High-reliability DPC ceramic substrate and preparation method thereof

Abstract

The application provides a high-reliability DPC ceramic substrate and a preparation method thereof, and the preparation method comprises the following steps: (1) after an active metal seed layer is arranged on the upper and lower surfaces of a ceramic substrate, sintering treatment is performed to obtain a sintered ceramic substrate; (2) a patterned mask layer is formed on the surface of the active metal seed layer of the sintered ceramic substrate, and copper layer thickening treatment is performed on the exposed surface of the active metal seed layer; (3) the patterned mask layer is removed, and the active metal seed layer not covered by the copper layer is etched and removed to form an independent circuit pattern, thereby obtaining the high-reliability DPC ceramic substrate. Through the sintering treatment after the introduction of the active metal seed layer, the stress concentration of the thickened copper layer and the ceramic substrate during the cold and hot cycle is effectively slowed down, and the reliability of the DPC ceramic substrate is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of ceramic substrate technology, and in particular to a high-reliability DPC ceramic substrate and its preparation method. Background Technology

[0002] The applications of high-power semiconductor devices are expanding rapidly, now widely covering core components in high-power LED lighting, lasers, 5G communication RF devices, and high-end aerospace electronic equipment. However, with the continuous increase in device power, heat dissipation has become increasingly prominent. Currently used heat dissipation substrates are unable to quickly dissipate the heat accumulated inside the chip, leading to increased junction temperature, performance degradation, and shortened lifespan. Therefore, developing heat dissipation substrates with low thermal resistance, high thermal conductivity, and high reliability has become a key requirement in high-power device packaging systems.

[0003] DPC (Direct Plated Copper) ceramic substrates, also known as direct copper-plated ceramic substrates, are currently the mainstream technology for high-power heat dissipation substrates. The process involves first sputtering a seed layer onto the ceramic substrate surface, then creating the circuit pattern through exposure, development, and etching processes, and finally increasing the copper layer thickness through electroplating or chemical plating to complete the final DPC substrate fabrication. However, the DPC process relies on the mechanical interlocking between the copper layer, seed layer, and ceramic layer for bonding, which is a physical bonding process and suffers from low bonding strength. Furthermore, stress concentration can easily occur between the metal and ceramic layers during thermal cycling, leading to delamination failure between the metal and ceramic layers.

[0004] CN115279042A discloses a method for preparing a chemically plated nickel-gold DPC ceramic substrate, comprising the following steps: S1. Cleaning the ceramic substrate; S2. Sputtering a TiW layer as the bottom layer onto the ceramic substrate, and then sputtering a Cu layer on top of it; S3. Cleaning the surface of the ceramic substrate after sputtering, and performing film deposition, exposure, and development on the surface to create a pattern transfer; S4. Electroplating copper to thicken the ceramic substrate; S5. Removing the dry film on the surface of the copper plating solution and etching the residual copper layer between the developed patterns, then immersing the copper-clad laminate with hydrogen peroxide to etch the TiW layer; S6. Grinding the surface of the copper-clad laminate to remove the oxide layer and grinding it to a smooth surface, followed by sandblasting to remove grinding marks; S7. Plating nickel-gold onto the surface of the copper-clad laminate, cleaning the surface of the copper-clad laminate, and sealing the holes to obtain the chemically plated nickel-gold DPC ceramic substrate.

[0005] CN114501857A discloses a method for fabricating a multilayer ceramic circuit board, which is formed by stacking and bonding multiple electroplated ceramic substrates (DPCs). First, a DPC ceramic substrate containing a surface circuit layer and vertical interconnect metal pillars is prepared using a patterned electroplating process. Then, metal solder is prepared on the circuit layer of the DPC ceramic substrate. Multiple DPC ceramic substrates are stacked, aligned, and bonded to achieve a stable mechanical connection and electrical interconnection between the DPC substrates. Finally, high-temperature resistant insulating adhesive is filled between the DPC substrates, and after curing, the multilayer ceramic circuit board is obtained.

[0006] CN107978567A discloses a three-dimensional ceramic substrate, which includes a planar ceramic substrate and a ceramic cavity disposed on the planar ceramic substrate. The planar ceramic substrate is an electroplated ceramic substrate (DPC), a high-temperature bonded ceramic substrate (DBC), a thick-film ceramic substrate (TFC), or a ceramic substrate prepared by other processes, and its surface is provided with a metal circuit layer. The ceramic cavity is prepared by low-temperature curing of non-fired ceramic slurry, and its structure is annular, square, rectangular, or other closed ring.

[0007] However, the metal and ceramic layers of the aforementioned ceramic substrate are prone to stress concentration during thermal cycling, leading to delamination failure between the metal and ceramic layers. Summary of the Invention

[0008] In view of the problems existing in the prior art, the present invention provides a high-reliability DPC ceramic substrate and its preparation method. By setting an active metal seed layer on the ceramic surface and then performing sintering treatment, the sputtering seed layer of the traditional DPC substrate is replaced, thereby improving the bonding strength of the DPC substrate, effectively reducing stress concentration between the copper layer and the ceramic during thermal cycling, and improving the reliability of the DPC ceramic substrate.

[0009] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a high-reliability DPC ceramic substrate, the method comprising the following steps: (1) After setting active metal seed layers on the upper and lower surfaces of the ceramic substrate, sintering is performed to obtain the sintered ceramic substrate. (2) A patterned mask layer is formed on the surface of the active metal seed layer of the sintered ceramic substrate, and a copper layer thickening treatment is performed on the exposed surface of the active metal seed layer. (3) Remove the patterned mask layer and etch away the active metal seed layer that is not covered by the copper layer to form an independent circuit pattern and obtain the high reliability DPC ceramic substrate.

[0010] The method for preparing a high-reliability DPC ceramic substrate according to the present invention first involves depositing active metal seed layers on the upper and lower surfaces of the ceramic substrate, followed by sintering. Compared with the traditional method of forming the seed layer by sputtering, the DPC ceramic substrate has a higher bonding strength. Subsequently, a patterned mask layer is formed on the surface of the active metal seed layer of the sintered ceramic substrate, and a copper layer thickening treatment is performed on the exposed surface of the active metal seed layer. The introduction of the active metal seed layer can effectively reduce the stress concentration between the thickened copper layer and the ceramic substrate during thermal cycling, significantly improving the reliability of the DPC ceramic substrate. The failure rate of the DPC ceramic substrate after thermal shock is significantly increased.

[0011] Preferably, the ceramic substrate in step (1) includes any one of an alumina ceramic substrate, an aluminum nitride ceramic substrate, or a silicon nitride ceramic substrate.

[0012] Preferably, the thickness of the ceramic substrate is 0.25~1mm, for example, it can be 0.25mm, 0.4mm, 0.55mm, 0.7mm, 0.85mm or 1mm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0013] Preferably, the active metal seed layer in step (1) comprises a copper-based alloy with a mass fraction of 50% to 90%, and the remainder is active metal, such as 50%, 60%, 70%, 80%, 90% or 95%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0014] Preferably, the copper-based alloy includes any one of copper-silver alloy, copper-tin alloy, copper-zinc alloy, or copper-nickel-zirconium alloy.

[0015] Preferably, the active metal element includes any one or a combination of at least two of Ti, Zr, Hf, Cr, V, Si or Al, wherein typical but non-limiting combinations include combinations of Ti and Zr, Hf and Cr, V and Ti, Zr and Cr, or Si and Al.

[0016] Preferably, the method of setting the active metal seed layer in step (1) includes any one of screen printing, spraying or roller coating.

[0017] Preferably, the sintering temperature in step (1) is 800~950℃, for example, it can be 800℃, 825℃, 850℃, 875℃, 900℃ or 950℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] The present invention preferably involves setting an active metal seed layer on the upper and lower surfaces of the ceramic substrate, followed by sintering at a temperature of 800~950℃. This method offers advantages such as sufficient interfacial reaction, controllable thermal stress, and the ability to achieve high-strength metallurgical bonding. Lower sintering temperatures result in insufficient diffusion of the active metal, weak interfacial bonding, and poor conductivity; higher sintering temperatures lead to an increase in brittle phases at the interface and abnormal grain growth, affecting the reliability of the DPC ceramic substrate.

[0019] Preferably, the sintering time is 10 to 60 minutes, for example, it can be 10 minutes, 20 minutes, 25 minutes, 30 minutes, 40 minutes, 50 minutes or 60 minutes, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] Preferably, the sintering process is carried out in a vacuum or inert atmosphere.

[0021] Preferably, the inert atmosphere includes a nitrogen atmosphere and / or an argon atmosphere.

[0022] Preferably, the method of forming the patterned mask layer in step (2) includes wet film or photoresist coating.

[0023] Preferably, the copper layer thickening method in step (2) includes electroplating or chemical plating.

[0024] Preferably, the thickness of the copper layer in step (2) is 5~75μm, for example, it can be 5μm, 20μm, 35μm, 50μm, 65μm or 75μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] The present invention does not impose detailed limitations on the method of removing the patterned mask layer and etching away the active metal seed layer not covered by the copper layer in step (3) to form an independent circuit pattern. Conventional operating methods in the art can be used.

[0026] As a preferred technical solution of the present invention, the preparation method includes the following steps: (1) After setting an active metal seed layer on the upper and lower surfaces of a ceramic substrate with a thickness of 0.25~1mm, a sintering treatment is performed at a temperature of 800~950℃ for 10~60min to obtain a sintered ceramic substrate; the ceramic substrate includes any one of alumina ceramic substrate, aluminum nitride ceramic substrate or silicon nitride ceramic substrate; the active metal seed layer includes 50%~90% copper-based alloy by mass, with the remainder being active metal; the copper-based alloy includes any one of copper-silver alloy, copper-tin alloy, copper-zinc alloy or copper-nickel-zirconium alloy; the active metal element includes any one or a combination of at least two of Ti, Zr, Hf, Cr, V, Si or Al; the active metal seed layer is set by any one of screen printing, spraying or roller coating; the sintering treatment is performed in a vacuum or inert atmosphere; the inert atmosphere includes nitrogen atmosphere and / or argon atmosphere. (2) A patterned mask layer is formed by coating the surface of the active metal seed layer of the sintered ceramic substrate with wet film or photoresist, and a copper layer is thickened by electroplating or chemical plating on the exposed surface of the active metal seed layer; the thickness of the copper layer is 5~75μm. (3) Remove the patterned mask layer and etch away the active metal seed layer that is not covered by the copper layer to form an independent circuit pattern and obtain the high reliability DPC ceramic substrate.

[0027] In a second aspect, the present invention also provides a high-reliability DPC ceramic substrate prepared by the preparation method of the high-reliability DPC ceramic substrate described in the first aspect.

[0028] Preferably, the thickness of the active metal seed layer in the high-reliability DPC ceramic substrate is 5~25μm, for example, it can be 5μm, 8μm, 11μm, 14μm, 17μm, 20μm or 25μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] The high-reliability DPC ceramic substrate of this invention features an active metal seed layer with a thickness of 5-25 μm, offering advantages such as stable adhesion, good thermal matching, and uniform copper plating growth. A thinner active metal seed layer leads to insufficient bonding sites with the ceramic substrate, making subsequent copper plating prone to peeling and pinhole defects, thus reducing interfacial bonding strength. Conversely, a thicker active metal seed layer results in increased internal stress accumulation, making it prone to microcracks, increasing the overall thermal resistance of the DPC ceramic substrate, reducing heat dissipation efficiency, and raising production costs and the difficulty of subsequent etching processes. The high-reliability DPC ceramic substrate of this invention exhibits high bonding strength, effectively mitigating stress concentration between the copper layer and the ceramic substrate during thermal cycling, and achieving a thermal shock failure cycle of over 200 times.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects: The method for preparing a high-reliability DPC ceramic substrate provided by this invention is reasonably designed and simple to operate. By introducing an active metal seed layer, not only is the bonding strength of the ceramic substrate improved, but the stress concentration between the thickened copper layer and the ceramic substrate during thermal cycling is also effectively reduced, resulting in a high-reliability DPC ceramic substrate that is suitable for widespread application. Attached Figure Description

[0031] Figure 1 This is a flowchart of the preparation method of the high-reliability DPC ceramic substrate in Embodiment 1 of the present invention.

[0032] Figure 2 This is a schematic diagram of the structure of the high-reliability DPC ceramic substrate prepared in Example 1 of the present invention.

[0033] In the figure: 1-Ceramic substrate; 2-Active metal seed layer; 3-Copper layer. Detailed Implementation

[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0036] Example 1 This embodiment provides a method for preparing a high-reliability DPC ceramic substrate, the flowchart of which is shown below. Figure 1 As shown; the preparation method includes the following steps: (1) After setting an active metal seed layer with a thickness of 10 μm on the upper and lower surfaces of a ceramic substrate with a thickness of 0.38 mm, the substrate is sintered at a temperature of 900 °C for 40 min to obtain the sintered ceramic substrate. The ceramic substrate is an aluminum nitride ceramic substrate; the active metal seed layer comprises 70% copper-based alloy by mass, with the remainder being active metal; the copper-based alloy is a copper-silver alloy; the active metal element is Ti; the active metal seed layer is set by screen printing; the sintering process is carried out in a vacuum. (2) A patterned mask layer is formed by coating the surface of the active metal seed layer of the sintered ceramic substrate with photoresist, and a copper layer is thickened by electroplating on the exposed surface of the active metal seed layer; the thickness of the copper layer is 40 μm. (3) Remove the patterned mask layer and etch away the active metal seed layer that is not covered by the copper layer to form an independent circuit pattern and obtain the high reliability DPC ceramic substrate.

[0037] A schematic diagram of the structure of the high-reliability DPC ceramic substrate prepared in this embodiment is shown below. Figure 2 As shown.

[0038] The high-reliability DPC ceramic substrate includes a copper layer 3, an active metal seed layer 2, a ceramic substrate 1, and the copper layer 3 stacked together. The ceramic substrate 1 is an aluminum nitride ceramic substrate.

[0039] The copper layer 3 has a thickness of 40 μm, the active metal seed layer 2 has a thickness of 10 μm, and the ceramic substrate 1 has a thickness of 0.38 mm.

[0040] Comparative Example 1 This comparative example provides a method for preparing a DPC ceramic substrate, the method comprising the following steps: (1) Sputtered metal seed layers were obtained on the upper and lower surfaces of a ceramic substrate with a thickness of 0.38 mm by target sputtering method; The ceramic substrate is an aluminum nitride ceramic substrate; the sputtered metal seed layer includes a metal conductive layer of 80% pure Cu by mass, and the remainder is a metal adhesion layer of pure Ti; the active metal seed layer is set by target sputtering; the sputtering process is carried out in a vacuum; (2) A patterned mask layer is formed by coating the sputtered metal seed layer with photoresist, and a copper layer is thickened by electroplating on the exposed metal seed layer surface; the thickness of the copper layer is 40 μm. (3) Remove the patterned mask layer and etch away the sputtered metal seed layer that is not covered by the copper layer to form an independent circuit pattern and obtain the DPC ceramic substrate.

[0041] The DPC ceramic substrate prepared in this comparative example includes a copper layer, a sputtered metal seed layer, an aluminum nitride ceramic substrate, a sputtered metal seed layer, and a copper layer stacked together.

[0042] The copper layer has a thickness of 40 μm, and the sputtered metal seed layer consists of a 2 μm thick Ti adhesion layer and an 8 μm thick Cu conductive layer. The Ti adhesion layer is close to the aluminum nitride ceramic substrate. The aluminum nitride ceramic substrate has a thickness of 0.38 mm.

[0043] The DPC ceramic substrates in Example 1 and Comparative Example 1 underwent 5 tests, and the results of the number of thermal shock failures are shown in Table 1. Example 2 This embodiment provides a method for preparing a high-reliability DPC ceramic substrate, the method comprising the following steps: (1) After setting an active metal seed layer with a thickness of 10 μm on the upper and lower surfaces of a ceramic substrate with a thickness of 0.38 mm, the substrate is sintered at 800 °C for 60 min to obtain a sintered ceramic substrate; the ceramic substrate is an aluminum nitride ceramic substrate; the active metal seed layer comprises 90% copper-based alloy by mass, with the remainder being active metal; the copper-based alloy is a copper-tin alloy; the active metal element is Zr; the active metal seed layer is set by spraying; the sintering process is carried out in a nitrogen atmosphere; (2) A patterned mask layer is formed on the surface of the active metal seed layer of the sintered ceramic substrate by using a wet film, and a copper layer is thickened by chemical plating on the exposed surface of the active metal seed layer; the thickness of the copper layer is 27.5 μm. (3) Remove the patterned mask layer and etch away the active metal seed layer that is not covered by the copper layer to form an independent circuit pattern and obtain the high reliability DPC ceramic substrate.

[0044] Comparative Example 2 This comparative example provides a method for preparing a DPC ceramic substrate, which is the same as that of Comparative Example 1 except that the thickness of the copper layer is 27.5 μm.

[0045] The DPC ceramic substrates in Example 2 and Comparative Example 2 underwent 5 tests, and the results of the number of thermal shock failures are shown in Table 2. Example 3 This embodiment provides a method for preparing a high-reliability DPC ceramic substrate, the method comprising the following steps: (1) After setting an active metal seed layer with a thickness of 10 μm on the upper and lower surfaces of a ceramic substrate with a thickness of 0.38 mm, the substrate is sintered at 950 °C for 10 min to obtain a sintered ceramic substrate; the ceramic substrate is an alumina ceramic substrate; the active metal seed layer comprises 50% copper-based alloy by mass, and the remainder is active metal; the copper-based alloy is a copper-zinc alloy; the active metal element is Hf; the active metal seed layer is set by roller coating; the sintering process is carried out in an argon atmosphere; (2) A patterned mask layer is formed by coating the surface of the active metal seed layer of the sintered ceramic substrate with photoresist, and a copper layer is thickened by electroplating on the exposed surface of the active metal seed layer; the thickness of the copper layer is 15 μm. (3) Remove the patterned mask layer and etch away the active metal seed layer that is not covered by the copper layer to form an independent circuit pattern and obtain the high reliability DPC ceramic substrate.

[0046] Comparative Example 3 This comparative example provides a method for preparing a DPC ceramic substrate, which is the same as that of Comparative Example 1 except that the thickness of the copper layer is 15 μm.

[0047] The DPC ceramic substrates in Example 3 and Comparative Example 3 underwent 5 tests, and the results of the number of thermal shock failures are shown in Table 3. As can be seen from the results in Tables 1-3, the DPC ceramic substrates obtained by the high-reliability DPC ceramic substrate preparation method provided by the present invention in Examples 1-3 have a higher number of thermal shock failures than the DPC ceramic substrates obtained by the conventional preparation method in Comparative Examples 1-3. The high-reliability DPC ceramic substrate preparation method provided by the present invention first sets active metal seed layers on the upper and lower surfaces of the ceramic substrate and performs sintering treatment; then, a patterned mask layer is formed on the surface of the active metal seed layer of the sintered ceramic substrate, and a copper layer thickening treatment is performed on the exposed surface of the active metal seed layer; finally, the patterned mask layer is removed, and the active metal seed layer not covered by the copper layer is etched away to form an independent circuit pattern. Among them, the introduction of the active metal seed layer not only improves the bonding strength of the ceramic substrate, but also effectively reduces the stress concentration between the thickened copper layer and the ceramic substrate during thermal cycling. The resulting DPC ceramic substrate can achieve a thermal shock failure count of 200 to 450 times, with high reliability.

[0048] It should be noted that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a high-reliability DPC ceramic substrate, characterized in that, The preparation method includes the following steps: (1) After setting active metal seed layers on the upper and lower surfaces of the ceramic substrate, sintering is performed to obtain the sintered ceramic substrate. (2) A patterned mask layer is formed on the surface of the active metal seed layer of the sintered ceramic substrate, and a copper layer thickening treatment is performed on the exposed surface of the active metal seed layer. (3) Remove the patterned mask layer and etch away the active metal seed layer that is not covered by the copper layer to form an independent circuit pattern and obtain the high reliability DPC ceramic substrate.

2. The preparation method according to claim 1, characterized in that, The ceramic substrate in step (1) includes any one of alumina ceramic substrate, aluminum nitride ceramic substrate or silicon nitride ceramic substrate; Preferably, the thickness of the ceramic substrate is 0.25~1mm.

3. The preparation method according to claim 1 or 2, characterized in that, The active metal seed layer in step (1) comprises 50% to 90% copper-based alloy by mass, with the remainder being active metal; Preferably, the copper-based alloy includes any one of copper-silver alloy, copper-tin alloy, copper-zinc alloy, or copper-nickel-zirconium alloy; Preferably, the active metal element includes any one or a combination of at least two of Ti, Zr, Hf, Cr, V, Si, or Al.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The method of setting the active metal seed layer in step (1) includes any one of screen printing, spraying or roller coating.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The sintering temperature in step (1) is 800~950℃; Preferably, the sintering time is 10-60 min; Preferably, the sintering process is carried out in a vacuum or inert atmosphere; Preferably, the inert atmosphere includes a nitrogen atmosphere and / or an argon atmosphere.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The method of forming the patterned mask layer in step (2) includes wet film or photoresist coating.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The copper layer thickening method in step (2) includes electroplating or chemical plating.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The thickness of the copper layer in step (2) is 5~75μm.

9. A high-reliability DPC ceramic substrate prepared by the preparation method of the high-reliability DPC ceramic substrate according to any one of claims 1 to 8.

10. The high-reliability DPC ceramic substrate according to claim 9, characterized in that, The thickness of the active metal seed layer in the high-reliability DPC ceramic substrate is 5~25μm.

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