Conductive paste, metallized substrate and metallization process for manufacturing metallized substrate

Abstract

The invention discloses a conductive paste, a metallized substrate and a metallization process for manufacturing the metallized substrate, the conductive paste comprises metal particles, the particle size of the metal particles is 0.1-10 [mu] m, and the mass ratio of the metal particles is 80-98%; in the metallization process, a copper layer is arranged on the hole wall of a through hole or a blind hole of a substrate, then conductive slurry is filled in the hole with the copper layer, heating sintering treatment is carried out, and after heating sintering is carried out in an inert gas atmosphere at the temperature of less than or equal to 300 DEG C, metal particles can be fused to form a connection structure or a eutectic structure. A reinforcing layer can be formed between the nano metal particles and the copper layer, and the reinforcing layer is a metal bonding layer or an intermetallic compound layer. The metallization mode is suitable for a through hole or a blind hole of a glass / silicon / ceramic substrate with a high aspect ratio and a micro aperture, and the technical problems that complete filling is difficult to achieve and filling defects exist in an existing electroplating process, the electrical resistivity of conductive paste is high, and the interface bonding force is insufficient can be solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of packaging, and particularly relates to a conductive paste, a metalized substrate and a metalization process for manufacturing the metalized substrate. BACKGROUND

[0002] Glass through via (TGV) technology is derived from through silicon via (TSV) technology. With the development of advanced packaging technology towards three-dimensional integration and miniaturization, TSV / TGV technology is widely used in MEMS sensors, radio frequency devices and three-dimensional packaging due to its excellent insulation, high frequency characteristics and thermal stability. Glass through via (TGV) technology includes glass through via formation, glass through via metallization and multi-layer bonding steps. The process for preparing TGV glass through via is also generally applicable to the preparation of glass blind via. The glass blind via filled with metal can realize signal shielding function and plays a key role in specific devices. However, the glass through via / blind via metallization process with high aspect ratio and micro-pore diameter still faces severe challenges.

[0003] The traditional TGV metallization filling methods mainly include chemical vapor deposition, physical vapor deposition, electroless plating and electroplating. The most common method is electroplating. However, the traditional electroplating copper filling method often fails to achieve complete filling when facing micro vias with a depth-to-diameter ratio of more than 10:1, and is prone to form holes or cracks. In addition, the conductive paste used in the general TGV metallization filling method also has problems such as high resistivity and insufficient interfacial bonding force. SUMMARY

[0004] In view of the above technical problems, the present application provides a conductive paste, a metalized substrate and a metalization process for manufacturing the metalized substrate, which is particularly suitable for glass through via or blind via with high aspect ratio (10:1-60:1) and micro-pore diameter (10-70 μm), and is also suitable for silicon or ceramic through via / blind via.

[0005] The technical scheme of the present application is as follows:

[0006] The present application relates to a conductive paste, which comprises metal particles, the particle size of the metal particles is 0.1-10 μm, and the mass of the metal particles accounts for 80-98% of the total mass of the conductive paste.

[0007] The conductive paste is of sintering type. After the conductive paste is filled into a hole provided with a copper layer and heated and sintered under an inert gas atmosphere at ≤300℃, the metal particles can form a connecting structure or a eutectic structure, and the metal particles can form a reinforcing layer with the copper layer, the reinforcing layer being a metal bonding layer or an intermetallic compound layer.

[0008] Preferably, the metal particles are at least one of gold, silver, copper, nickel, tin, silver-coated copper, silver-coated nickel and silver-coated glass particles.

[0009] After sintering at 150-300℃, the metal particles can melt to form a connecting structure, and a dense metal bonding layer can be formed between the metal particles and the copper layer through atomic diffusion.

[0010] Preferably, the conductive paste is a nano-silver paste or a nano-copper paste, wherein the metal particles are silver or copper, and the particle size D50 of the metal particles is 0.01-1 μm. From the perspective of sintering and oxidation resistance, the particle size D50 of the silver or copper particles is preferably 0.1-0.5 μm, and from the perspective of ion migration and nucleation with the electroplated layer, the particle size D50 of the nano-copper particles is more preferably 0.1-0.3 μm. The sintering temperature of the nano-particles is ≤300℃, and the nano-copper particles can form a sintering neck connecting structure, and the nano-particles can easily diffuse to the electroplated layer during the heating and melting process, thereby forming a metal bonding layer between the electroplated copper layer.

[0011] The paste of the present application is of a sintering type. After the paste is inserted into a hole, the resin inside the paste is hardened by heating, and the metal powder partially or completely melts to form a pure metal conductive path. In addition, the metal powder can directly form a metal connection with the metal substrate through melting, and the bonding force and conductivity are both good.

[0012] Preferably, the thickness of the metal bonding layer is 0.01 μm-10 μm.

[0013] Preferably, the metal particles are composed of low-melting-point metal powder and high-melting-point metal powder, and the mass ratio of the low-melting-point metal powder to the high-melting-point metal powder is 1:0.5-1:5. The melting point of the low-melting-point metal powder is 100-300℃, and the melting point of the high-melting-point metal powder is 600-1100℃.

[0014] When heated to 100-300℃, the low-melting-point metal melts to form a liquid phase, and the molten low-melting-point metal instantly forms a eutectic structure with the high-melting-point metal. The low-melting-point metal can also form an intermetallic compound (IMC) layer with the copper layer through an interfacial reaction.

[0015] Preferably, the low-melting-point metal powder is tin-lead alloy, tin-bismuth alloy, tin-indium alloy, tin-silver-copper alloy, or tin, and the high-melting-point metal powder is gold, silver, or copper. From the perspective of conductivity and ion migration characteristics, copper powder is more preferably used as the high-melting-point metal, and a Cu-X eutectic structure can be formed between copper and the low-melting-point metal.

[0016] Preferably, the thickness of the intermetallic compound layer is 0.1-3 μm. For example, the molten tin ball reacts with copper to form an IMC reaction layer, Cu3Sn, Cu6Sn5, and the presence of this reaction layer can improve the intermetallic welding strength.

[0017] Preferably, the conductive paste further comprises a binder and a solvent, the binder is at least one of epoxy resin, polyurethane, phenolic resin, acrylic resin, silicon resin, and the solvent is at least one of ethylene glycol, glycerol, isobutyl alcohol, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether, diethylene glycol ethyl ether, diethylene glycol methyl ether, diethylene glycol butyl ether, diethylene glycol butyl ether acetate, terpineol, benzyl alcohol, ethyl acetate, and butyl acetate;

[0018] Preferably, the mass of the binder accounts for 2-10% of the total mass of the conductive paste, and the mass of the solvent accounts for 1-10% of the total mass of the conductive paste.

[0019] Preferably, the conductive paste further comprises a small amount of additives, and the additives include dispersants, curing agents, coupling agents, etc. according to needs.

[0020] The application further relates to a metallization process using the conductive paste.

[0021] (1) forming a copper layer on the wall of a through hole or a blind hole of a substrate; wherein the substrate is a glass, ceramic or silicon substrate, the depth-diameter ratio of the through hole or the blind hole is 10:1-60:1, and the copper layer is formed on the wall of the hole by a magnetron sputtering method or an electroplating method, or a combination of the two methods.

[0022] (2) filling the conductive paste into the hole with the copper layer;

[0023] (3) performing a heating sintering treatment on the product obtained in the step (2), and the heating sintering temperature is less than or equal to 300°C in an inert gas atmosphere, the metal particles in the conductive paste can be fused to form a connecting structure or a eutectic structure, and the metal particles can form a reinforcing layer with the copper layer, and the reinforcing layer is a metal bonding layer or an intermetallic compound layer.

[0024] Preferably, the diameter of the through hole or the blind hole of the substrate is 10-70 μm, and the thickness of the copper layer in the step (1) is 0.1-10 μm.

[0025] Preferably, in the step (2), the conductive copper paste is filled by a vacuum printing process, and the printing machine cavity is vacuum, and the vacuum degree is 20 Pa-1000 Pa, preferably 20 Pa-100 Pa. The vacuum printing process can be performed by a vacuum plug hole machine, a vacuum screen printing machine or a vacuum resin plug hole machine.

[0026] Preferably, in the step (3), the sintering is performed in a nitrogen atmosphere.

[0027] The application further relates to a metallized substrate prepared by the metallization process.

[0028] The application has the following beneficial effects:

[0029] (1) The metallization method of the present application is suitable for holes with a high aspect ratio of 10:1-60:1 and a hole diameter of 10-70 μm. The hole wall is treated by electroplating to form a copper layer, and then the hole is filled with a slurry which can provide conductivity, air tightness and heat dissipation effect. The copper layer can provide good conductivity and can be used in the field of high conductivity. Meanwhile, the slurry contains components which can be sintered with the electroplated copper layer. During the heating process, the metal particles can form a connecting structure or eutectic structure, and the nano metal particles can form a metal bonding layer or intermetallic compound layer between the copper layer, thereby providing good conductivity and adhesion.

[0030] (2) The present application provides a metallization process which is suitable for the metallization of through holes or blind holes of glass / ceramic / silicon, especially the through holes / blind holes of glass substrates. In the metallization process, the hole plugging method is simple and easy to operate. Compared with the traditional electroplating hole plugging metallization process, the present application has the advantages of low cost, short process flow and high process efficiency. The single-hole filling time is much lower than that of the conventional electroplating hole plugging process, and the problem of copper electrode explosion from the hole due to CTE mismatch in the electroplating process can be solved. BRIEF DESCRIPTION OF DRAWINGS

[0031] The present application will be further described below in conjunction with the accompanying drawings and examples:

[0032] Figure 1 : X-ray observation of the filling state of the hole after hole plugging in Example 1;

[0033] Figure 2 : Partial cross-sectional view of the product after sintering in Example 1. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions and advantages of the present application clearer and more intelligible, the present application will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present application. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present application.

[0035] Example 1

[0036] A through hole array was prepared on a glass substrate with a hole diameter of 50 μm and a hole depth of 500 μm, and the aspect ratio was 10:1. The glass substrate was used as the object, and the glass through hole metallization manufacturing method included the following steps:

[0037] (1) A pulse electroplating process was used to deposit a 2 μm thick copper layer on the hole wall.

[0038] (2) The conductive copper paste is filled by a vacuum hole filling machine, the pressure of the vacuum cavity is adjusted to 80 Pa, the hardness of the scraper is 85, the steel plate is printed, and the printing speed is 50 mm / s.

[0039] The conductive copper paste used is a nano-sintered copper paste, and the metal phase in the paste includes nano copper particles.

[0040] The components are as follows (mass percentage): D50=150nm copper powder 91%, epoxy resin 2%, terpineol 6%, dispersant 0.5%, and curing agent 0.5%.

[0041] Preparation method: nano copper powder is added to a solvent, mixed uniformly by a self-rotation and revolution stirring machine, then epoxy resin is added, other additives are added after stirring, and the viscosity is tested by a Brookfield viscosity meter.

[0042] The thixotropy index of the paste is 1, and the viscosity at a rotation speed of 5 rpm is 210 Pa.s.

[0043] As shown in Figure 1 , using a vacuum hole filling machine, the hole is filled without holes after filling the paste, and better connection can be achieved.

[0044] (3) Sintering

[0045] The product obtained in step (2) is sintered under a nitrogen atmosphere, heated to 260°C at a heating rate of 10°C / min, and kept for 20 min.

[0046] As shown in Figure 2 , the cross-sectional view shows that the copper particles inside the copper paste are sintered to form a connection, called a sintering neck.

[0047] The average value of the single hole column resistance of the product prepared in this example is 0.4Ω; after thermal cycle test (-55°C~125°C, 200 times), the interface has no delamination, and the resistance drift is <10%.

[0048] The air tightness of the product prepared in this example meets the MIL-STD-883 air tightness detection standard.

[0049] Example 2

[0050] A via array is prepared on a glass substrate, the via aperture is 50μm, the via depth is 500μm, the depth-diameter ratio is 10:1, and the glass substrate is taken as the object. The glass via metallization manufacturing method includes the following steps:

[0051] (1) A pulse plating process is used to deposit a 2μm thick copper layer on the via wall.

[0052] (2) The conductive copper paste is filled by a vacuum hole filling machine, the pressure of the vacuum cavity is adjusted to 80 Pa, the hardness of the scraper is 85, the steel plate is printed, and the printing speed is 50 mm / s.

[0053] The conductive copper paste used is an alloy sintering type copper paste, and the metal phase in the paste includes micron copper particles (D50=4 μm).

[0054] Components: micron copper powder 40%, tin powder 50%, epoxy resin 2%, ethylene glycol monobutyl ether 5%, dispersant 0.2%, coupling agent 0.5%, curing agent 2.3%.

[0055] Preparation method: mix the epoxy resin with the solvent, add other additives, disperse uniformly by a self-rotation and rotation stirring device, then add the micron copper powder and stir well, then add the tin powder and stir uniformly, and test the viscosity by a Brookfield viscometer.

[0056] The thixotropy index of the paste is 1, and the viscosity at a speed of 5 rpm is 180 Pa.s.

[0057] (3) Sintering

[0058] The product obtained in step (2) is sintered under a nitrogen atmosphere, heated to 200°C at a heating rate of 10°C / min, and kept for 20 min.

[0059] The average value of the single hole column resistance of the product prepared in this example is 0.48Ω; after the thermal cycle test (-55°C~125°C, 200 times), the interface is not delaminated, and the resistance drift is <10%.

[0060] The air tightness of the product prepared in this example meets the MIL-STD-883 air tightness detection standard.

[0061] Comparative Example 1

[0062] A via array is prepared on a glass substrate, the via aperture is 50 μm, the via depth is 500 μm, the depth-diameter ratio is 10:1, and the glass substrate is taken as the object. The manufacturing method of the glass via metallization includes the following steps:

[0063] (1) A pulse plating process is used to deposit a 3 μm thick copper layer on the via wall.

[0064] (2) The conductive copper paste is filled by a vacuum hole filling machine, the pressure of the vacuum cavity is adjusted to 80 Pa, the hardness of the scraper is 85, the steel plate is printed, and the printing speed is 50 mm / s.

[0065] The conductive copper paste used is a solidified type copper paste.

[0066] Components: micron copper powder 85%, epoxy resin 8%, benzyl alcohol 6%, dispersant 0.5%, curing agent 0.5%.

[0067] Preparation method: mix epoxy resin with benzyl alcohol, stir uniformly with self-rotating and revolving stirring equipment, add other additives and stir, then add copper powder, fully stir to form copper paste, and test viscosity with Brookfield viscometer.

[0068] The viscosity of the paste is 70 Pa·S at a rotation speed of 2 rpm.

[0069] (3) Sintering

[0070] The product obtained in step (2) is kept in an oven at 150°C for 40 min in an air atmosphere.

[0071] The average value of the resistance of the single hole column of the product prepared in the present comparative example is 0.9 Ω; after thermal cycle test (-55°C~125°C, 200 times), the interface is not delaminated, and the resistance drift is <40%.

[0072] The air tightness of the product prepared in the present comparative example reaches the air tightness detection standard of MIL-STD-883.

[0073] By comparison with Comparative Example 1, it is found that the resistance of the metal paste in the hole of the product using the curing type copper paste is relatively large compared with Examples 1 and 2, and the resistance drift is large after thermal cycle test.

[0074] Comparative Example 2

[0075] A via array is prepared on a glass substrate, the via aperture is 50 μm, the via depth is 500 μm, and the depth-diameter ratio is 10:1. The manufacturing method of glass via metallization taking the glass substrate as the object comprises the following steps:

[0076] (1) Fill the conductive copper paste by using a vacuum plug machine, adjust the pressure of the vacuum cavity to 80 Pa, the hardness of the scraper is 85, print on a steel plate, and the printing speed is 50 mm / s.

[0077] The conductive copper paste used comprises micron copper particles (D50=4 μm) in the metal phase.

[0078] Components: micron copper powder 40%, tin powder 50%, epoxy resin 2%, ethylene glycol monobutyl ether 5%, dispersant 0.5%, and curing agent 2.5%.

[0079] Preparation method: mix epoxy resin with solvent, add other additives, disperse uniformly by using self-rotating and revolving stirring equipment, then add micron copper powder and fully stir, then add tin powder and stir uniformly, and test viscosity with Brookfield viscometer.

[0080] The thixotropy index of the paste is 1, and the viscosity is 180 Pa·s at a rotation speed of 5 rpm.

[0081] (2) sintering

[0082] The product obtained in step (2) was sintered under nitrogen atmosphere, and heated to 200℃ at a heating rate of 10℃ / min, and kept for 20 min.

[0083] The conductive copper paste used in the present comparative example was the same as that in Example 2, and the same preparation condition was used. After preparation, the holes were not electroplated, but directly plugged with the copper paste. The average resistance of the single hole column of the product prepared in the present comparative example was 1.1Ω. After thermal cycle test (-55℃~125℃, 200 times), the interface was not delaminated, and the resistance drift was <15%.

[0084] The air tightness of the product prepared in the present comparative example reached the air tightness detection standard of MIL-STD-883.

[0085] As seen from Comparative Example 1, the cured copper paste was bonded between the electroplated layer and the paste by resin, and the conductive path between the electroplated layer and the paste was relatively less, and the resistance was relatively large. In the cold and hot cycle test, due to the cold and hot expansion and contraction, the conductive path was reduced, and the resistance change was relatively large.

[0086] Comparative Example 2 and Example 2 were compared. The only difference was that the paste was plugged into the hole, and there was no electroplated layer. The resistance of the through hole was obviously larger, and in the cold and hot cycle test, the resistance change was relatively high.

[0087] It should be understood that the above specific embodiments of the present application are only used for illustrative or explanatory purposes of the principles of the present application, and do not constitute a limitation of the present application. Therefore, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present application shall be included in the protection scope of the present application. In addition, the appended claims of the present application are intended to cover all variations and modifications falling within the scope and boundary of the appended claims, or the equivalent forms of such scope and boundary.

Claims

1. A conductive paste, characterized in that, The conductive paste includes metal particles with a particle size of 0.1–10 μm, and the mass of the metal particles accounts for 80–98% of the total mass of the conductive paste. The conductive paste is sintering type. The conductive paste is filled into the holes with copper layers. After sintering at ≤300℃ in an inert gas atmosphere, the metal particles can melt to form a connection structure or eutectic structure, and the metal particles can form a reinforcing layer with the copper layer. The reinforcing layer is a metal bonding layer or an intermetallic compound layer.

2. The conductive paste according to claim 1, characterized in that, The metal particles are at least one of gold, silver, copper, nickel, tin, silver-coated copper, silver-coated nickel, and silver-coated glass particles; After sintering at 150–300°C, the metal particles can melt to form a connecting structure, and a dense metal bonding layer is formed between them and the copper layer through atomic diffusion.

3. The conductive paste according to claim 2, characterized in that, The conductive paste is a nano-silver paste or a nano-copper paste, wherein the metal particles are silver or copper, and the particle size D50 of the metal particles is 0.01 to 1 μm.

4. The conductive paste according to claim 1, characterized in that, The metal particles are composed of low-melting-point metal powder and high-melting-point metal powder, with a mass ratio of 1:0.5 to 1:

5. The melting point of the low-melting-point metal powder is 100-300℃, and the melting point of the high-melting-point metal powder is 600-1100℃. When heated to 100–300°C, the low-melting-point metal melts and forms a liquid phase. When the molten low-melting-point metal encounters the high-melting-point metal, it instantly forms a eutectic structure with the high-melting-point metal. The low-melting-point metal can also react with the copper layer through the interface to form an intermetallic compound layer.

5. The conductive paste according to claim 4, characterized in that, The low-melting-point metal powder is a tin-lead alloy, a tin-bismuth alloy, a tin-indium alloy, a tin-silver-copper alloy, or tin, and the high-melting-point metal powder is gold, silver, or copper.

6. The conductive paste according to claim 1, characterized in that, The conductive paste further includes a binder and a solvent. The binder is at least one of epoxy resin, polyurethane, phenolic resin, acrylic resin, and silicone resin. The solvent is at least one of ethylene glycol, glycerol, isobutanol, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether, diethylene glycol ethyl ether, diethylene glycol methyl ether, diethylene glycol butyl ether, diethylene glycol butyl ether acetate, terpineol, benzyl alcohol, ethyl acetate, and butyl acetate. The binder accounts for 2-10% of the total mass of the conductive slurry, and the solvent accounts for 1-10% of the total mass of the conductive slurry.

7. A metallization process, characterized in that, Using the conductive paste according to any one of claims 1-6, the metallization process includes the following steps: (1) A copper layer is provided on the wall of the through hole or blind hole of the substrate; wherein the substrate is a glass, ceramic or silicon substrate, and the depth-to-diameter ratio of the through hole or blind hole is 10:1 to 60:

1. (2) Fill the holes with copper layers with conductive paste; (3) The product obtained in step (2) is subjected to heating and sintering treatment. Under an inert gas atmosphere, the heating and sintering temperature is ≤300℃. The metal particles in the conductive paste can melt to form a connection structure or eutectic structure, and the metal particles can form a reinforcing layer with the copper layer. The reinforcing layer is a metal bonding layer or an intermetallic compound layer.

8. The metallization process according to claim 7, characterized in that, The diameter of the through holes or blind holes in the substrate is 10-70 μm, and the thickness of the copper layer in step (1) is 0.1-10 μm.

9. The metallization process according to claim 7, characterized in that, In step (2), a vacuum printing process is used to fill conductive copper paste. The printing machine cavity is a vacuum with a vacuum degree of 20 Pa to 1000 Pa, preferably 20 Pa to 100 Pa.

10. A metallized substrate, characterized in that, It is prepared by the metallization process described in any one of claims 1-9.

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