The electromagnetic shielding characteristics of PI silver plated film in high frequency range

1、 Introduction

With the high-frequency development of modern electronic devices, the problem of electromagnetic interference (EMI) is becoming increasingly serious, and the performance requirements for electromagnetic shielding materials in the high-frequency range are also increasing.PI (polyimide) silver plated filmAs a high-performance electromagnetic shielding material, its electromagnetic shielding characteristics in the high-frequency range have attracted much attention. This article will delve into the electromagnetic shielding characteristics of PI silver plated film in the high-frequency range and its related influencing factors.

2、 The basic structure and electromagnetic shielding principle of PI silver plated film

1. Basic structure
   • PI silver plated film is based on polyimide and coated with a layer of silver nanoparticles on its surface through vacuum coating technology. The PI film itself has advantages such as high temperature resistance, insulation, and mechanical strength, while the silver plating layer endows it with excellent conductivity.
2. Electromagnetic shielding principle
   • In the high frequency range, electromagnetic shielding is mainly achieved through three mechanisms: reflection, absorption, and multiple reflection.
   • Reflection mechanism: Silver is a highly conductive material, and at high frequencies, free electrons in the silver plating layer can interact with incident electromagnetic waves, causing them to reflect. Due to the high conductivity of silver, PI silver plated film has a high reflectivity in the high-frequency range, effectively blocking the propagation of some electromagnetic waves.
   • Absorption mechanism: Electromagnetic waves interact with electric/magnetic dipoles, electrons, and phonons in the PI silver plated film, converting electromagnetic energy into heat and being absorbed. The silver nanoparticles in the PI silver plated film and the characteristics of the PI substrate jointly affect the absorption effect. In the high frequency range, as the frequency increases, the role of absorption mechanism in electromagnetic shielding gradually strengthens.
   • Multiple reflection mechanism: When electromagnetic waves propagate inside the PI silver plated film, multiple reflections occur between different interfaces, further attenuating the energy of the electromagnetic waves.

3、 Performance of electromagnetic shielding characteristics of PI silver plated film in high frequency range

1. Shielding effectiveness (SE)
   • In the high frequency range (such as GHz level), PI silver plated film usually exhibits high shielding effectiveness. Experimental studies have shown that as the frequency increases,PI silver plated filmThe shielding effectiveness may vary. At lower high frequencies (such as 1-5 GHz), its shielding effectiveness may gradually improve with increasing frequency. This is because in this frequency band, the reflection mechanism dominates, and the high conductivity of silver increases the proportion of reflected electromagnetic waves, thereby improving the shielding effectiveness.
   • As the frequency further increases (such as exceeding 5 GHz), the role of absorption mechanism gradually becomes prominent. The interaction between silver nanoparticles in PI silver plated film and PI substrate enhances the ability to absorb electromagnetic waves. Meanwhile, due to the skin effect at high frequencies, electromagnetic waves are more concentrated on the surface of the silver plating layer, which is also beneficial for improving shielding effectiveness.
2. Frequency Stability
   • The PI silver plated film has good frequency stability in the high frequency range. Compared with some other electromagnetic shielding materials, its shielding effectiveness fluctuates relatively less in a wider high-frequency range. This is due to the stability of the PI substrate and the uniformity of the silver plating layer. The molecular structure of the PI film itself is stable and can provide good support for the silver plating layer, making it difficult for the structure and properties of the silver plating film to change under the action of high-frequency electromagnetic waves, thereby ensuring the stability of electromagnetic shielding characteristics.
3. Comparison with other materials
   • Compared to traditional metalselectromagnetic shielding materialCompared to copper, aluminum, etc., PI silver plated film has unique advantages in the high-frequency range. Although metal materials have good electromagnetic shielding performance in the low frequency range, in the high frequency range, due to the intensification of skin effect, the thickness of metal materials needs to be increased to maintain good shielding effectiveness, which will increase the weight and cost of the material. Due to its thinning characteristics, PI silver plated film can achieve good electromagnetic shielding effect in the high-frequency range with lighter weight and thinner thickness.
   • Compared with other polymer based electromagnetic shielding materials, the conductivity of PI silver plated film is higher, which makes its reflection and absorption ability stronger in the high frequency range, thus possessing better electromagnetic shielding characteristics.

4、 Factors affecting the electromagnetic shielding characteristics of PI silver plated film in high frequency range

1. Quality of silver plating layer
   • The thickness, uniformity, and particle size of the silver plating layer have a significant impact on the electromagnetic shielding characteristics of PI silver plated film in the high-frequency range. A thicker silver plating layer can provide more free electrons, thereby enhancing reflection and absorption capabilities, but an excessively thick silver plating layer may lead to increased costs and decreased flexibility. A uniform silver plating layer can ensure uniform reflection and absorption of electromagnetic waves in the high-frequency range, avoiding differences in local shielding effectiveness. Smaller silver particle size helps to increase the contact area between silver particles and electromagnetic waves, improving electromagnetic shielding effectiveness.
2. Characteristics of PI substrate
   • The dielectric constant, loss factor and other characteristics of PI substrate will affectPI silver plated filmElectromagnetic shielding characteristics. A lower dielectric constant and appropriate loss factor are beneficial for improving the absorption and reflection efficiency of electromagnetic waves. In addition, the purity and crystallinity of the PI substrate can also affect the adhesion and overall electromagnetic shielding performance of the silver plating layer.
3. Preparation process
   • Different preparation processes, such as magnetron sputtering and evaporation plating in vacuum coating technology, can affect the structure and properties of PI silver plated films. For example, magnetron sputtering technology can prepare silver plated films with smaller and uniformly distributed silver particles, which often have better electromagnetic shielding performance in the high-frequency range.

5、 Conclusion

PI silver plated film has good electromagnetic shielding properties in the high frequency range, effectively shielding high-frequency electromagnetic waves through reflection, absorption, and multiple reflection mechanisms. It exhibits high shielding effectiveness and good frequency stability in the high frequency range, and has unique advantages compared to other materials. The quality of the silver plating layer, the characteristics of the PI substrate, and the preparation process all affect its electromagnetic shielding properties in the high frequency range. With the continuous development of high-frequency electronic devices, the application prospects of PI silver plated film in the field of electromagnetic shielding will be even broader. In the future, further in-depth research is needed on its electromagnetic shielding performance in higher frequency bands and complex electromagnetic environments to meet the constantly improving technical requirements.
The above data is for reference only, and specific performance may vary due to production processes and product specifications.