| With the advent of the high-speed era,electronic information products are increasingly developing in the direction of miniaturization,integration and functionalization.The interconnection between the printed circuit board and the components mainly relies on soldering.Now the requirements for high-precision soldering are getting higher and higher.At the same time,the transmission frequency increases,and the clock frequency continues to increase,resulting in the continuous reduction of the signal rise time.Signal transmission loss has become a problem that cannot be ignored.In this work,the signal transmission loss of the interconnection aiming at laser soldering is studied,and the insertion loss is used as the characterization parameter.Aiming at the signal integrity problem of the current printed circuit board in high-speed transmission,a high-speed electrical signal transmission interconnection is designed and manufactured.For the printed circuit board for circuit test,the influence of conventional soldering and non-contact laser precision soldering on high-speed signal transmission is compared and discussed,and some new ideas for signal transmission loss of new laser soldering are provided.First of all,in the simulation experiment of surface roughness,with the increase of frequency,the insertion loss of the transmission line with different surface roughness increases linearly,and the greater the surface roughness,the greater the transmission loss.In the simulation experiment of the hole diameter,the effect of the hole diameter on the transmission loss is very small and can be ignored.In the simulation experiment of the number of holes,with the increase of the number of holes,the transmission loss of the transmission line will also slightly increase,but with the increase of the frequency,the skin effect is more obvious,resulting in the transmission loss gap getting smaller and smaller,the increase in transmission loss is almost unchanged.A comparative analysis of the signal transmission loss of reflow soldering and laser soldering surface roughness was carried out.The experimental results show that the size of the laser power has a certain influence on the soldering effect,and the soldering effect is better when the laser power is 28 W and the scanning speed is 1 mm/s.Atomic force microscopy data showed that the arithmetic means deviation of the profile for laser soldering was 10.19 nm,while that for reflow soldering was 21.65 nm.The insertion loss data of the final vector network analyzer test shows that with the increase of frequency,the transmission loss of laser soldering and reflow soldering increases,but not linearly,but in stages,and with the increase of signal as the transmission frequency continues to increase,the difference between the transmission loss of laser soldering and reflow soldering is also greater.In the research on the signal transmission loss of the intermetallic compounds and voids of non-contact laser precision soldering,it is found that the intermetallic compounds of laser soldering hardly grow,while the reflow soldering produces a large number of scallop-like protrusions.After analysis and calculation,the result is that the reflow soldering average thickness of the intermetallic compound layer is 3.02 ?m,while the average thickness of the laser soldering intermetallic compound layer is 0.51 ?m.At the same time,the number and area of voids in laser soldering are much smaller than those in reflow soldering.Finally,comparing the signal transmission loss of the laser soldering and reflow soldering,it is found that the transmission loss of laser soldering and reflow soldering is similar,this is also the reason for the skin effect.At the same time,at20 GHz,the insertion loss of laser soldering is-40.5 d B/m,and the insertion loss of reflow soldering is-43.2 d B/m,this data also fully shows that intermetallic compounds and voids have little effect on signal transmission loss during high-frequency signal transmission. |
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