KR101292040B1 - Manufacturing method of low teperature co-fired ceramics substrate - Google Patents

Abstract

In the present invention, the step of manufacturing a plurality of low-temperature co-fired ceramic (LTCC) sheet having a sintering temperature of 900 ℃ or less, the step of manufacturing at least one support layer sheet having a sintering temperature of 1150 ℃ or more, and on each side of the plurality of LTCC sheet Forming an electric circuit pattern, stacking the plurality of LTCC sheets on which the electric circuit pattern is formed, to form a subassembly, and attaching the at least one support layer sheet to at least one of an upper surface and a lower surface of the subassembly; A method of making an LTCC substrate is provided that includes forming an assembly, sintering the assembly at a temperature of 900 ° C. or less, and removing the one or more support layer sheets attached thereto from the sintered assembly. .

Description

Method for manufacturing low temperature simultaneous firing ceramic substrate {MANUFACTURING METHOD OF LOW TEPERATURE CO-FIRED CERAMICS SUBSTRATE}

The present invention relates to a method for manufacturing a low temperature co-fired ceramics (LTCC) substrate, and more particularly, to a method for manufacturing a low temperature co-fired ceramic substrate having excellent flatness and flexibility.

In recent years, as the electronic devices including mobile communication devices and the like become thin and short, packages having internal electronic circuits such as semiconductor chips are required to be thinner in thickness.

In particular, in the case of a thin semiconductor package, in addition to the strength and flatness, it is necessary to secure the characteristics of easy circuit mounting. Conventional package substrates include organic based packages using PCB substrate materials, ceramics consisting of high temperature co-fired ceramics (HTCC) and low temperature co-fired ceramics (LTCC). There is a package of substrates. However, in the implementation of the thin package, the package using the organic-based PCB material is not available due to the limitation of strength, and also has a problem of low thermal conductivity. On the other hand, low temperature co-fired ceramics capable of firing circuits and ceramic substrates together at low temperatures using Ag electrodes due to high frequency semiconductors have high strength and high thermal conductivity of about 3 W / mK while reducing the resistance of the circuit at high frequencies. It will be called the most promising material.

Such low temperature co-firing technology, for example, as disclosed in U.S. Patent No. 4,654,095 (announced on March 31, 1987), is prepared in a powder state using a ceramic composition calcinable at low temperature, and then mixed with a polymer binder in a solvent to form a thick film. To tape. Then, the thick film material is printed on the surface of each layer for lamination, and is laminated and cut into a number of layers designed through via punching and filling processes for electrical connection between the layers. After the fabrication, the ceramic module is manufactured to satisfy the sufficient strength and electrical properties through heat treatment processes of calcination and sintering.

However, in order to cope with the miniaturization and integration of electronic components, such low temperature co-fired ceramic substrates tend to increase the number of stacked layers and the number of interlayer via holes, but they exhibit a line shrinkage of about 10% or more during the necessary plastic shrinkage of the ceramic process. Therefore, as the thickness of the substrate becomes thinner, when simultaneously firing in a state where various circuits are formed, it is not easy to maintain the flatness of the substrate due to the line shrinkage, so that defects such as disconnection of a complicated internal circuit occur frequently. Moreover, according to the recent trend, as the substrate for a package becomes larger, it becomes more difficult to maintain flatness.

Therefore, fabrication of a substrate that can be manufactured in a large size and maintain flatness is a key technology that can lead to thinner packages and lower costs in the long term.

Accordingly, the present invention is to provide a method for producing a low temperature co-fired ceramic substrate having excellent flatness and flexibility and can be used as a substrate of a large size.

The method for manufacturing a low temperature co-fired ceramic (LTCC) substrate according to the present invention for achieving the above object may include the following steps:

Preparing a plurality of LTCC sheets having a sintering temperature of 900 ° C. or less;

Preparing at least one support layer sheet having a sintering temperature of at least 1150 ° C .;

Forming an electrical circuit pattern on each side of the plurality of LTCC sheets;

Stacking the plurality of LTCC sheets on which electric circuit patterns are formed to form a subassembly;

Attaching the at least one support layer sheet to at least one of an upper surface and a lower surface of the subassembly to form an assembly;

Sintering the assembly at a temperature of 900 ° C. or less; And

Removing the at least one support layer sheet attached from the sintered assembly.

In this case, the support layer sheet may be made of one or more of high temperature co-fired ceramics (HTCC), Al ₂ O ₃ , ZrO ₂ , SiO ₂ and mullite (Mulite).

The removing of the at least one support layer sheet may be at least one of ultrasonic cleaning, brushing, sand blasting, and bead blasting.

In addition, the step of sintering the assembly at a temperature of 900 ° C or less may include a step of applying a pressure to the assembly, the process of applying the pressure is a cold isostatic press (CIP: Cold Isostatic Press) or a warm water press (HIP: Hot Isostatic Press) or may be performed by placing an object having an arbitrary weight on the upper surface of the assembly.

In addition, removing the at least one support layer sheet may include grinding one or more of the top and bottom surfaces of the subassembly after removing the support layer sheet.

In the forming of the assembly, when the thickness of the subassembly is 300 μm or less, the at least one support layer sheet may be attached to only one of the upper and lower surfaces of the subassembly, and the thickness of the subassembly may exceed 300 μm. In one case, the at least one support layer sheet may be attached to both the top and bottom surfaces of the subassembly. In this case, when the one or more support layer sheets are attached to only one of the top and bottom surfaces of the subassembly, the thickness of the one or more support layer sheets is not less than 0.5 times of the thickness of the subassembly, and on both the top and bottom surfaces of the subassembly. In the case of attaching the at least one support layer sheet, the thickness of the at least one support layer sheet may be at least 0.2 times the thickness of the subassembly.

The LTCC board | substrate which becomes the assembly manufactured as mentioned above has a flatness of 50 micrometers or less.

Low temperature co-fired ceramic (LTCC) substrates produced by the present invention are particularly promising as substrates of large size because they have an excellent flatness of 50 μm or less and also have good flexibility.

1a to 1b are preferred embodiments of the present invention,
1A is a cross-sectional support structure diagram for attaching a support layer to one surface of an LTCC substrate;
1B is a double-sided support structure for attaching a support layer to both sides of an LTCC substrate, respectively.
2 is a flowchart illustrating a manufacturing process diagram of an LTCC substrate according to the present invention.
3a to 3c are electron micrographs of the surface of the LTCC substrate with the support layer removed after firing according to the present invention,
3A and 3B are electron micrographs of the glass impregnated layer cross section and surface, respectively;
3C is an electron micrograph of the surface of an LTCC substrate without supporting layer bonded thereto.
Figure 4 is a photograph of the state bent by pressing the both ends of the final LTCC substrate produced by the manufacturing method according to the present invention.

First, the term "LTCC substrate" refers to a Low Temperature Co-fired Ceramics (LTCC) substrate. In addition, the "low temperature simultaneous firing ceramics" refers to all ceramics known in the art having a sintering temperature range of 900 ° C. or less.

As described above, in order to increase the flatness of a large-area LTCC substrate according to the thinning of the substrate, it is necessary to minimize the frictional force between the substrate and the bottom surface and the shrinkage difference between the circuit and the ceramic included in the substrate during firing. It is important. However, it is fundamentally difficult to reduce these frictional force and shrinkage difference, so it is very difficult to maintain flatness in the manufacture of large area substrates of thin layers.

In this regard, the present inventors, when the support layer having a higher sintering temperature than the LTCC substrate is attached to both sides or one side of the LTCC substrate and fired, the support layer is not fired when firing at 900 ° C. or less, which is the sintering temperature range of the LTCC substrate. Since no shrinkage occurred, it was found that the frictional force and shrinkage of the LTCC substrate were suppressed, thereby improving the flatness of the substrate. In particular, when the present inventors fire a thin LTCC substrate having a thickness of 200 μm or less, the x and y axis shrinkage ratios are 0.2 to 1% or less, and a good flatness of 50 μm or less is achieved by only attaching the support layer to only one surface of the LTCC substrate. Was found to be maintained.

Preferred embodiments of this invention are shown in FIGS. 1A-1B, respectively. That is, in FIG. 1A, the cross-sectional support structure for attaching the support layer 2 to one surface of the LTCC substrate 1 is shown, and in FIG. 1B, the double-side support for attaching the support layers 2 'and 2 "to both surfaces of the LTCC substrate 1 is shown. In the cross-sectional support, the thickness of the support layer 2 is 0.5 times or more the thickness of the LTCC substrate 1, and in the case of the double-side support, the thickness of the support layers 2 'and 2 "is the LTCC substrate ( 1) It should be more than 0.2 times the thickness. In addition, as described above, the object of the present invention can be sufficiently achieved by the cross-sectional support, but as an example, when the thickness of the LTCC substrate 1 is 300 μm or less, the cross-sectional support is performed, and when the thickness exceeds 300 μm, the double-sided support is performed. Can be.

According to the present invention, such a support layer is selected as a composition having a sintering temperature higher than the sintering temperature of the LTCC substrate, and particularly preferably a composition having a sintering temperature of at least 1150 ° C.

In addition, as described above, since the support layer is not baked, it is removed after the LTCC cofiring is completed. Such a removal method may be any method known in the art including ultrasonic cleaning, brushing, sand blasting, bead blasting, and the like.

On the other hand, the reaction between the support layer and the LTCC substrate should be suppressed so that no new phase due to the reaction should be produced. However, during firing, glass, which is a liquid, exists in the LTCC substrate, whereas the support layer is not fired and thus remains in a powder state, so that a part of the glass may be absorbed between the powders in the support layer.

Electron micrographs of this phenomenon are shown in Figs. 3A to 3C. 3A to 3C are photographs of the LTCC substrate from which the support layer is removed after firing according to the present invention, and FIGS. 3A and 3B show the glass impregnated layer cross section and the surface, respectively, and FIG. 3C shows the surface of the LTCC substrate to which the support layer is not bonded. .

Referring to FIGS. 3A and 3B, it can be seen that a part of the glass is impregnated into the support layer during firing to form a layer (“A”) in which the glass is absorbed in the support layer. Therefore, the smaller the impregnated depth of the glass can function as a good support layer. That is, according to the present invention, the support layer may be made of a material having low wetting of the glass without chemical reaction with the glass. For example, the sintering temperature is 900 ° C, in particular, 1150 ° C or higher HTCC Ceramics), Al ₂ O ₃ , ZrO ₂ , SiO ₂ , Mullite (Mulite), and the like, and among these may be selected as the composition with the lowest invasiveness experimentally according to the selected LTCC composition.

2 is a flowchart illustrating a manufacturing process diagram of an LTCC substrate according to the present invention.

2, first, the LTCC substrate sheet and the support layer sheet are manufactured, respectively (S201 and S211). Such sheets may be manufactured by a conventional tape casting method such as a doctor blade, and the present invention is not limited thereto.

Then, a circuit pattern is printed on the surface of the LTCC substrate sheet (S202), and vias and electrodes for electrical conduction between the circuit patterns on each substrate layer to be stacked later are formed (S203). Such electrode formation may be by conventional methods including sputtering, screen printing, etc., and the formation of vias may be by conventional methods including drilling, punching, laser, and the like. In addition, after the via is formed, a deburring, a desmear process, or the like may be performed to remove various contaminants and foreign matters generated during the processing.

Then, the plurality of LTCC substrate sheets thus formed are aligned and stacked to complete a sub assembly (S204), and the supporting layer sheets are aligned and stacked on one surface of the sub assembly (cross-sectional support method of FIG. 1A) or the The assembly is completed by aligning and attaching the supporting layer sheets to both surfaces of the subassembly (double-sided supporting method of FIG. 1B), respectively (S205).

Then, the assembly is sintered (ie co-sintered) at a low temperature of 900 ° C. or less (S206). In this case, the firing may be performed by any firing method known in the art. Particularly, in order to further improve the flatness of the substrate, the assembly may be pressurized and calcined, and for this, a cold isostatic press (CIP) or a hot isostatic press (HIP) may be performed. Alternatively, firing may be performed by further placing a substrate having an arbitrary weight on the assembly.

Then, the unsintered support layer sheet may be removed (S207), and in addition, the surface of the sintered LTCC substrate may optionally be polished by a conventional method (S208).

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in 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

A slurry was prepared by dispersing in a toluene-ethanol solvent using an LTCC raw material having CaO-Al ₂ O ₃ -SiO ₂ as a main composition, and mixing PVB binder and DBP plasticizer. The slurry was molded to a thickness of about 120㎛ using a tape casting equipment to prepare a LTCC sheet.

As the support layer, a support layer sheet having a thickness of 100 μm was prepared using the alumina raw material having a particle size of about 1 μm in the same manner as in the method of manufacturing the LTCC sheet.

Subsequently, a circuit pattern was printed by screen printing using Ag paste on the LTCC sheet, and via holes were formed by punching to manufacture and stack 10 LTCC sheets, thereby forming a subassembly. Five sheets (500 μm thick) were attached and pressed together to form an assembly. The assembly was sufficiently baked out at 600 ° C. to remove organics and then sintered at 900 ° C. for 30 minutes.

And, the sintered assembly was removed for 10 minutes by using an ultrasonic cleaner to remove the support layer, the thickness of the final produced LTCC substrate was 80㎛, the flatness was 50㎛ or less based on a 10 × 10 mm2 substrate .

4 is a photograph of a state in which both ends of the final LTCC substrate is pressurized by hand and shows excellent flexibility.

In the above-described embodiments and examples of the present invention, the powder characteristics such as the average particle size, distribution and specific surface area of the composition powder, and the purity of the raw material, the amount of the impurity added, and the heat treatment conditions, It is quite natural for a person of ordinary skill in the field to have such a possibility.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. , Changes, additions, and the like are to be regarded as falling within the scope of the claims.

1: LTCC substrate 2 ', 2 ": support layer

Claims (11)

In the method of manufacturing a low temperature simultaneous firing ceramic (LTCC) substrate,
Preparing a plurality of LTCC sheets having a sintering temperature of 900 ° C. or less;
Preparing at least one support layer sheet having a sintering temperature of at least 1150 ° C .;
Forming an electrical circuit pattern on each side of the plurality of LTCC sheets;
Stacking the plurality of LTCC sheets on which the electric circuit patterns are formed to form a subassembly;
The at least one support layer sheet is attached to at least one of the top and bottom surfaces of the subassembly to form an assembly. When the thickness of the subassembly is 300 μm or less, the at least one support layer sheet is formed on only one of the top and bottom surfaces of the subassembly. Attaching the at least one support layer sheet to both the top and bottom surfaces of the subassembly when the thickness of the subassembly exceeds 300 µm;
Sintering the assembly at a temperature of 900 ° C. or less;
Removing the at least one support layer sheet attached thereto from the sintered assembly. The method of claim 1,
The support layer sheet is a method of manufacturing an LTCC substrate, characterized in that the composition of at least one of High Temperature Co-fired Ceramics (HTCC), Al ₂ O ₃ , ZrO ₂ , SiO ₂ and Mullite (Mulite). The method of claim 1,
Removing the at least one support layer sheet comprises at least one of ultrasonic cleaning, brushing, sandblasting and bead blasting. The method of claim 1,
The step of sintering the assembly at a temperature of 900 ° C or less comprises the step of applying a pressure to the assembly. 5. The method of claim 4,
The process of applying pressure to the assembly may be performed by a cold isostatic press (CIP) or a hot isostatic press (HIP) or by placing an object having an arbitrary weight on an upper surface of the assembly. Method for producing an LTCC substrate. The method of claim 1,
Removing the at least one support layer sheet comprises removing at least one of the support layer sheet and polishing at least one of the top and bottom surfaces of the subassembly. delete delete The method of claim 1,
When the one or more support layer sheets are attached to only one of the top and bottom surfaces of the subassembly, the thickness of the at least one support layer sheet is 0.5 times or more of the thickness of the subassembly. The method of claim 1,
When the one or more support layer sheets are attached to both the top and bottom surfaces of the subassembly, the thickness of the at least one support layer sheet is 0.2 times or more of the thickness of the subassembly. The method of claim 1,
And the sintered assembly has a flatness of 50 μm or less.

Images