JP4606115B2 - Multilayer substrate and manufacturing method thereof - Google Patents

Description

  The present invention relates to a laminated molded body, a multilayer substrate, and a method for producing the same, and more particularly, to a multilayer substrate having high strength, excellent dimensional accuracy, and suitable for a circuit board, and a method for producing the same.

  Conventionally, a multilayer substrate using ceramics as an insulating substrate has been used, but in recent years, addition of various functions to the multilayer substrate has been demanded, and a multilayer substrate combining different ceramics has been proposed. For example, in order to reinforce a weak ceramic insulating layer with a strong insulating layer or to incorporate a capacitor with a high capacitance value in a multilayer substrate, a high dielectric constant ceramic insulating layer is incorporated in a low dielectric constant ceramic insulating layer. A multilayer substrate in which layers are laminated is known.

  In such a multilayer substrate, in order to prevent ceramic cracks and delamination (delamination), the characteristics of the insulating layer material are selected and controlled so that the firing shrinkage rate and thermal expansion coefficient match between different types of ceramic insulating layers. It is usually done.

  However, in recent years, in order to reduce the cost of the multilayer substrate and improve the dimensional accuracy of the electrodes formed on the multilayer substrate, it is required to reduce the shrinkage rate of the multilayer substrate in the XY direction during firing. Therefore, this requirement cannot be achieved by the conventional multilayer substrate.

  In order to satisfy such requirements, in recent years, the surface of the laminate is constrained by a non-sintered insulating layer that is not sintered at the firing temperature of the laminate, and after shrinking only in the thickness direction, Although a method of removing has been developed (see, for example, Patent Document 1), the method of Patent Document 1 in which shrinkage is suppressed by an unfired insulating layer requires removal of the unfired insulating layer after completion of firing. Increased or complicated, and the manufacturing cost increased.

  Accordingly, it has been proposed to suppress dimensional changes due to shrinkage of firing by laminating two types of ceramic molded bodies having different firing shrinkage start temperatures and firing them simultaneously (for example, see Patent Document 2).

  However, in the manufacturing method described in Patent Document 2, although the dimensional change can be suppressed, only the firing shrinkage start temperature is controlled, so that the behavior of shrinkage suppression is large, and the shrinkage rate itself is large. There has been a problem that the dimensional accuracy in the case varies.

Therefore, two types of insulating sheets containing crystallized glass powder and ceramic powder are prepared so that the crystallization temperature of the crystallized glass powder contained in one is lower than the softening point of the crystallized glass powder contained in the other. In addition, a method has been proposed in which a multilayer substrate is manufactured by simultaneously firing a laminate obtained by laminating these layers (see, for example, Patent Document 3), whereby the dimensional accuracy is excellent and the shrinkage in the plane direction is close to zero. A multilayer substrate with a small variation in shrinkage rate is manufactured.
Japanese Patent No. 2554415 Japanese Patent Laid-Open No. 2001-15875 Japanese Patent Application No. 2003-418485

  However, in the multilayer substrate described in Patent Document 2, since the two kinds of insulating sheets shrink at different temperatures, the shrinkage is limited to each other. Therefore, although the dimensional accuracy is greatly improved, the strength of the porcelain is low, There was a problem that cracks occurred when dropped or mounted by reflow, and in the worst case, they were broken.

  Accordingly, an object of the present invention is to provide a multilayer substrate with improved substrate strength and high dimensional accuracy, and a method for manufacturing the same.

  Since the present invention uses at least two kinds of glass powders having different firing shrinkage start temperatures, in order to suppress the shrinkage in the planar direction, the high dimensional accuracy is improved and the crystallinity of the glass powder is increased. This is based on the novel knowledge that the bending strength of the laminated body after firing can be improved, which improves the dimensional accuracy during firing and realizes a high-strength multilayer substrate.

That is, the multilayer substrate of the present invention includes a first insulating layer containing a first crystallized glass and a second insulation containing a second crystallized glass having a crystallization temperature different from that of the first crystallized glass. will be a layer disposed surface and inside the electrode of the ceramic laminated substrate formed by laminating state, and are a crystallinity of 80% or more each of the crystallized glass, the crystallization of the first crystallized glass The temperature is lower than the softening point of the second crystallized glass, and the difference between the coefficient of thermal expansion of the first crystallized glass and the coefficient of thermal expansion of the second crystallized glass is 2 × 10 ⁻⁶ / ℃ characterized der Rukoto below.

Before SL crystallization temperature of the first crystallized glass, the second more low this than the softening point of the crystallized glass, sintering the first dielectric layer is earlier than the second insulating layer Since this starts and ends, high dimensional accuracy can be more easily obtained and warpage can be further reduced by suppressing the shrinkage between the closely contacting surfaces.

The thermal expansion coefficient of the first crystallized glass, the occurrence of the second difference between the thermal expansion coefficient of the crystallized glass is more and this is 2 × 10 -6 ^/ ° C. or less, during firing interlayer stress Since it suppresses, it becomes easier to suppress generation | occurrence | production of interphase peeling.

  Further, it is preferable that a third insulating layer containing crystallized glass different from the first and second is included. Thereby, a dimension system can be raised further.

  The insulating layers preferably each contain 30% by mass or more of glass powder. This facilitates low temperature sintering due to the softening flow of the glass.

  The crystallized glass preferably contains at least one of diopside, hardistonite, celsian, cordierite, anorthite, garnite, willemite, spinel, mullite, forsterite and sourite. This facilitates increasing the strength and reducing the dielectric loss.

A method for manufacturing a multilayer substrate of the present invention, the first glass powder including first the green sheet and the first crystallization temperature than the crystallization temperature of the crystallized glass consisting of a first crystallized glass and wherein the second glass powder consisting of high softening point second crystallized glass, a forming step of the first even the firing shrinkage initiation temperature by the green sheets to produce a high second green sheet, the first and before including a conductor forming step that forms the shape of the conductive pattern by using at least a part of the surface and inside the conductor paste of the second green sheet, what the conductor pattern is formed
Laminating the serial first and second green sheets, and laminating steps to produce a product layer body, and firing the laminate, the crystallinity of the first and second crystallized glass to 80% or more In addition, the method includes a firing step in which a difference in thermal expansion coefficient between the first and second crystallized glasses is 2 × 10 ⁻⁶ / ° C. or less .

  By adopting such a manufacturing method, it is possible to suppress shrinkage in the planar direction of the green sheet during firing, reduce variation in firing shrinkage, increase the dimensional system, and crystallized glass with high crystallinity on each green sheet. By including, strength can be improved.

The crystallization temperature of the first crystallized glass, the second more low this than the softening point of the crystallized glass, before the layer of the first green layer of the sheet is the second green sheet Since the sintering starts and ends at the same time, it is easier to obtain high dimensional accuracy and warpage can be further reduced by suppressing the shrinkage between the closely contacting surfaces.

Since the difference in thermal expansion coefficient between the second crystallized glass and the first crystallized glass, more and 2 × 10 -6 ^/ ° C. or less this, to suppress the occurrence of sintering during the interlayer stress, It becomes easier to suppress the occurrence of phase separation.

As the first and second green sheets, it is preferable to use those each comprising the first and second glass powder 30% by weight or more. As a result, it improves the sintering property.

After the firing step, the first and second crystallized glass, diopside, hardystonite, celsian, cordierite, anorthite, gahnite, willemite, spinel, mullite, at least one of forsterite and Suanaito it is preferable that form the. This makes it easy to increase the strength.

  The present invention relates to a multilayer substrate having a high strength and a high dimensional system. The first insulating layer including the first crystallized glass and the first crystallized glass have different crystallization temperatures. Electrodes are provided on the surface and inside of a ceramic laminated substrate formed by laminating a second insulating layer containing crystallized glass.

  Hereinafter, the multilayer substrate of the present invention will be specifically described with reference to the drawings.

  FIG. 1 is a schematic sectional view of the structure of a multilayer substrate according to an embodiment of the present invention. According to FIG. 1, the multilayer substrate 10 includes a ceramic insulating substrate 1 on which ceramic insulating layers 1 a to 1 g are laminated, a surface conductor layer 2 formed on the front and back surfaces of the ceramic insulating substrate 1, and the interior of the ceramic insulating substrate 1. The inner conductor layer 3 is formed on the inner conductor layer 3, and the via-hole conductor 4 is used for electrical connection between the inner conductor layers 3 or between the surface conductor layer 2 and the inner conductor layer 3.

  According to the present invention, the multilayer substrate 10 includes two or more kinds of glass powders having different crystallization temperatures, and is obtained by firing a laminate in which a plurality of green sheets having different firing shrinkage start temperatures are laminated. For example, in FIG. 1, as will be described in detail later, among the insulating layers 1 a to 1 g constituting the multilayer substrate 10, the shrinkage end temperatures of the green sheets to be the insulating layers 1 a and 1 g are set to the other insulating layers 1 b to 1 g. What is necessary is just to make it become lower than shrinkage | contraction start temperature with the green sheet used as 1f. Moreover, you may make it the shrinkage | contraction start temperature of the green sheet contained in the insulating layers 1a and 1g become higher than the shrinkage end temperature of the green sheet contained in the other insulating layers 1b-1f.

  The crystallinity of the glass contained in the insulating layers 1a and 1g and the insulating layers 1b to 1f is important to be 80% or more, and the bending strength of the laminate is easily improved. In particular, in order to achieve higher strength, it is desirable that the crystallinity of all the glass contained in each insulating layer is 85% or more, and more preferably 90% or more.

  It is important that the bending strength of the ceramic multilayer substrate is 250 MPa or more in order to prevent cracks from being generated when stress or impact is applied to the porcelain during dropping or reflow mounting. In particular, in order to reduce the defective rate and to stably supply the product, it is desirable that the pressure be 270 MPa or more, further 300 MPa or more, and more preferably 320 MPa or more.

  It is preferable that the crystallization temperature of the crystallized glass contained in the insulating layers 1a and 1g is lower than the softening point of the crystallized glass of the crystallized glass contained in the other insulating layers 1b to 1f. By adopting such a configuration, it becomes easy to reduce the shrinkage rate during firing to 3% or less, and it is possible to easily achieve an increase in the dimensional system.

  That is, the shrinkage end temperature of the green sheets to be the insulating layers 1a and 1g is lower than the shrinkage start temperature of the green sheets to be the other insulating layers 1b to 1f, and the insulating layers 1a and 1g are lower than the insulating layers 1b to 1f. Shrinkage starts at low temperatures. At that time, since the crystallization temperature of one of the two or more types of crystallized glass is lower than the softening point of the other one type of crystallized glass, the insulating layers 1b to 1f start to shrink. The firing shrinkage of the layers 1a and 1g is almost finished (97% or more of the final firing volume shrinkage amount), and it becomes possible to suppress shrinkage in the XY directions (plane direction of the green sheet) of each other, and firing. Reproducibility can be improved. In particular, in order to more effectively suppress shrinkage in the XY direction and further improve reproducibility, the difference between the softening point of one glass and the crystallization temperature of the other glass is 5 ° C. or more, particularly 10 It is desirable that the temperature be at least 15 ° C.

The difference in thermal expansion coefficient between the two types of crystallized glass contained in the ceramic laminated substrate is preferably 2 × 10 ⁻⁶ / ° C. or less. For example, in FIG. 1, the difference between the thermal expansion coefficient of the crystallized glass contained in the insulating layers 1a and 1g and the thermal expansion coefficient of the crystallized glass contained in the insulating layers 1b to 1f is 2 × 10 ⁻⁶ / ° C. or less. In particular, it is desirable to set it to 1 × 10 ⁻⁶ / ° C. or less. Thereby, at the time of cooling from the maximum firing temperature, a difference in thermal shrinkage occurs, and the generation of cracks and delamination at the interface between the insulating layer and the dissimilar material insulating layer can be more effectively suppressed.

  According to the present invention, the insulating layers 1a and 1g and the insulating layers 1b to 1f each contain 30% by mass or more, particularly 35% by mass or more, and further 40% by mass or more of crystallized glass. Is preferable in terms of enhancing the sinterability.

As the ceramic is a major component of the insulating layer 1a~1g constituting the ceramic multilayer _{substrate, Al 2 O 3, SiO 2} , MgTiO 3, CaZrO 3, CaTiO 3, Mg 2 SiO 4, BaTi 4 O 9, ZrTiO 4, Examples include SrTiO ₃ , BaTiO ₃ , TiO ₂ , AlN, SiN, and the like.

  In addition, the crystallized glass contained in each of the insulating layers 1a to 1g is at least one selected from diopside, hardistonite, celsian, cordierite, anorsite, garnite, willemite, spinel, mullite, forsterite and suurite. It is desirable that the bending strength of the multilayer substrate is further increased and the dielectric loss is further decreased.

  By adopting crystallized glass and precipitating the above ceramic crystal, it becomes easy to be fired at a temperature of 1000 ° C. or lower, and as a result, a low resistance conductor such as Cu, Ag, Al or the like is used as the conductor layer. In addition, it is easy to reduce the dielectric constant and is suitable for high-speed transmission.

  As described above, the combination of the two types of insulating layers has been described. However, the number of insulating layers may be three or even four or more. By controlling various compositions of the insulating layers, the firing shrinkage behavior Can be easily controlled and changed.

  Next, the method for producing a multilayer substrate of the present invention comprises a molding step, a conductor formation step, a lamination step, and a firing step, and for each of these steps, the multilayer substrate of FIG. This will be described below.

  First, as a molding process, a volatile organic binder that easily volatilizes during firing, an organic solvent, and plastic as needed, for the first glass powder made of crystallized glass having a crystallinity of 80% or more. The slurry is mixed with the agent. Using these slurries, tape molding is performed by a lip coater method, a doctor blade method, or the like, and cut into a predetermined size to produce a green sheet A. Next, for the second glass powder made of crystallized glass having a crystallinity of 80% or more, a volatile organic binder that easily volatilizes during firing, an organic solvent, and a plasticizer as necessary, And green sheet B is produced in the same manner as green sheet A. In this case, the glass powder is selected so that the green sheet A and the green sheet B have different firing shrinkage start temperatures.

  Instead of using the green sheet B, a paste containing the second glass powder can be produced and applied to the surface of the green sheet A.

  Next, as a conductor forming step, the surface conductor layer and the inside are formed by screen printing using a conductor paste on the surface of a desired green sheet among the plurality of green sheets A and B obtained in the forming step. A conductor pattern to be a conductor layer is deposited and formed. Further, a through hole is formed in a desired green sheet by punching, laser drilling, or the like, and a conductor paste is filled in the through hole of the green sheet. In this manner, a plurality of conductor-equipped green sheets in which a conductor pattern is formed on the surface or inside of the green sheet are produced.

  Next, as a laminating process, each green sheet with a conductor obtained in the conductor forming process and green sheets A, B, etc., on which a conductor pattern is not formed, are laminated as desired. In this case, it goes without saying that the conductor patterns are combined so as to become a predetermined designed circuit.

  According to the present invention, it is preferable to design the laminate so that the contraction rate in the plane direction of the green sheet is 3% or less.

  Next, as a firing step, the laminate obtained in the lamination step is fired. The firing can be performed by multi-stage firing which is temporarily held at a temperature intermediate between the shrinkage start temperature of the green sheet at which the shrinkage starts on the low temperature side and the crystallization temperature of the glass contained in the green sheet. It is possible to perform simultaneous firing by adjusting the temperature rising rate even at a temperature. In such firing, firing shrinkage in the XY direction (plane direction of the green sheet) is suppressed, and Z A substrate with high dimensional accuracy that is fired and contracted in the direction (the thickness direction of the green sheet) can be manufactured.

  In addition, the ceramics which are the main components contained in the two types of green sheets having different firing shrinkage temperatures and the crystallized glass of the subcomponent are not only different in sintering shrinkage behavior, but also have a dielectric constant depending on the purpose. The method of the present invention may be different in other properties such as bending strength, dielectric loss, thermal conductivity, bulk density, temperature coefficient, or even in the presence of an insulating layer of a partially different material in one layer. If is used, warpage and delamination can be suppressed, so there is no problem.

  As a lamination form of two types of green sheets A and B having different firing shrinkage behaviors in FIG. 1, lamination was performed with ABBBBBBA. , ABBAAAA, ABBBAAA, ABBBBAA, and the like may be used. The number of layers may be changed, or A and B may be reversed.

  Furthermore, as a lamination form when two types of green sheets A, B, and C having different firing shrinkage behaviors are used, any combination of ABCCCBA, ABBCBBA, ABBCCCBA, ABCBABCBA, AAABCBAAA, and any number of laminations can be set. Of course, it is needless to say that symmetry is preferable.

  In addition, the kind of green sheet may be comprised with the 4 or more types of green sheet from which a baking shrinkage | contraction behavior differs, respectively. In particular, the firing end temperature of one type of green sheet is set to be lower than the firing start temperature of at least one type of other green sheet, that is, crystallized glass contained in one type of green sheet. The crystallization temperature is preferably set to be lower than the softening point contained in at least one of the other green sheets.

  The multilayer substrate shown in Table 1 was produced. First, ethyl cellulose as an organic binder and 2-2-4-trimethylpentadiol monoisobutyrate as an organic solvent are added to the respective compositions forming the glass ceramic insulating layers A and B having different firing shrinkage starting temperatures. The two types of slurries thus prepared were prepared and formed by the doctor blade method to produce green sheets A and B, respectively.

  Then, through holes are formed at predetermined positions of the green sheets A and B by punching or the like, and the conductive paste containing Ag powder is filled in the through holes, and the conductive paste is applied to the surfaces of the green sheets A and B. Was printed at a predetermined position and dried to produce a conductor-equipped green sheet.

  Green sheets A and B filled with a conductive paste and formed with a conductor layer having a predetermined shape were laminated to form a laminated molded body having the structure shown in FIG.

  Thereafter, the binder removal treatment was performed at 400 ° C. in the atmosphere, followed by baking at 910 ° C. to obtain the multilayer substrate shown in FIG. In addition, the thickness of each insulating layer 1a-1g before baking was 0.2 mm, and the magnitude | size of the multilayer board | substrate after baking was 10 mm long, 10 mm wide, and thickness 0.8mm.

  In addition, the shrinkage | contraction rate of the multilayer board | substrate of a XY direction was measured by measuring the length between predetermined points with respect to the green sheet laminated body and the multilayer board | substrate after baking. In addition, 10 samples were prepared for each sample, and the respective shrinkage rates were measured, and the difference between the maximum shrinkage rate and the minimum shrinkage rate of the 10 samples was evaluated as shrinkage variation. Moreover, the presence or absence of cracks and delamination in the substrate was evaluated by polishing the substrate and observing it with an optical microscope.

  The degree of crystallinity of the glass of each insulating layer was determined by the Rietveld analysis method from the XRD diffraction pattern of the sample fired under the same conditions as when each insulating layer was fired simultaneously as shown in Table 2. In the measurement of XRD diffraction, zinc oxide was mixed as a standard sample in order to reduce the error.

  As a sample for evaluation of the bending strength of a substrate, a structure in which five green sheets (thickness before firing 0.2 mm) serving as second insulating layers are sandwiched by green sheets (thickness 0.2 mm before firing) serving as first insulation layers Then, a test piece of 5 mm × 40 mm × 0.8 mm was obtained by simultaneous firing at the firing temperature shown in Table 2 for 1 hour. With respect to this test piece, a three-point bending strength was measured at room temperature under conditions of a crosshead speed of 0.5 mm / min and a distance between lower fulcrums of 30 mm.

  Further, a wax is added to the composition forming the ceramic A and the composition forming the ceramic B, and a green compact is formed by pressing at 100 MPa. The TMA (heat The shrinkage start temperature S, shrinkage end temperature E, and thermal expansion coefficient at room temperature to 900 ° C. of each ceramic were evaluated in the temperature range of room temperature to 1000 ° C. by mechanical analysis.

The softening point and crystallization temperature of the glass were evaluated from a curve obtained by heating at 10 ° C./min by DTA (suggested thermal analysis). The results are shown in Tables 1 and 2.

  Sample No. of the present invention. Nos. 1 to 8 were substrates having a shrinkage rate as small as 0 to 3.0%, a bending strength as large as 250 MPa or more, and no cracks or delamination during firing.

  On the other hand, sample No. 2 composed of the first insulating layer having a crystallinity of less than 80%. Nos. 9 and 10 have a high shrinkage rate of 8.5% or more and a low strength of 230 MPa or less. In No. 9, the softening point of the second insulating layer was significantly lower than the crystallization temperature of the first insulating layer, and the difference in thermal expansion coefficient was large. As a result, defects were observed.

The schematic sectional drawing which shows an example of the ceramic laminated substrate of this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ceramic laminated substrate 2 ... Surface conductor layer 3 ... Internal conductor layer 4 ... Via-hole conductor 10 ... Multilayer substrate

Claims (7)

Ceramic laminate formed by laminating a first insulating layer containing a first crystallized glass and a second insulating layer containing a second crystallized glass having a crystallization temperature different from that of the first crystallized glass. Electrodes are disposed on the surface and inside of the substrate, the crystallinity of the crystallized glass is 80% or more, respectively, and the crystallization temperature of the first crystallized glass is the second crystallized glass. A difference between the thermal expansion coefficient of the first crystallized glass and the thermal expansion coefficient of the second crystallized glass is 2 × 10 ⁻⁶ / ° C. or lower. substrate. The multilayer substrate according to claim 1, further comprising a third insulating layer including crystallized glass different from the first and second. The multilayer substrate according to claim 1, wherein each of the insulating layers contains 30% by mass or more of crystallized glass. The crystallized glass contains at least one of diopside, hardistonite, celsian, cordierite, anorthite, garnite, willemite, spinel, mullite, forsterite and sourite. 4. The multilayer substrate according to any one of 3 . A first green sheet including a first glass powder made of the first crystallized glass and a second crystallized glass having a crystallization temperature and a softening point higher than the crystallization temperature of the first crystallized glass. A molding step for producing a second green sheet containing a second glass powder and having a firing shrinkage start temperature higher than that of the first green sheet; and at least a part of the surface and the inside of the first and second green sheets A conductor forming step of forming a conductor pattern on the substrate, laminating the first and second green sheets including those having the conductor pattern formed thereon, a laminate step of producing a laminate, and firing the laminate. The crystallinity of the first and second crystallized glass is set to 80% or more, and the difference in thermal expansion coefficient between the first and second crystallized glass is set to 2 × 10 ⁻⁶ / ° C. or less. Equipped with a firing process A method for manufacturing a multilayer substrate. 6. The method for producing a multilayer substrate according to claim 5, wherein the first and second green sheets include those containing 30% by mass or more of the first and second glass powders, respectively. After the firing step, the first and second crystallized glasses are at least one of diopside, hardestite, celsian, cordierite, anorsite, garnite, willemite, spinel, mullite, forsterite and suurite. 7. The method for producing a multilayer substrate according to claim 5, wherein the seed crystal is formed.

Images