Solution to the deformation problem of PP substrate during gold plating process

Brief introduction

With the rapid development of industries such as electronics and decoration,PP gold-plated filmThe application is becoming increasingly widespread. However, deformation of PP substrate has always been a difficult problem for production enterprises during the gold plating process. Advanced Institute (Shenzhen) Technology Co., Ltd. has conducted in-depth exploration on this issue through long-term research and practice, accumulated rich experience, and formed a series of effective solutions.

2、 Analysis of Deformation Causes of PP Substrate

（1） Difference in thermal expansion coefficient

There is a significant difference in the thermal expansion coefficient between PP substrate and gold plating layer. In the process of gold plating, especially when it involves heating, such as high temperature of plating solution or subsequent drying treatment, due to the uneven thermal expansion of the two materials, stress will be generated inside the substrate. When the stress exceeds the bearing limit of the substrate, it will cause deformation.

（2） Changes in the internal structure of the substrate

The chemical treatment and physical effects during the gold plating process may have an impact on the internal structure of the PP substrate. For example, certain chemical reagents may penetrate into the interior of the substrate, causing rearrangement or partial degradation of molecular chains, thereby altering the mechanical properties of the substrate and making it more prone to deformation.

（3） Unreasonable gold plating process parameters

Improper setting of process parameters such as current density, plating time, and plating solution composition during electroplating may result in uneven thickness of the gold plating layer. Uneven gold plating can cause uneven stress on the surface of the substrate, leading to deformation. For example, in areas with excessive current density, the growth rate of the gold plating layer is fast and the thickness is large, which will cause significant pulling force on the substrate.

3、 Solution

（1） Substrate pretreatment

1. Annealing treatment
   Annealing the PP substrate and maintaining it at a certain temperature (usually 120-150 ° C) for a period of time (about 30-60 minutes) can eliminate the internal stress generated during the early processing of the substrate and improve its stability. The annealing process should be carried out under inert gas protection to prevent the substrate from oxidizing at high temperatures.
2. modification
   Using plasma treatment, etcSurface modification technologyIntroduce polar functional groups such as hydroxyl and carboxyl groups on the surface of PP substrate. This can enhance the adhesion between the substrate surface and the gold plating layer, and also help improve the substrate's resistance to subsequent chemical treatments, reducing the possibility of internal structural changes. The process parameters for plasma treatment can be set as follows: power of 100-300W, processing time of 5-15 minutes, and gas atmosphere of a mixture of argon and oxygen (argon flow rate of 30-50 sccm, oxygen flow rate of 5-10 sccm).

（2） Optimization of gold plating process parameters

1. Current density control
   Determine the appropriate range of current density through extensive experiments. Generally speaking, for PP substrate gold plating, the current density should be controlled between 0.5-1.5 A/dm ². The use of pulse electroplating technology can further optimize the distribution of current density and reduce the uneven thickness of the gold plating layer caused by current concentration. The parameters for pulse electroplating can be set to a pulse frequency of 500-1000 Hz and a duty cycle of 20% -50%.
2. Electroplating time adjustment
   Adjust the electroplating time reasonably according to the required thickness of the gold plating layer. On the premise of ensuring the quality of the gold plating layer, try to shorten the electroplating time as much as possible to reduce the immersion time of the substrate in the plating solution, and reduce the thermal impact and chemical erosion. For example, if the thickness of the gold plating layer is required to be 0.5-1.0 μ m, the electroplating time can be controlled within 10-20 minutes.
3. Optimization of plating solution composition
   Develop a special plating solution formula by adding an appropriate amount of stress regulator and leveling agent to the plating solution. Stress regulators can reduce the stress between the gold plating layer and the substrate, while leveling agents help to obtain a more uniform gold plating layer. For example, adding 0.1-0.5 g/L of organic sulfur compounds as stress regulators and 0.2-0.8 g/L of polyethyleneimine as leveling agents to conventional gold plating solutions.

（3） Post processing

1. Slow cooling
   After the gold plating is completed, slowly cool the product. Avoid excessive temperature gradient caused by rapid cooling, thereby reducing stress caused by differences in thermal expansion and contraction. The product can be placed in an environment with a small temperature gradient and naturally cooled to room temperature, or a segmented cooling method can be used, such as first holding at 80 ° C for 10-15 minutes, then holding at 50 ° C for 10-15 minutes, and finally cooling to room temperature.
2. Type processing
   To shape the cooled product, mechanical fixtures or molds can be used to fix it and maintain its shape stability for a certain period of time. The molding time depends on the size and shape of the product, usually 2-6 hours.

4、 Verification of Implementation Effectiveness of the Plan

existAdvanced Institute (Shenzhen) Technology Co., LtdOn the experimental production line, the PP substrate gold plating process was improved according to the above solution. After production verification of multiple batches of products, the results show that the deformation rate of PP substrate during the gold plating process has been reduced from the original 20% -30% to below 5%, the uniformity of the gold plating layer has been significantly improved, the quality and qualification rate of the product have been greatly improved, and the production efficiency has also been guaranteed to a certain extent.

5、 Conclusion

The deformation of PP substrate during gold plating process is a complex problem involving multiple factors. The complete solution proposed by Advanced Institute (Shenzhen) Technology Co., Ltd., which includes substrate pretreatment, gold plating process parameter optimization, and post-treatment, can effectively reduce the occurrence rate of substrate deformation and improve product quality. In the actual production process, enterprises can further adjust and optimize these plans according to their own equipment conditions, product requirements, etc., to achieve the best production effect and meet the market's demand for high-quality PP gold-plated film products.
The above data is for reference only, and specific performance may vary due to production processes and product specifications.