A kind of hanger for nickel-palladium-gold processing of IC carrier plate sheet

Abstract

The application belongs to the technical field of electroplating equipment, and particularly relates to a hanger for processing nickel-palladium-gold of an IC carrier plate thin plate, which comprises a hanger main frame, an intelligent contact array, a partition independent anode module and an intelligent control module, and the key lies in that an in-situ precision thickness measuring module independent of an electroplating tank and a matched automatic transfer mechanism are arranged, in an electroplating process, the intelligent control module periodically controls the transfer mechanism to move the carrier plate out of the plating solution for high-precision thickness measurement, and uses the obtained thickness true value data to online calibrate the built-in digital twin electroplating model, based on the calibrated high-confidence model, the controller dynamically adjusts the current output of each partition anode, and realizes self-adaptive precision control of the plating layer growth. The application effectively solves the problem that the precision sensor is difficult to work in the plating solution, and through the mechanism of discrete measurement and continuous optimization, the plating layer uniformity is significantly improved, and the consumption of noble metal is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of electroplating equipment technology, and in particular to a fixture for processing nickel-palladium-gold on thin IC substrates. Background Technology

[0002] In the electroless nickel-palladium-gold plating process of thin IC substrates (thickness typically ≤0.2mm), the mounting fixture is a key tool for supporting the substrate and achieving electrical connection. Due to the extreme warping of the thin substrate, there are differences in the contact resistance between it and the fixed contacts of the mounting fixture, resulting in a severely uneven distribution of current density during the electroplating process, which in turn causes uneven plating thickness (the industry average is ≥±8%). This not only affects the reliability of subsequent micro-pad soldering, but also leads to overall overplating to ensure that the thinnest area meets the standard, resulting in a serious waste of precious metals (palladium, gold).

[0003] Currently, most mainstream mounting fixtures are passive mechanical structures, which cannot sense and compensate for the real-time deformation and contact status of the substrate. Process control relies on experience and lacks closed-loop adjustment capabilities. Although there have been some attempts to integrate sensors, placing precision measuring components in highly corrosive and highly conductive chemical plating solutions for extended periods presents insurmountable technical bottlenecks such as signal interference, packaging failure, and measurement inaccuracies.

[0004] Therefore, developing an intelligent hanger that can achieve adaptive precision control under complex working conditions and is stable and reliable in engineering has become an urgent need in the industry. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a mounting fixture for processing nickel-palladium-gold alloys onto thin IC substrates. This fixture, through an innovative system architecture, combines periodic precision liquid separation measurement with real-time online monitoring, constructing a closed-loop control system based on digital twins. This enables intelligent and high-precision management of coating thickness uniformity, provided it is engineering-feasible.

[0006] To achieve the above objectives, the present invention proposes a mounting fixture for processing nickel-palladium-gold alloys onto thin IC substrates, comprising a main frame and a contact array disposed on the main frame, and further comprising: The in-situ precision thickness measurement module includes a measuring chamber set independently of the electroplating tank and a high-precision non-contact thickness gauge installed in the measuring chamber. The high-precision non-contact thickness gauge is a confocal color difference sensor or a white light interferometer. An automatic transfer mechanism, driven and connected to the main frame of the fixture, is used to remove the main frame of the fixture carrying the carrier plate from the electroplating solution and transfer it to the measuring chamber when a measurement command is executed, and to return it to the electroplating solution after the measurement is completed. The partitioned independent anode module has its anode body divided into multiple independent conductive partitions, each of which is electrically connected to an independently controllable power supply. The intelligent control module is connected to the in-situ precision thickness measurement module, the automatic transfer mechanism, the multi-parameter online monitoring module, and the partitioned independent anode module. The intelligent control module has a built-in digital twin electroplating model and an optimization controller. The intelligent control module is configured to: trigger the automatic transfer mechanism and the in-situ precision thickness measurement module to work together according to a preset strategy to obtain periodic thickness distribution data; use this data to perform online calibration of the digital twin electroplating model; and then generate adjustment commands for the partitioned independent anode module and each contact circuit through the optimization controller based on the calibrated model. The optimization controller is a model predictive controller.

[0007] Preferably, the contact array is a smart contact array, and each contact unit in the smart contact array includes an elastic conductive probe, a piezoelectric actuator for driving the elastic conductive probe to make micro-displacement, and a measuring circuit for measuring the contact resistance of the contact, wherein the piezoelectric actuator is mechanically coupled to the elastic conductive probe.

[0008] Preferably, the intelligent control module is also signal-connected to each of the contact units and is configured to adjust the piezoelectric actuator to make the contact resistance distribution uniform in the initial stage based on the contact resistance measurement value of each contact unit.

[0009] Preferably, the system further includes a multi-parameter online monitoring module, which includes current and voltage sensors disposed in each contact circuit, and an online analyzer for monitoring the composition of the plating solution; the multi-parameter online monitoring module is signal-connected to the intelligent control module.

[0010] Preferably, the intelligent control module further includes a model predictive controller, which performs rolling optimization with the coating thickness uniformity as the optimization objective and the current of each conductive zone as the control variable.

[0011] Preferably, the high-precision non-contact thickness gauge is a confocal chromatic aberration sensor or a white light interferometer.

[0012] Preferably, the intelligent control module is configured to trigger the periodic collaborative operation based on the electroplating time or the thickness value predicted by the digital twin electroplating model.

[0013] Preferably, the digital twin electroplating model is a simulation model based on multi-physics coupling, and the calibration process adopts a parameter estimation algorithm based on filtering or least squares.

[0014] Preferably, the intelligent control module further includes a process knowledge base storing historical process data.

[0015] Preferably, the automatic transfer mechanism includes a high-precision linear module and a lifting device, used to achieve precise positioning and smooth movement of the main frame of the hanger in three-dimensional space; specifically, the automatic transfer mechanism consists of a high-precision linear module, a lifting machine and a clamp, which are rigidly connected to the main frame of the hanger. After receiving control commands, the mechanism can automatically complete a series of actions such as "lifting, translating, positioning and returning" of the hanger, ensuring that the carrier plate is stable and vibration-free during the transfer process.

[0016] Compared with the prior art, the present invention provides a fixture for processing nickel-palladium-gold alloys onto thin IC substrates, which has the following advantages: This invention introduces a mechanism that combines periodic in-situ liquid separation measurement with online model calibration based on the hanger. The core advantage of this mechanism is: On the one hand, it enables the high-precision thickness gauge to work in a clean, dry, and stable environment, fundamentally solving the problem of precision sensors failing in plating solutions and obtaining reliable true thickness data; On the other hand, by continuously inputting these discrete but accurate true values ​​and calibrating the digital twin model, the model can make high-confidence predictions during measurement intervals, thereby driving the actuator to achieve continuous closed-loop control. This constitutes an intelligent control mode of discrete measurement and continuous optimization. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the first angle structure of a fixture for processing nickel-palladium-gold on thin IC substrates, as proposed in this invention. Figure 2 This is a schematic diagram of the second angle structure of a fixture for processing nickel-palladium-gold on thin IC substrates, as proposed in this invention. Figure 3 For the present invention Figure 2 A magnified structural diagram at point A; Figure 4 This is a flowchart of the periodic measurement and model calibration control logic of the present invention.

[0018] In the diagram: 10. Main frame of the hanger; 11. Hook; 20. Contact unit; 21. Elastic conductive probe; 22. Miniature piezoelectric ceramic actuator; 23. Housing. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] Example 1, see Figures 1 to 4 This embodiment provides a fixture for processing nickel-palladium-gold alloys onto thin IC substrates.

[0022] 1. System Hardware Configuration Hanging fixture body: The main frame 10 of the hanging fixture is made of high-strength titanium alloy and has excellent corrosion resistance and structural stability. The top crossbeam of the main frame 10 of the hanging fixture is equipped with hooks 11 that are used in conjunction with the automatic transfer mechanism.

[0023] Intelligent contact array: Dozens of contact units 20 are distributed and fixed in a matrix on the crossbeams of the main frame, such as... Figure 3 As shown, each contact unit 20 includes components mounted within the housing 23: Elastic conductive probe 21: The head has a hemispherical rhodium-plated structure to ensure good contact and conductivity.

[0024] Miniature piezoelectric ceramic actuator 22: It adopts a stacked structure and can achieve a precise displacement of ±1.5mm under a driving voltage of 0-150V, which is used to dynamically adjust the probe pressure.

[0025] Four-wire measurement circuit: directly connected to the root of the elastic conductive probe 21, used to measure the contact resistance between the contact and the carrier plate in real time with an accuracy of ±0.1mΩ.

[0026] In-situ precision thickness measurement module: A sealed, clean, temperature-controlled measurement chamber is built next to the electroplating tank. A high-precision confocal color difference thickness gauge is fixedly installed inside the chamber. Its measuring head is perpendicular to the plane of the carrier plate, and it can quickly scan the thickness of the entire surface of the carrier plate through a one-dimensional or two-dimensional scanning mechanism.

[0027] Automatic transfer mechanism: Composed of high-precision linear module, lifting machine and clamp, rigidly connected to the main frame 10 of the hanger. After receiving control commands, the mechanism can automatically complete a series of actions such as "lifting, translation, positioning and return" of the hanger, ensuring that the carrier plate is stable and vibration-free during the transfer process.

[0028] Multi-parameter online monitoring module: A Hall current sensor is connected in series on the power supply bus of each contact unit 20, and a high impedance voltage sampling circuit is connected in parallel to acquire the current I_i(t) and voltage U_i(t) flowing through each contact in real time.

[0029] An online ion concentration analyzer and pH meter are integrated into the circulation pipeline of the electroplating tank to monitor the concentration of nickel ions, palladium ions and pH value in the plating solution in real time.

[0030] Independent anode module: The traditional flat anode is divided into multiple mutually insulated strip anode zones, for example, 8 independent zones along the width of the carrier plate. Each anode zone is connected to an independent programmable pulse power supply through a separate cable, thereby realizing independent current control.

[0031] Intelligent control module: Based on an industrial computer as the core hardware platform, including: Data fusion layer: Real-time synchronization and preprocessing of data from all sensors; Digital twin model: An electrochemical-mass transfer-flow field multiphysics coupling model established based on the finite element method, which can simulate the coating growth process under given current distribution, contact conditions and solution parameters; Model Predictive Controller (MPC): With the goal of achieving optimal coating thickness uniformity over a future period, and using the current of each anode zone as the control variable, it performs rolling time-domain optimization calculations. Process knowledge base: Stores historical production data, model parameter evolution records, and optimization cases.

[0032] 2. Intelligent workflow and control logic Combination Figure 4 The fixture operates according to the following process in a complete electroplating process: Step 1: Initialization and Adaptive Pressing After the carrier plate is loaded, the elastic conductive probes 21 of all contact units 20 contact the edge of the carrier plate under the preset base pressure. The intelligent control module reads the initial contact resistance value of all contacts and calculates its statistical distribution. If the distribution is not uniform (e.g., standard deviation σ>1.0mΩ), the contact pressure is finely adjusted by adjusting the voltage of the corresponding contact micro piezoelectric ceramic actuator 22 until the contact resistance distribution is uniform (σ≤set threshold), laying the foundation for current equalization.

[0033] Step 2: Start electroplating and model predictive control The carrier plate is immersed in the electroplating solution, and electroplating begins. The intelligent control module starts the digital twin model and MPC controller. The model makes predictions based on the initial parameters and the real-time monitored I_i(t) and solution concentration. The MPC calculates the optimized current setpoint I_anode_j for each anode zone based on the predicted thickness distribution and sends it to each independent power supply for execution.

[0034] Step 3: Triggering and Execution of Periodic In-situ Measurements When preset conditions are met (e.g., the cumulative electroplating time reaches T1, or the model predicts the average thickness to reach D1), the intelligent control module triggers the automatic transfer mechanism. The automatic transfer mechanism smoothly moves the carrier plate out of the electroplating solution and into the measuring chamber. The thickness gauge performs a full scan of the carrier plate surface to obtain the real thickness distribution matrix M_measured at the current moment. After the measurement is completed, the mechanism sends the carrier plate back to the electroplating tank to continue electroplating.

[0035] Step 4: Online calibration of the digital twin model This is the core of achieving high-precision control. The control module compares the measured true value M_measured with the predicted thickness distribution M_predicted of the digital twin model at the same time. Using the extended Kalman filter algorithm, based on the deviation between the two, it back-estimates and updates the key state variables and parameters in the model (such as the local current efficiency matrix η, equivalent boundary layer thickness, etc.). This process enables the model to quickly correct its prediction error and more accurately reflect the current actual process state.

[0036] Step 5: Control command re-optimization Based on the calibrated, more confident new model, the MPC controller is re-optimized to generate more accurate anode current control commands for subsequent process stages.

[0037] Step Six: Iterate until the process is complete. Repeat steps two through five to form a closed loop of "predictive control → periodic measurement → model calibration → re-optimization". As the number of measurement and calibration increases, the prediction accuracy and control effect of the model are continuously improved. Usually, 2-4 periodic measurements are sufficient to achieve excellent control effect. At the end of the process, a final measurement can be performed to verify the final quality.

[0038] 3. Application Examples Taking an IC substrate with processing dimensions of 510mm×515mm×0.15mm and a target electroless nickel plating layer thickness of 5.0μm as an example.

[0039] Hanger configuration: The hanger is equipped with 96 smart contacts, divided into 12 groups, with the anodes divided into 6 independent zones. The contact resistance uniformity threshold σ_th is set to 1.0mΩ.

[0040] Measurement strategy: When the predicted thickness is approximately 1.0 μm, 2.5 μm, and 4.0 μm, three periodic in-situ measurements are automatically triggered.

[0041] Implementation process: After initialization, the standard deviation of contact resistance was adaptively reduced from the initial 1.8mΩ to 0.6mΩ.

[0042] First measurement (1.0μm): The measurement revealed that the thickness of the upper left region was about 12% thinner than the model prediction. After model calibration, it was found that the effective current density in this region was low due to the micro-warping of the carrier plate. In response to the MPC, the current of the two anode partitions corresponding to this region was increased by 18%.

[0043] Second measurement (2.5μm): The data showed that the thickness difference in the upper left region had been reduced to 5%, but there was an overthickness trend of about 3% in the middle of the right side of the plate. The model was recalibrated and the relevant anode partition current was slightly reduced.

[0044] Third measurement (4.0μm): The thickness uniformity of the entire plate is better than ±2.0%, and the model parameters tend to be stable.

[0045] Process completion: The final in-situ measurement results show that the nickel layer thickness distribution ranges from 4.94μm to 5.07μm, with a uniformity of ±1.3%, which is significantly better than the design target of ≤±3%. According to statistics, the palladium consumption in this production was reduced by 22% compared with the baseline of using traditional racks.

[0046] Example of model calibration formula: Let X be the state vector of the model to be calibrated (including local current efficiency, etc.), Z_k be the true thickness value M_measured of the k-th measurement, and H(X_{k|k-1}) be the thickness M_predicted predicted by the model based on the previous state. Kalman filtering is used for state update: X_{k|k} = X_{k|k-1} + K_k [Z_k-H(X_{k|k-1})]; where K_k is the Kalman gain matrix, which is dynamically calculated based on the model prediction error covariance and measurement noise covariance. Through this formula, the system uses the measurement residuals to optimally correct the internal state of the model.

[0047] Example 2 Based on Example 1, the process knowledge base in the intelligent control module further integrates a machine learning module. This module can autonomously learn the optimal initial model parameter set and measurement node strategy under different plate types, materials and thickness targets by analyzing model calibration data, final uniformity results and process parameters in previous production processes. When processing new type of carrier plate, the system can automatically recommend similar process formulas to achieve rapid trial production and shorten the process debugging cycle from several weeks to several days.

[0048] In summary, the system design of this invention integrates offline precision measurement with online intelligent control, achieving a revolutionary improvement in precision and cost control for the thin-plate electroplating process of IC substrates while ensuring engineering reliability.

[0049] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A mounting fixture for processing nickel-palladium-gold alloys onto thin IC substrates, comprising a main frame (10) and a contact array disposed on the main frame (10), characterized in that, Also includes: The in-situ precision thickness measurement module includes a measuring chamber set up independently of the electroplating tank and a high-precision non-contact thickness gauge installed in the measuring chamber. An automatic transfer mechanism is driven to connect with the main frame (10) of the fixture and is used to transfer the main frame (10) carrying the carrier plate between the electroplating tank and the measuring chamber. The partitioned independent anode module has its anode body divided into multiple independent conductive partitions, each of which is electrically connected to an independently controllable power supply. The intelligent control module is connected to the in-situ precision thickness measurement module, the automatic transfer mechanism, and the partitioned independent anode module via signals. The intelligent control module has a built-in digital twin electroplating model and is configured to: control the automatic transfer mechanism and the in-situ precision thickness measurement module to work together periodically to obtain thickness distribution data, use the thickness distribution data to calibrate the digital twin electroplating model, and output current control commands to the partitioned independent anode module based on the calibrated model.

2. The fixture for processing nickel-palladium-gold alloy onto thin IC substrates according to claim 1, characterized in that, The contact array is a smart contact array, and each contact unit (20) in the smart contact array includes an elastic conductive probe (21), a piezoelectric actuator for driving the elastic conductive probe (21) to make micro-displacement, and a measuring circuit for measuring the contact resistance of the contact.

3. The fixture for processing nickel-palladium-gold alloy onto thin IC substrates according to claim 2, characterized in that, The intelligent control module is also signal-connected to each of the contact units (20) and is configured to adjust the piezoelectric actuator to make the contact resistance distribution uniform in the initial stage according to the contact resistance measurement value of each contact unit (20).

4. The fixture for processing nickel-palladium-gold alloy onto thin IC substrates according to claim 1, characterized in that, It also includes a multi-parameter online monitoring module, which includes current and voltage sensors installed in each contact circuit, and an online analyzer for monitoring the composition of the plating solution; the multi-parameter online monitoring module is signal-connected to the intelligent control module.

5. A fixture for processing nickel-palladium-gold alloys onto thin IC substrates according to claim 1, characterized in that, The intelligent control module also includes a model predictive controller, which performs rolling optimization with the coating thickness uniformity as the optimization objective and the current of each conductive zone as the control variable.

6. The fixture for processing nickel-palladium-gold alloy onto thin IC substrates according to claim 1, characterized in that, The high-precision non-contact thickness gauge is a confocal chromatic aberration sensor or a white light interferometer.

7. A fixture for processing nickel-palladium-gold alloys onto thin IC substrates according to claim 1, characterized in that, The intelligent control module is configured to trigger the periodic collaborative operation based on the electroplating time or the thickness value predicted by the digital twin electroplating model.

8. A fixture for processing nickel-palladium-gold alloys onto thin IC substrates according to claim 1, characterized in that, The digital twin electroplating model is a simulation model based on multi-physics coupling, and the calibration process adopts a parameter estimation algorithm based on filtering or least squares.

9. A fixture for processing nickel-palladium-gold alloys onto thin IC substrates according to claim 1, characterized in that, The intelligent control module also includes a process knowledge base that stores historical process data.

10. A fixture for processing nickel-palladium-gold alloys onto thin IC substrates according to claim 1, characterized in that, The automatic transfer mechanism includes a high-precision linear module and a lifting device, which are used to achieve precise positioning and smooth movement of the main frame (10) of the hanger in three-dimensional space.

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