Prefabricated gold-tin ceramic packaging structure, multilayer ceramic packaging structure and production process

Abstract

The invention relates to a prefabricated gold-tin ceramic packaging structure, a multi-layer ceramic packaging structure and a production process, and solves the problems that in the prior art, when packaging structures such as crystal oscillator bases are welded, welding flux pieces are difficult to position, and the production cost is high due to large gold-tin welding flux consumption. Comprising a ceramic base and a ceramic cover plate, a metal box dam is arranged on the ceramic base, when the ceramic base and the ceramic cover plate are mutually covered and packaged, the portion, in butt joint with the metal box dam, of the ceramic cover plate is a flat plate welding area, the top face of the metal box dam is a boss welding area, and the boss welding area is a convex plate welding area. A gold-tin welding layer is arranged on the surface of at least one of the flat plate welding area and the boss welding area, and a solder mask layer is arranged on the peripheral surface of the flat plate welding area.

Description

Technical Field

[0001] This invention relates to a packaging device, and more particularly to a pre-fabricated gold-tin ceramic packaging structure, a multi-layer ceramic packaging structure, and a manufacturing process. Background Technology

[0002] A quartz crystal oscillator (QSO) is a high-precision frequency control device manufactured based on the piezoelectric effect of quartz crystals. Its core function is to provide a stable oscillation signal for electronic systems. A QSO consists of a crystal base, specifically a ceramic substrate package structure. Electronic components are encapsulated within the crystal base, which provides electromagnetic shielding and mechanical protection. The crystal base comprises a ceramic substrate, a dam, and a cover plate. The dam can be fabricated on the ceramic substrate using existing processes such as LTCC, HTCC, or DPC. The dam and cover plate are typically hermetically sealed using gold-tin solder sheets. During soldering, the gold-tin solder sheets need to be precisely aligned. Since the thickness of the gold-tin solder sheets is typically around 50µm, positioning becomes extremely difficult when dealing with products with small solder joints, significantly increasing the complexity of the packaging process. Furthermore, gold-tin solder sheets are relatively expensive. Significantly reducing the use of gold-tin solder would be of great significance to crystal oscillator base manufacturers. Therefore, how to simplify the welding process and reduce the use of gold-tin solder during the welding process has become a challenge for the crystal oscillator base manufacturing industry. Summary of the Invention

[0003] This invention provides a prefabricated gold-tin ceramic packaging structure, a multilayer ceramic packaging structure, and a manufacturing process; it solves the problems in the prior art where the positioning of solder sheets is difficult during the welding of packaging structures such as crystal oscillator bases, and the high consumption of gold-tin solder leads to high production costs.

[0004] The above-mentioned technical problems of the present invention are mainly solved by the following technical solution: a prefabricated gold-tin ceramic encapsulation structure, including a ceramic base and a ceramic cover plate, wherein a metal dam is provided on the ceramic base, and when the ceramic base and the ceramic cover plate are sealed together, the part of the ceramic cover plate that is connected to the metal dam is a flat soldering area, the top surface of the metal dam is a boss soldering area, at least one of the flat soldering area and the boss soldering area has a gold-tin soldering layer on its surface, and the outer surface of the flat soldering area has a solder resist layer.

[0005] This invention attaches gold-tin solder to flat or raised solder areas, or both, using electroplating, vapor deposition, or magnetron sputtering processes. This not only eliminates the need for solder sheet positioning but also adapts to small-size packaging structures. The pattern size of the gold-tin solder layer can overcome the size limitations of existing soldering processes, broadening its application range. Furthermore, because the gold-tin solder layer is attached to the ceramic substrate and ceramic cover, its thickness can exceed the thickness limitations of traditional gold-tin solder sheets. By controlling the growth time and speed of the gold-tin solder, the thickness of the gold-tin solder layer can be significantly reduced, thereby minimizing gold-tin loss and lowering production costs.

[0006] The present invention also provides a prefabricated gold-tin multilayer ceramic encapsulation structure, comprising a plurality of ceramic bases and ceramic cover plates stacked vertically.

[0007] The ceramic base is composed of a substrate, a metal dam, and copper pillars. The copper pillars have signal channels inside. The substrate has ceramic sheets, connecting pillars penetrating the ceramic sheets, several upper welding pads, and several lower welding pads. The upper and lower welding pads are vertically aligned and electrically connected through the connecting pillars. The metal dam and the copper pillars are grown on different upper welding pads. The ceramic cover plate has a similar structure to the substrate. The ceramic cover plate also has ceramic sheets, connecting pillars penetrating the ceramic sheets, several upper welding pads, and several lower welding pads. The upper and lower welding pads on the ceramic cover plate are arranged in the same way as those on the ceramic base.

[0008] The upper and lower surfaces of the ceramic cover plate or the lower surface of the ceramic base are designed as flat welding areas where they meet the metal dam or the copper column. The top surfaces of the metal dam and the copper column are designed as raised welding areas. At least one of the flat welding areas and the raised welding areas has a gold-tin welding layer on its surface. The outer surface of the flat welding area has a solder resist layer, which is generally an organic polymer material, used to prevent the molten solder generated during the welding process from flowing out.

[0009] Through the above scheme, this invention can realize the stacking of multiple ceramic substrates. Each internal packaging area defined by a metal dam can encapsulate chip devices. Copper pillars on adjacent ceramic substrates are electrically connected by welding. The copper pillars are mainly used for signal communication and can also serve as pin connections for chip devices. This stacked structure is suitable for some special products. Although the stacked structure occupies a small vertical dimension, it occupies very little horizontal dimension and can encapsulate multiple chip devices, resulting in high integration and reducing overall size.

[0010] This invention also provides a manufacturing process for prefabricated gold-tin ceramic plates, the manufacturing process including:

[0011] A ceramic substrate is prepared, and a ceramic base and a ceramic cover plate are obtained by any one of the processes of LTCC, HTCC, and DPC.

[0012] To prepare the solder resist layer, a solder resist layer is prepared on the bottom surface of the ceramic substrate excluding the welding area, and on the upper and lower surfaces of the ceramic cover plate excluding the welding area. Here, screen printing is generally used to prepare the solder resist layer.

[0013] To prepare a gold-tin solder layer, electroplating, vapor deposition, or magnetron sputtering processes are used to prepare the gold-tin solder layer in the soldering area.

[0014] Therefore, the present invention has the following characteristics compared with the prior art: 1. The present invention can eliminate the solder sheet positioning process and can adapt to small-size packaging structures. The pattern size of the gold-tin solder layer can break through the size limitations of the existing soldering process, and the application field is wider; 2. At the same time, since the gold-tin solder layer is attached to the ceramic base and ceramic cover plate, its own thickness can break through the thickness limitation of the original gold-tin solder sheet. By controlling the growth time and speed of the gold-tin solder, the thickness of the gold-tin solder layer can be greatly reduced, so as to reduce the loss of gold-tin and reduce production costs. Attached Figure Description

[0015] Appendix Figure 1 This is a schematic diagram of the disassembled structure of the prefabricated gold-tin ceramic encapsulation structure;

[0016] Appendix Figure 2 This is a structural schematic diagram of Example 2;

[0017] Appendix Figure 3 This is a schematic diagram of the structure of Example 3;

[0018] Appendix Figure 4 It is a process that uses vapor deposition or magnetron sputtering to prepare the gold-tin solder layer;

[0019] Appendix Figure 5 It is a process that uses electroplating to prepare the gold-tin solder layer. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0021] 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.

[0022] This invention provides a manufacturing process for prefabricated gold-tin ceramic plates. Specifically, the ceramic plates are prepared using the DPC process, which includes:

[0023] Make holes by machining several interconnected holes on the ceramic sheet 10;

[0024] Prepare the underlayer by depositing the underlayer on the surface of the ceramic sheet and the connecting holes;

[0025] A mask is prepared on the upper and lower surfaces of the ceramic sheet, and then exposed and developed.

[0026] Copper plating is performed on the exposed area of ​​the ceramic sheet to form the connecting pillar 20, the upper pad 30 and the lower pad 40. The difference between the ceramic base and the ceramic cover plate is that the ceramic base needs to repeat the mask preparation and copper plating processes multiple times to grow the metal dam 50 and the copper pillar 60 on it.

[0027] Mask removal: Remove excess mask from the ceramic sheet;

[0028] Remove the base layer, removing any exposed base layer from the ceramic tile;

[0029] A solder resist layer is prepared using a screen printing process. A solder resist layer 70 is prepared on the bottom surface of the ceramic substrate excluding the solder area, and a solder resist layer is prepared on the upper and lower surfaces of the ceramic cover plate excluding the solder area. The thickness is between 10 and 50 μm.

[0030] Finally, a gold-tin solder layer 80 is prepared in the soldering area. The soldering area is divided into a flat soldering area and a boss soldering area. Since the boss soldering area is more difficult to prepare, the gold-tin soldering layer is generally only prepared in the flat soldering area.

[0031] See Figure 4 The preparation of gold-tin solder layers can be divided into electroplating, vapor deposition, or magnetron sputtering. When electroplating is used to prepare gold-tin solder layers, the process is as follows:

[0032] A seed layer was prepared on the surface of a ceramic substrate and a ceramic cover plate by a sputtering process.

[0033] A mask is prepared on the bottom surface of the ceramic substrate and the top and bottom surfaces of the ceramic cover plate, and then exposed and developed to create windows in the mask so that the flat solder area is fully exposed.

[0034] Electroplated gold-tin solder layer;

[0035] Mask removal: Remove excess mask from the ceramic sheet;

[0036] Etch the seed layer to remove excess seed layer.

[0037] See Figure 5 When gold-tin solder layers are prepared by vapor deposition or magnetron sputtering, the process is as follows:

[0038] A mask is prepared on the bottom surface of the ceramic substrate and the top and bottom surfaces of the ceramic cover plate, and then exposed and developed to create windows in the mask so that the flat solder area is fully exposed.

[0039] A gold-tin layer is formed on a ceramic substrate by vapor deposition or magnetron sputtering;

[0040] Next, a mask is prepared on the gold-tin layer, and a window is made in the area where the mask is not a flat soldering area.

[0041] The gold and tin layer is etched away by chemical etching or dry etching to remove the gold and tin layer in the windowed area, leaving only the gold and tin layer in the flat solder area.

[0042] Remove the mask to expose the solder mask and the gold-tin layer in the flat solder area.

[0043] Specifically, the thickness of the gold-tin solder layer is between 3 and 50 μm.

[0044] The above production process yields a ceramic base and a ceramic cover plate. The ceramic base consists of a ceramic sheet, a connecting post, an upper welding plate, a lower welding plate, a metal dam, and a copper pillar. The copper pillar contains a signal channel. The specific number and outline of the upper and lower welding plates are customized according to the actual product. The upper and lower welding plates are vertically aligned and electrically connected through the connecting post. The metal dam and the copper pillar are grown on different upper welding plates. A gold-tin solder layer is placed on the lower welding plate and is completely aligned with the metal dam and the copper pillar. The ceramic cover plate consists of a ceramic sheet, a connecting post, an upper welding plate, and a lower welding plate. The upper and lower welding plates on the ceramic cover plate are identical to those on the ceramic base, and each upper and lower welding plate has a gold-tin solder layer.

[0045] Example 1: See Figure 1A prefabricated gold-tin ceramic encapsulation structure includes a ceramic base 100 and a ceramic cover plate 200. The ceramic base and ceramic cover plate are produced using the above-described manufacturing process. The metal dam and copper pillars on the ceramic base are simultaneously welded and fixed to the gold-tin solder layer on the ceramic cover plate. The ceramic cover plate of this ceramic encapsulation structure has a pre-reserved upper solder pad and gold-tin solder layer to facilitate subsequent electrical connection or soldering with other devices.

[0046] Example 2: See Figure 2 A pre-fabricated gold-tin multilayer ceramic packaging structure includes N ceramic substrates and one ceramic cover plate. The ceramic substrates and cover plate are produced using the above-described manufacturing process. The N ceramic substrates are sequentially welded and stacked, with the ceramic cover plate located on the outermost side. Adjacent ceramic substrates are simultaneously welded and fixed to the gold-tin solder layer on the back of the ceramic substrate via metal dams and copper pillars. This structure is suitable for situations where multiple internally packaged chip devices 300 have the same orientation.

[0047] Example 3: See Figure 3 A pre-fabricated gold-tin multilayer ceramic package structure includes N ceramic bases and a ceramic cover plate. The ceramic bases and ceramic cover plate are obtained by the above-described manufacturing process, and several ceramic bases are welded and stacked on both sides of the ceramic cover plate. This structure is suitable for situations where the orientations of multiple internally packaged chip devices 300 are inconsistent.

[0048] 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 prefabricated gold-tin ceramic encapsulation structure, comprising a ceramic base and a ceramic cover plate, wherein a metal dam is provided on the ceramic base, and when the ceramic base and the ceramic cover plate are sealed together, the portion of the ceramic cover plate that abuts with the metal dam is a flat soldering area, and the top surface of the metal dam is a boss soldering area, characterized in that: At least one of the flat solder area and the boss solder area has a gold-tin solder layer on its surface, and the outer surface of the flat solder area has a solder resist layer.

2. A pre-fabricated gold-tin multilayer ceramic encapsulation structure, characterized in that: It includes several ceramic bases and ceramic cover plates stacked on top of each other; The ceramic base is composed of a substrate, a metal dam, and copper pillars. The copper pillars have signal channels inside. The substrate has ceramic sheets, connecting pillars penetrating the ceramic sheets, several upper welding pads, and several lower welding pads. The upper and lower welding pads are vertically aligned and electrically connected through the connecting pillars. The metal dam and the copper pillars are grown on different upper welding pads. The ceramic cover plate also has ceramic sheets, connecting pillars penetrating the ceramic sheets, several upper welding pads, and several lower welding pads. The upper / lower welding pads on the ceramic cover plate are arranged in the same way as those on the ceramic base. The upper and lower surfaces of the ceramic cover plate or the lower surface of the ceramic base are connected to the metal dam or the copper column at the locations where they meet, forming flat welding areas. The top surfaces of the metal dam and the copper column are forming boss welding areas. At least one of the flat welding areas and the boss welding areas has a gold-tin welding layer on its surface, and the outer surface of the flat welding area has a solder resist layer.

3. A manufacturing process for precast gold-tin ceramic plates, characterized in that, The production process includes: A ceramic substrate is prepared, and a ceramic base and a ceramic cover plate are obtained by any one of the processes of LTCC, HTCC, and DPC. Prepare a solder resist layer by preparing a solder resist layer on the bottom surface of the ceramic substrate excluding the welding area, and prepare a solder resist layer on the upper and lower surfaces of the ceramic cover plate excluding the welding area. To prepare a gold-tin solder layer, electroplating, vapor deposition, or magnetron sputtering processes are used to prepare the gold-tin solder layer in the soldering area.

4. The production process of the precast gold-tin ceramic plate according to claim 3, characterized in that: The thickness of the gold-tin solder layer is between 3 and 50 μm.

5. The production process of the precast gold-tin ceramic plate according to claim 2, characterized in that: The solder resist layer is an organic polymer material with a thickness between [thickness range missing].

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