Environment-friendly encapsulating slurry for thick film circuit and preparation method of environment-friendly encapsulating slurry

Abstract

The invention discloses environment-friendly encapsulating slurry for a thick film circuit and a preparation method thereof, and belongs to the technical field of electronic slurry. The encapsulating slurry comprises the following components: lead-free glass powder, a machine carrier and a coloring agent. The lead-free glass powder is prepared from the following components: Bi2O3, B2O3, ZnO, Al2O3, SiO2, Li2O, Sb2O3, TiO2 and ZrO2; the organic carrier is prepared from the following components: ethyl cellulose, diethylene glycol monobutyl ether, terpilenol and dioctyl phthalate; and the coloring agent is cobalt green. The preparation method comprises a glass powder preparation method, an organic carrier preparation method and a slurry preparation method. The problems that the performance of conductor paste and resistance change of a resistor body are affected due to the fact that existing lead system glass encapsulating paste is prone to being diffused into the conductor paste and the resistor paste, and meanwhile metal powder and bonding phases in the conductor paste and the resistor paste react with powder in the encapsulating paste, the structure of an encapsulating layer is damaged, and encapsulating fails are solved. The packaging film is widely applied to the technical field of circuit and electronic component packaging.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic pastes, and further relates to the technical field of electronic component encapsulation pastes, and specifically, to an environmentally friendly encapsulation paste for thick film circuits and a preparation method thereof. Background Art

[0002] The conductor paste and resistor paste in thick film circuits are printed, sintered and packaged to form electronic circuits. The performance of electrodes and resistors in the exposed state is easily affected by environmental conditions, and the stability and reliability face severe challenges. Therefore, thick film circuits generally require printed encapsulation paste for protection.

[0003] The encapsulation paste for thick film circuits is mainly printed on the conductor paste and resistor paste. After sintering, a uniform and dense film layer is formed to isolate the electrodes and resistors from the external environment, protecting the electronic circuits from environmental factors (temperature, humidity, impurities and dust, etc.), while providing a certain mechanical strength and enhancing the reliability of the electronic circuits.

[0004] At present, the encapsulation slurry used for thick film circuits is mainly lead-containing slurry, which has good glazing after sintering, high film density and good electrical insulation. However, the lead-based glass used in encapsulation slurry has good fluidity, and good wettability makes it easy for the encapsulation slurry to diffuse into the conductor slurry and resistor slurry, affecting the performance of the conductor slurry and the change in the resistance value of the resistor body. The properties of the encapsulation slurry are quite different from those of the conductor slurry and resistor slurry, and the adaptability is poor. The metal powder and adhesive phase in the conductor slurry and resistor slurry react with the powder in the encapsulation slurry, destroying the structure of the encapsulation layer and causing the failure of the entire electronic circuit.

[0005] Some technicians have improved the diffusion and reaction of the encapsulation slurry after sintering by ion doping and adjusting the crystallization strength of the glass powder used in the encapsulation slurry. However, the migration ability of lead ions themselves is strong. After the crystallinity of the glass powder used in the encapsulation slurry is enhanced, the density and electrical insulation of the film layer decrease to a certain extent, and the improvement effect is not ideal.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The technical problem to be solved by the present invention is to solve the problem that the existing lead system glass encapsulation slurry is easily diffused into the conductor slurry and the resistor slurry, affecting the performance of the conductor slurry and the change of the resistance value of the resistor body, and at the same time, the metal powder and the bonding phase in the conductor slurry and the resistor slurry react with the powder in the encapsulation slurry, destroying the encapsulation layer structure and causing encapsulation failure.

[0008] The inventive concept of the present invention is: In response to the technical problems existing in the encapsulation paste for lead-containing thick film circuits, a lead-free, halogen-free, environmentally friendly encapsulation paste is developed. Considering the compatibility with the thick film circuit manufacturing process, the encapsulation paste must be suitable for the thick film process platform and printed and sintered on an alumina ceramic substrate to prepare the product. At the same time, the sintering temperature range of the material system is relatively wide (such as 500℃~600℃). After sintering, the film layer is dense and the surface is smooth, the process adaptability is good, the diffusion after sintering is low and it is not easy to react with the conductor paste and resistor paste, and the impact on the conductor paste and resistor paste is relatively small.

[0009] To this end, the present invention provides an environmentally friendly encapsulation slurry for thick film circuits, which comprises, by mass percentage of raw material composition: 65% to 75% lead-free glass powder, 20% to 33% organic carrier, and 1% to 5% colorant.

[0010] The raw material compositions of the lead-free glass powder are as follows: 50% to 75% Bi2O3, 2% to 8% B2O3, 5% to 20% ZnO, 1% to 10% Al2O3, 5% to 20% SiO2, 0 to 5% Li2O, 0 to 5% Sb2O3, 0 to 5% TiO2, and 0 to 5% ZrO2.

[0011] The raw materials of the organic carrier are resin and solvent, and the mass percentage components are: 10% to 20% of ethyl cellulose, 55% to 70% of diethylene glycol butyl ether, 15% to 30% of pinene alcohol, and 0% to 5% of dioctyl phthalate.

[0012] The colorant is cobalt green.

[0013] The preparation method of the environmentally friendly encapsulation slurry for thick film circuits is as follows: (1) Preparation method of organic carrier: Mix the resin and solvent and stir until the resin is completely dissolved and there are no bubbles; (2) Glass powder preparation method: a) Ingredients: weigh the raw materials and put them into a mixer to mix evenly; b) Melting: The uniformly mixed mixture is placed in an alumina ceramic crucible and placed in a melting furnace, and melted at 1100°C to 1250°C for 0.5h to 1h to form a clear and uniform glass liquid, and the glass liquid is cooled by water quenching to obtain glass slag; c) Glass powder refinement: glass slag is refined with deionized water through a grinding device for 5h to 10h and then dried, and passed through a 400-mesh sieve to obtain glass powder; (3) Slurry preparation method: glass powder, colorant and organic carrier are mixed according to mass percentage, mixed and rolled to a fineness of less than 15 μm to obtain encapsulation slurry for thick film circuits.

[0014] The mechanism of action of the glass component in the encapsulation slurry of the present invention is as follows: Bi2O3 mainly forms glass and lowers the glass temperature; B2O3 and ZnO lower the composition temperature; SiO2 improves the glass composition and chemical stability; Al2O3, ZrO2, and TiO2 adjust the glass crystallinity and chemical stability; Li2O and Sb2O3 lower the high-temperature viscosity of the glass liquid.

[0015] The beneficial effects of the present invention are as follows: (1) After the lead-free glass of the present invention is refined by deionized water and passed through a 400-mesh sieve, the particle size distribution of the glass powder is uniform, and the density of the film layer after slurry sintering is good.

[0016] (2) The lead-free glass of the present invention is microcrystalline glass. The glass crystallizes after softening. The crystals are small and dense. After the slurry is sintered, the film layer is dense and has a certain mechanical strength. The diffusion is also relatively low.

[0017] (3) After the encapsulation paste of the present invention is printed and sintered, it has little effect on the resistance value of the resistor in the thick film circuit.

[0018] (4) The organic carrier for the encapsulation slurry of the present invention is a combination of ethyl cellulose, diethylene glycol butyl ether, terpineol, and dioctyl phthalate, and the slurry has good printability and wettability.

[0019] It is widely used in the field of circuit and electronic component packaging technology. DETAILED DESCRIPTION

[0020] The environmentally friendly encapsulation slurry for thick film circuit and the preparation method thereof are specifically implemented as follows: Embodiment 1:

[0021] (1) Preparation of lead-free glass powder: Lead-free glass is prepared according to Table 1. The weighed mixture is placed in a mixer and mixed evenly. The mixture is then loaded into an alumina ceramic crucible and placed in a melting furnace and smelted at 1100°C to 1250°C for 0.5h to 1h to form a clear and uniform glass liquid. The glass liquid is cooled by water quenching to obtain glass slag. The glass slag is refined with deionized water for 5h to 10h and then dried. The glass powder 1 is obtained after passing through a 400-mesh sieve.

[0022] Table 1 Lead-free glass powder composition of Example 1 name <![CDATA[Bi2O3]]> <![CDATA[B2O3]]> ZnO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> <![CDATA[Li2O]]> <![CDATA[Sb2O3]]> <![CDATA[TiO2]]> <![CDATA[ZrO2]]> Components 72% 6% 7% 3% 8% 1% 0.5% 1.5 1% (2) Preparation of organic carrier: The organic carrier is prepared according to Table 2, placed in a stainless steel barrel and stirred until the resin is completely dissolved and homogeneous without bubbles to obtain organic carrier 1.

[0023] Table 2 Table of organic carrier components in Example 1 name Ethyl cellulose Diethylene glycol butyl ether Terpineol Dioctyl phthalate Components 10% 70% 18% 2% (3) Slurry preparation: The encapsulation slurry was prepared according to Table 3. After all components were mixed and fully wetted, they were rolled with a three-roll mill to a fineness of less than 15 μm to obtain encapsulation slurry 1.

[0024] Table 3 Encapsulation slurry composition table of Example 1 name Glass powder 1 Organic carrier 1 Cobalt Green Components 74% 25% 1% The encapsulation slurry of the above-mentioned Example 1 is printed onto an alumina ceramic substrate (the conductor slurry and the resistor slurry have been printed and sintered), and is placed in an oven at 100°C to 150°C for drying for 10min to 20min. After drying, it is placed in a mesh belt sintering furnace for sintering. The sintering cycle is 1h, the sintering peak temperature is (510±10)°C, and the peak insulation time is 10min to 20min. After sintering, the surface of the film layer is flat, and the change rate of the resistor resistance before and after encapsulation of the encapsulation slurry is less than 0.8%. Embodiment 2:

[0025] (1) Preparation of lead-free glass powder: lead-free glass is prepared according to Table 4. The weighed mixture is placed in a mixer and mixed evenly. The mixture is then loaded into an alumina ceramic crucible and placed in a melting furnace and smelted at 1100°C to 1250°C for 0.5h to 1h to form a clear and uniform glass liquid. The glass liquid is cooled by water quenching to obtain glass slag. The glass slag is refined with deionized water for 5h to 10h and then dried. The glass powder 2 is obtained after passing through a 400-mesh sieve.

[0026] Table 4 Lead-free glass powder composition of Example 2

[0027] (2) Preparation of organic carrier: The organic carrier is prepared according to Table 5, placed in a stainless steel barrel and stirred until the resin is completely dissolved and homogeneous without bubbles to obtain organic carrier 2.

[0028] Table 5 Table of organic carrier components in Example 2 name Ethyl cellulose Diethylene glycol butyl ether Terpineol Dioctyl phthalate Components 14% 62% 21% 3% (3) Slurry preparation: The encapsulation slurry was prepared according to Table 6. After all components were mixed and fully wetted, they were rolled with a three-roll mill to a fineness of less than 15 μm to obtain encapsulation slurry 2.

[0029] Table 6 Composition of encapsulation slurry in Example 2 name Glass powder 2 Organic Carrier 2 Cobalt Green Components 70% 28% 2% The encapsulation slurry of the above-mentioned Example 2 is printed onto an alumina ceramic substrate (the conductor slurry and the resistor slurry have been printed and sintered), and is placed in an oven at 100°C to 150°C for drying for 10min to 20min. After drying, it is placed in a mesh belt sintering furnace for sintering. The sintering cycle is 1h, the sintering peak temperature is (545±10)°C, and the peak insulation time is 10min to 20min. After sintering, the surface of the film layer is flat, and the change rate of the resistor resistance before and after encapsulation of the encapsulation slurry is less than 1.0%. Embodiment 3:

[0030] (1) Preparation of lead-free glass powder: lead-free glass is prepared according to Table 7. The weighed mixture is placed in a mixer and mixed evenly. The mixture is then loaded into an alumina ceramic crucible and placed in a melting furnace and smelted at 1100°C to 1250°C for 0.5h to 1h to form a clear and uniform glass liquid. The glass liquid is cooled by water quenching to obtain glass slag. The glass slag is refined with deionized water for 5h to 10h and then dried. The glass powder 3 is obtained after passing through a 400-mesh sieve.

[0031] Table 7 Composition of lead-free glass powder in Example 3

[0032] (2) Preparation of organic carrier: The organic carrier is prepared according to Table 8, placed in a stainless steel barrel and stirred until the resin is completely dissolved and homogeneous without bubbles to obtain organic carrier 3.

[0033] Table 8 Organic carrier components of Example 3 name Ethyl cellulose Diethylene glycol butyl ether Terpineol Dioctyl phthalate Components 19% 58% 20% 3% (3) Slurry preparation: The encapsulation slurry was prepared according to Table 9. After all components were mixed and fully wetted, they were rolled with a three-roll mill to a fineness of less than 15 μm to obtain encapsulation slurry 3.

[0034] Table 9 Composition of encapsulation slurry in Example 3 name Glass powder 3 Organic Carrier 3 Cobalt Green Components 65% 33% 2% The encapsulation slurry of the above-mentioned Example 3 is printed onto an alumina ceramic substrate (the conductor slurry and the resistor slurry have been printed and sintered), and is placed in an oven at 100°C to 150°C for drying for 10min to 20min. After drying, it is placed in a mesh belt sintering furnace for sintering. The sintering cycle is 1h, the sintering peak temperature is (590±10)°C, and the peak insulation time is 10min to 20min. After sintering, the surface of the film layer is flat, and the change rate of the resistor resistance before and after encapsulation of the encapsulation slurry is less than 1.3%.

[0035] It can be seen from Examples 1 to 3 that the surface of the film layer of the encapsulation slurry of Examples 1 to 3 is smooth after printing and sintering, the diffusion after sintering is low, and the influence on the structure of the resistor body is small. As the sintering temperature decreases, the influence on the resistance value of the resistor body shows a downward trend.

[0036] Finally, it should be noted that the above embodiments are merely examples for the purpose of clear explanation. The present invention includes but is not limited to the above embodiments. It is not necessary and impossible to list all implementation methods exhaustively. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. All implementation methods that meet the requirements of the present invention belong to the protection scope of the present invention.

Claims

1. An environmentally friendly encapsulation slurry for thick film circuits, characterized in that: According to the mass percentage of raw materials, it includes 65% to 75% lead-free glass powder, 20% to 33% organic carrier and 1% to 5% colorant; The raw material mass percentage composition of the lead-free glass powder is: 50% to 75% Bi2O3, 2% to 8% B2O3, 5% to 20% ZnO, 1% to 10% Al2O3, 5% to 20% SiO2, 0 to 5% Li2O, 0 to 5% Sb2O3, 0 to 5% TiO2, and 0 to 5% ZrO2; The raw materials of the organic carrier are resin and solvent, and the mass percentage components are: 10% to 20% ethyl cellulose, 55% to 70% diethylene glycol butyl ether, 15% to 30% terpineol, and 0% to 5% dioctyl phthalate; The colorant is cobalt green.

2. The method for preparing an environmentally friendly encapsulation slurry for thick film circuits according to claim 1, characterized in that: The preparation method is as follows: (1) Preparation method of organic carrier: Mix the resin and solvent and stir until the resin is completely dissolved and there are no bubbles; (2) Glass powder preparation method: a) Ingredients: weigh the raw materials and put them into a mixer to mix evenly; b) Melting: The uniformly mixed mixture is placed in an alumina ceramic crucible and placed in a melting furnace, and melted at 1100°C to 1250°C for 0.5h to 1h to form a clear and uniform glass liquid, and the glass liquid is cooled by water quenching to obtain glass slag; c) Glass powder refinement: glass slag is refined with deionized water through a grinding device for 5h to 10h and then dried, and passed through a 400-mesh sieve to obtain glass powder; (3) Slurry preparation method: glass powder, colorant and organic carrier are mixed according to mass percentage, mixed and rolled to a fineness of less than 15 μm to obtain encapsulation slurry for thick film circuits.

3. The method for preparing an environmentally friendly encapsulation slurry for thick film circuits according to claim 2, characterized in that: The specific method is as follows: (1) Preparation of lead-free glass powder: Prepare the ingredients according to the following table: ， The weighed mixture is put into a mixer and mixed evenly, and then put into an alumina ceramic crucible, and placed in a melting furnace at 1100°C to 1250°C for 0.5h to 1h to form a clear and uniform glass liquid. The glass liquid is cooled by water quenching to obtain glass slag, which is refined with deionized water for 5h to 10h and then dried, and passed through a 400-mesh sieve to obtain glass powder 1; (2) Preparation of organic carrier: Prepare the ingredients according to the following table: ， Place the mixture in a stainless steel barrel and stir until the resin is completely dissolved and homogeneous without bubbles to obtain an organic carrier 1; (3) Slurry preparation: Prepare the ingredients according to the following table: ， After all the components are mixed and fully wetted, they are dispersed and rolled with a three-roll mill until the fineness reaches less than 15 μm to obtain encapsulation slurry 1.

4. The method for preparing an environmentally friendly encapsulation slurry for thick film circuits according to claim 3, characterized in that: The encapsulation slurry 1 is printed on the alumina ceramic substrate on which the conductor slurry and the resistor slurry have been printed and sintered, and is placed in an oven at 100°C to 150°C for drying for 10min to 20min. After drying, it is placed in a mesh belt sintering furnace for sintering. The sintering cycle is 1h, the sintering peak temperature is (510±10)°C, and the peak insulation time is 10min to 20min. After sintering, the surface of the film layer is flat, and the change rate of the resistor body resistance before and after encapsulation of the encapsulation slurry is less than 0.8%.

5. The method for preparing an environmentally friendly encapsulation slurry for thick film circuits according to claim 2, characterized in that: The specific method is as follows: (1) Preparation of lead-free glass powder: Prepare the ingredients according to the following table: ， The weighed mixture is put into a mixer and mixed evenly, and then put into an alumina ceramic crucible, and placed in a melting furnace at 1100°C to 1250°C for 0.5h to 1h to form a clear and uniform glass liquid. The glass liquid is cooled by water quenching to obtain glass slag. The glass slag is refined with deionized water for 5h to 10h and then dried, and passed through a 400-mesh sieve to obtain glass powder 2; (2) Preparation of organic carrier: Prepare the ingredients according to the following table: ， Place the mixture in a stainless steel barrel and stir until the resin is completely dissolved and homogeneous without bubbles to obtain an organic carrier 2; (3) Slurry preparation: Prepare the ingredients according to the following table: ， After all the components are mixed and fully wetted, they are dispersed and rolled with a three-roll mill until the fineness reaches less than 15 μm to obtain encapsulation slurry 2.

6. The method for preparing an environmentally friendly encapsulation slurry for thick film circuits according to claim 5, characterized in that: The encapsulation slurry 2 is printed onto the alumina ceramic substrate on which the conductor slurry and the resistor slurry have been printed and sintered, and is placed in an oven at 100°C to 150°C for drying for 10min to 20min. After drying, it is placed in a mesh belt sintering furnace for sintering. The sintering cycle is 1h, the sintering peak temperature is (545±10)°C, and the peak insulation time is 10min to 20min. After sintering, the surface of the film layer is smooth, and the change rate of the resistor resistance before and after encapsulation by the encapsulation slurry is less than 1.0%.

7. The method for preparing an environmentally friendly encapsulation slurry for thick film circuits according to claim 2, characterized in that: The specific method is as follows: (1) Preparation of lead-free glass powder: Prepare the ingredients according to the following table: ， The weighed mixture is put into a mixer and mixed evenly, then put into an alumina ceramic crucible, and placed in a melting furnace at 1100°C to 1250°C for 0.5h to 1h to form a clear and uniform glass liquid. The glass liquid is cooled by water quenching to obtain glass slag. The glass slag is refined with deionized water for 5h to 10h and then dried, and passed through a 400-mesh sieve to obtain glass powder 3; (2) Preparation of organic carrier: Prepare the ingredients according to the following table: ， Place in a stainless steel barrel and stir until the resin is completely dissolved and homogeneous without bubbles to obtain the organic carrier 3; (3) Slurry preparation: Prepare the ingredients according to the following table: ， After all the components are mixed and fully wetted, they are dispersed and rolled with a three-roll mill until the fineness reaches less than 15 μm to obtain encapsulation slurry 3.

8. The method for preparing an environmentally friendly encapsulation slurry for thick film circuits according to claim 7, characterized in that: The encapsulation slurry 3 is printed onto the alumina ceramic substrate on which the conductor slurry and the resistor slurry have been printed and sintered, and is placed in an oven at 100°C to 150°C for drying for 10min to 20min. After drying, it is placed in a mesh belt sintering furnace for sintering. The sintering cycle is 1h, the sintering peak temperature is (590±10)°C, and the peak insulation time is 10min to 20min. After sintering, the surface of the film layer is smooth, and the change rate of the resistor resistance before and after encapsulation by the encapsulation slurry is less than 1.3%.

9. The environmentally friendly encapsulation slurry for thick film circuits according to claim 1, characterized in that: The sintering temperature of the encapsulation slurry is 500°C to 600°C.

10. The environmentally friendly encapsulation slurry for thick film circuits according to claim 1, characterized in that: After the encapsulation slurry is printed on the thick film resistor, as the sintering temperature of the encapsulation slurry decreases, the influence on the resistance value of the resistor body shows a downward trend.

Images