3, solder oxidation.
CU dissolution. As we all know whether it is wire, electronic components, pins or printed circuit board pads contain high levels of lead. In the dip soldering process, the above copper dissolved in the molten solder with smaller wire diameter smaller or fuse.
Lead-free dip soldering the biggest problem is that the clearance of the melting of the CU's CUSN intermetallic compounds. This aspect of the SN-PB solder compared with unexpected difficulties.
CU SN formation CU6SN5 intermetallic compounds, and its melting point above 500 ℃. SN63PB37 density /-cc CU6SN5 density as 8.80G 8.28G / cc.
The density of lead-free solder is 7.40G / cubic centimeter in the lead-free solder CU6SN5 easy to deposition of the bottom of the pot caused by heat transfer bad so they requested that an average of one month clear furnace 1.
Lead-free technology wave soldering
Wave soldering - by means of mechanical pumps vertically upwards towards the narrow export pouring molten brazing continue to form the 20-40MM crest.
Lead-free wave soldering process and the device's technical features explore
Lead is a toxic metallic element, long-term contact with the leaded material will be human health hazards. With the increasing demands of human environmental awareness is growing, large-scale ban on the use of leaded substance, one of the main direction is to promote the electronics industry in the lead-free.
February 13, 2003, the European Union officially announced the WEEE and ROHS directives, and from July 1, 2006, a total ban on lead in electronic products. The public memory of these two instructions, which greatly promoted the process of lead-free electronic products.
With the advance of electronic products lead-free, lead-free solder, lead-free flux, lead-free soldering equipment have achieved great success, the other lead-free PCB assembly and electronic pcb assembly components has been greatly developed. For lead-free soldering equipment, lead-free wave soldering and lead-free reflow, the following technical characteristics of the lead-free wave soldering equipment and workmanship for a brief overview of classification.
Throughout the wave soldering process, including the flux coating system, preheating systems, wave soldering system. Each system for the entire welding process is very important, direct impact to the PCB quality of welded joints. Printed circuit board assembly on the conveyor belt in accordance with the provisions of the route through these processes. Under normal circumstances, the left side of the wave soldering equipment into the right output. For lead-free wave soldering, one of the main system is nitrogen protection system.
1, the flux coating system
As electronic devices smaller, lighter, especially the development of high-density packaging technology, increasingly higher PCB welding quality requirements, while the flux is an important factor to ensure the quality of welding. Traditional flux solid residue after welding, more needs to be cleaned, the cleaning process has been the product of the CFC HCFC and 1,1,1 - trichloroethane and other cleaning agents as the PCB after welding to eliminate the surface of the PCB residues conductive substances or other pollutants to ensure the reliable use of products containing ODS (ozone depleting substances) in the CFC and other cleaning agents, destruction of the ecological environment, a serious threat to human security.
No-clean flux is a new type of flux with the electronics industry and the need for environmental protection. It solves not use CFC cleaning agent to reduce environmental pollution and difficult to clean because of the small gap, high-density component pcb assembly services is of great significance.
For lead-free wave soldering, the use of no-clean flux has become an inevitable trend, but due to the free no-clean flux solids content is generally low, generally around 2%. This is a higher demand on the flux coating system.