Method for eliminating laser sintering pore defect of 3D printing circuit

Abstract

The invention discloses a method for eliminating a 3D printing circuit laser sintering pore defect, which comprises the following steps: S1, aiming at a conductive material used in 3D printing, obtaining the maximum weight loss rate temperature and boiling point temperature of a solvent-containing conductive material in a 3D printing heating process in a printing circuit; s2, a first laser beam with the large defocusing amount and the low energy density is adopted for curing the printing circuit, and the curing temperature is controlled to be above the maximum weight loss rate temperature of the solvent-containing conductive material and below the boiling point temperature; and S3, a second laser beam with high power and high energy density is adopted to sinter the cured printing circuit, conductive material particles in the printing circuit are fused, and densification sintering of the printing circuit is achieved. According to the method, on-line rapid sintering and effective suppression of pore defects are achieved, and key process support is provided for 3D printing technology application in the field of electronic circuit manufacturing.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit manufacturing technology, and specifically to a method for eliminating porosity defects in laser sintering of 3D printed circuits. Background Technology

[0002] With the rapid development of 3D printing technology, the fabrication of conductive circuits using this technology has become an important research direction. Laser sintering is a common method for manufacturing complex three-dimensional electronic circuits. However, current technologies typically employ an oven for initial curing followed by laser sintering. Due to the inconvenience of oven sintering, this method struggles to achieve online, rapid sintering of printed circuits. Direct laser sintering, on the other hand, involves solvents and thixotropic agents in the silver paste. Under the influence of a high-energy-density laser beam, these organic compounds rapidly decompose due to the sharp increase in temperature. Solvents constitute the largest volume component, and their decomposition produces a large amount of gaseous products. This results in numerous pore defects within the circuit, severely impacting its electrical performance, strength, and reliability. Therefore, effectively suppressing pore defects during laser sintering and fabricating highly dense conductive circuits is a critical problem that urgently needs to be solved in this field. Summary of the Invention

[0003] The purpose of this invention is to address the difficulties of online and rapid sintering in current methods such as oven sintering for printed circuits, as well as the numerous porosity defects in single-pass laser sintering, by providing a method to eliminate porosity defects in laser sintering of 3D printed circuits.

[0004] To achieve the above objectives, the technical solution provided by the present invention is as follows: The first aspect of this application provides a method for eliminating porosity defects in laser-sintered 3D printed circuits, comprising the following steps: S1: For the conductive materials used in 3D printing, obtain the maximum weight loss rate temperature and boiling point temperature of the solvent-containing conductive material in the printing circuit during the 3D printing heating process. S2: The printed circuit is cured by a first laser beam with a large defocusing amount and low energy density. The curing temperature is controlled above the maximum weight loss rate temperature and below the boiling point temperature of the conductive material containing solvent. S3: A high-power, high-energy-density second laser beam is used to sinter the solidified printed circuit, causing the conductive material particles in the printed circuit to fuse together, thus achieving densification sintering of the printed circuit. To optimize the above technical solution, the specific measures also include: The first laser beam, characterized by large defocusing amount and low energy density, has a defocusing amount ranging from 25 to 40 mm and a power density ranging from 1.87 to 4.48 W / cm². 2 .

[0005] The high-power, high-energy-density second laser beam has a power range of 3~10 W and a power density range of 469~1563 W / cm². 2 .

[0006] In step S1, the maximum weight loss rate temperature and boiling point temperature of the solvent-containing conductive material in the 3D printing heating process are obtained using the following thermal analysis methods: TG, DTG, and DSC.

[0007] Furthermore, the specific method for obtaining the maximum weight loss rate temperature and boiling point temperature is as follows: the weight loss of the conductive material containing solvent as the temperature increases is analyzed by TG, the temperature at which the weight decreases the fastest is obtained by the DTG curve and taken as the maximum weight loss rate temperature, and the temperature corresponding to the solvent boiling is determined by the endothermic peak in the DSC curve and taken as the boiling point temperature.

[0008] In step S2, the curing temperature control specifically involves using an infrared thermal imager to observe the curing temperature and adjusting the laser sintering parameters to control the curing temperature.

[0009] In step S3, the sintering temperature is greater than the maximum weight loss rate temperature and boiling point temperature of the solvent-containing conductive material, and the sintering temperature is above the sintering neck formation temperature of the conductive material particles.

[0010] Furthermore, in step S3, the sintering temperature is controlled by setting laser sintering parameters including laser power, defocusing amount, and scanning speed.

[0011] The conductive material is conductive silver paste, conductive copper paste, or conductive silver ink.

[0012] The second aspect of this application provides a 3D printed circuit that uses the above-described method to eliminate the porosity defects caused by laser sintering of the 3D printed circuit.

[0013] Compared with the prior art, the beneficial effects of the present invention are: This invention solves the porosity defect problem in 3D printed conductive circuits through a multi-stage laser sintering process. Its core innovation lies in using a first laser beam with high defocusing and low energy density for pre-curing, based on temperature analysis, and then combining it with a second laser beam with high power and high energy density for densification sintering, forming a step-by-step temperature control strategy. The specific effects are reflected in the following three aspects: First, the maximum weight loss rate temperature and boiling point temperature of the solvent are accurately determined by thermal analysis technology (TG, DTG, DSC), and the pre-curing temperature is strictly controlled between the two to achieve a smooth and stable removal of the solvent and avoid the formation of pores caused by violent boiling of gas. Secondly, an infrared thermal imager is used to monitor and control the curing temperature in real time to ensure process stability. At the same time, a uniform temperature field is obtained by optimizing the defocusing amount, which significantly improves the surface quality of the circuit. Finally, high-power sintering is carried out on the pre-cured base, which enables the conductive particles to fuse efficiently under solvent-free conditions, forming a dense microstructure and significantly improving the electrical performance and mechanical reliability of the circuit.

[0014] Overall, the method of this invention breaks through the limitations of traditional single-pass sintering or oven processes, achieving online rapid sintering and effective suppression of porosity defects, providing key process support for the application of 3D printing technology in the field of electronic circuit manufacturing. Attached Figure Description Figure 1 This is a flowchart illustrating the invention's method for eliminating porosity defects in 3D printed circuit laser sintering.

[0015] Figure 2 The results of thermal analysis of a certain type of conductive silver paste in this embodiment of the invention include TG, DTG, and DSC curves.

[0016] Figure 3 This is a high-defocus sintering process for a certain type of conductive silver paste printed circuit in an embodiment of the present invention.

[0017] Figure 4 This is a high-power sintering morphology of a certain type of conductive silver paste printed circuit in an embodiment of the present invention, including CT and SEM scans. Detailed Implementation

[0018] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0019] The following is a brief explanation of some of the terms related to this invention: TG: Thermogravimetry; DTG: Derivative Thermogravimetry; DSC: Differential Scanning Calorimetry.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.

[0021] This invention provides a method for eliminating porosity defects in laser-sintered 3D printed circuits, such as... Figure 1 As shown, it includes the following steps: For conductive materials used in 3D printing, the maximum weight loss rate temperature and boiling point temperature of the solvent-containing conductive material in the printing circuit during the 3D printing heating process were obtained. The printed circuit is cured using a first laser beam with a large defocusing amount and low energy density. The curing temperature is controlled above the maximum weight loss rate temperature and below the boiling point temperature of the solvent-containing conductive material. A high-power, high-energy-density second laser beam is used to sinter the solidified printed circuit, causing the conductive material particles in the printed circuit to fuse together, thereby achieving densification sintering of the printed circuit. In some implementations, the first laser beam with a large defocusing amount and low energy density has a defocusing amount ranging from 25 to 40 mm and a power density ranging from 1.87 to 4.48 W / cm². 2 .

[0022] In some embodiments, the power range of the high-power, high-energy-density second laser beam is 3~10 W, and the power density range is 469~1563 W / cm². 2 .

[0023] The maximum weight loss rate temperature and boiling point temperature were obtained using the following thermal analysis methods: TG, DTG, and DSC. Specifically, TG was used to analyze the weight loss of the conductive material containing solvent as the temperature increased. The temperature at which the weight decreased the most rapidly was obtained from the DTG curve and was taken as the maximum weight loss rate temperature. The temperature at which the solvent boiled was determined from the endothermic peak in the DSC curve and was taken as the boiling point temperature.

[0024] In some implementations, curing temperature control specifically involves using an infrared thermal imager to observe the curing temperature and adjusting the laser sintering parameters to control the curing temperature.

[0025] The sintering temperature is greater than the maximum weight loss rate temperature and boiling point temperature of the solvent-containing conductive material, and the sintering temperature is above the sintering neck formation temperature of the conductive material particles.

[0026] The sintering temperature is controlled by setting laser sintering parameters including laser power, defocusing amount, and scanning speed.

[0027] The conductive materials to which this invention is applicable include conductive silver paste, conductive copper paste, and conductive silver ink.

[0028] The present invention also provides a 3D printed circuit that uses the above method to eliminate the porosity defects of laser sintering in 3D printed circuits.

[0029] The technical solution of the present invention will be further described in detail below with reference to specific embodiments: This invention provides a method for eliminating porosity defects in 3D printed circuits through laser sintering. This embodiment involves a step-by-step laser sintering process using a certain type of conductive silver paste to eliminate porosity defects. Step 1: Obtain the temperature at which the solvent decomposes and boils during the heating process of the conductive material.

[0030] A certain type of conductive silver paste was tested using thermal analysis methods such as TG, DTG, and DSC. The test results are as follows: Figure 2 As shown, the weight loss of the conductive material mixture as the temperature increases is analyzed by TG. The temperature at which the weight decreases the most is obtained by the DTG curve and is taken as the temperature of the maximum weight loss rate. The temperature at which the solvent boils is determined by the endothermic peak in the DSC curve and is taken as the boiling point temperature.

[0031] During the heating process, a certain type of conductive silver paste undergoes sequential decomposition of solvent, thixotropic agent, and thickener. The solvent decomposition occurs at a maximum temperature of 112°C, and the solvent boiling temperature is approximately 210°C.

[0032] Step 2: Use a laser beam with high defocusing amount and low energy density to cure the printed lines, and control the temperature above the solvent decomposition temperature and below the boiling point to eliminate pore defects.

[0033] The specific operation is as follows: by adjusting the relative height between the laser sintering device and the printed circuit, the printed circuit is placed on the laser working plane with a large defocusing amount to obtain a larger laser spot and a more uniform temperature field; the curing temperature is observed using an infrared thermal imager, and the curing temperature is controlled between the maximum weight loss rate temperature and the boiling point temperature obtained in step one by adjusting the laser sintering parameters, so as to achieve the gradual and stable removal of solvent and complete the curing of the circuit.

[0034] Based on the test results obtained in step one, the temperature should be controlled within the range of 112~210℃ during the first sintering (curing). The laser sintering process of the printed circuit was observed using an infrared thermal imager. When the laser power was 1W, the scanning speed was 0.1mm / s, and the defocusing amount was 28mm, the average sintering temperature was 175℃.

[0035] The sintering process of the printed circuit under this parameter is as follows: Figure 3 As shown, the solvent was removed stably, and no obvious bumps or pore defects appeared on the circuit surface. Step 3: By adjusting laser power and other laser sintering parameters to obtain a higher sintering temperature, the solidified circuit is sintered to achieve effective fusion of conductive material particles in the circuit, thus completing the circuit sintering.

[0036] Based on the circuit obtained in step two, a second sintering is performed using parameters of 10W laser power, 0.1mm / s scanning speed, and 0mm defocusing amount.

[0037] The conductive circuit obtained after the second sintering is as follows Figure 4 As shown, according to the CT scan results, there are no pore defects inside the circuit. According to the SEM scan results, the microstructure of the circuit is in a dense sintered state, and the resistivity of the circuit is as low as 3.95 μΩ·cm.

[0038] This step raises the sintering temperature above the sintering neck formation temperature of the conductive material particles. At the same time, macroscopic defects such as breakage should not occur in the circuit.

[0039] The method for eliminating porosity defects in 3D printed circuits via laser sintering, as described in this invention, is based on temperature analysis. It utilizes a large defocusing amount and high-power laser sintering to remove solvent and sinter particles in the printed circuit, respectively, effectively suppressing porosity defects and achieving ideal sintering results. The laser sintering method used is prior art and is not the subject of this application.

[0040] The first sintering (curing) process utilizes a high defocusing amount and low energy density laser to gently and stably remove the solvent, avoiding violent gas boiling that could lead to porosity defects. The second sintering, performed in the absence of or with minimal solvent, uses a high-power, high-energy-density laser to efficiently melt the conductive particles, achieving densified sintering of the conductive circuitry and resulting in excellent electrical properties, strength, and reliability. This invention overcomes the limitations of current oven-based sintering methods for printed circuits, which cannot achieve online, rapid sintering, and the numerous porosity defects inherent in single-stage laser sintering. It significantly promotes the application and development of conductive circuit 3D printing technology in the field of electronic circuit manufacturing.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for eliminating porosity defects in laser-sintered 3D printed circuits, characterized in that, Includes the following steps: S1: For the conductive materials used in 3D printing, obtain the maximum weight loss rate temperature and boiling point temperature of the solvent-containing conductive material in the printing circuit during the 3D printing heating process. S2: The printed circuit is cured by a first laser beam with a large defocusing amount and low energy density. The curing temperature is controlled above the maximum weight loss rate temperature and below the boiling point temperature of the conductive material containing solvent. S3: A high-power, high-energy-density second laser beam is used to sinter the solidified printed circuit, causing the conductive material particles in the printed circuit to fuse together, thus achieving densification sintering of the printed circuit.

2. The method for eliminating porosity defects in laser sintering of 3D printed circuits according to claim 1, characterized in that: The first laser beam, characterized by large defocusing amount and low energy density, has a defocusing amount ranging from 25 to 40 mm and a power density ranging from 1.87 to 4.48 W / cm². 2 .

3. The method for eliminating porosity defects in laser sintering of 3D printed circuits according to claim 1, characterized in that: The high-power, high-energy-density second laser beam has a power range of 3~10 W and a power density range of 469~1563 W / cm². 2 .

4. The method for eliminating porosity defects in laser sintering of 3D printed circuits according to claim 1, characterized in that: In step S1, the maximum weight loss rate temperature and boiling point temperature of the solvent-containing conductive material in the 3D printing heating process are obtained using the following thermal analysis methods: TG, DTG, and DSC.

5. The method for eliminating porosity defects in laser sintering of 3D printed circuits according to claim 4, characterized in that: The specific methods for obtaining the maximum weight loss rate temperature and boiling point temperature are as follows: the weight loss of the conductive material containing solvent is analyzed by TG, the temperature at which the weight decreases the fastest is obtained by DTG curve and taken as the maximum weight loss rate temperature, and the temperature corresponding to the solvent boiling is determined by the endothermic peak in the DSC curve and taken as the boiling point temperature.

6. The method for eliminating porosity defects in laser sintering of 3D printed circuits according to claim 1, characterized in that: In step S2, the curing temperature control specifically involves using an infrared thermal imager to observe the curing temperature and adjusting the laser sintering parameters to control the curing temperature.

7. The method for eliminating porosity defects in laser sintering of 3D printed circuits according to claim 1, characterized in that: In step S3, the sintering temperature is greater than the maximum weight loss rate temperature and boiling point temperature of the solvent-containing conductive material, and the sintering temperature is above the sintering neck formation temperature of the conductive material particles.

8. The method for eliminating porosity defects in laser sintering of 3D printed circuits according to claim 1, characterized in that: In step S3, the sintering temperature is controlled by setting laser sintering parameters including laser power, defocusing amount, and scanning speed.

9. The method for eliminating porosity defects in laser sintering of 3D printed circuits according to claim 1, characterized in that: The conductive material is conductive silver paste, conductive copper paste, or conductive silver ink.

10. A 3D printed circuit, characterized in that: The method described in any one of claims 1 to 9 is used to eliminate the porosity defects in the laser sintering of 3D printed circuits.

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