Backward compatible mixed welding method for lead-free BGA device

Abstract

The invention provides a backward compatible mixed welding method for a lead-free BGA device. According to the method, the lead solder is used to realize the welding of a lead-free BGA device mixed loading plate by accurately controlling the welding parameters. Compared with a reballing lead method and a forward compatible welding method which are adopted in the industry, the method is more economical, simpler and higher in feasibility, and solves the technical problem that the lead-free BGA device generally uses the lead solder for mixed loading in the domestic military industry. A large number of practical applications prove that the method and the parameters can significantly improve the assembly first pass yield of the lead-free BGA mixed loading plate, so that the mixed loading BGA welding spots reach the service life equivalent to that of tin-lead welding spots, and the long-service-life and high-reliability use requirements of military electronic products are met.

Description

technical field [0001] The invention relates to the field of assembly of printed board components, in particular to a backward compatible mixed assembly welding method for lead-free BGA devices. Background technique [0002] RoHS Directive and WEEE Directive promote the lead-free process of electronic products. IC devices in the electronic industry are basically lead-free, especially imported BGA packaged devices that are widely used. According to incomplete statistics, at least 80% of them are lead-free packaged. . Based on the high reliability requirements of military products and the use requirements in harsh environments, the RoHS directive stipulates that military products are not subject to lead-free constraints, and the US military such as NASA has not adopted lead-free processes so far. In domestic military enterprises, the use of lead-free technology is also restricted due to the unknown reliability of lead-free soldering, but imported devices such as BGA packaged ...

AI Technical Summary

Problems solved by technology

In order to ensure that the printed board has lead components not to be overheated and damaged, the soldering temperature must be lowered, and the lower limit temperature in the lead soldering temperature window should be used, which can easily lead to insufficient melting of lead-free solder balls, uneven diffusion of elements, and poor metallurgical bonding. , forming cold welding and virtual welding faults

[0005] (2) The welding temperature is too high, and the lead equipment is easy to be damaged by heat

Second, the forward-compatible soldering method is used, that is, lead-free BGA devices are soldered with lead-free solder paste. However, the application of lead-free solder has just started at present, and the reliability of the solder itself and the quality of the solder joints are not conclusive. Many military companies have also made it clear that they will not use lead-free solder for the time being. In addition, other domestic components on domestic military products still contain lead, so the feasibility of this method is relatively poor.

Images