Film inductor processing technology without cavity for positive and negative surface conduction copper column

Abstract

The present application relates to the technical field of thin film inductor through copper pillar processing, and discloses a thin film inductor front and back surface through copper pillar cavity-free processing technology, including the following steps: preparing the inductor material to be processed, including the substrate with front and back surface lines and an insulating layer PI in the middle, drilling on the material in step S1, fixing the inductor to be drilled on the processing platform, determining the drilling position by using the positioning system of the numerical control drilling machine, starting the drilling machine, the drill starts to rotate and feeds downward according to the set parameters, drilling the inductor material to form a hole for subsequent copper pillar filling. The thin film inductor front and back surface through copper pillar cavity-free processing technology performs copper cutting treatment on the copper foil of the hole before copper plating, avoids sharp end electricity absorption during copper plating, causes sharp end pain speed too fast, performs one-time copper plating protection on the hole during copper pillar plating, improves the integrity of the copper foil in the hole, and avoids the formation of cavities due to bubbles during copper pillar processing.

Description

Technical Field

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

[0002] Thin film inductors are made using a vacuum thin film process. They are highly reliable, easy to integrate and manufacture in chips, and are very suitable for automated surface mount technology (SMT). They also have the advantages of small size and good high-frequency characteristics.

[0003] During the copper plating process on the front and back sides of the inductor, there is an insulating layer between the front and back sides. The front and back circuits are connected by drilling holes at the same position and filling copper pillars to form a loop. Since bubbles are generated during the copper plating process, cavities will exist in the copper pillars, resulting in insufficient effective area of ​​the copper pillars, causing quality risks and poor conduction after batch reliability (high temperature and high humidity) at the terminal. Currently, existing chemicals and equipment are temporarily unable to meet the process capabilities of a 40um aperture. 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] (1) Technical solution

[0005] The present invention provides the following technical solution: a cavity-free processing process for copper pillars with conductive contacts on both sides of a thin film inductor, comprising the following steps:

[0006] S1. Initial Preparation

[0007] Prepare the inductor material to be processed, including a substrate with front and back circuits and an insulating layer PI in the middle.

[0008] S2. Drilling

[0009] 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 using 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.

[0010] S3, hole copper foil shrinkage treatment

[0011] The copper foil on the front and back sides of the copper column end is subjected to the copper foil shrinkage operation, and the chemical etching method is used to achieve the shrinkage of the copper foil at the hole, 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 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.

[0012] S4, orifice protection copper plating

[0013] The orifice is protected by copper plating processing, a chemical cleaning solution is used to remove oil, oxide, 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, the current density is set according to the size of the orifice, the composition of the plating solution and the required copper plating layer thickness, copper plating is formed, and after copper plating is completed, the orifice is immediately washed with deionized water to remove residual plating solution and impurities on the surface, and a low-temperature drying method is used to dry the orifice.

[0014] S5, copper plating to form a copper column

[0015] The copper plating process is performed, a special copper plating solution is prepared according to the process requirements, the inductance substrate after the orifice protection copper plating pretreatment is checked again to ensure that the orifice is clean, free of impurities, the orifice protection copper plating layer is complete and uniform, copper plating processing is performed to deposit copper in the orifice to form a copper column, and the front and back circuits are connected, after copper plating is completed, the inductance substrate is immediately taken out of the plating tank, washed with a large amount of flowing deionized water to remove residual plating solution on the surface, then rinsed multiple times, and then the inductance substrate after copper plating is dried by a low-temperature drying method.

[0016] S6, finished product inspection

[0017] The finished product is subjected to sampling inspection.

[0018] S7, finished product formation

[0019] The product that passes the sampling inspection is the final product and enters the subsequent application link.

[0020] Preferably, in step S2, after drilling is completed, an optical detection device is used to detect the quality of the hole, and the detection content includes the diameter accuracy, perpendicularity, hole wall roughness and whether there are cracks.

[0021] Preferably, in step S3, a mask or protective coating method is used to protect the insulating layer during the copper foil in the orifice shrinking process.

[0022] Preferably, in step S3, a high-precision measuring instrument is used to monitor the copper foil in the orifice shrinking process in real time, to ensure that the shrinkage amount is stable within the range of 4-5um, and the etching liquid flow rate in the chemical etching is adjusted in a timely manner according to the measurement results.

[0023] Preferably, in step S4, the cleaning time is 5-15 minutes, the temperature is controlled between 30-60℃, and the micro-etching agent is a persulfate solution and an acidic copper chloride solution.

[0024] Preferably, in the step S4, the cleaning after copper plating is performed by combining spraying and soaking, and the cleaning time is not less than 3 minutes.

[0025] Preferably, in the step S5, a lower current density of 0.8 A / dm2 is used to make the copper nucleate uniformly at the bottom of the hole at the initial stage of copper plating, and then the current density is gradually increased to 1.0-1.2 A / dm2 to promote the stable growth of the copper column. The power output is adjusted in time to ensure that the current density is stable within the set range by monitoring the changes of current and voltage in real time.

[0026] Preferably, in the step S5, the rinsing time is not less than 5 minutes, and deionized water with a resistivity greater than 18 MΩ·cm is used for detection after the last rinsing.

[0027] (B) Beneficial effects

[0028] Compared with the prior art, the present application provides a thin film inductor positive and negative surface conduction copper column cavity-free processing technology, which has the following beneficial effects:

[0029] 1. The thin film inductor positive and negative surface conduction copper column cavity-free processing technology performs copper cutting treatment on the copper foil of the hole before copper plating, avoids sharp end electricity absorption during copper plating, causes the sharp end copper damage speed to be too fast, performs one-time copper plating protection on the hole during copper column plating, improves the integrity of the copper foil in the hole, and avoids the formation of cavities due to bubbles during copper column processing.

[0030] 2. The thin film inductor positive and negative surface conduction copper column cavity-free processing technology significantly reduces the abnormality rate of the cavity in the copper column, from 46% to 0%, greatly improves the product quality stability, solves the conduction failure problem, reduces from 100% to 0%, enhances the reliability of the product in actual application, improves the process capability, from the previous processing capability of ≥50 um hole diameter to the processing capability of ≥20 um, the capability is improved by 2.5 times, widens the technical boundary of the company in the field of thin film inductor processing, provides strong support for opening up a wider market, optimizes the inspection strategy from full inspection to sampling inspection, greatly reduces the inspection cost, saves the inspection and equipment investment cost, improves the production efficiency and economic benefit. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a schematic diagram of the structure after drilling of the present application;

[0032] Figure 2 It is a schematic diagram of the structure after the copper foil of the hole is retracted in the present application;

[0033] Figure 3 It is a schematic diagram of the structure after the copper plating protection of the hole in the present application;

[0034] Figure 4The structure diagram of the copper column after processing of the application. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the application will be apparently and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all the other embodiments obtained by a person of ordinary skill in the art without creative work belong to the protection scope of the application.

[0036] Please refer to Figures 1-4 The application provides a technical solution: a cavity-free processing technology for a thin-film inductor copper column with positive and negative surface conduction, comprising the following steps:

[0037] S1, initial preparation

[0038] The inductor material to be processed is prepared, including a substrate with positive and negative surface lines and an insulating layer PI in the middle.

[0039] S2, drilling processing

[0040] Drilling operation is performed on the material in step S1. The inductor to be drilled is fixed on the processing platform. The positioning system of the numerical control drilling machine is used to determine the drilling position. The drilling machine is started. The drill bit starts to rotate and feeds downward according to the set parameters. The inductor material is drilled to form a hole for subsequent copper column filling.

[0041] After drilling is completed, optical detection equipment is used to detect the quality of the hole. The detection content includes the diameter accuracy, perpendicularity, hole wall roughness and whether there are cracks. It is a key pretreatment to avoid hole closure and cavity formation in the subsequent process. The drilling position needs to be accurately corresponding to the positive and negative surface lines to ensure that the lines can be connected to form a loop.

[0042] S3, hole copper foil inward shrinkage processing

[0043] The hole copper foil inward shrinkage processing is performed on the positive and negative surface copper foils at the end of the copper column. The hole copper foil inward shrinkage is realized by chemical etching method. The hole copper foil is controlled to shrink inward by 4-5um, while ensuring that the insulating layer PI does not shrink inward. Then, a microscope and a profile measuring instrument are used to check the shape, size and surface quality of the hole copper foil after inward shrinkage. Whether the hole edge is smooth and the inward shrinkage amount is uniform is observed to ensure that the inward shrinkage effect meets the process requirements. In the process of hole copper foil inward shrinkage, the insulating layer is protected by using a mask or a protective coating. High-precision measuring instruments are used to monitor the hole copper foil inward shrinkage process in real time to ensure that the inward shrinkage amount is stable within the range of 4-5um. The flow rate of the etching liquid in the chemical etching is adjusted in time according to the measurement results.

[0044] S4, hole protection copper plating

[0045] The orifice is protected and plated with copper, a chemical cleaning solution is used to remove oil, oxide, 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 copper plating of the orifice is selected, the current density is set according to the size of the orifice, the composition of the plating solution and the required copper plating layer thickness, copper plating is formed, after copper plating is completed, the orifice is immediately washed with deionized water to remove residual plating solution and impurities on the surface, and the orifice is dried by a low-temperature drying method. The cleaning time is 5-15 minutes, the temperature is controlled between 30-60℃, the micro-etching agent is a solution of persulfate and acidic copper chloride, the cleaning after copper plating is a combination of spraying and soaking, and the cleaning time is not less than 3 minutes. This step can further prevent abnormal conditions of the orifice in the subsequent drilling and copper plating process, such as premature closure caused by tip discharge, and lay a foundation for the normal formation of the copper pillar in the subsequent process.

[0046] S5, copper plating to form a copper pillar

[0047] The copper plating process is carried out, a special copper plating solution is prepared according to the process requirements, the inductor substrate after the orifice protection and copper plating pretreatment is checked again to ensure that the hole is clean and free of impurities, the orifice protection and copper plating layer is complete and uniform, copper plating is carried out to deposit copper in the hole to form a copper pillar, and the front and back circuits are connected. After copper plating is completed, the inductor substrate is immediately taken out of the plating tank, washed with a large amount of flowing deionized water to remove residual plating solution on the surface, then rinsed multiple times, and then dried by a low-temperature drying method. In the initial stage of copper plating, a lower current density of 0.8 A / dm2 is used to make copper nucleate uniformly at the bottom of the hole, then the current density is gradually increased to 1.0-1.2 A / dm2 to promote the stable growth of the copper pillar, the current and voltage changes are monitored in real time, the power output is adjusted in time to ensure that the current density is stable within the set range. The rinsing time is not less than 5 minutes, and the last rinsing is detected with deionized water with a resistivity of greater than 18 MΩ·cm.

[0048] S6, product inspection

[0049] The processed finished products are sampled and inspected.

[0050] S7, product formation

[0051] The products that pass the sampling and inspection are the final products and enter the subsequent application link.

[0052] The thin film inductor positive and negative surface conduction copper column cavity-free processing technology, before copper plating, the copper foil of the orifice is treated by cutting copper to avoid the tip from absorbing electricity during copper plating, causing the tip to damage the copper too fast, during copper column plating, the hole is first plated with copper for protection, improving the integrity of the copper foil inside the hole, avoiding the formation of bubbles and cavities during copper column processing, the abnormality rate of the cavity in the copper column is significantly reduced, from 46% to 0%, greatly improving the product quality stability, the conduction failure problem is solved, from 100% to 0%, enhancing the reliability of the product in actual application, the process capability is improved, from the previous ability to process ≥50um hole diameter to ≥20um processing capability, the ability is improved by 2.5 times, widening the company's technical boundaries in the field of thin film inductor processing, providing strong support for opening up a wider market, optimizing the inspection strategy, from full inspection to sampling inspection, greatly reducing the inspection cost, saving inspection and equipment investment cost, improving production efficiency and economic benefit.

[0053] While embodiments of the present application have been shown and described with reference to particular embodiments thereof, it will be understood by those skilled in the art that various changes in form and details can be made therein without departing from the spirit and scope of the application. The scope of the application is defined by the appended claims and their equivalents.

Claims

1. A cavity-free processing technology for copper pillars with conductive contacts on both 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 using the positioning system of the CNC drilling machine. The drilling machine is started, and the drill bit begins to rotate and feed downward according to the set parameters to drill holes in the inductor material, forming channels for subsequent copper pillar filling. S3, hole copper foil shrinkage treatment The copper foil on both sides of the copper pillar end is subjected to copper shrinkage operation. Chemical etching is used to achieve the shrinkage of the copper foil at the hole, and the shrinkage of the copper foil at the hole is controlled to 4-5um. At the same time, it is ensured that the insulating layer PI does not shrink. Then, a microscope and profilometer are used to check the shape, size and surface quality of the copper foil after shrinkage. The hole edge is observed to see whether the shrinkage is uniform, and the shrinkage effect is ensured to meet 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 protection copper plating is selected. According to the orifice size, plating solution composition, 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 thoroughly 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. S5, copper plating to form copper pillars Conduct copper plating, prepare a special copper plating solution according to the process requirements, re-check the inductor substrate after the hole protection copper plating pretreatment to ensure that the hole is clean and free of impurities, and the hole protection copper plating layer is complete and uniform. Then perform copper plating to deposit copper in the hole to form copper pillars, connecting the front and back circuits. After the copper plating is completed, immediately remove the inductor substrate from the plating tank, rinse it with a large amount of running deionized water to remove the residual plating solution on the surface, then rinse it multiple times, and then dry the copper-plated inductor substrate using a low-temperature drying method; S6. Finished product inspection Conduct random inspections on finished products; S7, finished product formation Products that pass random inspections are final products and enter the subsequent application stage.

2. The cavity-free processing process for copper pillars with conductive contacts on both 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 using optical inspection equipment. The inspection content includes the hole diameter accuracy, verticality, hole wall roughness and whether there are crack defects.

3. The cavity-free processing technology for copper pillars with conductive contacts on both sides of a thin film inductor according to claim 1, characterized in that: In 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 both 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 4-5 μm, and the etching solution flow rate in the chemical etching is adjusted in time according to the measurement results.

5. The cavity-free processing technology for copper pillars with conductive contacts on both 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 uses a persulfate solution or an acidic copper chloride solution.

6. The cavity-free processing technology for copper pillars with conductive contacts on both 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 process for processing copper pillars on both sides of a thin film inductor without cavities 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 is 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 pillars. 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 copper pillars with conductive contacts on both 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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