JPH0544190B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a novel ceramic multilayer circuit board, and more particularly to a semiconductor module in which a semiconductor element mounted on a carrier substrate is further mounted on a ceramic multilayer circuit board. In particular, the present invention relates to a semiconductor module structure in which highly conductive copper or silver conductors can be used in a multilayer circuit board, and in which the solder connections of semiconductor elements have high reliability. [Prior Art] In order to increase the calculation speed of large electronic computers, it is necessary to increase the signal propagation speed in semiconductor elements and the system in which they are mounted. In recent years, semiconductor devices have become much faster and more integrated due to the development of high-integration technology.
Implementation technology is beginning to have a significant impact on increasing the calculation speed. As for mounting technology, ceramic multilayer circuit boards have come to be used in order to mount semiconductor elements at high density and reduce delays in electrical signals. Alumina has conventionally been generally used as an insulating material for ceramic multilayer circuit boards. However, in order to further improve performance, in recent years, low-temperature sintered substrate materials such as those described in Japanese Patent Publication No. 59-22399 ``Multilayer Ceramic Substrates'' and ``Ceramics Multilayer Wiring Circuit Boards'' in JP Patent Publication No. 59-11700 have been developed. A low dielectric constant, low temperature sintered material in which SiO ₂ is bonded with glass is being researched and developed. These circuit board materials are densely sintered so that they do not contain pores as much as possible, but the relative dielectric constant, which has a large effect on increasing the calculation speed, is limited to about 4 to 5. Ta. In addition, for the purpose of heat insulation, heat retention, weight reduction, soundproofing, etc., for example, JP-A No. 57-89212 "Composite Ceramic Electronic Materials" and JP-A No. 59-83985 "Method for Manufacturing Foamed Ceramic Boards" As described, a substrate containing pores inside the ceramic is obtained. However, no consideration has been given to this material as a substrate material for large electronic computers, which require high signal propagation speeds. On the other hand, as semiconductor devices become faster and more densely packed, a method of mounting semiconductor devices directly on a ceramic multilayer circuit board has come to be used in order to dissipate heat and increase the speed of devices. However, this mounting method has a problem in that as the size of the semiconductor element increases, the stress generated between the semiconductor element material and the ceramic multilayer wiring circuit board material due to temperature changes during mounting increases. Therefore, attempts have been made to bring the coefficient of thermal expansion of ceramic multilayer wiring circuit board materials closer to that of semiconductor elements. However, in order to conduct high-density wiring using gold, copper, silver, or the like having low resistance as a wiring conductor material, the coefficient of thermal expansion of the ceramic insulating material must be close to that of these conductor materials. Thus, ceramic insulating materials are required to have thermal expansion coefficients close to those of semiconductor element materials and conductor materials. However, no consideration was given to mounting techniques for these contradictory conditions. [Problems to be Solved by the Invention] In ceramic multilayer circuit boards, the dielectric constant of the insulating material is required to be as small as possible in order to increase the signal propagation speed. Furthermore, it is necessary to use a material with low electrical resistance as the conductor material. For example, as described in JP-A No. 59-11700 "Ceramics Multilayer Wiring Circuit Board", a substrate material with a dielectric constant of 4 to 5 can be obtained by bonding silica, which has a low dielectric constant, with glass. It is being Furthermore, since this material can be fired at a temperature of 1000° C. or lower, gold, copper, silver, or the like with low electrical resistance can be used as the conductive material. Furthermore, the coefficient of thermal expansion of ceramic multilayer circuit board materials is approaching that of semiconductor elements as much as possible, and the difference from that of conductor materials is increasing. Therefore, little consideration has been given to wiring internal circuits at high density and mounting semiconductor elements at high density and with high reliability. An object of the present invention is to manufacture semiconductor elements in a semiconductor module using a ceramic multilayer circuit board in which a low resistance material such as gold, copper or silver is interconnected as a conductive material in a ceramic insulating material with a lower dielectric constant in high density. The objective is to provide a mounting technology that allows high-density and reliable mounting. [Means for Solving the Problems] The present invention provides a semiconductor module having a ceramic multilayer circuit board in which ceramic layers and wiring conductor layers are alternately laminated, wherein the ceramic layer has a coefficient of thermal expansion equal to that of the wiring conductor. The present invention provides a ceramic multilayer circuit board characterized in that it is made of glass which has a coefficient of thermal expansion smaller than the coefficient of thermal expansion of the wiring conductor layer and one-half or more of the coefficient of thermal expansion of the wiring conductor layer, and which softens below the melting point of the wiring conductor layer. The thermal expansion coefficient of the ceramic layer is 7.2×10 ^-6 /℃
and a relative dielectric constant of 4.5 or less at 1 MHz, and the wiring conductor layer is made of gold, silver, or copper. Furthermore, the ceramic multilayer circuit board can be made to have a lower dielectric constant by dispersing hollow silica with a particle size of 100 μm or less in the ceramic layer. The content of hollow silica is preferably 35 to 60% by volume of the ceramic layer. In order to lower the dielectric constant of ceramic insulating materials, which is one of the above objectives, it is possible to combine fillers with a low dielectric constant with glass. Silica has a small dielectric constant, and the dielectric constant of silica is about 4. Therefore, it is difficult to produce a ceramic insulating material with a dielectric constant of 4 or less using the conventional method of densely sintering ceramics. Therefore, we set the relative permittivity to 4
Since the dielectric constant of air is approximately 1, it was thought that in order to further reduce the dielectric constant, it would be sufficient to include pores in the ceramic insulating material. Structural materials containing many pores have been known for the purpose of heat insulation, soundproofing, etc., but the pores contained in such materials are generally large, on the order of several millimeters, and are not suitable for multilayer circuit boards. is difficult to apply. Therefore, in order to be used in multilayer circuit boards, internal wiring must be highly integrated.
Since there is a risk of short circuits and disconnections, the diameter of the pores must be reduced to at least 100 μm or less. To create an insulating material that contains pores inside ceramics, for example, ceramic powder and a foaming agent are mixed together and foamed during firing to create ceramics that contain pores. One possible method is to mix hollow microspheres with ceramic powder and sinter it, but the method using a foaming agent is difficult to disperse a large number of uniform, fine pores in ceramics. A method of combining spheres and ceramics was adopted. In order to minimize the relative permittivity of these hollow microspheres, we selected hollow silica microspheres whose main component is silica, which has the lowest permittivity among inorganic materials, and whose particle size is 100 μm or less. In addition, as a ceramic that binds hollow silica microspheres,
Since it is necessary to sinter at a temperature below the melting point of the wiring conductor material such as gold, copper, or silver, the bonding was performed using glass or crystallized glass that softens at a temperature below the melting point of these materials. Crystallized glass is a material that precipitates a crystalline phase from an amorphous state when heated, and has low-temperature sinterability and strength. Since hollow silica microspheres need to be microscopic, about 100 μm or less, those produced in the following manner were used. In other words, silica containing Na was made into a hollow granulated powder using a spray drying method, this was rapidly heated to make it hollow, and after cooling, acid treatment, water washing, etc. were performed to reduce the Na content to 2 wt% or less. . When the Na content is 2wt% or less, there is no softening phenomenon at temperatures below 1000°C, and the material has sufficient heat resistance. In order to wire low-resistance conductor materials at high density, which is another purpose, it is necessary to reduce the difference in thermal expansion coefficient between the ceramic insulating materials and the conductor materials. Furthermore, as a conductive material, it is desirable that it be as close to pure metal as possible in order to minimize electrical resistance. That is, the coefficient of thermal expansion of gold, copper or silver is 1.44 to 1.44 respectively.
10 ^-5 /℃, 1.68 x ^{10 -5} /℃ or 1.92 x 10 ^-5 /℃, so the stress analysis results indicate that the thermal expansion coefficient of ceramic insulation materials must be at least half of these values. . From this, when gold is used as a conductive material, the thermal expansion coefficient of the ceramic insulating material must be 7.2×10 ^-6 /°C or higher. In addition, when copper is used as a conductor material, the coefficient of thermal expansion of ceramic insulation material is 8.4.
Must be at least ×10 ^-6 /°C. For this reason, attempts have been made to make the coefficient of thermal expansion of ceramic insulating materials close to that of silicon, which is a semiconductor element, but in order to achieve high-density wiring, it is necessary to increase the coefficient of thermal expansion of conductive materials to be close to that of silicon. There is. Therefore, since the thermal expansion coefficient of a ceramic multilayer circuit board is relatively large, it is difficult to directly mount silicon, which is a semiconductor element. In order to package silicon, which is a semiconductor element, with high density, new packaging methods must be considered. Therefore, we considered providing a carrier substrate between the ceramic multilayer circuit board and the semiconductor element to alleviate the difference in thermal expansion coefficient between the ceramic multilayer circuit board and the semiconductor element. First, semiconductor elements were directly mounted on a carrier substrate using solder bumps. Next, a material mainly composed of an organic material with a coefficient of thermal expansion equivalent to that of solder was inserted between the semiconductor element and the carrier substrate. Afterwards, it was connected to a ceramic multilayer circuit board using solder bumps to form a module. In this case, the carrier board and the ceramic multilayer circuit board are connected only by solder, so the coefficients of thermal expansion of the carrier board and the ceramic multilayer circuit board must be approximately the same in order to ensure the reliability of the connection. . From the results of stress analysis and thermal cycle tests, the difference in thermal expansion coefficient between the carrier substrate and the ceramic multilayer circuit board must be 1×10 ^-6 /°C or less. On the other hand, the thermal stress caused by the difference in thermal expansion coefficient between the semiconductor element and the carrier substrate is alleviated by the material whose main component is an organic material inserted between the semiconductor element and the ^carrier substrate. It was confirmed through thermal cycle tests and stress analysis that the reliability of the parts could be maintained. Due to this,
We were able to create a mounting method that allows the use of a ceramic multilayer circuit board, which has a larger coefficient of thermal expansion than semiconductor elements. Additionally, the solder materials used for these connections must have different melting points due to the process. That is, the solder material used to connect the semiconductor element and the carrier substrate must have a higher melting point than the solder material used to connect the carrier substrate and the ceramic multilayer circuit board. It is preferable to mix rubber particles and ceramic powder into the organic resin, and the former is preferably mixed in an amount of 5 to 10 parts by weight per 100 parts by weight of the resin, and the latter is preferably mixed in a total amount of 35 to 60% by volume. . The rubber particles are one or more of polybutadiene and/or silicone rubber, and the ceramic powder is one or more of silicon carbide containing quartz, silicon carbide, silicon nitride, calcium carbonate, and beryllium.
Preferably, it consists of more than one species. The ceramic layer for the carrier substrate and multilayer circuit board is preferably made of glass having the following composition (% by weight). _SiO2 20-95% and _{Al2O3 not} more than 25% by weight,
MgO15~25%, _B2O3 less than 50%, ZnO15~ ₂₅ %,
Preferably, it contains at least one of 10 to 25% CaO and 4 to 20% _Li2O . More specifically, it is as follows. (1) SiO ₂ 50-70%, Al ₂ O ₃ 15-25% and MgO15
~twenty five%. Furthermore, B ₂ O ₃ , K ₂ O, P ₂ O ₅ , ZrO ₂ ,
5% of one or more of CaF ₂ , AlN, Cs ₂ O, V ₂ O ₅
May include: (2) _SiO2 70-95%, _Li2O4-15 , _{Al2O3 1-10} %,
5% or less of one or more of K ₂ O, MgO and B ₂ O ₃ . Furthermore, P ₂ O ₅ , ZrO ₂ , CaF ₂ , AlN,
It can contain at least 5% of at least one of Cs ₂ O and V ₂ O ₅ . (3) _SiO2 30-50%, _{B2O3 30-50} %, CaO10-25
% and _La2O10-20 %. Furthermore, K ₂ O, MgO, CaF ₂ , P ₂ O ₅ ,
One or more of ZrO ₂ , AlN, Cs ₂ O and V ₂ O ₅
% or less. (4) _SiO2 55-82%, _{B2O3 15-25} %, _Li2O2-15 %
and _{Al2O3 1-10} %. Furthermore, CaF ₂ , P ₂ O ₅ , ZrO ₂ , AlN, Cs ₂ O,
It can contain 5% or less of one or more of V ₂ O ₅ , MgO, and K ₂ O. (5) _SiO2 55-65%, ZnO15-25%, _{Al2O3 , Li2}
10% or less of at least two of O and K ₂ O. Furthermore, B ₂ O ₃ , CaF ₂ , MgO, K ₂ O, P ₂ O ₅ ,
It can contain at least 5% of at least one of ZrO ₂ , AlN, Cs ₂ O, and V ₂ O ₅ . (6) _SiO2 20-30%, _Li2O10-15 %, _{B2O3 40-50}
% and CaO15-25%. Furthermore, CaF ₂ , Al ₂ O ₃ , K ₂ O, P ₂ O ₅ , ZrO ₂ ,
It can contain at least 5% of at least one of AlN, Cs ₂ O, and V ₂ O ₅ . [Function] Ceramic multilayer circuit boards with high-density wiring of ceramic insulating materials with a dielectric constant of 3.0 to 4.5 and wiring conductor materials whose main components are gold, copper, or silver with low resistance have thermal expansion coefficients that are similar to those of semiconductor elements. Since the coefficient of thermal expansion is larger than that of the ceramic multilayer circuit board, a carrier substrate with a coefficient of thermal expansion equivalent to that of the ceramic multilayer circuit board is provided between the semiconductor element and the ceramic multilayer circuit board, and is connected by solder. By inserting a material whose main component is an organic material with a coefficient of thermal expansion equivalent to that of solder,
Improved reliability of solder joints. in this way,
Even when a ceramic multilayer circuit board with a relatively large coefficient of thermal expansion is used, a mounting method with high density of semiconductor elements and high reliability of connection parts has been obtained.
In addition, the solder portion connecting the carrier substrate on which the semiconductor element is mounted and the ceramic multilayer circuit board can be detached and detached, and the surface of the semiconductor element can be protected. [Example] An example of the present invention will be described below. In the following description, unless otherwise specified, "part" means part by weight, and "%" means weight %. Example 1 40 parts of hollow silica microspheres with an average particle size of 28 μm were
Blend 60 parts of the glass composition powder shown in the table (average particle size 1 μm), 12.5 parts of polyvinyl butyral resin with an average degree of polymerization of 1000, 4.0 parts of butyl phthalyl glycolate, 62.0 parts of trichlorethylene, 16.0 parts of tetrachloroethylene, and n-butyl alcohol. 22.0
and mixed in a wet ball mill for 8 hours to prepare a slurry. Next, using a stirring vacuum deaerator,
Pores introduced during ball milling were removed and the viscosity was adjusted to an appropriate level. Next, the slurry was applied to a thickness of 0.2 mm on a silicone-treated polyester film support using a doctor blade method, and the solvent was removed in a drying oven to produce a green sheet.

[Table] 210mm square green sheet, heated to 100℃
Pressing was performed at a pressure of Kgf/cm ² to remove irregularities on the green sheet. Next, using a puncher, it was cut into 200 mm square pieces and holes were made for guides.
Then, use the guide holes to fix the green sheet, and use the electron beam method to calibrate it in place.
I drilled a 0.1mm through hole. Furthermore, gold powder: nitrocellulose: ethyl cellulose: polyvinyl butyral: trichlorethylene = 100:
The through holes made in the green sheet are filled with conductor paste in a ratio of 3:1:2:23 (weight ratio), and then the conductor paste is printed according to a predetermined circuit pattern by screen printing. Fifty of these green sheets were laminated with the guide holes aligned, and laminated at 120° C. and a pressure of 25 kgf/cm ² . Next, the outer shape was cut into a 150 mm square green sheet laminate, which was set in an atmospheric firing furnace. Firing was carried out at a maximum temperature of 850 to 960°C for 1 hour. In this way, a ceramic multilayer circuit board measuring 120 mm square and 7 mm thick was produced. The carrier substrate was manufactured in the same manner as the ceramic multilayer circuit board. The differences are the through hole position, wiring pattern, number of laminated sheets of 7, and the dimensions of the carrier board after firing are 11 mm square and 1 mm thick. A 10 mm square semiconductor element (silicon) was connected to a carrier substrate using 95% lead-5% tin solder. Next, between the carrier substrate and the semiconductor element, 35 to 60 volume percent of quartz powder with an average particle size of 1 μm was added to a mixed organic material of 100 parts of epoxy resin (EP-828) and 5 to 10 parts of polybutadiene (CTBN1300×9). A material with the same coefficient of thermal expansion as the mixed solder material was inserted. Next, 9 pins were placed on a ceramic multilayer circuit board with Kovar pins connected with gold-germanium solder.
×9=81 carrier substrates (to which semiconductor elements are connected and a material mainly composed of an organic material is inserted) were connected with 60% lead-40% tin solder to fabricate a semiconductor module. Table 2 shows the characteristics of the manufactured ceramic multilayer circuit board and the reliability of the solder joints on the module board. The ceramic insulating material used in the ceramic multilayer circuit board has a dielectric constant of 3.0.
~4.5 (1MHz), and the electrical signal delay time is 5.7
It was ~7.0ns. This is due to the large dielectric constant of 9.5 in ceramic multilayer circuit boards whose main component is alumina, and the delay time of electrical signals.
Since it was 10.2ns, the speed was increased by 31-44% compared to this. In addition, the ceramic multilayer circuit board No. 20 had a thermal expansion coefficient of 7.0 to 9.0 × 10 ^-6 °C, so in some material systems, the thermal expansion coefficient between gold, the internal wiring conductor material, and the ceramic insulating material Due to the difference, some cracks occurred internally. However, the ceramic multilayer circuit boards No. 21 to 38 are
Since the thermal expansion coefficient was 8.0 to 13.0×10 ^-6 /°C, it matched well with gold, which is the internal wiring conductor material, and no cracks were generated inside the board. On the other hand, in semiconductor modules, even after 3,000 thermal cycles from -55℃ to 150℃, no solder connection occurs.

【table】

[Table] No breakage occurred in the continuation section. This sufficiently satisfied the life span required for large-scale electronic computers. Example 2 A semiconductor module was manufactured in the same manner as in Example 1 except for the following changes.・ Polymethacrylate resin is used instead of polyvinyl butyral resin with an average degree of polymerization of 1000. - Use diethyl phthalate instead of butyl phthalyl glycolate.・Using copper powder instead of gold powder. - Polymethacrylate is used instead of polyvinyl butyral. - A nitrogen atmosphere firing furnace is used instead of an atmospheric firing furnace. Table 3 shows the characteristics of the manufactured ceramic multilayer circuit board and the reliability of the solder joints on the module board. The ceramic insulating material used in the ceramic multilayer circuit board has a dielectric constant of 3.0.
~4.5 (1MHz), the delay time of the electrical signal

【table】

[Table] was 5.7 to 7.0 ns. This is 31 to 44% faster than an alumina ceramic multilayer circuit board. In addition, some of the ceramic multilayer circuit boards No. 39, 48, 54, and 55 have thermal expansion coefficients that are 0.5 times or less than the thermal expansion coefficient of copper, which is the internal wiring conductor material. There were some cases where cracks occurred due to poor matching with the ceramic insulating material. However, in ceramic multilayer circuit boards other than these, no cracks occurred and the matching between copper and ceramic insulating material was good. On the other hand, as a result of 3000 repetitions of heat cycles between -55 and 150°C in modules, cracks occurred in the solder connections in Nos. 44, 49, and 52, and repeated heat cycles caused wire breakage. It became possible. Other than these, there was no change in the soldered joints, and it was confirmed that the product was sufficiently durable for actual use. Example 3 Example 1 and 2 above except for the following changes.
A module was produced in the same manner as above. - The carrier board was a white board (no through holes, wiring patterns, etc.) made by laminating and firing seven green sheets and cutting it into 11 mm square pieces. Thereafter, a hole with a diameter of 0.1 mm was formed using a laser, and the hole was filled with copper by plating to produce a carrier substrate. The produced module gave similar results to Examples 1 and 2. Example 4 A multilayer wiring circuit made of copper and polyimide was formed on the ceramic multilayer circuit board produced in Examples 1 and 2. Furthermore, the ceramic multilayer circuit board is 26
layered. A chromium film with a thickness of 0.03 μm and a copper film with a thickness of 0.1 μm were formed on a ceramic multilayer circuit board by vacuum evaporation. Next, a positive type photoresist was applied to a thickness of 22 .mu.m to form a wiring pattern, and then a 20 .mu.m thick copper wiring layer was formed by electrolytic plating. Subsequently, a positive type photoresist was applied to a thickness of 22 μm to form an interlayer connection pattern, and then copper interlayer connection protrusions with a thickness of 20 μm were formed by electrolytic plating. After removing the positive type photoresist, unnecessary portions of the copper film and chromium film were etched away using an ion miller using argon. Subsequently, a low thermal expansion polyimide resin was applied to a thickness of 50 μm and cured to form an insulating layer, and then the low thermal expansion polyimide resin layer was flattened by surface polishing, and then a foamy hydrazine-ethylenediamine mixture was used. The interlayer connection protrusions were exposed by wet etching. Next, using the same method as the first layer wiring,
A copper wiring layer with a thickness of 20 μm was formed. In this way, three copper wiring layers are formed on the ceramic multilayer circuit board.
Layered. Semiconductor elements and carrier substrates are Examples 1 to 3
A module board was fabricated using the same method as above. The module substrate manufactured according to this example is different from the module substrate manufactured according to Examples 1 to 3.
The signal propagation delay time could be reduced by about 5%. This is due to the relative dielectric constant of the low thermal expansion polyimide insulating material being 3.5. Also,
The reliability of the soldered joints was equivalent to Examples 1-3. This is because the multilayer wiring circuit of copper and polyimide formed on the ceramic multilayer circuit board is thin, so there is little change in the coefficient of thermal expansion. [Effects of the Invention] According to the present invention, since the coefficient of thermal expansion of the ceramic insulating material is relatively large, gold, which has a low resistance,
A wiring conductor material containing copper or silver as a main component can be wired with high density. In addition, a carrier substrate is provided between the semiconductor element and the ceramic multilayer circuit board, which are connected by solder, and a material mainly composed of an organic material having a coefficient of thermal expansion equivalent to that of the solder is placed between the semiconductor element and the carrier substrate. By inserting it, even when using a ceramic multilayer circuit board with a relatively large coefficient of thermal expansion, it was possible to implement a mounting method that allows semiconductor elements to be mounted in high density and has good connection reliability.

[Brief explanation of drawings]

1 and 2 are longitudinal sectional views of a semiconductor module showing an embodiment of the present invention. 1, 10... Semiconductor element, 2, 11... Material mainly composed of organic material, 3, 12... Carrier substrate, 4, 13... Solder, 5, 16... Through-hole conductor material, 6, 17 ...Wiring conductor material, 7,
18... Ceramics insulating material, 8, 19... Gold-germanium solder, 9, 20... Kovar pin, 14... Polyimide resin, 15... Copper conductor wiring material.

Claims (1)

[Scope of Claims] 1. A semiconductor module in which a semiconductor element is mounted on a ceramic carrier substrate, and the substrate is mounted on a ceramic multilayer circuit board, wherein the carrier substrate and the multilayer circuit board include a ceramic layer and a wiring conductor layer. The ceramic layers are alternately laminated, the ceramic layers are made of glass, and the ceramic carrier substrate and the semiconductor element are joined by solder bumps, and the solder bumps are covered with an organic resin. A semiconductor module featuring: 2. Claim 1, wherein the organic resin contains 5 to 10 parts by weight of rubber particles and 35 to 60% by volume of ceramic powder as a whole based on 100 parts by weight of the resin. semiconductor module. 3 The rubber particles are polybutadiene and/or silicone rubber, and the ceramic powder is quartz,
silicon carbide, silicon nitride, calcium carbonate,
The semiconductor module according to claim 2, characterized in that it is made of one or more types of silicon carbide containing beryllium.