material powder It is a component for increasing the addition amount and adjusting the thermal conductivity and bending strength of the sintered body. In addition, optional components CaO and SrO have the property of controlling the softening point behavior of glass like B ₂ O ₃ and at the same time can be precipitated as anisotropic crystals like Serdian crystals. It is a component for precipitating other anorthite crystal phases and slausonite crystal phases, or for precipitating other crystal phases from the glass, and contributes to improvement of bending strength and control of dielectric constant. Further, optional components ZrO ₂ , SnO ₂ and TiO ₂ are components that act as glass crystallization agents and contribute to the control of bending strength and thermal conductivity by improving the crystallinity.

Thus a sintered body described above insulating substrate X (insulating layer 3), flexural strength is extremely high strength and the 400 MPa or more, yet, thermal conductivity 3.5 W / mK or more on a pole Me Is expensive. The dielectric constant is preferably lower than the dielectric constant of conventional alumina ceramics and adjusted to 9 or less.

Furthermore, the content of alkali metal oxides (A ₂ O) and PbO in the sintered body in terms of impact on the environment, chemical resistance, water resistance, improvement in adhesion strength with the thin-film wiring conductor layer, etc. These are preferably suppressed to 0.1% by mass or less, particularly 0.01% by mass or less.

  In the present invention, not only the open pores of the insulating substrate X (insulating layer 3) but also the closed pores can be reduced. For example, by polishing the surface of the insulating substrate X after firing, the polishing surface The surface roughness Ra (JIS B0601) is 0.1 μm or less, particularly 0.07 μm or less, optimally 0.05 μm or less, and the area ratio of pores existing on the polished surface is 10% or less, particularly 8% or less, optimal. Is preferably 5% or less. By forming the thin-film wiring conductor layer 1 (lower layer 1a) on such a polished surface, the layer 1 can be miniaturized, reduced in resistance, improved in adhesive strength, and the like. It can be realized more effectively.

  On the other hand, in order to simplify the process by improving the productivity by omitting the polishing process of the surface of the insulating substrate X (that is, forming the thin film wiring conductor layer 1 directly on the burned surface without polishing) It is desirable that the surface roughness (Ra) of the substrate X on the skin surface is 1.0 μm or less, particularly 0.7 μm or less.

  In the present invention, the thin-film wiring conductor layer 1 in the multilayer wiring layer Y is a low-resistance conductor containing at least one low-resistance metal selected from the group consisting of Cu, Ag, Au, and Al from the viewpoint of increasing the signal propagation speed. Although it is necessary to be a layer, at least one metal layer selected from the group consisting of Ti, W, Mo, Cr, Ni, Ta, and Sn is laminated on the low-resistance conductor layer as other conductor components. It is desirable to have a structured.

  In particular, the lower layer 1a directly formed on the surface of the insulating substrate X in the thin film wiring conductor layer 1 has a thickness of 0.1 to 3 μm, particularly 0.3 to 1.5 μm, in order to increase the adhesive strength with the insulating substrate X. It is preferable that a low resistance conductor layer made of Cu or the like is formed on the surface of the insulating substrate X through a metal layer containing W or Mo having a thickness. Such a metal layer preferably contains 50% by weight or more, particularly 70% by weight or more of W and / or Mo, and is particularly preferably made of an alloy layer with Ti. In order to further increase the adhesive strength with the surface of the insulating substrate X, a Ti layer having a thickness of 0.05 to 0.5 μm is provided on the surface of the insulating substrate X, and the W, Mo is formed on the Ti layer. It is desirable that a low resistance conductor layer such as Cu is formed with a thickness of 1 to 10 μm through the contained metal layer, and the total thickness is in a range of 1.5 to 15 μm. Moreover, in order to improve the adhesiveness with the insulating film 2, a Cr layer can be formed on the surface in contact with the insulating film.

  Further, in the thin film wiring conductor layer 1, the intermediate layer 1b and the surface layer 1c have a structure in which a low resistance conductor layer such as Cu has a thickness of 1 to 10 μm, and the above metal layer is laminated on the low resistance conductor layer. However, by interposing a Cr layer between the low-resistance conductor layer and the insulating film 2, it is possible to increase the adhesive force with the insulating film. The total thickness of the intermediate layer 1b and the surface layer 1c is suitably 1.5 to 15 μm.

  As the insulating film 2 in the multilayer wiring layer Y, a polyimide-based or epoxy-based organic polymer material can be used. In particular, a polyimide-based organic polymer material is low in terms of low dielectric constant and low dielectric loss. It is desirable to use The thickness of the insulating film 2 is preferably 5 to 100 μm, particularly 10 to 50 μm.

(Method for manufacturing a wiring board)
The wiring board of the present invention used for the package A described above is manufactured by the following steps (A) to (D).

Step (A):
First, mixed powders such as various oxide powders are used so that the components that do not volatilize in the heat treatment at 700 to 1000 ° C. and the composition ratio in terms of oxide match the composition of the sintered body of the insulating layer 3 described above. Prepare. That is, this mixed powder is converted into oxide,
SiO ₂ : 5 to 36% by mass, particularly 8 to 31% by mass,
Al ₂ O ₃ : 11 to 65% by mass, in particular 13 to 32% by mass,
MgO: 2 to 22% by mass, particularly 3 to 18% by mass,
BaO: 5-36% by mass, in particular 8-36% by mass,
RE ₂ O ₃ (in particular _Y 2 _O 3): _0.5~18% by weight, in particular 1.5 to 13% by weight,
Has a composition of at least selected depending on the physical properties control the type and purpose of the crystal phase to be free Yes _{B 2 O 3, CaO, SrO} , from ZrO 2, SnO ₂ and the group of TiO ₂ to further It is desirable to contain one kind in a total amount of 20% by mass or less, particularly 13% by mass or less. This mixed powder is mixed with an organic binder and a solvent to prepare a slurry, that is, a sheet forming slurry.

The above mixed powder as long as it has a composition as described above, is not particularly limited, as a _{component, S iO 2, Al 2 O} 3, MgO, BaO and _RE 2 _{O 3} containing seen, silicate-based glass powder 50-60% by weight free of ZnO, alumina powder 35 to 50 wt% and, forsterite, enstatite, mullite, zirconia, at least selected from the group consisting of aluminum nitride and silicon nitride 1 It is desirable that the ceramic powder is mixed with 0 to 5 % by mass of the seed and adjusted to the above composition. That is, by using a mixed powder of glass powder and ceramic powder, the filler can be efficiently aligned by the softening flow of the glass, and by sintering at a lower temperature and in a shorter time, dense sintering with fewer pores can be achieved. You can get a body. Incidentally, in order to perform the sintering uniformly, the average particle size based on the volume of the silicate based glass powder and ceramic powder _{(D 50)} is, 0.5 to 10 [mu] m, in particular 0.8～7Myuemu, more 1 It is preferable to be in the range of 5 μm.

  For example, if the amount of the silicate glass powder is less than the above range, the sintered body cannot be densified at a low temperature of 1000 ° C. or lower. The aggregate cannot maintain its original shape due to the flow of glass.

Further, the silicate glass powder contains SiO ₂ , Al ₂ O ₃ , MgO, BaO, and RE ₂ O ₃ as constituent components. Of these constituent components, SiO ₂ is a glass-forming oxide. In the absence of this component, the glass is not formed, and SiO ₂ , Al ₂ O ₃ , MgO and BaO are components necessary for precipitating the Serdian crystal phase and forsterite crystal from the glass. Furthermore, RE ₂ O ₃ (particularly Y ₂ O ₃ ) has the property of improving the Young's modulus of the residual glass phase by being present in the residual glass after the crystal phase is precipitated after firing, It is an effective component for improving the bending strength of the sintered body.

Therefore, the silicate glass powder used for the preparation of the mixed powder has each component as its composition,
SiO _2: 10 to 40 wt%, in particular 15 to 35 wt%,
Al ₂ O ₃ : 1 to 30% by mass, particularly 3 to 25% by mass,
MgO: 3 to 25% by mass, particularly 5 to 20% by mass,
BaO: 10 to 40% by weight, in particular 15 to 37% by weight,
RE ₂ O ₃ (in particular _Y 2 _O 3): _1~20 wt%, particularly 3 to 15 wt%,
Contained so as to satisfy, it is as an optional component in _{al, B 2 O 3, CaO,} SrO, at least one selected from ZrO _2, SnO _2, TiO ₂ group, satisfies the sintered body composition described above Thus, for example, the total content is preferably 20% by mass or less, particularly preferably 15% by mass or less. That is, in order to obtain optimum softening characteristics for obtaining a dense sintered body and at the same time to effectively precipitate hexagonal serdian crystal phase, forsterite crystal phase, etc., the content of each component of silicate glass powder Is effectively within the above range. If the composition of the silicate glass powder deviates from the above range, it may be difficult to obtain a sintered body having desirable ceramic characteristics at a firing temperature of 1000 ° C. or lower.

Further, as described above, among the optional components in the glass, B ₂ O ₃ lowers the softening point of the glass and makes it present in the mixed powder, thereby increasing the amount of ceramic powder added and firing. It is a component for adjusting the thermal conductivity and bending strength of the bonded body. On the other hand, CaO and SrO control the softening point behavior of glass, and at the same time, exist as constituent components of anorthite crystal phase and slausonite crystal phase that can be precipitated as anisotropic crystals. Since it has the property of being deposited, it is useful for improving the bending strength and controlling the dielectric constant. ZrO ₂ , SnO ₂ and TiO ₂ function as a glass crystallization agent, and contribute to the control of the bending strength and the thermal conductivity by improving the crystallinity.

  On the other hand, the ceramic powder mixed with the silicate glass powder has an effect of improving the bending strength of the sintered body, and as described above, among the ceramic powders, alumina has an effect of improving the bending strength. In addition to having the greatest effect of improving thermal conductivity, it also has excellent wettability with glass powder, reducing the open porosity of the sintered body and the area ratio of the pores on the polished surface. Also useful for. In the ceramic powder, aluminum nitride or silicon nitride also has an effect of improving the thermal conductivity.

  When a large amount of the ceramic powder is used, it becomes difficult to densify the sintered body at a low temperature of 1000 ° C. or lower. The original form cannot be maintained. The ceramic powder is therefore used in an amount of 10 to 60% by weight, in particular 20 to 50% by weight.

  Further, in the present invention, Serdian crystals can be used as powder and contained in the sintered body, but a denser sintered body can be easily obtained and a Serbian crystal having a high aspect ratio can be easily obtained. In this respect, it is preferable that the Serdian crystal is precipitated from the silicate glass. That is, it is advantageous to precipitate the Serdian crystal from the silicate glass in order to lower the open porosity and the pore area ratio on the polished surface and to increase the bending strength. Moreover, it is desirable to deposit at least one selected from the forsterite crystal phase and the garnite crystal phase from the glass in terms of obtaining a denser sintered body.

Further, as long as the amount of the silicate-based glass powder is ensured, ceramic powder other than the above, for example _{SiO 2, Sr 2 MgSi 2 O} 7, Ba 2 MgSi 2 O 7, CaZrO 2, CaMgSi 2 O 6, ZnO, ZrO ₂ , Zn ₂ SiO ₄ or the like may be used by adding to the mixed powder according to the application.

  The above mixed powder is mixed with a known organic binder (for example, polyvinyl alcohol) and a solvent (for example, isopropyl alcohol) to prepare a slurry for molding having an appropriate viscosity.

Step (B):
Next, the slurry is formed into a sheet shape to produce a green sheet. The green sheet can be formed by, for example, a die press, cold isostatic pressing, injection molding, extrusion molding, doctor blade method, calendar roll method, rolling method, etc. It is formed into a sheet shape adapted to the insulating layer 3). In particular, a doctor blade method is suitable for producing a green sheet.

Step (C):
The green sheet is laminated and pressure-bonded in accordance with the number of insulating layers 3 constituting the insulating substrate X, and is baked at 700 to 1000 ° C. following debinding.

  Prior to debinding, a through-hole for forming the via-hole conductor 8 is formed in the green sheet by punching or laser processing, and at least one selected from the group of Cu, Ag, and Au is formed in the through-hole. A conductor paste containing the above as a main component is filled. Further, the pattern of the metallized pad 7 is formed by using this conductor paste by a screen printing method or a gravure printing method. Further, for the green sheet corresponding to the insulating layer 3 located inside the insulating substrate X, a pattern corresponding to the internal wiring layer 6 is formed on the surface in the same manner as described above using the conductive paste. deep.

  The production of the conductor pattern corresponding to the metallized pad 7 and the internal wiring layer 6 is not limited to the printing method described above, and a transfer film provided on the surface with a wiring pattern formed by etching a metal foil or the like is used. It can also be formed by transferring to the green sheet surface.

  The binder removal removes the binder component blended for molding. When Ag or Au is used as the conductor material, the binder removal is performed by heating to around 500 ° C. in an air atmosphere. When Cu is used as a material, in order to avoid oxidation, it is performed by heating to around 700 ° C. in a nitrogen atmosphere containing water vapor.

  The firing performed after the binder removal is performed by firing at a temperature of 700 to 1000 ° C. in an oxidizing atmosphere or a non-oxidizing atmosphere for 0.2 hours to 10 hours, particularly 0.5 to 5 hours. It consists of a dense sintered body having a porosity of 0.3% or less, particularly 0.2% or less, and a pore area ratio on a polished surface to be described later of 10% or less, particularly 8% or less, and optimally 5% or less. An insulating substrate X is obtained. Further, the surface roughness (Ra) of the burned skin surface is 1.0 μm or less, particularly 0.7 μm or less. For example, if the firing temperature is lower than 700 ° C. or the firing time is shorter than 0.2 hours, the sintered body cannot be densified and the open porosity exceeds 0.3%. Conversely, if the firing temperature exceeds 1000 ° C. or the firing time is longer than 10 hours, the number of voids in the sintered body will increase again.

  When Cu is used as the conductor material, firing is performed in a non-oxidizing atmosphere such as nitrogen, a nitrogen / water vapor mixture, or a nitrogen / hydrogen mixed atmosphere in order to prevent oxidation.

Step (D):
A multilayer wiring layer Y including the thin film wiring conductor layer 1 is formed on the surface of the insulating substrate X obtained above by a thin film forming method.

  Prior to the multilayer wiring layer Y using this thin film formation method, if necessary, the surface of the insulating substrate X on which this layer is to be formed is polished and its surface roughness (Ra) is 0.1 μm or less, especially 0.07 μm or less, most preferably 0.05 μm or less, and the area ratio of pores present on the polished surface is 10% or less, particularly 8% or less, and optimally 5% or less, to improve the smoothness. It is good. However, this polishing step can be omitted, and the multilayer wiring layer Y can be directly formed on the surface of the insulating substrate X.

  Formation of the multilayer wiring layer Y using the thin film forming method is performed as follows.

(1) The thin film wiring conductor layer 1c is formed on the entire upper surface of the insulating substrate X by using a thin film forming method such as sputtering, ion plating, or vacuum deposition.
For example, the deposition source is appropriately changed, a Ti film having a thickness of 0.05 to 0.5 μm is formed on the surface of the insulating substrate X, W and / or Mo is contained on the Ti film, and the thickness is 0.1. A metal film (for example, W-Ti film, Mo-Ti film) having a thickness of ˜3 μm is formed, and a Cu, Ag, Au or Al film having a thickness of 1 to 10 μm is further formed thereon, and the total thickness is 1.5. A laminated metal film of ˜15 μm is formed. A Cr film may be further formed on the laminated metal film.

Next, a photosensitive photoresist is applied on the entire surface of the laminated metal film. Then, an etching mask is prepared by a well-known photolithography technique, and an unnecessary portion is removed by reactive ion dry etching using an acidic etchant or a reactive gas (CCl ₄ , BCl ₃ ) on a part of the laminated metal film. A thin film wiring conductor layer 1a (lower layer) having a predetermined pattern is obtained, and the etching mask is removed by peeling.

(2) Next, an insulating film 2 made of an organic polymer insulating material such as polyimide is formed on the thin-film wiring conductor layer 1a. For example, a polymer solution of an organic polymer material is uniformly applied to the upper surface of the wiring board X by a spin coating method or the like, and heated to a temperature at which the organic polymer material is cured.

(3) Next, connection through holes for connecting the upper and lower thin film wiring conductor layers are formed by using the well-known photolithography technique as described above.

  By repeatedly performing the above steps (1), (2), and (3), a plurality of predetermined thin film wiring conductor layers 1b, 1c (intermediate layer, surface layer) and insulating film 2 can be formed. As a result, a package A including the wiring board of the present invention can be manufactured. In addition, the thin film wiring conductor layers 1b and 1c may be replaced with the metal source as appropriate, and the wiring conductor layer having the above-described laminated structure may be used.

  In addition, a connection terminal 9 for electrically connecting to the external circuit board B is appropriately attached to the package A, and a semiconductor element 4 such as silicon is attached to the thin film wiring conductor layer 1c (surface layer) on the upper surface. Positioning is performed so that the electrode terminals of the semiconductor element 4 are connected, and mounting is performed by solder or the like by a known flip-chip connection method.

A multilayer wiring board for evaluation was produced as follows.
First, glass powders A to E having the compositions shown in Table 1 (average particle size is 2 μm) were prepared.

  Ceramic powder shown in Table 2 is mixed with the glass powder, and a slurry is prepared by adding toluene as a methacrylic acid-based organic binder and a solvent, and a molded body is prepared by a doctor blade method using this slurry. This molded body was debindered by heat treatment at 500 ° C. for 2 hours in the air, and then fired in the air atmosphere under the conditions shown in Table 1 to produce a sintered body for an insulating substrate. About the obtained sintered compact, physical properties etc. were measured as follows, and the results are shown in Table 2.

(Open porosity)
The open porosity was measured by Archimedes method.
(Thermal conductivity)
The sintered body was processed to have a diameter of 10 mm and a thickness of 1.5 mm, and the thermal conductivity was measured by a laser flash method.
(Folding strength)
The sintered body was processed to 3 mm × 4 mm × 50 mm, and the three-point bending strength was measured using an autograph in accordance with JIS R1601.
(Surface roughness and pore area ratio)
The surface roughness Ra (JIS B0601) of the surface of the sintered body was measured using a surface roughness meter.
Further, for the polished surface finished by polishing the sintered body and using a # 2000 grindstone, the surface roughness Ra was measured in the same manner as described above using a surface roughness meter, and the void ratio ( The pore area ratio) was determined by performing a Luzex analysis from a metal micrograph.

(Identification of crystal phase)
Crystal phases in the sintered body were identified from the X-ray diffraction measurement, and are shown in Table 2 in descending order of peak intensity.
Further, the sintered body is mirror-polished, a photograph of the structure is taken using a scanning electron microscope, and the aspect ratio of the Serdian crystal phase (BaAl ₂ Si ₂ O ₈ ) that is a needle-like crystal is calculated for the maximum one, The results are shown in Table 2.

  Moreover, using each mixed powder in Table 2, a green sheet having a thickness of 300 μm is prepared by a doctor blade method, via holes are formed in the sheet, and a metallized paste mainly composed of copper is filled in a screen printing method. A metallized pad pattern was applied by screen printing.

  Then, six green sheets coated and filled with metallized paste were stacked and pressure-bonded while aligning the through holes. The laminate was heat-treated in air at 500 ° C. for 2 hours to remove the binder, and then fired under the same conditions as in Table 2 to produce a wiring board.

  Further, after forming a Ti layer with a thickness of 0.2 μm on the insulating substrate surface of the wiring substrate by a vacuum deposition method, a metal layer made of TiW is formed with a thickness of 10 μm, and then a Cu layer with a thickness of 3 μm. Formed. The W content in the TiW alloy layer is 90% by weight.

  Thereafter, a photosensitive photoresist is applied to the entire surface of the thin film metal layer, an etching mask is formed by photolithography technique, and an unnecessary portion of the thin film is removed from the thin film layer with an acidic etching solution. A 1 mm evaluation pad was formed.

  Then, a pin made of Cu is soldered to the pad, and 100 cycles of holding the wiring board in a constant temperature bath controlled at -40 ° C. and 125 ° C. for 15 minutes / 15 minutes. After the thermal cycle, this pin was pulled up vertically, and the strength when the solder or thin film metal layer was separated was evaluated as the adhesive strength of the thin film metal layer. The results are shown in Table 2. In addition, the adhesive strength set 22.5 MPa or more as the pass.

As apparent from the results in Table 2, based on the present invention, it insulating substrate, S i, Al, Mg, B a, a sintered body containing as a constituent element of rare earth elements RE and O, the sintered body but a hexagonal Akirase Rujian _(BaAl 2 _Si 2 _{O 8)} crystal phase as a crystal phase, forsterite (2MgO · SiO ₂₎ containing a crystal phase及beauty alumina crystal phase, an open porosity of 0.3 %, A thermal conductivity of 3.5 W / mK or more, a bending strength of 400 MPa or more, a dielectric constant of 9 or less, and a good insulating substrate showing a surface roughness (Ra) of 1.0 μm or less are obtained, As a result, even after the thermal cycle, the adhesive strength of the thin film wiring layer was as high as 22.5 MPa or higher.

  On the other hand, the sample No. in which the amount of the glass powder is more than 90% by weight. In No. 21, the sintered body could not maintain its original shape, and an evaluable sample could not be obtained.

  In addition, sample No. in which the amount of glass powder is less than 40% by weight. In No. 4, a dense sintered body could not be obtained.

Sample No. Nos. 24-27 are cases where the hexagonal serdian crystal phase is not included, but any sample has an open porosity of more than 0.3%, a thermal conductivity of less than 3.5 W / mK, and a bending strength. Is lower than 400 MPa, surface roughness (Ra) is 1.0 μm or more, and adhesive strength is also lower than 22.5 MPa.

Further, as the glass powder with glass D, E Sample No. In each of 25 to 30, the open porosity was larger than 0.3%, the thermal conductivity was lower than 3.5 W / mK, and the bending strength was lower than 400 MPa.

It is a figure which shows the cross-sectional structure of the package for a semiconductor element which consists of a wiring board of this invention with the semiconductor element mounted in this. It is a schematic sectional drawing which shows the mounting structure to the external circuit board of the package of FIG.

Explanation of symbols

A. Package B. External circuit board X Insulating board Y Multilayer wiring layers 1a, 1b, 1c; Thin-film wiring conductor layer 2; Insulating film 3; Insulating layer 4; Semiconductor element 5; Electrode terminal 6; Metallized pad 8; via hole conductor 9; connection terminal

Claims (7)

In a wiring board comprising an insulating substrate and a thin-film wiring conductor layer formed on the surface thereof,
The insulating substrate contains SiO ₂ , Al ₂ O ₃ , MgO, BaO, and RE ₂ O ₃ (RE is a rare earth element), 50 to 60% by mass of silicate glass powder not containing ZnO, and alumina powder 35 to 50 An organic binder and a solvent are mixed into a mixed powder composed of 0% by mass and at least one ceramic powder selected from the group consisting of forsterite, enstatite, mullite, zirconia, aluminum nitride and silicon nitride. It is obtained by firing a green sheet, contains Si, Al, Mg, Ba , RE and O as constituent elements , does not contain Zn, contains a forsterite crystal phase as a crystal phase , containing hexagonal celsian crystal phase and the alumina crystal phase as a large crystal phases of the peak intensity than stellite crystalline phase And, it does not contain gahnite crystal phase and the spinel crystal phase is formed of a sintered body having an open porosity of 0.3% or less,
Wiring board prior Symbol thin-film wiring conductor layer, Cu, Ag, characterized in that it contains at least one conductor selected from the group of Au and Al. Before SL sintered body, the respective elements, in terms of oxide, _S iO 2: 5 to 36 _{wt%, Al} 2 O 3: _11~65 wt%, MgO: 2 to 22 wt%, BaO: 5 to 36% by weight and RE ₂ O _3: 0.5~18 in a proportion at which the _{mass%, B 2 O 3, CaO} , SrO, at least one selected from ZrO 2, SnO ₂ and the group consisting of TiO ₂ The wiring board according to claim 1, wherein the total content is 18% by mass or less . The circuit board according to claim 1 or 2, wherein R _E 2 _{O 3} is is _Y 2 _{O 3.} The sintered body is, as a crystal phase, further, et Nsutataito, mullite, zirconia, interconnect according to any one of the group of aluminum nitride 及 beauty silicon nitride of at least one the of which claims 1 to 3 containing selected substrate. The silicate-based glass powder, 2 to the SiO ₂ 10 to 40 wt%, _Al 2 _{O 3} 1 to 30 wt%, the MgO 6 to 25 wt%, a BaO 10 to 40% by weight and the _RE 2 _{O 3} Contains 20% by mass, does not contain ZnO, and further contains at least one selected from the group of B ₂ O ₃ , CaO, SrO, ZrO ₂ , SnO ₂ and TiO _{2 in} a total amount of 20% by mass or less . The wiring board according to claim 1. Wherein the insulating substrate is a wiring board according to any one of claims 1 to 5 thermal conductivity flexural strength of a sintered body above 400 MPa at 3.5 W / mK or more. 2. The insulating substrate is formed of a plurality of insulating layers, and an internal wiring layer containing at least one selected from the group consisting of Cu, Ag, Au, Pd and Pt is formed between the insulating layers. The wiring board according to any one of 1 to 6 .

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