HTCC ceramic tube shell structure and preparation method thereof

Abstract

The invention discloses an HTCC ceramic tube shell structure and a preparation method thereof, the HTCC ceramic tube shell structure comprises a ceramic body, the periphery of the ceramic body is provided with a plurality of groups of internal through holes and side wall semi-circular grooves, the internal through holes and the side wall semi-circular grooves are correspondingly parallel and equal in number, the internal through holes are filled with tungsten conductive wires, and the inner ends of the tungsten conductive wires are electrically connected to bonding fingers arranged in an inner cavity of the ceramic body. The surfaces of the side wall semicircular grooves are covered with tungsten material layers, and the lower ends of the tungsten material layers are connected to the bottom tungsten conducting layer. The internal through hole and the side wall hole which are paired are arranged to realize signal transmission, and due to the addition of the side wall hole, a high-frequency signal forms a differential resonance phenomenon, return loss is effectively improved, and the problem that in a single signal transmission mode, the transmission performance of the signal in a 20GHz frequency range is poor due to impedance mismatching is solved. In addition, the side wall hole is reserved, so that a welding flux wrap angle can be formed in the side wall hole after the chip is welded, and the welding reliability can be detected more visually.

Description

Technical Field

[0001] The invention relates to a HTCC ceramic tube shell structure and a preparation method thereof, belonging to the technical field of HTCC ceramic tube shells. Background Art

[0002] As the times continue to progress, big data and artificial intelligence are booming at an unprecedented rate. In this process, the requirements for chip heat dissipation and miniaturization are becoming increasingly stringent. Packaging, as the only bridge connecting external circuits and chips, plays a vital role in ensuring the normal operation of chips.

[0003] HTCC high temperature ceramic substrate stands out among many substrates, and it is significantly different from general PCB substrates. HTCC high temperature ceramic substrate can act as a high-performance package shell, with many advantages such as good heat dissipation performance and high strength. Because of this, it is widely used in many important fields such as aerospace equipment and consumer electronics. It has rich and diverse forms and shapes, mainly divided into CSOP, CLCC and CDFN series.

[0004] Among them, the CLCC series ceramic housing has shown unique advantages. It has the characteristics of short transmission lines, which can effectively reduce the loss in signal transmission. At the same time, it has high reliability and can work stably in various complex environments. It is also easy to integrate, providing strong support for the miniaturization and multifunctionality of electronic products. These advantages make the CLCC series ceramic housing widely used in the field of microwave radio frequency chips, contributing important forces to improving chip performance and promoting the development of the electronics industry.

[0005] At present, the quad-leadless high-temperature co-fired ceramic (CLCC) packaging technology is mainly used in single-channel transmission systems. When designing the packaging structure, in order to ensure signal integrity, internal through holes are usually used to achieve inter-layer signal transmission, such as Figure 5 and Figure 7 The signal transmission structure shown in the figure. However, due to the high resistivity of the conductive material tungsten used, impedance mismatch often occurs in high-frequency applications, which in turn affects the integrity of high-speed signals. In low-frequency applications, since impedance mismatch has little effect on the signal and is convenient for detecting welding reliability, sidewall holes are often used for signal transmission. However, in high-frequency signal transmission, the problem of impedance mismatch is usually avoided by adjusting the aperture. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a HTCC ceramic tube shell structure and a preparation method thereof, which can ensure impedance matching and signal integrity and effectively solve the board-level reliability problem.

[0007] The technical solution adopted by the present invention is: a HTCC ceramic tube shell structure, including a ceramic body, a plurality of groups of internal through holes and side wall semicircular grooves are arranged around the ceramic body, the internal through holes and the side wall semicircular grooves are parallel and equal in number, the internal through holes are filled with tungsten conductive wires, the inner ends of the tungsten conductive wires are electrically connected to the bonding fingers arranged in the inner cavity of the ceramic body, and the outer ends are connected to the bottom tungsten conductive layer, the surface of the side wall semicircular groove is covered with a tungsten material layer, and the lower end of the tungsten material layer is connected to the bottom tungsten conductive layer. Furthermore, the diameter of the semicircular groove on the side wall is 0.15-0.3 mm.

[0008] Furthermore, the diameter of the internal through hole is 0.1-0.2 mm.

[0009] Furthermore, the surface of the bottom tungsten conductive layer and the surface of the tungsten material layer are plated with a nickel-palladium-gold layer. A method for preparing a HTCC ceramic tube shell structure, the method comprising the following steps: Step 1. Laser opening or cavity: Carve out the corresponding cavity, through hole and side wall hole on each layer of raw porcelain tape. Laser opening can achieve very precise aperture size and position, and has smooth hole walls, which helps to improve the adhesion and conductivity of the subsequent metallization process; compared with traditional mechanical drilling, laser opening is fast, efficient and suitable for mass production; the heat-affected zone of the substrate is small, reducing damage and stress to surrounding materials. Complex cavity and through-hole structures can be easily processed to meet special design requirements; the process can be easily automated, reducing manual intervention and improving production consistency; Step 2: Filling holes: Use steel mesh to fill holes in order to ensure that the conductive paste can be accurately and evenly filled into the through holes on the circuit board so that signals can be transmitted between layers. Using steel mesh can improve production efficiency, reduce material waste, and ensure consistency in hole filling quality; Step 3: Printing: Print the corresponding pattern of each layer of raw porcelain tape onto the corresponding raw porcelain tape by screen printing, including printing of side wall holes. Screen printing technology can accurately print conductive paste or other functional materials onto the raw porcelain tape to form the required circuit pattern. The steps include preparing the raw porcelain tape, preparing the conductive paste, making the screen template, screen printing, and drying. It has the advantages of low cost, simple operation, strong adaptability, and good repeatability. Step 4: Forming: stack and press the raw porcelain strips in a preset order. Then use a hot cutting machine to cut them one by one at the cutting line position to produce a single raw porcelain semi-finished product; Step 5, sintering: Place the green ceramic semi-finished product in a high-temperature sintering furnace, and first heat it to 500~600℃ at a slower heating rate. The main purpose of this stage is to remove organic components such as solvents and plasticizers in the green body, which is the debinding process. Slow heating helps prevent the generation of bubbles and ensure the sintering quality. After the organic components are completely burned out, continue to heat to 1375~1650℃ (or 1500~2000℃) at an appropriate rate according to the type of ceramic and thick film metal used, and stay at the highest temperature for several hours for sintering. During this stage, the green porcelain becomes mature and the metal powder is metallized to form a dense and strong ceramic substrate structure. After sintering is completed, the ceramic substrate is cooled to room temperature at a slower cooling rate. This process helps prevent cracks or deformation caused by too fast cooling. The sintered ceramic substrate is subjected to necessary inspections, including appearance, size, strength, electrical properties, etc., to ensure the reliability of its performance; Step 6: Nickel plating: A nickel layer of 1.3um to 8.9um is plated on the sintered porcelain by chemical plating or electroplating. The plating should avoid creeping plating and leakage plating; Step 7, brazing: braze the surrounding frame with the nickel-plated porcelain through a brazing furnace to form a semi-finished product with a frame. When brazing, a suitable heating curve should be used to avoid excessive thermal stress due to excessive heating and causing edge collapse of the porcelain body; Step 8, gold plating: Use an appropriate solvent to clean the HTCC ceramic substrate to remove oil and dust on the surface; put the cleaned substrate into an acid solution for pickling to remove the oxide layer on the surface; after pickling, use an activator to treat the substrate surface to improve the adhesion of the coating. Then first plate a layer of copper on the substrate as a conductive layer for subsequent gold plating; plate a layer of nickel on the copper layer to prevent the gold layer from directly contacting the copper layer and causing the gold to diffuse. Plate a layer of gold on the nickel layer, and the thickness of the gold layer depends on actual needs; after the gold plating is completed, use deionized water to thoroughly clean the substrate to remove the residual chemicals on the surface; put the cleaned substrate into an oven to dry to ensure that the surface of the substrate is dry; finally, inspect the gold plating layer to ensure that the plating is uniform, defect-free, and meets the technical requirements, and finally select qualified products, namely finished products.

[0010] Beneficial effects of the present invention: Compared with the prior art, the present invention realizes signal transmission by introducing internal through holes and side wall holes on the flat ceramic housing. The addition of the side wall holes enables high-frequency signals to form a differential resonance phenomenon, effectively improving the return loss, and solving the problem of poor signal transmission performance in the 20GHz frequency range due to impedance mismatch in a single signal transmission mode. In addition, retaining the side wall holes allows solder wrap angles to be formed on the side wall holes after chip welding, thereby more intuitively detecting the reliability of welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the HTCC ceramic tube shell structure; Figure 2 It is a three-dimensional perspective diagram of the HTCC ceramic shell structure; Figure 3 This is the simulation curve of the 0.15mm side semicircular groove; Figure 4 It is a simulation curve of the side semicircular groove of 0.30mm; Figure 5 It is a structural schematic diagram of comparative example 1; Figure 6 It is a simulation curve diagram of comparative example 1; Figure 7 It is a structural schematic diagram of comparative example 2; Figure 8 It is a simulation curve diagram of comparative example 2; DETAILED DESCRIPTION

[0012] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0013] Example 1: Figure 1-2 A HTCC (CLCC type) ceramic tube shell structure includes a ceramic body 1, the ceramic body 1 is a ceramic tube shell structure, a surrounding frame 9 is arranged around the top, the material of the surrounding frame 9 is Kovar alloy 4J29, the ceramic material used by the ceramic body 1 is 92% black alumina, the co-fired metal material used is tungsten, the metal surface is plated with nickel palladium gold, a plurality of groups of internal through holes 2 and side wall semicircular grooves 3 are arranged around the ceramic body 1, the internal through holes 2 and the side wall semicircular grooves 3 are parallel and equal in number, the internal through holes 2 are filled with tungsten conductive wires 4 as a signal transmission medium, the inner end of the tungsten conductive wire 4 is electrically connected to a bonding finger 5, the bonding finger 5 is arranged around the inner cavity 10 of the ceramic body 1, and the outer end is connected to a bottom tungsten conductive layer 6, the bottom tungsten conductive layer 6 contacts the upper surface of the PCB board 8, the surface of the semicircular groove 3 on the side wall is covered with a tungsten material layer 7, the lower end of the tungsten material layer 7 is connected to the bottom tungsten conductive layer 6, the tungsten material layer 7 of the side wall hole is used as an auxiliary transmission path, one end is connected to the external pin (bottom tungsten conductive layer 6), and the other end is open and not connected to other signal layers; the diameter of the semicircular groove 3 on the side wall is 0.15-0.3mm; the diameter of the internal through hole 2 is 0.1-0.2mm; the surface of the bottom tungsten conductive layer 6 and the surface of the tungsten material layer 7 are plated with a nickel-palladium-gold layer, and the signal is transmitted from the input of the PCB board 8 to the core area of ​​the inner cavity through the internal through hole of the ceramic shell, completing the integrity of the signal loop, and at the same time retaining the metal side wall space as a key link to improve the welding reliability of the ceramic shell. The present invention effectively solves the problem that the signal transmission quality of the ceramic substrate at 20GHz is affected by the impedance mismatch, resulting in discontinuity of the signal, and the signal distortion or low transmission quality in the core area.

[0014] The inner through hole with a diameter of 0.15mm is used as the transmission medium of the signal inside the shell, and the side wall hole with a diameter of 0.15mm is reserved. Figure 3 It can be seen that when the signal frequency band is DC~20G, the return loss S11 is less than -10dB, which has good transmission performance. The addition of the side wall hole makes the high-frequency signal form a differential resonance phenomenon, which effectively improves the return loss at 11~18GHz.

[0015] The inner through hole with a diameter of 0.15 mm is used as the transmission medium of the signal inside the tube shell, and the side wall hole with a diameter of 0.3 mm is reserved. The structure is shown in the first embodiment. The result is as follows Figure 4 As shown in the figure, the increase in the diameter of the sidewall hole improves the transmission performance in the high-frequency band, and the transmission return loss within DC~20GHz is less than -13dB Embodiment 2: A method for preparing a HTCC (CLCC type) ceramic tube shell structure, the method comprising the following steps: Step 1. Laser opening or cavity: Carve out the corresponding cavity, through hole and side wall hole on each layer of raw porcelain tape. Laser opening can achieve very precise aperture size and position, and has smooth hole walls, which helps to improve the adhesion and conductivity of the subsequent metallization process; compared with traditional mechanical drilling, laser opening is fast, efficient and suitable for mass production; the heat-affected zone of the substrate is small, reducing damage and stress to surrounding materials. Complex cavity and through-hole structures can be easily processed to meet special design requirements; the process can be easily automated, reducing manual intervention and improving production consistency; Step 2: Filling holes: Use steel mesh to fill holes in order to ensure that the conductive paste can be accurately and evenly filled into the through holes on the circuit board so that signals can be transmitted between layers. Using steel mesh can improve production efficiency, reduce material waste, and ensure consistency in hole filling quality; Step 3: Printing: Print the corresponding pattern of each layer of raw porcelain tape onto the corresponding raw porcelain tape by screen printing, including printing of side wall holes. Screen printing technology can accurately print conductive paste or other functional materials onto the raw porcelain tape to form the required circuit pattern. The steps include preparing the raw porcelain tape, preparing the conductive paste, making the screen template, screen printing, and drying. It has the advantages of low cost, simple operation, strong adaptability, and good repeatability. Step 4: Forming: stack and press the raw porcelain strips in a preset order. Then use a hot cutting machine to cut them one by one at the cutting line position to produce a single raw porcelain semi-finished product; Step 5, sintering: Place the green ceramic semi-finished product in a high-temperature sintering furnace, and first heat it to 500~600℃ at a slower heating rate. The main purpose of this stage is to remove organic components such as solvents and plasticizers in the green body, which is the debinding process. Slow heating helps prevent the generation of bubbles and ensure the sintering quality. After the organic components are completely burned out, continue to heat to 1375~1650℃ (or 1500~2000℃) at an appropriate rate according to the type of ceramic and thick film metal used, and stay at the highest temperature for several hours for sintering. During this stage, the green porcelain becomes mature and the metal powder is metallized to form a dense and strong ceramic substrate structure. After sintering is completed, the ceramic substrate is cooled to room temperature at a slower cooling rate. This process helps prevent cracks or deformation caused by too fast cooling. The sintered ceramic substrate is subjected to necessary inspections, including appearance, size, strength, electrical properties, etc., to ensure the reliability of its performance; Step 6: Nickel plating: A nickel layer of 1.3um to 8.9um is plated on the sintered porcelain by chemical plating or electroplating. The plating should avoid creeping plating and leakage plating; Step 7, brazing: braze the surrounding frame with the nickel-plated porcelain through a brazing furnace to form a semi-finished product with a frame. When brazing, a suitable heating curve should be used to avoid excessive thermal stress due to excessive heating and causing edge collapse of the porcelain body; Step 8, gold plating: Use an appropriate solvent to clean the HTCC ceramic substrate to remove oil and dust on the surface; put the cleaned substrate into an acid solution for pickling to remove the oxide layer on the surface; after pickling, use an activator to treat the substrate surface to improve the adhesion of the coating. Then first plate a layer of copper on the substrate as a conductive layer for subsequent gold plating; plate a layer of nickel on the copper layer to prevent the gold layer from directly contacting the copper layer and causing the gold to diffuse. Plate a layer of gold on the nickel layer, and the thickness of the gold layer depends on actual needs; after the gold plating is completed, use deionized water to thoroughly clean the substrate to remove the residual chemicals on the surface; put the cleaned substrate into an oven to dry to ensure that the surface of the substrate is dry; finally, inspect the gold plating layer to ensure that the plating is uniform, defect-free, and meets the technical requirements, and finally select qualified products, namely finished products.

[0016] Comparative Example 1: A CLCC type ceramic shell structure that uses internal through-holes to transmit signals; the ceramic material is 92% black alumina, the co-fired metal material used is tungsten, and the metal surface is plated with nickel, palladium and gold; a bonding finger is provided inside the cavity (the input port of the chip signal inside the core area), and a through-hole with an aperture of 0.15mm is used inside the shell as a pure medium for the signal. Its structure is recorded as internal through-hole transmission, such as Figure 5 As shown. Figure 6 It can be seen that when the signal frequency band is DC~20G, the return loss S 11 <-10dB, with good transmission performance. But in 11~18GHz, the return loss S11 >-10dB, the signal reflectivity reaches 30%, causing more serious distortion.

[0017] Comparative Example 2: A CLCC type ceramic tube shell structure using side wall holes to transmit signals; the ceramic material is 92% black alumina, the co-fired metal material used is tungsten, and the metal surface is plated with nickel palladium gold; a bonding finger (input port of the chip signal inside the core area) is provided inside the cavity, and a side wall hole with an aperture of 0.15 mm is used as a signal transmission medium. The structure is recorded as side wall hole transmission, such as Figure 7 shown.

[0018] Depend on Figure 8 It can be seen that within the signal frequency band of DC~20G, the return loss S11 gradually increases with the increase of frequency, and is greater than -10dB after 14GHz. Therefore, the transmission performance is poor in the high frequency band.

[0019] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A HTCC ceramic tube shell structure, characterized in that: The invention comprises a ceramic body (1), wherein a plurality of groups of internal through holes (2) and side wall semicircular grooves (3) are arranged around the ceramic body (1), the internal through holes (2) and the side wall semicircular grooves (3) are parallel to each other and the number is equal, the internal through holes (2) are filled with tungsten conductive wires (4), the inner ends of the tungsten conductive wires (4) are electrically connected to bonding fingers (5) arranged in the inner cavity of the ceramic body (1), and the outer ends are connected to the bottom tungsten conductive layer (6), the groove surfaces of the side wall semicircular grooves (3) are covered with a tungsten material layer (7), and the lower ends of the tungsten material layer (7) are connected to the bottom tungsten conductive layer (6).

2. The HTCC ceramic tube shell structure according to claim 1, characterized in that: The diameter of the semicircular groove (3) on the side wall is 0.15-0.3 mm.

3. The HTCC ceramic tube shell structure according to claim 1, characterized in that: The inner through hole (2) has a diameter of 0.1-0.2 mm.

4. The HTCC ceramic tube shell structure according to claim 1, characterized in that: The surface of the bottom tungsten conductive layer (6) and the surface of the tungsten material layer (7) are plated with a nickel-palladium-gold layer.

5. The method for preparing a HTCC ceramic tube shell structure according to claim 1, characterized in that: The method comprises the following steps: Step 1: Laser opening holes or cavities: Use laser to carve corresponding cavities, through holes and side wall holes on each layer of raw porcelain tape; Step 2: Filling holes: Use steel mesh to fill holes; Step 3, printing: printing the corresponding pattern of each layer of raw porcelain tape onto the corresponding raw porcelain tape by silk screen printing, including printing of side wall holes; Step 4: Forming: stack and press the green porcelain strips in a preset order, and then cut them one by one by a hot cutting machine aligned with the cutting line position to form a single green porcelain semi-finished product; Step 5: Sintering: Place the green ceramic semi-finished product in a high-temperature sintering furnace and heat it to 500-600°C at a relatively slow heating rate. After the organic components are completely burned off, continue to heat it to 1375-1650°C at a set speed according to the types of ceramics and thick film metals used, and stay at the highest temperature for several hours for sintering. Step 6: Nickel plating: A nickel layer of 1.3um to 8.9um is plated on the sintered porcelain by chemical plating or electroplating; Step 7, brazing: braze the surrounding frame with the nickel-plated porcelain through a brazing furnace to form a semi-finished product including the frame; a set temperature rise curve should be used during brazing; Step 8, gold plating: Use solvent to clean the HTCC ceramic substrate; put the cleaned substrate into an acid solution for pickling; after pickling, use an activator to treat the surface of the substrate; then plate a layer of copper on the substrate as a conductive layer for subsequent gold plating; plate a layer of nickel on the copper layer; plate a layer of gold on the nickel layer; after gold plating, use deionized water to thoroughly clean the substrate; put the cleaned substrate into an oven for drying; finally, inspect the gold-plated layer to ensure that the coating is uniform, defect-free, and meets the technical requirements, and finally select qualified products, i.e. finished products.

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