Multilayer ceramic substrate and preparation method thereof

Abstract

The invention discloses a multilayer ceramic substrate and a preparation method thereof. The method comprises the following steps: step 1, forming a through hole in a green ceramic chip by adopting a laser trepanning mode; step 2, filling the through holes in the green ceramic chip in a spraying manner; 3, laminating the plurality of raw ceramic chips, and then pressing the plurality of raw ceramic chips into a whole raw ceramic in an isostatic pressing manner; and 4, cutting the whole raw ceramic to obtain a plurality of raw ceramic crusts, and sintering and molding the raw ceramic crusts. By adopting the scheme to prepare the multilayer ceramic substrate, the product yield can be improved, and the production cost can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of probe cards, in particular to a multilayer ceramic substrate and a preparation method thereof. Background Art

[0002] Wafer-level testing IC testing is very necessary in semiconductor production. By screening and discarding defective components at an early stage, unnecessary packaging costs can be avoided. At the same time, wafer test data also provides early feedback on the overall manufacturing process status so that deviations can be detected early and corrective measures can be taken.

[0003] The probe card is the interface between the tester and the wafer chip, and is a semiconductor core testing consumable. According to the type of probe, the probe card can be divided into vertical probe cards, cantilever probe cards, MEMS probe cards, etc., among which MEMS probe cards are widely used in the testing of memory chips. In the probe card manufacturing process, the MEMS cantilever probe needs to be welded on the space converter (one of the common space converters is a multi-layer ceramic substrate) to achieve the electrical connection between the chip on the wafer → probe card → tester. Therefore, the quality of the substrate manufacturing directly determines whether the probe card can work properly.

[0004] The existing preparation methods of multilayer ceramic substrates are mostly as follows: mechanical / laser drilling of raw ceramic sheets → filling holes with metal slurry using a scraper → isostatic pressing after lamination of raw ceramic sheets → cutting into the desired shape → sintering. This method has the following defects: the traditional hole filling process is to place a mask on top of the punched raw ceramic sheet, with the mask pattern corresponding one-to-one to the punching position on the raw ceramic sheet. Then, metal slurry (Ag / Au, etc.) is applied on top of the mask, and a scraper is used to apply a certain pressure on the mask to squeeze the slurry into the corresponding holes to complete the hole filling. This process is complex and requires a perfect match between the slurry viscosity and the scraper pressure to obtain good hole filling quality. Different hole filling patterns require a corresponding mask, which increases the process cost. Defects such as missing filling, bleeding, and incomplete filling are difficult to avoid, resulting in a decrease in yield. Summary of the Invention

[0005] In order to overcome the defects in the prior art, an embodiment of the present invention provides a multilayer ceramic substrate and a preparation method thereof, which are used to solve the above problems.

[0006] The present invention discloses a method for preparing a multilayer ceramic substrate, comprising the following steps:

[0007] Step 1: Use laser drilling to open a through hole on the green ceramic sheet;

[0008] Step 2: Filling the through holes on the green ceramic sheet by spraying;

[0009] Step 3: stacking the plurality of green porcelain sheets, and then pressing the plurality of green porcelain sheets into a green porcelain whole by isostatic pressing;

[0010] Step 4: cutting the green porcelain as a whole to obtain a plurality of green porcelain blocks, and sintering the green porcelain blocks into shape.

[0011] Specifically, in step 1, before drilling the green ceramic sheet, the method further includes: providing a protective film on the surface of the green ceramic sheet, wherein the protective film is located on a side of the green ceramic sheet away from the laser generator.

[0012] Specifically, the protective film is made of PET, and the thickness of the protective film is between 60 and 80 μm.

[0013] Specifically, in step 1, the through hole is a tapered through hole, and the through hole gradually decreases in a direction away from the laser generator.

[0014] Specifically, the ratio of the lower aperture to the upper aperture of the through hole is between 0.7 and 0.8.

[0015] Specifically, in step 2, a nozzle is used to spray the through holes on the green ceramic sheet. The diameter of the nozzle is 50-100 μm smaller than the aperture of the through holes, and the distance between the nozzle and the surface of the green ceramic sheet is between 280-320 μm.

[0016] Specifically, in step 2, before spraying the through holes of the green porcelain sheet, breathable paper is first laid on a vacuum adsorption platform, and then the green porcelain sheet to be filled is placed on the breathable paper. The side of the green porcelain sheet with the protective film is in contact with the vacuum adsorption platform. After the green porcelain sheet is adsorbed by the vacuum adsorption platform, the through holes on the green porcelain sheet are filled.

[0017] Specifically, step 3 includes the following steps:

[0018] Step 3-1: providing a backing plate, placing a first PET film on the backing plate, sequentially placing the plurality of green ceramic sheets to be laminated on the first PET film, and peeling off the protective film of each green ceramic sheet before lamination;

[0019] Step 3-2: placing a second PET film on the top green ceramic sheet, and then placing a pressing plate on the second PET film;

[0020] Step 3-3: Wrap the semi-finished product obtained in step 3-2 with a silicone pad;

[0021] Step 3-4: vacuum-sealing the semi-finished product obtained in step 3-3 with a plastic bag, and then isostatically pressing the plurality of green porcelain pieces into a green porcelain whole.

[0022] Specifically, in step 4, when the green porcelain is cut, the green porcelain is placed on a heating table and heated at a temperature of 80-90°C.

[0023] The embodiments of the present application also disclose: a multilayer ceramic substrate, which is prepared using the method described in the embodiments of the present application.

[0024] The present invention has at least the following beneficial effects:

[0025] 1. Compared with the traditional "mask + scraper" hole filling method, the above-mentioned solution in this embodiment can save 30-50% of metal slurry through the point-to-point spray filling method. At the same time, point-to-point spraying can ensure the consistency of the slurry in the hole, avoiding the occurrence of defects such as bleeding and incomplete filling of the hole mouth. In addition, the spray filling method does not require a mask and can be applied to various punching patterns, with strong applicability.

[0026] 2. The protective film can absorb the excess heat of laser processing during the laser opening process of the green ceramic piece, avoiding secondary damage to the green ceramic piece caused by excess heat and reducing the probability of vitrified molten beads appearing on the inner wall of the hole.

[0027] 3. Setting the through hole into a structure with a larger top and a smaller bottom can increase the contact area between the metal slurry and the green porcelain, so that the hole wall can better support the metal slurry, reduce the probability of leakage caused by the falling of the metal slurry, and improve the product yield.

[0028] 4. The vacuum adsorption platform can improve the fluidity of the metal slurry in the hole during the hole filling process and ensure the flatness of the metal slurry during the hole filling process.

[0029] 5. The pad and the pressing plate can effectively limit the irregular deformation of the green porcelain as a whole, making its deformation more uniform and improving the position accuracy of the metal holes of the substrate after sintering.

[0030] In order to make the above and other objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 This is a schematic diagram of the structure of a protective film provided on the bottom surface of a raw ceramic tile according to an embodiment of the present invention;

[0033] Figure 2This is a schematic structural diagram of a through hole formed on a raw ceramic sheet according to an embodiment of the present invention;

[0034] Figure 3 Schematic diagram of the structure of the nozzle spraying and filling holes on the green ceramic sheet in an embodiment of the present invention;

[0035] Figure 4 is a schematic diagram of a stack of multiple green ceramic sheets according to an embodiment of the present invention;

[0036] Figure 5 Schematic diagram of the green porcelain being entirely sealed in a plastic bag in an embodiment of the present invention.

[0037] The figure marks of the above drawings are: 1. raw porcelain sheet; 11. through hole; 2. protective film; 3. nozzle; 4. metal slurry; 5. vacuum adsorption platform; 6. breathable paper; 71. pad; 72. pressing plate; 81. first PET film; 82. second PET film; 91. silicone pad; 92. plastic bag. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," "fixed," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0040] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first feature and the second feature being in direct contact, or may include the first feature and the second feature being in contact not directly but through another feature therebetween. Furthermore, a first feature being "above," "below," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0041] In the description of this embodiment, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of this application.

[0042] In addition, the terms "first", "second", etc. are only used to distinguish in description and have no special meaning.

[0043] The method for preparing the multilayer ceramic substrate of this embodiment includes the following steps:

[0044] Step 1: A through hole 11 is formed on the green ceramic sheet 1 by laser drilling.

[0045] Step 2: Fill the through holes 11 on the green ceramic sheet 1 by spraying.

[0046] Step 3: stacking the multiple green porcelain sheets 1, and then pressing the multiple green porcelain sheets 1 into a green porcelain whole by isostatic pressing.

[0047] Step 4: Cut the green porcelain as a whole to obtain multiple green porcelain blocks, sinter the green porcelain blocks to obtain a multi-layer ceramic substrate.

[0048] Compared with the traditional "mask + scraper" hole filling method, the above-mentioned solution in this embodiment can save 30% to 50% of metal slurry through the point-to-point spraying hole filling method; at the same time, the point-to-point spraying can ensure the consistency of the slurry in the hole, avoiding the occurrence of defects such as bleeding and incomplete filling of the hole mouth; in addition, the spray filling method does not require a mask and can be applied to various punching patterns, with strong applicability.

[0049] Specifically, CO2 laser drilling can be used to drill holes in the green ceramic sheet 1. Figure 1 As shown, in step 1, before drilling a hole in the green ceramic sheet 1, a protective film 2 can be placed on the surface of the green ceramic sheet 1. The protective film 2 is located on the side of the green ceramic sheet 1 facing away from the laser generator. In other words, a protective film 2 is attached to the lower surface of the green ceramic sheet 1. The lower surface refers to the side of the green ceramic sheet 1 that contacts the workbench when drilling a hole. More specifically, the protective film 2 can be made of PET (polyethylene terephthalate) with a thickness between 60 and 80 μm. Using the above solution, the protective film 2 can absorb excess heat from the laser processing during the laser drilling of the green ceramic sheet 1, thereby preventing secondary damage to the green ceramic sheet 1 caused by the excess heat and reducing the probability of the formation of vitrified molten beads on the inner wall of the hole.

[0050] Specifically, combined Figure 2 and Figure 3 As shown, in step 1, the through hole 11 laser-processed on the raw porcelain sheet 1 is a tapered through hole 11, which gradually decreases in size in the direction away from the laser generator. The side of the raw porcelain sheet 1 facing the laser generator is defined as the upper surface, and the side of the raw porcelain sheet 1 facing the workbench is defined as the lower surface. Then, the end of the through hole 11 corresponding to the upper surface of the raw porcelain sheet 1 is defined as the upper hole, and the end of the through hole 11 corresponding to the lower surface of the raw porcelain sheet 1 is defined as the lower hole. In this embodiment, the ratio of the lower hole diameter to the upper hole diameter of the through hole 11 is between 0.7 and 0.8, that is, the upper hole diameter is larger than the lower hole diameter. Using the above solution, the through hole 11 is set to a structure with a larger upper portion and a smaller lower portion, which can increase the contact area between the metal slurry 4 and the raw porcelain, allowing the hole wall to better support the metal slurry 4, reducing the probability of leaks caused by the shedding of the metal slurry 4, and improving the product yield.

[0051] like Figure 3 As shown, in step 2 of this embodiment, a spray gun can be used to spray the through hole 11 on the green porcelain sheet 1. Preferably, the diameter of the nozzle 3 of the spray gun is 50 to 100 μm smaller than the aperture of the through hole 11 (in this embodiment, the upper aperture of the through hole 11). For example, when the upper aperture of the through hole 11 is 150 to 200 μm, a nozzle 3 of 100 to 150 μm can be selected. When the upper aperture of the through hole 11 is 200 to 250 μm, a nozzle 3 of 150 to 200 μm can be selected. In this way, the spraying efficiency can be improved and the spraying quality can be ensured. During the spraying process, the distance between the nozzle 3 and the upper surface of the green porcelain sheet 1 is between 280 and 320 μm, preferably 300 μm.

[0052] like Figure 3 As shown, in step 2, before spraying the through-holes 11 of the green ceramic sheet 1, breathable paper 6 can be laid on the vacuum adsorption platform 5, and then the green ceramic sheet 1 to be filled is placed on the breathable paper 6. At this time, the side of the green ceramic sheet 1 with the protective film 2 is in contact with the vacuum adsorption platform 5, and then the green ceramic sheet 1 is adsorbed by the vacuum adsorption platform 5 before the through-holes 11 on the green ceramic sheet 1 are filled. Specifically, the vacuum adsorption platform 5 can be a platform with multiple air paths, one end of the air path passes through the upper surface of the vacuum adsorption platform 5 to communicate with the outside world, and the other end of the air path is connected to the vacuum pumping system. In this way, the vacuum adsorption platform 5 can adsorb the green ceramic sheet 1. By adopting the above solution, the fluidity of the metal slurry 4 in the hole can be improved during the hole filling process, and the flatness of the metal slurry 4 can be ensured during the hole filling process.

[0053] Combine Figure 4 and Figure 5 As shown, in step 3 of this embodiment, the process of laminating the green ceramic sheets 1 specifically includes the following steps:

[0054] Step 3-1: Provide a backing plate 71, lay a first PET film 81 on top of it, and then sequentially place multiple green ceramic sheets 1 to be laminated onto the first PET film 81. Before lamination, remove the protective film 2 from the bottom surface of each green ceramic sheet 1. Place the green ceramic sheets 1 with the side corresponding to the large aperture facing upward.

[0055] Step 3-2: After the green ceramic sheets 1 are stacked, a second PET film 82 is placed on the upper surface of the topmost green ceramic sheet 1. A pressing plate 72 is then placed on top of the second PET film 82. Specifically, the backing plate 71 and pressing plate 72 can be made of aluminum alloy. The area of ​​the backing plate 71 and pressing plate 72 must not be smaller than the area of ​​the green ceramic sheet 1. In other words, the length and width of the backing plate 71 and pressing plate 72 must not be smaller than the length and width of the green ceramic sheet 1.

[0056] Step 3-3: Use a silicone pad 91 to wrap the semi-finished product obtained in step 3-2. Figure 5 Taking the orientation shown as an example, the semi-finished product obtained in step 3-2 is placed on the silicone pad 91, and then the silicone pads 91 on the left and right sides of the semi-finished product are wrapped upward until the upper surface of the semi-finished product (pressing plate 72) is covered.

[0057] Step 3-4: The semi-finished product obtained in step 3-3 is vacuum-sealed in a plastic bag 92, and then is compacted by isostatic pressing to press the multiple green porcelain pieces 1 into a green porcelain whole.

[0058] By adopting the above solution, the pad 71 and the pressing plate 72 can effectively limit the irregular deformation of the green porcelain as a whole, making its deformation more uniform and improving the position accuracy of the metal holes of the substrate after sintering.

[0059] Preferably, when the green porcelain is cut in step 4, the green porcelain can be placed on a heating table and heated at a temperature of 80-90° C. In other words, the green porcelain is cut while being heated.

[0060] Specific embodiments are used in the present invention to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing a multilayer ceramic substrate, characterized in that: The following steps are involved: Step 1: Use laser drilling to open a through hole on the green ceramic sheet; Step 2: Filling the through holes on the green ceramic sheet by spraying; Step 3: stacking the plurality of green porcelain sheets, and then pressing the plurality of green porcelain sheets into a green porcelain whole by isostatic pressing; Step 4: cutting the green porcelain as a whole to obtain a plurality of green porcelain blocks, and sintering the green porcelain blocks into shape.

2. The method for preparing a multilayer ceramic substrate according to claim 1, wherein: In step 1, before drilling the green ceramic sheet, the step further includes: providing a protective film on the surface of the green ceramic sheet, wherein the protective film is located on a side of the green ceramic sheet away from the laser generator.

3. The method for preparing a multilayer ceramic substrate according to claim 2, wherein: The protective film is made of PET, and the thickness of the protective film is between 60 and 80 μm.

4. The method for preparing a multilayer ceramic substrate according to claim 1, wherein: In step 1, the through hole is a tapered through hole, and the through hole gradually decreases in a direction away from the laser generator.

5. The method for preparing a multilayer ceramic substrate according to claim 4, wherein: The ratio of the lower aperture to the upper aperture of the through hole is between 0.7 and 0.

8.

6. The method for preparing a multilayer ceramic substrate according to claim 1, wherein: In step 2, spraying is performed on the through holes on the green ceramic sheet using a nozzle, wherein the diameter of the nozzle is 50-100 μm smaller than the aperture of the through holes, and the distance between the nozzle and the surface of the green ceramic sheet is between 280-320 μm.

7. The method for preparing a multilayer ceramic substrate according to claim 2, wherein: In step 2, before spraying the through holes of the green ceramic sheet, a breathable paper is first laid on a vacuum adsorption platform, and then the green ceramic sheet to be filled is placed on the breathable paper. The side of the green ceramic sheet with the protective film is in contact with the vacuum adsorption platform. After the green ceramic sheet is adsorbed by the vacuum adsorption platform, the through holes on the green ceramic sheet are filled.

8. The method for preparing a multilayer ceramic substrate according to claim 2, wherein: Step 3 specifically includes the following steps: Step 3-1: providing a backing plate, placing a first PET film on the backing plate, sequentially placing the plurality of green ceramic sheets to be laminated on the first PET film, and peeling off the protective film of each green ceramic sheet before lamination; Step 3-2: placing a second PET film on the top green ceramic sheet, and then placing a pressing plate on the second PET film; Step 3-3: Wrap the semi-finished product obtained in step 3-2 with a silicone pad; Step 3-4: vacuum-sealing the semi-finished product obtained in step 3-3 with a plastic bag, and then isostatically pressing the plurality of green porcelain pieces into a green porcelain whole.

9. The method for preparing a multilayer ceramic substrate according to claim 1, wherein: In step 4, when the green porcelain is cut, the green porcelain is placed on a heating table and heated at a temperature of 80-90°C.

10. A multilayer ceramic substrate, characterized in that: Prepared by the method according to any one of claims 1 to 9.

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