Packaging ceramic base with electroplated three-dimensional step structure and preparation process thereof

Abstract

The invention relates to a packaging ceramic base with an electroplated three-dimensional step structure and a preparation process of the packaging ceramic base. The structure comprises a ceramic substrate, a metal box dam, upper-layer bonding pads, copper columns and lower-layer bonding pads, the copper columns penetrate through the ceramic substrate and are electrically connected with a lower-layer metal layer and the upper-layer bonding pads, the upper-layer bonding pads are divided into a plurality of layers and are separated from one another, heightening bonding pads are conductively stacked on any upper-layer bonding pad, and the heightening bonding pads are electrically connected with the lower-layer bonding pads. And the height of the heightening bonding pad is lower than that of the metal box dam. Due to the fact that height differences exist between different heightening bonding pads and between the heightening bonding pads and the upper layer bonding pads, a plurality of chips are staggered in the height direction and can coincide in the projection direction, the space utilization rate of a sealing cavity can be greatly improved, the packaging size can be obviously reduced, and the requirement for small-size packaging can be met. Meanwhile, a multi-layer electroplating thickening process is adopted, the overall thermal conductivity and electrical conductivity are extremely good, the heat dissipation requirement can be met, and large current impact can be better borne.

Description

Technical Field

[0001] This invention relates to a ceramic base for packaging, and more particularly to a ceramic base for packaging with an electroplated three-dimensional stepped structure and its manufacturing process. Background Technology

[0002] Packaging substrates utilize the high thermal conductivity of their materials to dissipate heat from the chip (heat source), achieving heat exchange with the external environment. As chip input power increases, the requirements for the heat dissipation performance of packaging substrates become increasingly stringent. Direct-plated ceramic substrates (DPC - Direct Plating Copper, indicating that copper can be directly plated onto their surface) are increasingly widely used in electronic packaging, especially in power electronic devices (such as IGBTs, LDs, and high-power LEDs), due to their excellent thermal conductivity, low coefficient of thermal expansion, high pattern precision, and ability to vertically interconnect.

[0003] To protect chip components from external interference during operation, a three-dimensional ceramic substrate with a dam-like, enclosed cavity structure is used to package the chips, effectively improving device reliability. However, existing dam fabrication technologies have the following shortcomings: the working components within the dam are typically arranged only on the bottom layer, with all chips located at the same height. This requires a large space for products with many components and complex circuitry, failing to meet the requirements of small-size packaging. Furthermore, using a multi-layer ceramic dam structure (LTCC or HTCC) cannot meet the heat dissipation requirements of small components. Summary of the Invention

[0004] This invention provides a ceramic base for packaging with an electroplated three-dimensional stepped structure and its manufacturing process; it solves the problem in the prior art that the low utilization rate of the packaging space inside the ceramic base leads to difficulties in miniaturization.

[0005] The above-mentioned technical problems of the present invention are mainly solved by the following technical solution: a ceramic base for packaging with an electroplated three-dimensional stepped structure, comprising a ceramic substrate, a metal dam, an upper pad, a copper pillar, and a lower pad. The metal dam and the upper pad are both located on the upper surface of the ceramic substrate, and the upper pad is located within the area surrounded by the metal dam. The lower pad is located on the lower surface of the ceramic substrate. The copper pillar penetrates the ceramic substrate and electrically connects the lower metal layer and the upper pad. The upper pad is divided into several and separated from each other. A raised pad is electrically stacked on any upper pad, and the height of the raised pad is lower than the height of the metal dam.

[0006] This invention utilizes a multi-layer electroplating thickening process to grow multiple height-enhancing pads within a dam. The number, location distribution, and specific height of each height-enhancing pad are determined based on specific circumstances. The number of chips packaged within the dam and the specific types of chips will affect the characteristics of the height-enhancing pads. The raised pads and upper pads inside this invention are used to solder the gold wires (or copper wires, aluminum wires) of the chip to achieve conductive connection. Because there are height differences between different raised pads and between the raised pads and the upper pads, multiple mounting areas for chip installation can be allocated within the sealed cavity defined by the dam. These mounting areas are staggered in the height direction but can overlap in the projection direction, which significantly improves the space utilization of the sealed cavity and can significantly reduce the package size, meeting the requirements of small-size packaging. Furthermore, the multi-layer electroplating thickening process used in this invention provides excellent overall thermal and electrical conductivity, meeting heat dissipation requirements and withstanding high current surges. Each mounting area also has a corresponding raised pad with an appropriate height, ensuring that the gold wires connecting the chip and the raised pads are horizontally positioned, which helps to shorten the length of the gold wires and save production costs.

[0007] The present invention also provides a process for fabricating a ceramic base for packaging with an electroplated three-dimensional stepped structure, the process comprising:

[0008] Opening holes: creating several through holes in a ceramic substrate;

[0009] Prepare the underlayer by depositing the underlayer on the surface of the ceramic substrate and the through-hole;

[0010] Prepare the first mask by preparing masks on the upper and lower surfaces of the ceramic substrate;

[0011] The first window is made on the first layer of mask, which is divided into a dam window, an upper pad window and a lower pad window, wherein the upper pad window and the lower pad window are connected to the through hole;

[0012] The first copper plating is performed inside the through hole, the dam window, the upper pad window, and the lower pad window, forming copper pillars, dams, upper pads, and lower pads respectively.

[0013] Prepare a second mask layer, and continue to prepare masks on the upper and lower surfaces of the ceramic substrate to cover the dam, upper pad, and lower pad.

[0014] The second window is opened on the second layer of the mask, so that the upper surface of the first-order dam and part of the upper surface of the upper pad are exposed.

[0015] The second copper plating is performed in the area where the second window is opened, which allows the dam to continue to grow and rise, and grows additional pads on the upper pads.

[0016] Repeated masking, windowing, and copper plating allow the dam and upper pads to continue growing and eventually take shape;

[0017] Remove the mask; remove excess mask from the ceramic base.

[0018] Remove the underlying substrate, which is the exposed part of the ceramic substrate.

[0019] Furthermore, after the initial coating process, an anti-oxidation layer / solderable metal plating is included. The anti-oxidation layer, made of nickel-palladium-gold or nickel-gold, is plated onto the exposed copper layer surface. The solderable metal is plated onto the upper surface of the dam. The anti-oxidation layer protects the exposed copper layer, while the solderable metal can be directly used as solder in the dam welding cover plate process, eliminating the need for solder sheet positioning.

[0020] Therefore, this invention has the following characteristics compared to the prior art: 1. Due to the height difference between different height-adjusting pads and between the height-adjusting pads and the upper pads, multiple chips are staggered in the height direction but can overlap in the projection direction. This can significantly improve the space utilization of the sealing cavity, significantly reduce the package size, and meet the requirements of small-size packaging; 2. At the same time, the multi-layer electroplating thickening process used in this invention has excellent overall thermal and electrical conductivity, which can meet the heat dissipation requirements and withstand large current surges; 3. At the same time, each mounting area has a height-adaptive height-adjusting pad, so that the gold wire connecting the chip and the height-adjusting pad is set horizontally. This helps to shorten the length of the gold wire and save production costs. Attached Figure Description

[0021] Appendix Figure 1 This is a schematic diagram of one structure of the present invention after two chips are installed;

[0022] Appendix Figure 2 It is attached Figure 1 A sectional view;

[0023] Appendix Figure 3 It is attached Figure 1 Bottom view;

[0024] Appendix Figure 4 This is a process diagram of the preparation of the present invention. Detailed Implementation

[0025] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0026] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0027] Example 1: See Figure 1 , Figure 2 and Figure 3 A ceramic substrate for packaging with an electroplated three-dimensional stepped structure includes a ceramic substrate 10, a metal dam 20, an upper pad 30, a copper pillar 40, and a lower pad 50. The metal dam and the upper pad are both located on the upper surface of the ceramic substrate, and the upper pad is located within the area surrounded by the metal dam. The lower pad is located on the lower surface of the ceramic substrate. The copper pillar penetrates the ceramic substrate and electrically connects the lower metal layer and the upper pad. The upper pad is divided into several and separated from each other. A raised pad 60 is stacked on any upper pad and can conduct electricity. The height of the raised pad is lower than the height of the metal dam.

[0028] The thickness of the upper and lower pads is between 50um and 150um, and the gap between the upper pads or between the upper pads and the dam is between 0.08mm and 0.2mm.

[0029] This embodiment utilizes a multi-layer electroplating thickening process to grow multiple height-enhancing pads within the dam. The number, location distribution, and specific height of each height-enhancing pad are determined based on specific circumstances. The number of chips packaged within the dam and the specific types of chips will affect the characteristics of the height-enhancing pads. In this embodiment, both the raised pads and the upper pads are used to solder the gold wires of the chip to achieve conductive connections. Because there are height differences between the different raised pads and between the raised pads and the upper pads, multiple mounting areas for chip installation can be allocated within the sealed cavity defined by the dam. These mounting areas are staggered in the height direction but can overlap in the projection direction, which significantly improves the space utilization of the sealed cavity and can noticeably reduce the package size, meeting the requirements of small-size packaging. Furthermore, the multi-layer electroplating thickening process used in this embodiment provides excellent overall thermal and electrical conductivity, meeting heat dissipation requirements and withstanding high current surges. Each mounting area also corresponds to a raised pad with an appropriate height, ensuring that the gold wires connecting the chip and the raised pads are horizontally positioned, which helps to shorten the length of the gold wires and save production costs.

[0030] See Figure 4This embodiment also discloses a fabrication process for a ceramic base for packaging with an electroplated three-dimensional stepped structure, the fabrication process including:

[0031] A series of through holes 11 are made on the ceramic substrate, with the hole diameter between 0.05mm and 0.2mm.

[0032] The preparation of the underlayer involves depositing an underlayer, also known as a metal seed layer, on the surface of the ceramic substrate and the via. This is done using a magnetron sputtering process to deposit titanium and copper layers on the surface of the ceramic substrate and the via.

[0033] The first mask is prepared by preparing masks on the upper and lower surfaces of a ceramic substrate;

[0034] The first window is made on the first layer of mask, which is divided into a dam window, an upper pad window and a lower pad window. The upper pad window and the lower pad window are connected to the through hole, and the photolithography windowing process is used.

[0035] The first copper plating is performed inside the through holes, dam windows, upper pad windows, and lower pad windows, forming copper pillars, dams, upper pads, and lower pads respectively.

[0036] Prepare a second mask layer, and continue to prepare masks on the upper and lower surfaces of the ceramic substrate to cover the dam, upper pad, and lower pad.

[0037] The second window is created on the second mask, exposing the upper surface of the first-order dam and part of the upper surface of the upper pad.

[0038] The second copper plating is performed in the area where the second window is opened, which allows the dam to continue to grow and rise, and grows additional pads on the upper pads.

[0039] Repeated masking, windowing, and copper plating allow the dam and upper pads to continue growing and eventually take shape;

[0040] After the dam has grown, the top surface is polished to ensure its flatness.

[0041] Remove the mask; remove excess mask from the ceramic base.

[0042] Remove the base layer, exposing the ceramic substrate, to achieve an insulating effect.

[0043] Furthermore, after the undercoating process, an anti-oxidation layer is also plated. The anti-oxidation layer is plated on the exposed copper layer surface. The anti-oxidation layer is electroless nickel-palladium-gold plating, with a nickel layer thickness of 3-8μm, a palladium layer thickness of ≥0.05μm, and a gold layer thickness of ≥0.05μm. Alternatively, it can be electrolytic nickel-gold plating, with a nickel thickness of 3-8μm and a gold thickness of ≥0.2μm. The anti-oxidation layer is used to protect the exposed copper layer.

[0044] It will be apparent to those skilled in the art that the present invention can be modified in various ways, and such modifications are not considered to depart from the scope of the invention. All such modifications that are obvious to those skilled in the art are included within the scope of the claims.

Claims

1. A ceramic substrate for packaging with an electroplated three-dimensional stepped structure, comprising a ceramic substrate, a metal dam, an upper pad, a copper pillar, and a lower pad, wherein the metal dam and the upper pad are both located on the upper surface of the ceramic substrate, and the upper pad is located within the area enclosed by the metal dam; the lower pad is located on the lower surface of the ceramic substrate; and the copper pillar penetrates the ceramic substrate and electrically connects the lower metal layer and the upper pad, characterized in that: The upper pads are divided into several and separated from each other. Each upper pad has conductively stacked raised pads, the height of which is lower than the height of the metal dam.

2. The ceramic base for packaging with an electroplated three-dimensional stepped structure as described in claim 1, wherein the thickness of the upper and lower pads is between 50um and 150um, and the gap between the upper pads or between the upper pads and the dam is between 0.08mm and 0.2mm.

3. A fabrication process for a ceramic base for packaging with an electroplated three-dimensional stepped structure, characterized in that, The preparation process includes: Opening holes: creating several through holes in a ceramic substrate; Prepare the underlayer by depositing the underlayer on the surface of the ceramic substrate and the through-hole; Prepare the first mask by preparing masks on the upper and lower surfaces of the ceramic substrate; The first window is made on the first layer of mask, which is divided into a dam window, an upper pad window and a lower pad window, wherein the upper pad window and the lower pad window are connected to the through hole; The first copper plating is performed inside the through hole, the dam window, the upper pad window, and the lower pad window, forming copper pillars, dams, upper pads, and lower pads respectively. Prepare a second mask layer, and continue to prepare masks on the upper and lower surfaces of the ceramic substrate to cover the dam, upper pad, and lower pad. The second window is opened on the second layer of the mask, so that the upper surface of the first-order dam and part of the upper surface of the upper pad are exposed. The second copper plating is performed in the area where the second window is opened, which allows the dam to continue to grow and rise, and grows additional pads on the upper pads. Repeated masking, windowing, and copper plating allow the dam and upper pads to continue growing and eventually take shape; Remove the mask; remove excess mask from the ceramic base. Remove the underlying substrate, which is the exposed part of the ceramic substrate.

4. The fabrication process of the ceramic base for packaging with an electroplated three-dimensional stepped structure according to claim 3, characterized in that: After the base coat process, the process also includes plating an anti-oxidation layer / solderable metal, wherein the anti-oxidation layer is plated on the exposed copper layer surface and the material is nickel-palladium-gold or nickel-gold, and the solderable metal is plated on the upper surface of the dam.

5. The fabrication process of the ceramic base for packaging with an electroplated three-dimensional stepped structure according to claim 3, characterized in that: After the dam is completed, a top surface grinding process is required to ensure the flatness of its upper surface.

6. The fabrication process of the ceramic base for packaging with an electroplated three-dimensional stepped structure according to claim 3, characterized in that: The aperture of the opening is between 0.05mm and 0.2mm.

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