LTCC substrate manufacturing method

Abstract

The invention discloses a method for manufacturing an LTCC (Low Temperature Co-Fired Ceramic) substrate, which belongs to the technical field of LTCC substrate manufacturing, and comprises the following steps: carrying out tape casting on prepared slurry to obtain a green tape, cutting off the green tape, opening holes in the cut green tape, carrying out silk-screen printing, and carrying out leveling operation after all hole filling layers are filled in the silk-screen printing, and performing lamination and isostatic pressing on the printed green ceramic tape to form a Bar block, cutting the Bar block into product units, performing degumming sintering on the product units, and performing nickel-tin-lead plating on the sintered product to form a final product. According to the method, leveling operation is carried out on the raw tape after hole filling, silver paste at the positions of the leveled raw tape holes is completely pressed in the holes, and normal printing is continued after leveling, so that connection of the upper layer and the lower layer in a manufactured product is complete, the reliability of the product is improved, virtual connection of through holes of the LTCC substrate can be avoided, the reliability of electric connection between the upper layer and the lower layer of the LTCC substrate is improved, and the service life of the LTCC substrate is prolonged. And the product failure risk is avoided.

Description

Technical Field

[0001] The invention relates to a method for manufacturing an LTCC substrate, belonging to the technical field of LTCC substrates. Background Art

[0002] LTCC substrates are high-performance multilayer ceramic circuit substrates made by simultaneously sintering ceramic materials and metal conductors at low temperatures (usually below 1000°C). They combine the excellent performance of ceramics with the ability to integrate multiple layers, and are widely used in high-frequency, high-reliability electronic devices.

[0003] The through holes of a certain LTCC substrate product were found by CT, such as Figure 1-2 As shown in the figure, there is a virtual connection between the upper and lower layers of the through-hole position of the product. This problem can also be visually discovered after grinding. The virtual connection of the through-hole will cause the risk of open circuit between the upper and lower layers, which will lead to poor reliability. When the product flows into the customer's end, it will cause the risk of product failure for the customer. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for manufacturing an LTCC substrate, which can avoid virtual connection of through holes in the LTCC substrate, improve the reliability of electrical connection between the upper and lower layers of the LTCC substrate, and avoid the risk of product failure.

[0005] The technical solution adopted by the present invention is: a method for manufacturing an LTCC substrate, the method comprising the following steps: S1. Batching: The powder is ball-milled into a particle size of 0.5-1 μm. The slurry required is prepared according to the different formulations, mixing speed and time of each product. This step is to quantitatively and evenly mix the various raw materials required for the subsequent processes to form a slurry system with certain flow characteristics, which can form a film with certain toughness after drying. S2, tape casting: the milled ingredients are prepared into a slurry, and a green porcelain tape with a thickness of 10-250 μm is obtained by tape casting technology. This step forms a film with a certain thickness on the surface of the PET film; S3, cutting: cutting the green porcelain tape into 6-inch green porcelain tapes of various thicknesses; this step cuts the green tape into 6-inch green tapes; S4, drilling: according to the prepared drilling pattern, use a laser drilling machine to drill holes on the raw porcelain strip where holes need to be drilled; this step drills holes with a standard hole diameter and a good appearance; S5. Printing: The printing method is screen printing. The design pattern is prepared on the film. After exposure, the inductor is transferred to the 200-500 mesh steel screen covered with photosensitive adhesive to form a printing jig. The G layer, through-hole layer and surface layer of the LTCC substrate use 200-500 mesh. By controlling the thickness of the photosensitive adhesive: 37μm~110μm; the printing GAP value: 1mm~2mm; the printing scraper pressure: 0.05MPa~0.10MPa; the scraper step speed 0.05m / s~0.10m / s; each layer of the design model is printed Printing is done on a green tape of corresponding thickness. The line width and G layer thickness of the LTCC substrate are within 2μm. The BOT layer and TOP layer thickness of the LTCC substrate are 10-30μm. After all the hole-filling layers are filled, a leveling operation is required. After the leveling operation, warm water pressing is performed and the tape is naturally cooled. The Mylar paper and the PET film on the non-green tape are removed in sequence to obtain the leveled green tape. Normal printing can then be carried out. This step causes the conductive paste to form a pattern with a specified design shape on the substrate (cast film), forming a circuit or a component of a circuit. S6. Lamination: Use a fully automatic alignment lamination machine to laminate the printed raw porcelain tapes according to the design sequence. The purpose of this step is to accurately align the printed crosses and stack the raw tapes together to form a BAR block. S7, Isostatic Pressing: The laminated membrane is subjected to final isostatic pressing. The maximum isostatic pressing temperature is (60-90)°C; the holding time is (200-1000)s; the holding pressure is (3000-8000)psi to form a bar block. Different materials and products can be adjusted according to actual conditions. This step uses hot isostatic pressing to bridge the defects of the blank after drying and ensure the integrity of the blank before cutting. S8, cutting: divide the Bar block and cut it according to the cutting line of the designed product. The cutting accuracy is ±0.1mm. This step separates the product from the BAR block to form individual products. S9, debinding and sintering: Surface electrode products are sintered in a debinding and sintering-in-one manner, while products without surface electrodes are sintered in a debinding-first-then-sintering manner. Semi-finished products are sintered according to their respective debinding and sintering curves. The function and purpose of debinding is to remove the binder and residual solvent in the green body to prevent the rapid vaporization of organic matter during the sintering process and the generation of internal defects. The function of this sintering step is to heat-treat the green body after debinding so that the powder materials in the green body react with each other to form a whole and achieve the required physical and chemical performance indicators. S10, chamfering: according to the product material and product size, select different chamfering parameters and chamfering grinding media to achieve a certain chamfering arc according to the standard; the role of this step is to make the edges and corners smooth, and no magnets will be exposed at the edges and corners after silver firing; S11. Silver Dipping and Silver Burning: Silver dipping is performed according to the designed silver dipping surface, and a certain silver dipping size is required. After silver dipping, silver burning is performed as required. The purpose of silver dipping is to apply conductive paste to both ends of the product, thereby connecting the internal coil of the product with the external circuit. The purpose and purpose of silver burning in this step is to sinter the end paste into a dense silver electrode. S12, electroplating: chemical plating or electroplating of the required metal on the sintered product to finally form the product. The purpose of electroplating: electroplating a layer of metal to ensure the welding and use needs of downstream manufacturers; Furthermore, the above-mentioned leveling operation steps are as follows: S5.1. Clean the stainless steel, aluminum plate, and Mylar paper with dust-free paper and alcohol. S5.2. Place the first piece of Mylar paper in the center of the stainless steel plate; S5.3. Overlap the green tape on the Mylar paper with the hole-filled side facing up. S5.4, the oily side of the PET film is placed on the raw tape; S5.5. Place the second Mylar paper on top of the PET film in the center. S5.6. Repeat S5.2-5.5, stacking the first Mylar paper → green tape → PET film → second Mylar paper in this order. No more than 20 green tapes should be placed on each stainless steel plate. S5.7. Place the stainless steel and aluminum plates into the bag and vacuumize the bag. The vacuuming time is 50 seconds, the heat sealing time is 2.5-3 seconds, and the heat sealing temperature is low. See the operation instruction diagram. Figure 5 , stacking diagram see Figure 6 .

[0006] Furthermore, the above-mentioned warm water pressure is carried out according to the warm water pressure curve of time, pressure and temperature in the following table.

[0007] Beneficial effects of the present invention: Compared with the prior art, the present invention adds a leveling process in the printing process. After all the hole-filling layers are filled, the filled green tape is leveled. The silver paste at the positions of the holes in the leveled green tape is completely pressed into the holes. After leveling, normal printing is continued. In this way, the upper and lower layers inside the product are well connected, which increases the reliability of the product, can avoid virtual connection of the through-holes of the LTCC substrate, improve the reliability of the electrical connection between the upper and lower layers of the LTCC substrate, and avoid the risk of product failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is the DPA image of the silver paste-filled through-hole of the existing LTCC substrate; Figure 2 This is a CT image of a silver paste-filled through-hole on an existing LTCC substrate. Figure 3 This is the DPA image of the silver paste-filled through-hole of the LTCC substrate after the leveling process is added; Figure 4 This is the CT image of the silver paste-filled through-hole of the LTCC substrate after the leveling process is added; Figure 5 It is a schematic diagram of the leveling process; Figure 6 It is a schematic diagram of the leveling structure. DETAILED DESCRIPTION

[0009] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0010] like Figure 1-2 As shown, there is a virtual connection between the upper and lower layers at the through-hole position of the product. This problem can also be intuitively discovered after grinding. The virtual connection of the through-hole will cause the risk of open circuit between the upper and lower layers, which will lead to poor reliability. Once the product flows into the customer's end, it will cause the risk of product failure for the customer's end. To address this technical problem, Example 1 of the present invention provides a method for manufacturing an LTCC substrate. By adding a leveling process to the printing process, the virtual connection of the through-hole of the LTCC substrate can be avoided, the reliability of the electrical connection between the upper and lower layers of the LTCC substrate can be improved, and the risk of product failure can be avoided.

[0011] Example 1: Figure 3-6 As shown, a method for manufacturing an LTCC substrate comprises the following steps: S1. Ingredients: Ball mill the powder into a particle size of 0.5-1μm. According to the different formula ingredients, stirring speed and time of each product, we can achieve the slurry we need.

[0012] S2, tape casting: the milled ingredients are prepared into a slurry and a green porcelain tape with a thickness of 10-250 μm is obtained by tape casting technology; S3, cutting: cutting the raw porcelain strip into 6-inch raw porcelain strips of various thicknesses; S4. Drilling: according to the prepared drilling pattern, use a laser drilling machine to drill holes on the raw porcelain strip where holes need to be drilled; S5. Printing: The printing method is screen printing. The design pattern is prepared on the film. After exposure, the inductor is transferred to a 200-500 mesh steel screen covered with photosensitive adhesive to form a printing jig. The G layer, through-hole layer and surface layer of the LTCC substrate use 200-500 mesh. By controlling the thickness of the photosensitive adhesive: 37μm ~ 110μm; printing GAP value: 1mm ~ 2mm; printing scraper pressure: 0.05MPa ~ 0.10MPa; scraper step speed 0.0 5m / s~0.10m / s; print each layer of the design model on the green tape of corresponding thickness. The line width and G layer thickness of the LTCC substrate are within 2μm, and the thickness of the BOT layer and TOP layer of the LTCC substrate are 10-30μm. After all the hole-filling layers are filled, they need to be leveled. After the leveling operation, warm water pressing is carried out and natural cooling is carried out. The Mylar paper and the PET film on the non-green tape are removed in turn to obtain the leveled green tape, and then normal printing can be carried out; Specifically, the leveling steps are as follows: S5.1. Clean the stainless steel, aluminum plate, and Mylar paper with dust-free paper and alcohol. S5.2. Place the first piece of Mylar paper in the center of the stainless steel plate; S5.3. Overlap the green tape on the Mylar paper with the hole-filled side facing up. S5.4, the oily side of the PET film is placed on the raw tape; S5.5. Place the second Mylar paper on top of the PET film in the center. S5.6. Repeat S5.2-5.5, stacking the first Mylar paper → green tape → PET film → second Mylar paper in this order. No more than 20 green tapes should be placed on each stainless steel plate. S5.7. Place the stainless steel and aluminum plates into the bag and vacuumize the bag. The vacuuming time is 50 seconds, the heat sealing time is 2.5-3 seconds, and the heat sealing temperature is low. See the operation instruction diagram. Figure 5 , stacking diagram see Figure 6 .

[0013] The leveling device for obtaining LTCC substrate printing by leveling operation includes a stainless steel aluminum plate 1, a first Mylar paper 2, a raw tape 3, a PET film 4, and a second Mylar paper 5. Multiple groups of the first Mylar paper 2, the raw tape 3, the PET film 4, and the second Mylar paper 5 are stacked on the stainless steel aluminum plate 1 from bottom to top. A vacuum bag is wrapped around the stainless steel aluminum plate 1 and multiple groups of the first Mylar paper 2, the raw tape 3, the PET film 4, and the second Mylar paper 5. A vacuum plastic bag 6 wraps the stainless steel aluminum plate 1 and all the first Mylar paper 2, the raw tape 3, the PET film 4, and the second Mylar paper 5 stacked thereon and ensures that the vacuum inside the vacuum plastic bag 6 is vacuum. A vacuum packaging machine is used to seal and vacuum the vacuum plastic bag 6. A warm water press is used to perform warm water pressing operation on the vacuumed vacuum plastic bag 6. The number of stacked groups of the first Mylar paper 2, the raw tape 3, the PET film 4, and the second Mylar paper 5 is not more than 20.

[0014] The function of Mylar paper is: because Mylar paper is relatively hard and has a smooth surface, it has the function of flattening and supporting. The function of PET film is to protect the raw tape from being damaged. Stainless steel and aluminum plates have a relatively smooth surface and high hardness, and play a supporting role.

[0015] The leveling structure performs a leveling operation on all the hole-filling layers of the green tape in the printing process after filling the holes. After leveling, the silver paste at the positions of the holes in the green tape is completely pressed into the holes. The LTCC substrate produced by printing after leveling has the upper and lower layers of the LTCC substrate product connected intact at the filled holes, which increases the reliability of the product, can avoid virtual connection of the through-holes of the LTCC substrate, improve the reliability of the electrical connection between the upper and lower layers of the LTCC substrate, and avoid the risk of product failure.

[0016] The warm water pressure is carried out according to the warm water pressure curve of time, pressure and temperature in the following table.

[0017] S6. Lamination: The printed green ceramic strips are laminated according to the design sequence using a fully automatic alignment lamination machine. S7. Isostatic Pressing: The laminated membranes are subjected to final isostatic pressing. The maximum isostatic pressing temperature is (60-90)°C; the holding time is (200-1000) seconds; the holding pressure is (3000-8000) psi to form bar blocks. Different materials and products can be adjusted according to actual conditions. S8, cutting: divide the Bar block and cut it according to the cutting line of the designed product. The cutting accuracy is ±0.1mm; S9, debinding and sintering: Products with surface electrodes are sintered in an integrated debinding and sintering process, while products without surface electrodes are sintered in a debinding and then sintering process. Semi-finished products are sintered according to their respective debinding and sintering curves. S10, Chamfering: According to the product material and product size, different chamfering parameters and chamfering grinding media are selected to achieve a certain chamfering arc according to the standard; S11, silver dipping and silver burning: silver dipping is carried out according to the designed silver dipping surface, and a certain silver dipping size is required. After silver dipping, silver burning is carried out as required; S12. Electroplating: The sintered product is subjected to chemical plating or electroplating of the required metal to finally form the product.

[0018] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or replacements within the technical scope disclosed by the present invention, which should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for manufacturing an LTCC substrate, characterized in that: The method comprises the following steps: S1. Ingredients: ball mill the powder into 0.5-1μm particle size. According to the different formula ingredients, stirring speed and time of each product, we can achieve the slurry we need. S2, tape casting: the milled ingredients are prepared into a slurry and a green porcelain tape with a thickness of 10-250 μm is obtained by tape casting technology; S3, cutting: cutting the raw porcelain strip into 6-inch raw porcelain strips of various thicknesses; S4. Drilling: according to the prepared drilling pattern, use a laser drilling machine to drill holes on the raw porcelain strip where holes need to be drilled; S5. Printing: The printing method is screen printing. The design pattern is prepared on the film. After exposure, the inductor is transferred to a 200-500 mesh steel screen covered with photosensitive adhesive to form a printing jig. The G layer, through-hole layer and surface layer of the LTCC substrate use 200-500 mesh. By controlling the thickness of the photosensitive adhesive: 37μm~110μm; the printing GAP value: 1mm~2mm; the printing scraper pressure: 0.05MPa~0.10MPa; the scraper step speed 0.0 5m / s~0.10m / s; each layer of the design model is printed on a green tape of corresponding thickness. The line width and G layer thickness of the LTCC substrate are printed within 2μm, and the thickness of the BOT layer and TOP layer of the LTCC substrate are 10-30μm. After all the hole-filling layers are filled, they need to be leveled. After the leveling operation, warm water pressing is carried out and natural cooling is carried out. The Mylar paper and the PET film on the non-green tape are removed in turn to obtain the leveled green tape, and then normal printing can be carried out; S6. Lamination: Use a fully automatic alignment lamination machine to laminate the printed raw ceramic tapes according to the design sequence; S7, Isostatic Pressing: Final pressing is performed on the laminated diaphragm by isostatic pressing. The maximum isostatic pressing temperature is 60~90℃; the holding time is 200~1000s; the holding pressure is 3000~8000psi to form a bar block. Different materials and different products can be adjusted according to actual conditions. S8, cutting: divide the Bar block and cut it according to the cutting line of the designed product. The cutting accuracy is ±0.1mm; S9, debinding and sintering: Products with surface electrodes are sintered in an integrated debinding and sintering process, while products without surface electrodes are sintered in a debinding and then sintering process. Semi-finished products are sintered according to their respective debinding and sintering curves. S10, Chamfering: According to the product material and product size, different chamfering parameters and chamfering grinding media are selected to achieve a certain chamfering arc according to the standard; S11, silver dipping and silver burning: silver dipping is carried out according to the designed silver dipping surface, and a certain silver dipping size is required. After silver dipping, silver burning is carried out as required; S12. Electroplating: The sintered product is subjected to chemical plating or electroplating of the required metal to finally form the product.

2. The method for manufacturing an LTCC substrate according to claim 1, wherein: The leveling steps are as follows: S5.

1. Clean the stainless steel, aluminum plate, and Mylar paper with dust-free paper and alcohol. S5.

2. Place the first piece of Mylar paper in the center of the stainless steel plate; S5.

3. Overlap the green tape on the Mylar paper with the hole-filled side facing up. S5.4, the oily side of the PET film is placed on the raw tape; S5.

5. Place the second Mylar paper on top of the PET film in the center. S5.

6. Repeat S5.2-5.5, stacking the first Mylar paper → green tape → PET film → second Mylar paper in this order. No more than 20 green tapes should be placed on each stainless steel plate. S5.

7. Place the stainless steel and aluminum plates together in a bag and evacuate the bag. The evacuation time is 50 seconds, the heat sealing time is 2.5-3 seconds, and the heat sealing temperature is low.

3. The method for manufacturing an LTCC substrate according to claim 1, wherein: The warm water pressure is carried out according to the warm water pressure curve of time, pressure and temperature in the following table. 。

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