Cavity-free processing technology for front and back conducting copper cylinders of film inductor

Abstract

The invention relates to the technical field of thin-film inductor conducting copper cylinder processing, and discloses a thin-film inductor front and back conducting copper cylinder cavity-free processing technology which comprises the following steps: preparing an inductor material to be processed, including a base material with front and back circuits and an insulating layer PI in the middle, performing drilling operation on the material in the step S1, a to-be-drilled inductor is fixed to a machining platform, the drilling position is determined through a positioning system of a numerical control drilling machine, the drilling machine is started, a drill bit starts to rotate according to set parameters and is fed downwards, the inductor material is drilled, and a hole channel used for follow-up copper column filling is formed. According to the cavity-free processing technology for the front and back conducting copper cylinders of the film inductor, copper cutting treatment is carried out on the copper foil of the hole opening before copper plating, the situation that the tip sucks electricity and the pain speed of the tip is too high in the copper plating process is avoided, primary copper plating protection is carried out on the hole in the copper cylinder plating process, the integrity of the copper foil in the hole is improved, and the situation that the copper cylinder is damaged during copper cylinder processing is avoided. And bubbles are generated to form a cavity.

Description

Technical Field

[0001] The invention relates to the technical field of processing thin-film inductor conductive copper pillars, in particular to a cavity-free processing technology for conductive copper pillars on the front and back sides of a thin-film inductor. Background Art

[0002] Thin film inductors are an inductor made using a vacuum thin film process. They have high reliability, are easy to integrate and chip-type, and are very suitable for automated surface mounting technology (SMT). They also have the advantages of small size and good high-frequency characteristics.

[0003] During the copper plating process of the front and back sides of the inductor, there is an insulating layer in the middle of the front and back sides. The front and back lines are connected by drilling holes at the same position to form a copper pillar filling process. Bubbles will be generated during the copper plating process, resulting in cavities in the copper pillars, causing insufficient effective area of ​​the copper pillars, causing quality risks, and poor conduction after batch reliability (high temperature and high humidity) at the terminal. The current existing chemicals and equipment are temporarily unable to meet the process capabilities of 40um apertures. Therefore, it is necessary to invent a cavity-free processing technology for the copper pillars on the front and back sides of thin-film inductors to solve the above problems. Summary of the invention

[0004] The present invention provides the following technical solution: a cavity-free processing technology for copper pillars with conductive contacts on the front and back sides of a thin-film inductor, comprising the following steps: S1. Initial preparation Prepare the inductor material to be processed, including a substrate with front and back circuits and an insulating layer PI in the middle.

[0005] S2. Drilling A drilling operation is performed on the material in step S1, the inductor to be drilled is fixed on the processing platform, the drilling position is determined by the positioning system of the CNC drilling machine, the drilling machine is started, and the drill bit starts to rotate and feed downward according to the set parameters to drill the inductor material to form a channel for subsequent copper column filling.

[0006] S3. Hole copper foil shrinkage treatment The copper foil at the front and back sides of the copper column end are subjected to copper shrinkage and copper reduction operations. The shrinkage of the copper foil at the hole is achieved by chemical etching, and the shrinkage of the copper foil at the hole is controlled to be 4-5um. At the same time, it is ensured that the insulating layer PI does not shrink. Subsequently, a microscope and a profile measuring instrument are used to check the shape, size and surface quality of the copper foil at the hole after shrinkage, and observe whether the edge of the hole is flat and the shrinkage amount is uniform, to ensure that the shrinkage effect meets the process requirements.

[0007] S4, hole protection copper plating The orifice is subjected to protective copper plating. A chemical cleaning solution is used to remove oil, oxides, and dust on the surface of the orifice. Subsequently, a micro-etching agent is used to micro-etch the surface of the orifice to remove the passivation layer on the surface. A special plating solution suitable for orifice protection copper plating is selected. The current density is set according to the orifice size, plating solution composition, and required copper plating layer thickness to form copper plating. After the copper plating is completed, the orifice is immediately cleaned with deionized water to remove residual plating solution and impurities on the surface, and the orifice is dried using a low-temperature drying method.

[0008] S5, copper plating to form copper pillars Carry out copper plating process, prepare special copper plating solution according to process requirements, check the inductor substrate after pretreatment such as hole protection copper plating again, ensure that the hole is clean and free of impurities, and the hole protection copper plating layer is complete and uniform, and carry out copper plating processing to deposit copper in the hole to form copper pillars to connect the front and back lines. After the copper plating is completed, immediately take the inductor substrate out of the plating tank, rinse it with a large amount of flowing deionized water to remove the residual plating solution on the surface, then rinse it several times, and then use low-temperature drying method to dry the copper-plated inductor substrate.

[0009] S6. Finished product inspection Carry out random inspection on the processed finished products.

[0010] S7, finished product formation Products that pass random inspection are final products and enter the subsequent application stage.

[0011] Preferably, in step S2, after the drilling is completed, optical inspection equipment is used to inspect the quality of the hole, and the inspection content includes the diameter accuracy, verticality, hole wall roughness and whether there are defects such as cracks.

[0012] Preferably, in step S3, during the shrinkage of the hole copper foil, the insulating layer is protected by a mask or a protective coating.

[0013] Preferably, in step S3, a high-precision measuring instrument is used to monitor the shrinkage process of the orifice copper foil in real time to ensure that the shrinkage amount is stable within the range of 4-5 um, and the etching solution flow rate in the chemical etching is adjusted in time according to the measurement result.

[0014] Preferably, in step S4, the cleaning time is 5-15 minutes, the temperature is controlled between 30-60° C., and the micro-etching agent may be a persulfate solution or an acidic cupric chloride solution.

[0015] Preferably, in step S4, the cleaning after copper plating is carried out by a combination of spraying and immersion, and the cleaning time is not less than 3 minutes.

[0016] Preferably, in step S5, at the initial stage of copper plating, a relatively low current density of 0.8 A / dm² can be used to allow copper to nucleate uniformly at the bottom of the hole, and then the current density is gradually increased to 1.0-1.2 A / dm² to promote the stable growth of the copper column. By real-time monitoring of current and voltage changes, the power output is adjusted in time to ensure that the current density is stable within the set range.

[0017] Preferably, in step S5, the rinsing time is not less than 5 minutes, and after the last rinsing, the sample is tested with deionized water having a resistivity greater than 18 MΩ·cm.

[0018] (II) Beneficial effects Compared with the prior art, the present invention provides a cavity-free processing technology for conducting copper pillars on the front and back sides of a thin-film inductor, which has the following beneficial effects: 1. The copper pillars on the front and back sides of the thin film inductor are processed without cavity. The copper foil at the hole mouth is cut before copper plating to avoid the tip absorbing electricity during copper plating, which causes the tip to be injured too quickly. When plating the copper pillars, the holes are first protected by copper plating to improve the integrity of the copper foil in the holes and avoid the formation of bubbles and cavities during copper pillar processing.

[0019] 2. The cavity-free processing technology of the copper pillars on the front and back sides of the thin-film inductor has significantly reduced the abnormal defect rate of the cavity in the copper pillar from 46% to 0%, which greatly improves the product quality stability, solves the poor conduction problem from 100% to 0%, and enhances the reliability of the product in practical applications. The process capability has been improved from the previous processing capacity of only being able to process holes with a diameter of ≥50um to ≥20um, a 2.5-fold increase, which has broadened the company's technical boundaries in the field of thin-film inductor processing and provided strong support for opening up a broader market. The inspection strategy has been optimized from full inspection to random inspection, which has greatly reduced the inspection cost, saved the inspection and equipment investment costs, and improved production efficiency and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure after drilling of the present invention; Figure 2 This is a schematic diagram of the structure of the hole copper foil after shrinkage treatment of the present invention; Figure 3 This is a schematic diagram of the structure of the hole protection after copper plating of the present invention; Figure 4 This is a schematic diagram of the structure of the copper column after processing of the present invention. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] See also Figure 1-4 The present invention provides a technical solution: a cavity-free processing technology for copper pillars on the front and back sides of a thin film inductor, comprising the following steps: S1. Initial preparation Prepare the inductor material to be processed, including a substrate with front and back circuits and an insulating layer PI in the middle.

[0023] S2. Drilling A drilling operation is performed on the material in step S1, the inductor to be drilled is fixed on the processing platform, the drilling position is determined by the positioning system of the CNC drilling machine, the drilling machine is started, and the drill bit starts to rotate and feed downward according to the set parameters to drill the inductor material to form a channel for subsequent copper column filling.

[0024] After drilling is completed, optical inspection equipment is used to inspect the quality of the hole, including the hole diameter accuracy, verticality, hole wall roughness, and whether there are defects such as cracks. This is a key pretreatment to avoid premature closure of the hole and cavity formation in the future. The drilling position must accurately correspond to the front and back lines to ensure that the lines can be connected to form a loop.

[0025] S3. Hole copper foil shrinkage treatment The copper foil at the front and back of the copper column end is subjected to copper shrinkage and copper cutting operation. The copper foil at the hole is shrunk by chemical etching, and the copper foil at the hole is controlled to shrink by 4-5um. At the same time, the insulating layer PI is ensured not to shrink. Then, the shape, size and surface quality of the copper foil at the hole are checked by microscope and profile measuring equipment. It is observed whether the edge of the hole is flat and the shrinkage is uniform to ensure that the shrinkage effect meets the process requirements. During the shrinkage of the copper foil at the hole, the insulating layer is protected by means of mask or protective coating, and the shrinkage process of the copper foil at the hole is monitored in real time by high-precision measuring instruments to ensure that the shrinkage is stable within the range of 4-5um. The etching solution flow rate in chemical etching is adjusted in time according to the measurement results.

[0026] S4, hole protection copper plating The orifice is protected by copper plating. A chemical cleaning solution is used to remove oil, oxides, and dust on the surface of the orifice. Then, a micro-etching agent is used to micro-etch the surface of the orifice to remove the passivation layer on the surface. A special plating solution suitable for orifice protection copper plating is selected. According to the orifice size, plating solution composition, and required copper plating layer thickness, the current density is set to form copper plating. After the copper plating is completed, the orifice is immediately fully cleaned with deionized water to remove the residual plating solution and impurities on the surface, and the orifice is dried by low-temperature drying. The cleaning time is 5-15 minutes, and the temperature is controlled between 30-60℃. The micro-etching agent can use persulfate solution and acidic copper chloride solution. The cleaning after copper plating adopts a combination of spraying and immersion, and the cleaning time is not less than 3 minutes. This step can further prevent abnormal conditions at the orifice during subsequent drilling and copper plating, such as premature closure caused by tip discharge, and lay the foundation for the normal formation of subsequent copper columns.

[0027] S5, copper plating to form copper pillars Carry out copper plating process, prepare special copper plating solution according to process requirements, check the inductor substrate after pretreatment such as hole protection copper plating again, ensure that the hole is clean and free of impurities, and the hole protection copper plating layer is complete and uniform, and copper plating is carried out to deposit copper in the hole to form copper pillars, connecting the front and back lines. After copper plating is completed, immediately remove the inductor substrate from the plating tank, rinse it with a large amount of flowing deionized water to remove the residual plating solution on the surface, and then rinse it several times, and then use low-temperature drying to dry the copper-plated inductor substrate. In the early stage of copper plating, a lower current density of 0.8A / dm² can be used to make copper nucleate uniformly at the bottom of the hole, and then gradually increase the current density to 1.0-1.2A / dm² to promote the stable growth of copper pillars. By real-time monitoring of current and voltage changes, timely adjust the power output to ensure that the current density is stable within the set range. The rinsing time is not less than 5 minutes, and after the last rinse, use deionized water with a resistivity greater than 18MΩ・cm for testing.

[0028] S6. Finished product inspection Carry out random inspection on the processed finished products.

[0029] S7, finished product formation Products that pass random inspection are final products and enter the subsequent application stage.

[0030] The thin-film inductor adopts cavity-free processing technology for conducting copper pillars on both sides. Before copper plating, the copper foil at the hole mouth is cut to avoid tip absorption of electricity during copper plating, which causes tip damage too quickly. When copper pillars are plated, the holes are first copper-plated for protection to improve the integrity of the copper foil in the holes, and to avoid bubbles and cavity formation during copper pillar processing. The abnormal defect rate of cavities in copper pillars is significantly reduced from 46% to 0%, which greatly improves the product quality stability. The poor conduction problem is solved from 100% to 0%, which enhances the reliability of the product in practical applications. The process capability is improved from the previous processing capacity of ≥50um hole diameter to ≥20um, which is 2.5 times higher than before. It broadens the company's technical boundaries in the field of thin-film inductor processing and provides strong support for opening up a broader market. The inspection strategy is optimized from full inspection to random inspection, which greatly reduces the inspection cost, saves inspection and equipment investment costs, and improves production efficiency and economic benefits.

[0031] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A cavity-free processing technology for conducting copper pillars on the front and back sides of a thin film inductor, characterized in that: The following steps are involved: S1. Initial preparation Prepare the inductor material to be processed, including a substrate with front and back circuits and an insulating layer PI in the middle; S2. Drilling Drilling is performed on the material in step S1, the inductor to be drilled is fixed on the processing platform, the drilling position is determined by the positioning system of the CNC drilling machine, the drilling machine is started, and the drill bit starts to rotate and feed downward according to the set parameters to drill the inductor material to form a channel for subsequent copper column filling; S3, hole copper foil shrinkage treatment The copper foil at the front and back sides of the copper column end is subjected to copper shrinkage and copper cutting operation. The copper foil at the hole is shrunk by chemical etching, and the shrinkage of the copper foil at the hole is controlled to be 4-5um. At the same time, it is ensured that the insulating layer PI does not shrink. Then, a microscope and a profile measuring instrument are used to check the shape, size and surface quality of the copper foil at the hole after shrinkage, and observe whether the edge of the hole is flat and the shrinkage amount is uniform, to ensure that the shrinkage effect meets the process requirements; S4, hole protection copper plating The orifice is subjected to protective copper plating, and a chemical cleaning solution is used to remove oil, oxides, and dust on the surface of the orifice. Subsequently, a micro-etching agent is used to micro-etch the surface of the orifice to remove the passivation layer on the surface. A special plating solution suitable for orifice protective copper plating is selected. According to the orifice size, the composition of the plating solution, and the required copper plating layer thickness, the current density is set to form copper plating. After the copper plating is completed, the orifice is immediately fully cleaned with deionized water to remove the residual plating solution and impurities on the surface, and the orifice is dried by a low-temperature drying method; S5, copper plating to form copper pillars Conduct copper plating process, prepare special copper plating solution according to process requirements, check the inductor substrate after pretreatment such as hole protection copper plating again, ensure that the hole is clean and free of impurities, and the hole protection copper plating layer is complete and uniform, and copper plating is carried out to deposit copper in the hole to form copper pillars to connect the front and back circuits. After copper plating is completed, immediately take the inductor substrate out of the plating tank, rinse it with a large amount of flowing deionized water to remove the residual plating solution on the surface, and then rinse it several times, and then dry the copper-plated inductor substrate by low-temperature drying; S6. Finished product inspection Conduct random inspection on finished products; S7, finished product formation Products that pass random inspection are final products and enter the subsequent application stage.

2. The cavity-free processing technology for conducting copper pillars on the front and back sides of a thin film inductor according to claim 1, characterized in that: In step S2, after the drilling is completed, the quality of the hole is inspected by optical inspection equipment, and the inspection content includes the diameter accuracy, verticality, hole wall roughness and whether there are defects such as cracks.

3. The cavity-free processing technology for conducting copper pillars on the front and back sides of a thin film inductor according to claim 1, characterized in that: In the step S3, during the shrinkage of the hole copper foil, the insulating layer is protected by using a mask or a protective coating.

4. The process for processing copper pillars on the front and back sides of a thin film inductor without cavities according to claim 1, characterized in that: In step S3, a high-precision measuring instrument is used to monitor the shrinkage process of the orifice copper foil in real time to ensure that the shrinkage amount is stable within the range of 4-5um, and the etching solution flow rate in the chemical etching is adjusted in time according to the measurement result.

5. The cavity-free processing technology for conducting copper pillars on the front and back sides of a thin film inductor according to claim 1, characterized in that: In step S4, the cleaning time is 5-15 minutes, the temperature is controlled between 30-60° C., and the micro-etching agent can be a persulfate solution or an acidic cupric chloride solution.

6. The cavity-free processing technology for conducting copper pillars on the front and back sides of a thin film inductor according to claim 1, characterized in that: In step S4, the cleaning after copper plating is carried out by a combination of spraying and immersion, and the cleaning time is not less than 3 minutes.

7. The cavity-free processing technology for conducting copper pillars on the front and back sides of a thin film inductor according to claim 1, characterized in that: In step S5, at the initial stage of copper plating, a relatively low current density of 0.8 A / dm² can be used to uniformly nucleate copper at the bottom of the hole, and then the current density is gradually increased to 1.0-1.2 A / dm² to promote the stable growth of copper columns. By real-time monitoring of current and voltage changes, the power output is adjusted in time to ensure that the current density is stable within the set range.

8. The cavity-free processing technology for conducting copper pillars on the front and back sides of a thin film inductor according to claim 1, characterized in that: In step S5, the rinsing time is not less than 5 minutes, and after the last rinsing, the sample is tested with deionized water having a resistivity greater than 18 MΩ·cm.

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