SMD (Surface Mount Device) ceramic tube shell packaging base with box dam and preparation method of SMD ceramic tube shell packaging base

Abstract

The invention discloses an SMD (Surface Mount Device) ceramic tube shell packaging base with a box dam and a preparation method of the SMD ceramic tube shell packaging base. The preparation method comprises the following steps: filling a via hole with copper paste by adopting a capsule type hole filling machine, manufacturing a circuit metal layer of the ceramic substrate in a silk-screen printing thick film metallization and grinding leveling manner, and manufacturing a metal box dam structure on the periphery of an independent circuit through a hot-pressing welding and repeated overprinting process. The ceramic packaging substrate with the metal box dam and good air tightness is obtained, the metal box dam and the ceramic base are integrally connected, no air hole is generated, the connection firmness is better, the reliability is higher, the air tightness is better, the process is easy to control, and the cost is low.

Description

Technical Field

[0001] The invention relates to the field of microelectronic packaging technology, and in particular to an SMD ceramic tube shell packaging base with a dam and a preparation method thereof. Background Art

[0002] At present, for optoelectronic devices such as sensors, crystal oscillators, resonators, power semiconductors, lasers, etc. that have high requirements for packaging airtightness and reliability, ceramic base packaging is generally used. The common structure is to assemble a metal dam on a ceramic base with a conductive circuit layer of a certain thickness. The metal dam and the ceramic base form a sealed cavity structure for placing device chips, filling packaging glue, adding inert gas or directly evacuating, thereby achieving high-reliability airtight packaging.

[0003] There are two existing processes for ceramic base circuits. The first is the HTCC high-temperature co-firing process, which uses thick film screen printing of tungsten slurry to make the via holes on the upper and lower surface circuit layers of the base. The via holes are also filled with tungsten metal slurry by screen printing. The metal dam is fixed to the ceramic base by brazing the var ring. The second DPC (Direct Plating Copper) uses a sputtering process to composite the metal layer Ti / Cu on the surface of the substrate, and uses electroplating copper and photolithography to form the surface circuit and upper and lower interconnections, as well as electroplating thickening and polishing to form the dam structure. The first HTCC ceramic substrate packaging structure has the following defects: First, the circuits produced by thick-film screen printing of green sheets are not accurate and have a rough surface, which is not conducive to die bonding of packaged chips. Second, the tungsten slurry metal vias produced by screen printing and platform negative pressure adsorption have pores, which reduces the reliability of device electrical connection and thermal conduction; Third, if the metal dam is brazed with a kovar ring and connected to the ceramic base, the brazing process is a high-temperature process. The thermal stress during the welding process will cause the substrate to warp and deform, reducing the reliability and airtightness of the substrate and affecting the product yield. Fourthly, HTCC high-temperature co-firing is a high-temperature process, and nitrogen and wet hydrogen are used in the sintering process. The sintering process is complex and has a high safety level. The entire process requires a high level of professionalism from technical personnel and large equipment investment. It does not have an advantage in the environment of advocating energy conservation, emission reduction and carbon neutrality.

[0004] The second DPC ceramic substrate packaging structure has the following defects: First, the equipment investment is large and the wet process is used, which pollutes the entire environment. Second, the metal dam structure is based on the metal composite seed layer, and the pulse electroplating copper thickening and multiple grinding processes are carried out, which has low manufacturing efficiency and leads to extremely high process costs. Third, the method of filling holes with electroplated copper cannot meet the application scenarios with high depth-to-diameter ratio of the base hole. The conventional depth-to-diameter ratio of the DPC process is within 5:1. If this technical indicator is exceeded, the hole cannot be filled with electroplating. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the object of the present invention is to provide a method for preparing a SMD ceramic tube shell package base with a dam, in which the metal dam and the ceramic base are connected in an integrated manner, no pores are generated, the connection is firmer, the reliability is higher, the airtightness is better, and the process is easy to control.

[0006] Another object of the present invention is to provide a SMD ceramic tube shell packaging base with a dam.

[0007] The purpose of the present invention is achieved through the following technical solutions: The present invention provides a method for preparing a SMD ceramic tube shell package base with a dam, comprising the following steps: Step A: Filling the via holes on the ceramic substrate with copper paste using a capsule-type hole filling machine; Step B: thick-film screen printing thickened sintered copper paste on the front and back sides of the ceramic substrate according to the conductive circuit design to obtain a front independent circuit Cu layer and a back independent circuit Cu layer; Step C: sintering, metallizing the front independent circuit Cu layer and the back independent circuit Cu layer; Step D: The metallized Cu layer is ground and polished on a flat grinding line to ensure that the metallized Cu layer meets the roughness Ra: <0.03um; Step E: Prepare the metal dam by any of the following two methods: First way: Printing nano-interconnected copper paste on the dam area of ​​the ceramic substrate to obtain a ceramic substrate dam metal layer; Screen printing nano-copper-silver-tin alloy solder on the ceramic substrate dam metal layer to obtain a solder layer; Fixing the stamped copper-nickel-zinc alloy ring on the solder layer with a fixture, using a hot pressing process, first keeping the temperature at 1.5-3MPa and 155-165°C for 20-30min to form a tin-copper IMC layer at the welding interface, and then keeping the temperature at 1.5-3MPa and 230°C-250°C for 60-120min to complete the bonding process; The second method: multiple overprinting thickened sintered copper paste is used in the dam area of ​​the ceramic substrate to form a dam structure with a thickness of 300~400μm, sintered at a temperature between 850℃~950℃, and the sintering peak time is 10~30min; after sintering, the formed metallized Cu layer in the dam area is polished on the flat grinding line to make the metallized Cu layer in the dam area meet the roughness Ra: <0.03um; Step F: All metal surfaces on the ceramic substrate are plated with nickel or gold.

[0008] Preferably, the ceramic substrate is a 96% AL2O3 / 92 AL2O3 ceramic substrate or an ALN ​​ceramic substrate.

[0009] Preferably, the copper paste in step A is nano-interconnected copper paste; and the sintering in step C is specifically as follows: firstly put it into an oven at 150-160° C. for 30-50 minutes for pre-curing, and then heat it to 240-250° C. for 60-120 minutes for sintering.

[0010] Preferably, the copper paste in step A is a high-temperature sintered copper paste; the sintering in step C is specifically: the sintering temperature is between 850° C. and 950° C., and the sintering peak time is 10 to 30 minutes.

[0011] Preferably, the nano copper-silver-tin alloy comprises nano Cu particles, nano Ag particles, nano Sn particles, resin and solvent; wherein the content of the nano Sn particles is 40-50wt%.

[0012] Preferably, the content of the nano Cu particles is 20-30wt%.

[0013] Preferably, the content of the nano-Ag particles is 5-10wt%.

[0014] The present invention also provides an SMD ceramic tube shell packaging base with a dam, which is prepared by the preparation method of the SMD ceramic tube shell packaging base with a dam.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) In the method for preparing the SMD ceramic tube shell package base with dam of the present invention, the metal dam and the ceramic base are connected in an integrated manner, no pores are generated, the connection is firmer, the reliability is higher, the airtightness is better, the process is easy to control, and the cost is low.

[0016] (2) The preparation method of the SMD ceramic tube shell package base with a dam of the present invention uses a capsule-type hole filling machine to fill the conductive hole with copper paste, and then produces a ceramic substrate circuit metal layer by screen printing thick film metallization and grinding and leveling. Then, a metal dam structure around the independent circuit is produced by hot pressing welding and repeated overprinting process to obtain a ceramic package substrate with a metal dam and good airtightness. This method has the advantages of simple circuit metal layer production process and high surface flatness.

[0017] (3) In the method for preparing the SMD ceramic tube package base with dam of the present invention, the conductive holes between the circuit layers are completely filled with nano-interconnect copper paste or high-temperature plugging copper paste by capsule injection, and the reliability is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a process roadmap for preparing the SMD ceramic tube shell package base with dam according to Example 1 of the present invention.

[0019] Figure 2 This is a cross-sectional view of a ceramic substrate after executing step A in the preparation process of the SMD ceramic tube package base with dam according to Example 1 of the present invention.

[0020] Figure 3 This is a cross-sectional view of a ceramic substrate after executing step C in the preparation process of the SMD ceramic tube package base with dam according to Example 1 of the invention.

[0021] Figure 4 This is a cross-sectional view of a ceramic substrate after executing step E in the preparation process of the SMD ceramic tube package base with dam according to Example 1 of the invention.

[0022] Figure 5 This is a schematic diagram of a packaged product of the SMD ceramic tube package base with dam according to Example 1 of the invention.

[0023] Figure 6 This is a process roadmap for preparing the SMD ceramic tube shell package base with dam according to Example 2 of the present invention.

[0024] Description of the accompanying symbols: 10. Ceramic substrate 20. Conductive plug hole nano interconnect copper paste 30. Metal dam 25. Positive independent line 40. Packaging cavity 45. Independent line on the reverse side. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below in conjunction with the examples, but the embodiments of the present invention are not limited thereto. Example 1

[0026] like Figure 1 As shown, the method for preparing the SMD ceramic tube shell package base with a dam in this embodiment includes the following steps: Step A: Capsule-type hole filling: The laser-punched / scribed 96% AL2O3 / 92 AL2O3 ceramic substrate is filled with nano-interconnected copper paste using a capsule-type hole filling machine. The cross-section of the ceramic substrate is as follows: Figure 2 As shown; Step B: Printing the circuits on the front and back sides: thick-film screen printing thickened sintered copper paste is performed on the front and back sides of the ceramic substrate according to the conductive circuit design to obtain independent circuits on the front and back sides; Step C: Sintering of the front and back circuits: First put it into the oven at 150~160℃ for 30~50min for pre-curing, then heat it to 240~250℃ for 60~120min for sintering, metallize the Cu layer, and the cross-section of the ceramic substrate at this time is as follows Figure 3 As shown; Step D: Polishing and leveling: The metallized Cu layer is polished on the flat grinding line to make the metal Cu layer meet the roughness Ra: <0.03um and meet the requirements of die bonding; Step E: Preparation of metal dam by vacuum pressure heating welding of copper-nickel-zinc alloy ring: Print nano-interconnected copper paste on the dam area of ​​the ceramic substrate to obtain a ceramic substrate dam metal layer; screen print nano-copper-silver-tin alloy solder on the ceramic substrate dam metal layer to obtain a solder layer; fix the stamped copper-nickel-zinc alloy ring on the solder layer with a fixture, use the Donghe Intelligent DHF05-ZK-240KN vacuum hot pressing machine, adopt a hot pressing process, first keep the temperature at 1.5~3MPa and 155~165℃ for 20~30min to form a tin-copper IMC layer at the welding interface, and then keep the temperature at 1.5~3MPa and 230℃~250℃ for 60~120min to complete the bonding process; the cross-sectional view of the ceramic substrate at this time is as follows Figure 4 As shown; Step F: Surface gold plating: All metal surfaces on the ceramic substrate are electroplated with gold.

[0027] The SMD ceramic tube package base with dam prepared in this embodiment is used to place the device chip. The packaged product is as follows: Figure 5 shown.

[0028] The finished product of this embodiment was tested for reliability and air tightness. The reliability met the requirements of MIL-STD-883, and the leakage rate obtained by the air tightness test was less than 5.9. 10 -9 Pa.m 3 / s, reaching the excellent level. Example 2

[0029] like Figure 6 As shown, the method for preparing the SMD ceramic tube shell package base with a dam in this embodiment includes the following steps: Step A: Capsule-type hole filling: The laser-drilled / scribed ALN ceramic substrate is filled with a capsule-type hole filling machine using high-temperature sintered copper paste to fill the via holes; Step B: Printing the circuits on the front and back sides: thick-film screen printing thickened sintered copper paste is performed on the front and back sides of the ceramic substrate according to the conductive circuit design to obtain independent circuits on the front and back sides; Step C: Sintering of the front and back circuits: sintering temperature is between 850℃~950℃, sintering peak time is 10~30min, metallization Cu layer; Step D: Polishing and leveling: The metallized Cu layer is polished on a flat grinding line to ensure that the metallized Cu layer meets the roughness Ra: <0.03um and meets the requirements of die bonding. Step E: Preparation of metal dam by vacuum pressure heating welding of copper-nickel-zinc alloy ring: In the dam area of ​​the ceramic substrate, a dam structure with a thickness of 300-400μm is formed by multiple overprinting and thickening sintering copper paste, and the dam is sintered at a temperature between 850℃ and 950℃, with a sintering peak time of 10-30min. After sintering, the metallized Cu layer in the dam area is polished on a flat grinding line to make the metal Cu layer meet the roughness Ra: <0.03um, so as to meet the subsequent roller parallel sealing or laser welding requirements. Step F: All metal surfaces on the ceramic substrate are gold plated.

[0030] The structure of the SMD ceramic tube package base with dam prepared in this embodiment is the same as that in Embodiment 1.

[0031] The finished product of this embodiment was tested for reliability and air tightness. The reliability met the requirements of MIL-STD-883, and the leakage rate obtained by the air tightness test was less than 5.9. 10 -9 Pa.m 3 / s, reaching the excellent level.

[0032] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a SMD ceramic tube package base with a dam, characterized in that: The following steps are involved: Step A: Filling the via holes on the ceramic substrate with copper paste using a capsule-type hole filling machine; Step B: thick-film screen printing thickened sintered copper paste is performed on the front and back surfaces of the ceramic substrate according to the conductive circuit design to obtain a front independent circuit Cu layer and a back independent circuit Cu layer; Step C: sintering, metallizing the front independent circuit Cu layer and the back independent circuit Cu layer; Step D: The metallized Cu layer is ground and polished on a flat grinding line to ensure that the metallized Cu layer meets the roughness Ra: <0.03um; Step E: Prepare the metal dam by any of the following two methods: First way: Printing nano-interconnected copper paste on the dam area of ​​the ceramic substrate to obtain a ceramic substrate dam metal layer; Screen printing nano-copper-silver-tin alloy solder on the ceramic substrate dam metal layer to obtain a solder layer; Fixing the stamped copper-nickel-zinc alloy ring on the solder layer with a fixture, using a hot pressing process, first keeping the temperature at 1.5-3MPa and 155-165°C for 20-30min to form a tin-copper IMC layer at the welding interface, and then keeping the temperature at 1.5-3MPa and 230°C-250°C for 60-120min to complete the bonding process; The second method: multiple overprinting thickened sintered copper paste is used in the dam area of ​​the ceramic substrate to form a dam structure with a thickness of 300~400μm, sintered at a temperature between 850℃~950℃, and the sintering peak time is 10~30min; after sintering, the formed metallized Cu layer in the dam area is polished on the flat grinding line to make the metallized Cu layer in the dam area meet the roughness Ra: <0.03um; Step F: All metal surfaces on the ceramic substrate are plated with nickel or gold.

2. The method for preparing the SMD ceramic tube package base with dam according to claim 1, characterized in that: The ceramic substrate is a 96% AL2O3 / 92 AL2O3 ceramic substrate or an ALN ​​ceramic substrate.

3. The method for preparing the SMD ceramic tube package base with dam according to claim 1, characterized in that: The copper paste in step A is nano-interconnected copper paste; the sintering in step C is specifically as follows: firstly put it into an oven at 150-160° C. for 30-50 minutes for pre-curing, then heat it to 240-250° C. for 60-120 minutes for sintering.

4. The method for preparing the SMD ceramic tube package base with dam according to claim 1, characterized in that: The copper paste in step A is a high-temperature sintered copper paste; the sintering in step C is specifically: the sintering temperature is between 850°C and 950°C, and the sintering peak time is 10 to 30 minutes.

5. The method for preparing the SMD ceramic tube package base with dam according to claim 1, characterized in that: The nano copper-silver-tin alloy comprises nano Cu particles, nano Ag particles, nano Sn particles, resin and solvent; wherein the content of the nano Sn particles is 40-50wt%.

6. The method for preparing the SMD ceramic tube package base with dam according to claim 5, characterized in that: The content of the nano Cu particles is 20-30wt%.

7. The method for preparing the SMD ceramic tube package base with dam according to claim 5, characterized in that: The content of the nano-Ag particles is 5-10wt%.

8. A SMD ceramic tube package base with a dam, characterized in that: The ceramic tube package base with a dam is prepared by the preparation method of the SMD according to any one of claims 1 to 7.

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