Study On Surface Characteristics Of Laser-activated AlN Ceramics And Microporous Array Strengthening

Aluminum nitride ceramics have excellent thermoelectric properties,making them ideal semiconductor substrates and packaging materials.Metallization is the key process for aluminum nitride ceramic packaging.Laser activated metallization is a new metallization method for aluminum nitride ceramics.This method combines laser activation with electroless copper plating,which has the advantages of directly forming a patterned metal layer and high production efficiency.However,this metallization method still needs to address the following issues:On the one hand,laser activated metallization of aluminum nitride ceramics is very sensitive to laser parameters and gas environments,and the impact of laser parameters on the characteristics of aluminum nitride laser activated surfaces under different gas environments needs further research;On the other hand,the adhesive strength of the metal layer produced by laser activated metallization of aluminum nitride ceramics still needs to be improved.In response to the above issues,the research results of this article are as follows:1.The effects of different laser parameters on the surface properties of aluminum nitride ceramics in different gas environments were investigated.The experimental results showed that laser power had a significant impact on the surface morphology and element content of laser activated metal layers of aluminum nitride ceramics in different gas environments.The formation mechanism of surface morphology differences caused by laser power impact in different gas environments was analyzed.In addition,the influence of different laser power and spot overlap ratio on the size of grooves formed by machining aluminum nitride ceramics in different gas environments was investigated;The simulation of the laser used was conducted,and the light intensity distribution and cumulative light intensity of the laser focused beam were introduced.It was found that under different spot overlap rates,the variation of groove depth and width was determined by the cumulative light intensity distribution of the laser spot.2.A new method for calculating laser energy density proportional to the intensity distribution of the focused spot was used to describe the subtle differences in laser activated aluminum nitride ceramics under different gas environments.However,the energy of the focused light spot is too strong to obtain the light intensity distribution directly.In this paper,the light intensity distribution of the focused light spot is obtained indirectly by incident a parallel Gaussian beam.Based on the calculation method of laser energy density related to light intensity distribution,the minimum laser energy density for laser activation of aluminum nitride ceramics to produce a better aluminum layer in different gas environments was calculated.The minimum cumulative laser energy density required for laser activation in air,argon,and nitrogen was 47.8J/cm~2,42.5J/cm~2,and 43.7J/cm~2,respectively.The subtle differences in laser activated aluminum nitride ceramics under different gas environments were obtained:based on the multi-pulse cumulative energy density required for laser activation in argon,the required energy density in air increased by 12.3%,and the required energy density in nitrogen increased by 3%.3.The effects of laser activation with different laser energy densities on the surface roughness and adhesive strength of electroless copper plating layers were investigated.The experimental results show that the surface roughness of copper coatings increases nonlinearly with the increase of laser energy density;The adhesive strength of copper coatings first increases and then decreases with laser energy density,reaching a maximum of 8.75MPa at a spot overlap rate of 90%and a single pulse laser energy density of 19J/cm~2.A new method of using laser to process microporous arrays is further proposed to increase the adhesive strength of the copper plating layer.The experimental results show that the adhesive strength of the copper plating layer on the microporous array with a laser energy density of 5J/cm~2 and a single microporous processing time of 50ms reaches 11.69MPa,which is 33.6%higher than that of the copper plating layer without micropores under the same laser activation parameters.