KR20110075762A - Sintering metho of low teperature co-fired ceramics - Google Patents

Abstract

PURPOSE: A method for sintering low temperature co-fired ceramics(LTCC) is provided to prevent the sintering-shrinkage of the ceramics to the x-y axial direction by arranging restricting layers on the upper and/or the lower side of an LTCC layer. CONSTITUTION: A method for sintering an LTCC includes the following: An LTCC layer(2) and one or more restricting layers(3, 4) which form a stacked body. The restricting layers are based on alumina, zirconia, or a mixture of the same and are arranged on the upper side and/or the lower side of the LTCC layer. One or more rods are arranged on the upper side of the stacked body, and the stacked body with the rods is sintered at a temperature between 830 and 900 degrees Celsius for 20-40 minutes. The sintering temperature of the restricting layers is higher than that of the LTCC layer. The restricting layers and the rods are eliminated after the sintering process.

Description

Firing method of low temperature simultaneous firing ceramics {SINTERING METHO OF LOW TEPERATURE CO-FIRED CERAMICS}

The present invention relates to a firing method for low temperature co-fired ceramics, and more particularly to a firing method for low temperature co-fired ceramics in which sintering shrinkage in the x-y axis direction of the ceramic hardly occurs.

Recently, in order to implement a high frequency device, a technique of sintering and printing a conductor pattern on a green sheet of dielectric ceramics and stacking them has been developed. This enables inductors, capacitors, and resistors to be implemented without a separate lead in one module, thereby significantly reducing the volume of the package.

Particularly, as part of this, the electronic ceramic parts are increasing the degree of integration through the modularization process, and for this purpose, low temperature co-fired ceramics (LTCC), which enables simultaneous thickening with internal conductors, enables such a thick film lamination process. ), The development of the process using the same, and the improvement of the integration and the integration of the module is in progress. As a method for increasing the integration of parts, a passive integration technology has been proposed to integrate more passive elements into one module by increasing the number of thick films.

In this case, however, the control of uniform curvature of the entire substrate including the substrate edge portion of the LTCC substrate is a significant variable. For example, when the LTCC substrate is applied as an RF (Radio Frequency) component, the thickness thereof is reduced in thickness and size, so that a uniform substrate can be realized without relatively shrinking in the x-y axis direction during firing. However, when the LTCC substrate is applied to the semiconductor field, since the substrate is thick and manufactured as a large-area substrate, about 13 to 17% of bow axis is generated in the process of plastic shrinkage. Various defects such as disconnection occur, and thus, it is difficult to expand the scale of work applicable in the production process and lower the production cost.

Currently, in the manufacturing process of modules and systems for electronic ceramic components, other alternatives for securing interlayer accuracy and satisfying electrical characteristics have not been proposed. Research into so-called non-shrink processes is essential. In particular, as the application of LTCC materials has been expanded to semiconductor measuring substrates and the like, the thickness of the substrates has become thicker and larger, and thus, development of a shrinkage process is further required.

Accordingly, the present invention is to provide a firing method of LTCC that can effectively prevent the occurrence of shrinkage in the firing process of low-temperature co-fired ceramic (LTCC) material.

According to an aspect of the present invention, a method for firing low temperature co-fired ceramics (LTCC) according to an aspect of the present invention is disposed so as to be in surface contact with the LTCC layer and at least one of an upper surface and a rear surface of the LTCC layer. Constructing a laminate comprising one or more restraint layers having a higher firing temperature, placing one or more rods with a predetermined load on top of the laminate and firing them together, followed by removal of the restraint layer and rods can do. In this case, the LTCC layer may be formed of at least one laminated LTCC sheet. In addition, the restraint layer may be made of alumina, zirconia or a mixture thereof, which may be formed by molding the powder of the composition into a sheet. The rod may also be a stainless plate. In addition, a setter may be disposed between the laminate and the rod, and at least one of the rear surface of the laminate so as to be in surface contact therewith, thereby preventing mutual adhesion. In addition, the firing temperature may be 830 ~ 900 ℃, the firing time may be 20 ~ 40 minutes. In addition, the load may be 100 ~ 800g / ㎠. In addition, the thickness after the firing of the LTCC layer may be 1 mm or more and less than 5 mm. In addition, the thickness of the constraint layer may be 30 ~ 500㎛. In addition, during the firing, the glass component in the LTCC layer may be impregnated in the constraint layer forming an interface with the LTCC layer to a thickness of greater than 0 μm and less than 30 μm.

As described above, according to the firing method of the low-temperature co-fired ceramics (LTCC) of the present invention, the sintering shrinkage of the LTCC hardly occurs in the x-y direction, and thus, it is possible to manufacture an accurate LTCC having a larger thickness and a larger area.

First, Low Temperature Co-Fired Ceramics (LTCC), which is a term used in the present invention, includes LTCC of any composition known in the art, capable of firing at a low temperature of about 950 to 1000 ° C. or less, It is not limited to the composition of any particular LTCC.

In the present invention, the inventors pay attention to the stress distribution generated during firing of the LTCC substrate (or specimen). 1A and 1B are stress distribution diagrams and photographs generated when the upper and lower portions of the LTCC specimens are fixed and supported with a constant force and only the central portion of the specimen is contracted. 1A and 1B, it is observed that the stress generated during firing is concentrated at the edges of the upper and lower portions of the specimen, whereby a curvature occurs due to the difference in tensile force between the upper and lower interfaces and the central interface of the specimen. It was analyzed.

Accordingly, the present inventors can compensate for the difference in tensile force between the upper and lower interfaces and the center interface of the specimen by firing by placing a load applying a constant gravity to the LTCC substrate on the upper surface of the LTCC substrate, thereby greatly reducing shrinkage. I found out. That is, FIG. 1C is a stress distribution diagram and a photograph generated when the upper and lower portions of the LTCC specimen are fixed and supported by a constant force, and a rod having an appropriate load is disposed on the upper surface thereof and fired. Referring to FIG. 1C, unlike FIGS. 1A and 1B, it can be seen that uniform stress and tensile force are generated to almost eliminate shrinkage.

In addition, according to the present invention, the glass component of the LTCC generated during firing by firing in a structure in which the restraining layer (s) of a material having a higher firing temperature than the LTCC is disposed on the top and / or bottom of the LTCC substrate By allowing the support layer (s) to be impregnated, the shrinkage rate can be further reduced.

2 is a schematic laminated structure diagram in which a support layer is disposed on an upper surface and a rear surface of an LTCC layer and a rod is disposed on an upper surface of the non-shrinkable manufacturing method according to the present invention.

Referring to FIG. 2, in the LTCC non-shrinkage manufacturing method according to the present invention, the restraining layer (s) 3 and 4 of the material having a higher firing temperature than the LTCC are disposed on the upper and / or rear surfaces of the LTCC sheet 2. On the upper surface of the LTCC sheet 2, it is baked as a laminated structure 1 in which the rod 5 of predetermined load is arrange | positioned. At this time, the material having a higher firing temperature than the LTCC may be any composition known in the art including alumina or zirconia and mixtures thereof. In addition, the constraint layer (s) 3 and 4 may each be stacked in one or more numbers, and the glass component generated at the interface between the LTCC 2 and the constraint layers 3 and 4 during firing may contain the constraint layers 3. 4) and densified in such a way as to fill the pores inside these layers, and these restraining layers 3 and 4 and the rod 5 are removed from the LTCC substrate 2 after firing. The restraining layers 3 and 4 are preferably used by processing the powder in the form of a sheet, for example, alumina or zirconia powder or a mixed powder thereof may be processed into a sheet. 3A to 3D illustrate the LTCC substrate according to the thickness of the alumina constraining layers 3 and 4 during firing in the laminated structure of FIG. 3 except the rod 5 in the LTCC non-shrinkage manufacturing process according to the present invention. Electron micrograph showing shrinkage change of 2). That is, the thicknesses of the alumina constraining layers 3 and 4 were 30 μm (FIG. 3A), 100 μm (FIG. 3B), 250 μm (FIG. 3C) and 500 μm (FIG. 3D), respectively, and the shrinkage was increased as the thickness thereof increased. As the degree decreases, the shrinkage can be seen to come in a straight line. The restraint layers 3 and 4 may be set to a thickness greater than or equal to a predetermined value in order to effectively suppress the contraction of the substrate 2 in the x-y axis direction.

In addition, the firing of the laminated structure (1) is in the low temperature baking temperature range of 830 ~ 900 ℃ and the firing time is 20 to 40 minutes by alumina or zirconia restraint layers (3, 4) of the upper and lower LTCC sheet 2 during the firing ) Is preferably prevented from shrinking in the xy-axis direction of the LTCC substrate 2.

In addition, the material of the rod 5 is not limited to a specific material as long as it can withstand the low temperature baking temperature, and may be any material known in the art, for example, a stainless material may be used.

In addition, it is preferable to use the porous ceramic substrate 6 as a setter on the upper and / or rear surfaces of the alumina or zirconia confining layers 3 and 4. For example, the porous ceramic substrate may be disposed between the restraining layer 3 and the rod 5 disposed on the upper surface of the LTCC substrate 2 so as not to stick to each other after firing.

4 is an electron micrograph showing that a part of the LTCC glass is impregnated with the alumina restraint layer 3 at the interface between the alumina restraint layer 3 and the LTCC sheet 2 during firing with the lamination structure of FIG. 3. At this time, the impregnation thickness is preferably within about 30㎛.

In addition, Figure 5 is a high-temperature micrograph showing the shrinkage at each firing temperature during firing in the laminated structure of Figure 3 except the rod 5 in the LTCC non-shrinkage manufacturing process according to the present invention. Referring to FIG. 4, the substrate 2 does not undergo any shrinkage behavior up to 500 ° C. at which burnout of the binder contained in the LTCC substrate 2 occurs, but the substrate 2 rapidly contracts. After 750 ° C, at 800 ° C, the shrinkage to the z-axis and the shrinkage difference between the upper and lower edges and the center of the edge of the substrate 2 occur, and the shrinkage begins to occur. At 900 ° C, the z-axis shrinkage increases and Shrinkage is maximized at the interface between the substrates 2.

6A to 6C illustrate various load values of the rod 5 during firing in the laminated structure of FIG. 3 arranged up to the rod 5 in the LTCC non-shrinkage manufacturing process according to the present invention. Cm 2) shows shrinkage change.

Referring to FIG. 6A, the slope of the graph is 2.09 when the load of the load is 100g / cm 2, while the slope decreases as the load increases, and becomes 0.61 when the load is 700g / cm 2, and is almost zero. Also, when the load was 1000 g / cm 2, the slope was -0.37, indicating that the substrate 2 was deformed. When the thickness of the board | substrate 2 was 1.0 mm or more, the shrinkage rate of the x-y-axis direction was influenced by the load of the rod 5, but when it was less than 1.0 mm, it was not affected by the said load.

In addition, referring to FIG. 6B, when the edge shrinkage is expressed as a semi-circle, the degree of shrinkage is represented as a change in the radius of the rod 5 according to the load of the rod 5, and as the value increases, the shrinkage shape approaches a straight line shape. As a result, it can be seen that as the load of the rod 5 increases, shrinkage is reduced to the maximum peak at 800 g / cm 2, and when the load exceeds 800 g / cm 2 (the dotted line in FIG. 6b and the right electron micrograph thereof) It can be seen that the shrinkage is rather severe and the deformation of the substrate 2 occurs.

In addition, referring to FIG. 6C, a change in the radius of the edge shrinkage according to the thickness of the LTCC substrate 2 and the load of the rod 5 is shown. In particular, in this graph, the change of the normalized edge curvature of the radius is shown. It is calculated by dividing the radius value of the edge shrinkage by the thickness of the LTCC substrate (2). According to this graph, as the thickness of the LTCC substrate 2 increases, the normalization value of the radius decreases, indicating a negative slope. In particular, when the thickness of the substrate 2 is 5.0 mm or more, the rod 2 has a constant value. 5) It can be seen that it is not affected by the change in load.

Hereinafter, preferred embodiments of the present invention will be described in more detail. However, the examples described below are provided to help the overall understanding of the present invention, and the present invention is not limited only to the following examples.

Example

Two sheets of 50 μm thick each were formed from zirconia powder, and a commercially available composition of 27CaO-10Al ₂ O ₃ -45SiO ₂ -8ZnO-10B ₂ O ₃ , which is a CaO-Al ₂ O ₃ -SiO _{2 type} (anorthite type), was prepared. After the LTCC powder was molded into a sheet having a thickness of 200 μm, a laminated structure of a zirconia layer / LTCC layer / zirconia layer was formed, and then a porous setter was placed at the bottom of the laminated structure, and a rod made of stainless plate was placed on top of the 900. The LTCC substrate was prepared by sintering at 30 ° C. for 30 minutes. As a result, the LTCC glass layer penetrated into the zirconia layer at the interface of the zirconia layer to fill the glass between the zirconia particles, and the zirconia layer acted as a confining layer by this region, so that no sintering shrinkage of the LTCC layer occurred in the xy direction. Only the z-axis contraction occurred about 39%.

On the other hand, the overall shrinkage characteristics of the preferred embodiments of the present invention described above is somewhat within the usual error range depending on the powder characteristics such as the average particle size, distribution and specific surface area of the composition powder, the purity of the raw material, the amount of impurity addition and the sintering conditions It is only natural for those with ordinary knowledge in the field that there may be variations. In addition, preferred embodiments of the present invention are disclosed for the purpose of illustration, anyone of ordinary skill in the art will be possible to various modifications, changes, additions, etc. within the spirit and scope of the present invention, such modifications, changes And additions should be regarded as within the scope of the claims.

1A and 1B are stress distribution and photographs generated when the upper and lower portions of the LTCC specimen are fixed and supported with a constant force and only the center portion of the specimen is contracted.

Figure 2 is a schematic laminated structure diagram of the non-shrinkage manufacturing method according to the present invention, the support layer is disposed on the upper and rear surfaces of the LTCC layer and the rod is disposed on the upper surface.

3a to 3d are electron micrographs showing the shrinkage change of the LTCC substrate according to the thickness of the alumina constraining layer during firing in the laminated structure of FIG. 3 except the rod in the LTCC non-shrinkage manufacturing process according to the present invention.

 4 is an electron micrograph showing that a part of the LTCC glass is impregnated with the alumina confining layer at the interface between the alumina confining layer and the LTCC substrate during firing with the lamination structure of FIG. 3.

Figure 5 is a high-temperature micrograph showing the shrinkage at each firing temperature during firing in the laminated structure of Figure 3 except the rod in the LTCC non-shrinkage manufacturing process according to the present invention.

6a to 6c is a graph of shrinkage change according to various load values of the rod during firing in the laminated structure of FIG. 3 arranged up to the rod 5 in the LTCC non-shrinkage manufacturing process according to the present invention.

<Code Description of Main Parts of Drawing>

1: laminate for LTCC non-shrink firing according to the invention, 2: LTCC substrate (or sheet), 3, 4: restraint layer, 5: rod

Claims (12)

In the firing method of low temperature co-fired ceramics (LTCC), A laminate comprising at least one of the LTCC layer and at least one of an upper and a rear surface of the LTCC layer, the at least one restraining layer disposed in surface contact with the LTCC layer and having a firing temperature higher than that of the LTCC; Placing and firing together one or more rods having a predetermined load, and then removing the restraining layer and the rods. The method of claim 1, The constrained layer is a firing method of LTCC is alumina, zirconia or a mixture thereof. The method of claim 2, The constraint layer is a baking method of LTCC, wherein the powder of the composition is molded into a sheet. The method of claim 1, The rod is a firing method of LTCC made of a stainless plate. The method of claim 1, And a setter is disposed between the laminate and the rod and at least one of the rear surface of the laminate so as to be in surface contact therewith to prevent mutual adhesion. The method of claim 1, The firing temperature is LTCC firing method of 830 ~ 900 ℃. The method of claim 6, The firing time is LTCC firing method of 20 to 40 minutes. The method of claim 1, The firing method of the LTCC the load is 100 ~ 800g / ㎠. The method of claim 1, And said thickness after said firing of said LTCC layer is at least 1 mm and less than 5 mm. The method of claim 1, The thickness of the constraint layer is a baking method of the LTCC is 30 ~ 500㎛. The method of claim 1, And the glass component in the LTCC layer is impregnated in the constraint layer forming an interface with the LTCC layer to a thickness greater than 0 µm and less than or equal to 30 µm. The method of claim 1, And the LTCC layer comprises at least one laminated LTCC sheet.

Images