A manufacturing method of binding the PAD size CPK tube control greater than or equal to 1.33

Abstract

The application discloses a manufacturing method of binding PAD size CPK control >=1.33, and belongs to the technical field of PCB manufacturing. The method comprises the following steps: an engineering design step, in which a horn-shaped compensation pattern is added at the right-angle position of the binding PAD, and additional compensation design is performed; an electroplating step, in which direct current hole filling and pulse thickening are combined, and the copper thickness difference is controlled to be within ±3 μm; a circuit manufacturing step, in which LDI exposure with an analytical precision <=15 / 15 μm is adopted, nine-point method is used to measure the copper thickness to set parameters before etching, a vacuum two-fluid etching machine is adopted, and etching uniformity >=95% is controlled; and a detection control step, in which a flash tester is used to test the binding PAD size, Minitab is used to calculate CPK, and >=1.33 is ensured. Through horn-shaped compensation, differential compensation, pulse electroplating uniformity control, high-precision etching and CPK quantitative verification, the process capability index of the binding PAD size is improved from less than 1.00 to more than 1.33, the pattern precision and process stability are significantly improved, and the failure rate is reduced.

Description

Technical Field

[0001] This invention relates to the field of PCB (printed circuit board) manufacturing, and more particularly to a high-precision manufacturing method for bonding pads in die-on-brush (COB) technology. Background Technology

[0002] As electronic products evolve towards higher performance, miniaturization, and higher density, traditional discrete device packaging can no longer meet space and cost requirements. Die-on-board (COB) technology has emerged to address this need, as it directly mounts unpackaged bare chips onto a PCB or substrate, significantly reducing product size.

[0003] The bond pad is the core physical interface supporting this technology. It acts as a "bridge" between the chip electrodes and external circuitry, fulfilling multiple functions including electrical connection, mechanical fixation, and heat conduction. Without a properly designed bond pad, signal transmission between the chip and the PCB will be interrupted, and product functionality will be impossible.

[0004] Existing technologies for manufacturing bonded pads generally suffer from the following problems: 1) Dimensional deviations at right angles of the pattern are caused by the rounded corner effect of etching; 2) Small-sized pads suffer from severe side etching with insufficient compensation; 3) Poor uniformity of electroplated copper thickness affects etching consistency; 4) Lack of systematic CPK (process capability index) control measures, with process capability usually below 1.00. Summary of the Invention

[0005] The purpose of this invention is to provide a manufacturing method for controlling the size CPK of the binding PAD to ≥1.33.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A manufacturing method for binding PAD size CPK control ≥1.33 includes the following steps: Engineering design steps: Add ram's horn compensation graphics to the right-angle position of the binding PAD in the working draft, and perform additional compensation design on the binding PAD position; Electroplating steps: A combination of DC electroplating for filling holes and pulse electroplating for thickening is used to control the copper thickness difference after electroplating to within ±3μm; Circuit fabrication steps: An LDI exposure device with a resolution of ≤15 / 15μm is used. Before etching, the copper thickness on the board surface is measured using the nine-point method and the etching parameters are set based on the average value. Etching is performed using a vacuum two-fluid etching machine to control the etching uniformity to ≥95%. Inspection and control steps: After etching, the first piece is tested for the size of the bonded PAD using a flash tester, and the CPK is calculated using Minitab software to ensure that CPK ≥ 1.33.

[0007] Preferably, the ram's horn compensation pattern is a small square structure of 0.5 mil added at the right angle position to compensate for the etching rounded corner effect and ensure that the right angle position is straight after etching.

[0008] Preferably, the additional compensation design for the binding PAD position specifically involves: compensating the binding PAD in the working draft by 1.5-2 mil based on the original draft; for small-sized binding PADs with a size of 0.1 mm, an additional compensation of 0.5 mil is provided; and the spacing between binding PADs is controlled at 1.6 mil.

[0009] Preferably, the electroplating step specifically includes: DC electroplating parameters: 20 asf × 48min, one copper plating operation; Pulse electroplating parameters: 15 asf × 30 min, for secondary thickening plating; The process of reducing copper thickness by adding a capping hole is used to control the copper thickness difference after electroplating within ±3μm.

[0010] Preferably, the electroplating step includes a copper plating pretreatment step: confirming the copper thickness level of the incoming material and operating according to normal parameters.

[0011] Preferably, the circuit fabrication steps further include an ultra-roughening pretreatment and a dry lamination step before LDI exposure: Ultra-roughening pretreatment: grinding marks controlled at 10±2mm, water breaking time after grinding ≥35S, ultra-roughening micro-etching amount 0.6-0.9μm, copper ion concentration controlled at 15-40g / L; Dry lamination: lamination temperature 115±5℃, lamination pressure 0.45±0.05MPa, and stand for 15min-24hrs after lamination.

[0012] Preferably, the circuit fabrication steps further include a development step after LDI exposure: development pressure 1.5-2.0 kg / cm², development concentration 1±0.2%, development point controlled at 50±5%, and copper thickness tested using the nine-point method after development to confirm that the copper thickness is within the range of 25±3 μm.

[0013] Preferably, it also includes post-process control steps: AOI, solder mask, characterization, and surface treatment processes must not be reworked. If rework is necessary, the PAD dimensions must be confirmed a second time. After solder mask and nickel-palladium-gold plating, the PAD dimensions are tested again to ensure that the dimensions are continuously controlled throughout the process.

[0014] Preferably, the control target for the size of the bonded PAD tested by the flash meter is: the size of the bonded PAD is controlled within the range of 0.1mm ± 0.03mm.

[0015] Preferably, the LDI exposure equipment uses DI dry film, the exposure energy is controlled at 6-7 bars, and after exposure, it is left to stand for more than 15 minutes before development and etching.

[0016] In summary, the technical solution of this invention has the following beneficial effects: Through a series of technical means such as horn compensation design, differentiated compensation strategy, pulse electroplating uniformity control, vacuum two-fluid high uniformity etching, and flash meter + CPK quantitative verification, this invention improves the process capability index CPK of the PAD size from less than 1.00 to more than 1.33. Attached Figure Description

[0017] Figure 1 This is a compensation design drawing for Embodiment 1 of the present invention; Figure 2 This is the ram's horn compensation diagram of Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the energy ruler for confirming the light plate before exposure in Embodiment 1 of the present invention; Figure 4 This is a CPK calculation diagram from Embodiment 1 of the present invention; Figure 5-8 This is a schematic diagram of the OK monitoring after solder resist application in Embodiment 1 of the present invention. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, but this does not constitute a limitation on the scope of protection of the present invention.

[0019] This invention provides a manufacturing method for binding PADs with a CPK control of ≥1.33, comprising the following steps: Engineering design steps: Add horn-shaped compensation graphics to the right-angle positions of the binding PADs in the working draft, and perform additional compensation design for the binding PAD positions; specifically, to ensure that the binding PADs are as straight as possible, the sharp corners need to be treated with horn-shaped graphics to ensure that the angles are as straight as possible after etching. Add a small square of 0.5mil at the angle position to ensure that the right angle is straight after etching; the additional compensation design for the binding PAD positions is as follows: the binding PADs in the working draft are compensated by 1.5-2mil based on the original draft, and an additional 0.5mil is compensated for small-sized binding PADs with a size of 0.1mm, and the spacing between binding PADs is controlled at 1.6mil.

[0020] Electroplating steps: A combination of DC electroplating for filling holes and pulse electroplating for thickening is used to control the copper thickness difference after electroplating within ±3μm. The electroplating steps specifically include: DC electroplating parameters: 20asf × 48min, for a first copper plating; pulse electroplating parameters: 15asf × 30min, for a second thickening plating; and an additional process for reducing copper thickness by covering holes, ensuring the copper thickness difference after electroplating is controlled within ±3μm. In a preferred embodiment of the invention, a pre-treatment step for copper plating is included before the electroplating steps: confirming the copper thickness level of the incoming material and operating according to normal parameters. Circuit fabrication steps: An LDI exposure device with a resolution of ≤15 / 15μm is used. Before etching, the copper thickness on the board surface is measured using the nine-point method and the etching parameters are set based on the average value. Etching is performed using a vacuum two-fluid etching machine to control the etching uniformity to ≥95%. LDI exposure equipment uses DI dry film with a resolution of less than 35μm. The exposure energy is controlled at 6-7 divisions. After exposure, the film is left to stand for more than 15 minutes before development and etching. In the circuit fabrication process, before LDI exposure, there are also ultra-roughening pretreatment and dry lamination steps: Ultra-roughening pretreatment: scratches controlled at 10±2mm, water breaking time after grinding ≥35S, ultra-roughening micro-etching amount 0.6-0.9μm, copper ion concentration controlled at 15-40g / L; Dry lamination: lamination temperature 115±5℃, lamination pressure 0.45±0.05MPa, and standing for 15min-24hrs after lamination.

[0021] In the circuit fabrication process, after LDI exposure, there is also a development step: development pressure 1.5-2.0 kg / cm², development concentration 1±0.2%, development point control at 50±5%, and after development, the copper thickness is tested using the nine-point method to confirm that the copper thickness is within the range of 25±3 μm.

[0022] Inspection and control steps: After etching, the first piece is tested for the size of the bonded PAD using a flash tester, and the CPK is calculated using Minitab software to ensure that CPK ≥ 1.33.

[0023] Specifically, the control target for the size of the bonded PAD tested by the flash meter is: the size of the bonded PAD should be controlled within the range of 0.1mm ± 0.03mm.

[0024] In one embodiment of the present invention, a post-process control step is also included: each process, including AOI, solder mask, character printing, and surface treatment, must not be reworked. If rework is necessary, the PAD dimensions must be confirmed a second time. After solder mask and nickel-palladium-gold plating, the PAD dimensions are tested again to ensure that the dimensions are continuously controlled throughout the process.

[0025] Example 1: 1. Engineering Design: Original design on pad is 4mil, working design is 5.94mil, with a compensation of 1.94mil. Figure 1 As shown; The outer horn design of the pad is a 0.5mil square, such as... Figure 2 As shown; 2. Electroplating: Through-hole electroplating + thickening electroplating, copper reduction process, with copper thickness controlled at 25±3um.

[0026] When producing this model, the copper thickness of the incoming material is randomly inspected before copper plating. The copper thickness specification is 6-8um, and the actual measured copper thicknesses are 6.7um, 7.2um, 7.3um, 6.9um, 7.3um, 7.4um, 7.3um, 6.8um, and 6.9um, which meet the specifications. Through-hole plating is then performed according to the established process, with plating parameters of 20asf × 48min. After through-hole plating, the copper thickness specification is 25±2.5um, and the actual measured copper thicknesses are 24.2um, 25.3um, 25.2um, 23.7um, 24.2um, 22.9um, 26.2um, 26.7um, and 27.1um, which meet the copper thickness requirements. The thickening electroplating process was performed according to the established procedure, with the clamping point positions changed during electroplating. The electroplating parameters were 15 asf × 30 min. After thickening, the copper thickness specification was 37±3um, and the actual measured copper thicknesses were 35.1um, 34.6um, 35.8um, 36.7um, 38.2um, 38.8um, 39.4um, 39.5um, and 38.9um, which met the copper thickness requirements. A copper reduction process was then performed, resulting in a copper thickness specification of 25±3um. The actual measured copper thicknesses were 22.3um, 24.2um, 26.3um, 25.7um, 27.6um, 26.2um, 25.2um, 26.3um, and 27.7um, which also met the copper thickness requirements.

[0027] 3. Circuitry: When producing this model, the pretreatment confirmation includes a wear mark test result of 10±2mm, a water breakage time ≥35S, an ultra-roughening micro-etching amount of 0.6-0.9um, and a copper ion concentration of 15-40g / L; the actual confirmation is shown in the table below:

[0028] Apply the LDI-specific high-resolution DuPont dry film. Before application, ensure the film temperature is 115±5℃ and the application pressure is 0.45±0.05MPa, as shown in the table below:

[0029] After applying the film, let it stand for 20 minutes. Then, use a high-precision exposure machine from Han's Laser to produce the film. Before exposure, confirm the energy scale on the light plate is at 6 divisions. Figure 3 As shown; After exposure, allow the sample to stand for 20 minutes before development. The copper thickness (µm) of the first developed piece is measured, as shown in the table below.

[0030] Based on the copper thickness etching confirmation, the etching parameters were 4.9 m / min, with an upward spray pressure of 2.2 kg / cm² and a downward spray pressure of 2.0 kg / cm². Three etching cylinders were used; the etching direction was horizontal. After etching, the size of the bonding pad was measured using a flash meter, and the CPK was calculated using Minitab. The CPK reached 1.45, meeting the requirement of ≥1.33. The data collection is shown in the table below, and the Minitab calculation is as follows. Figure 4 As shown.

[0031]

[0032] 4. Solder resist: Post-solder resist measurement: data still meets requirements, such as... Figure 5-8 As shown, from the production line to the subsequent processes, strict control is required to prevent rework and violations of regulations.

[0033] Compared with the prior art, the present invention has the following beneficial effects: Process capability improvement: Through a series of technical means such as horn compensation design, differentiated compensation strategy, pulse electroplating uniformity control, vacuum two-fluid high uniformity etching, and flash meter + CPK quantitative verification, the process capability index CPK bound to the PAD size has been improved from less than 1.00 to more than 1.33.

[0034] Improved graphic accuracy: A 0.5mil horn compensation was added during the engineering design phase, which solved the technical problem of right angles becoming rounded after etching; a strategy of 2mil basic compensation plus an additional 0.5mil compensation for small-sized PADs was adopted to effectively offset the side etching effect and ensure the final dimensional accuracy of small-sized PADs.

[0035] Enhanced process stability: The thickness difference of electroplated copper is reduced from ±5μm to ±3μm, the etching uniformity is increased from 90% to over 95%, and the exposure resolution is improved from 35 / 35μm to 15 / 15μm, providing process assurance for stable control of PAD dimensions.

[0036] Closed-loop management throughout the entire process: Establish a comprehensive management system from engineering design, electroplating, circuit fabrication to subsequent processes, clarify the rules for non-rework or rework requiring secondary confirmation, and retest the PAD dimensions after solder resist and nickel-palladium-gold bonding to ensure continuous process control.

[0037] Significant economic benefits: greatly improves yield, reduces rework and scrap, lowers production costs, and meets the access requirements of high-end electronic products for high-reliability PCBs.

[0038] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for controlling the size of the PAD (Plug-in Device) and its corresponding CPK (Chip-Based The manufacturing method of 1.33 is characterized by, Includes the following steps: project Design steps: Add ram's horn compensation graphics to the right-angle position of the binding PAD in the working draft, and perform additional compensation design on the binding PAD position; Electroplating steps: A combination of DC electroplating for filling holes and pulse electroplating for thickening is used to control the copper thickness difference after electroplating to within ±3μm; Circuit fabrication steps: An LDI exposure device with a resolution of ≤15 / 15μm is used. Before etching, the copper thickness on the board surface is measured using the nine-point method and the etching parameters are set based on the average value. Etching is performed using a vacuum two-fluid etching machine to control the etching uniformity to ≥95%. Inspection and control steps: After etching, the first piece is tested for the size of the bonded PAD using a flash tester, and the CPK is calculated using Minitab software to ensure that CPK ≥ 1.

33.

2. The manufacturing method for controlling the CPK size of the binding PAD to ≥1.33 according to claim 1, characterized in that, The ram's horn compensation pattern is a small square structure of 0.5 mil added at the right angle position to compensate for the rounded corner effect of etching and ensure that the right angle position is straight after etching.

3. The manufacturing method for controlling the CPK size of the binding PAD to ≥1.33 according to claim 1, characterized in that, The additional compensation design for the binding PAD position is as follows: the binding PAD in the working draft is compensated by 1.5-2 mil based on the original draft, and an additional 0.5 mil is compensated for small-sized binding PADs with a size of 0.1 mm, and the spacing between binding PADs is controlled at 1.6 mil.

4. A method for controlling the size CPK of a bound PAD according to claim 1. The manufacturing method of 1.33 is characterized by, The electroplating step specifically includes: DC electroplating parameters: 20 asf × 48min, one copper plating operation; Pulse electroplating parameters: 15 asf × 30 min, for secondary thickening plating; The process of reducing copper thickness by adding a capping hole is used to control the copper thickness difference after electroplating within ±3μm.

5. The manufacturing method for controlling the CPK size of the binding PAD to ≥1.33 according to claim 1, characterized in that, The electroplating step is preceded by a copper plating pretreatment step: confirming the copper thickness level of the incoming material and operating according to normal parameters.

6. The manufacturing method for controlling the CPK size of the binding PAD to ≥1.33 according to claim 1, characterized in that, The circuit fabrication process includes an ultra-roughening pretreatment and a dry lamination step before LDI exposure: Ultra-roughening pretreatment: grinding marks controlled at 10±2mm, water breaking time after grinding ≥35S, ultra-roughening micro-etching amount 0.6-0.9μm, copper ion concentration controlled at 15-40g / L; Dry lamination: lamination temperature 115±5℃, lamination pressure 0.45±0.05MPa, and stand for 15min-24hrs after lamination.

7. The manufacturing method for controlling the CPK size of the binding PAD to ≥1.33 according to claim 1, characterized in that, In the circuit fabrication process, after LDI exposure, a development step is also included: development pressure 1.5-2.0 kg / cm², development concentration 1±0.2%, development point controlled at 50±5%, and after development, the copper thickness is tested using the nine-point method to confirm that the copper thickness is within the range of 25±3 μm.

8. The manufacturing method for controlling the CPK size of the binding PAD to ≥1.33 according to claim 1, characterized in that, It also includes post-process control steps: AOI, solder mask, characterization, and surface treatment processes must not be reworked. If rework is necessary, the PAD dimensions must be confirmed a second time. After solder mask and nickel-palladium-gold plating, the PAD dimensions must be tested again to ensure that the dimensions are continuously controlled throughout the process.

9. The manufacturing method for controlling the CPK size of the binding PAD to ≥1.33 according to claim 1, characterized in that, The target for controlling the size of the bonded PAD tested by the flash meter is: the size of the bonded PAD is controlled within the range of 0.1mm ± 0.03mm.

10. A method for controlling the size CPK of a bound PAD according to claim 1. The manufacturing method of 1.33 is characterized by, The LDI exposure equipment uses DI dry film, and the exposure energy is controlled at 6-7 bars. After exposure, the film is left to stand for more than 15 minutes before development and etching.

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