LED products SMT production process the sulfur matters needing attention

In LED application products SMT production process, sulfide is most likely to appear in the reflow soldering. Because Jin Jian from all kinds of bad case happened, stents, silver sulfide layer of strong, speed and sulfur content, as well as a direct relationship between the temperature and time. And reflow soldering link is a typical high temperature and high humidity environment, is also likely to encounter a large amount of sulfur material. Jin Jian found in the detection process of PCB, solder paste, water washing board, other pump glue records of sulfur. These materials will be in the SMT process with leds for reflow oven, placed after a period of time will appear after reflux stent part in black, silver plated is mainly sulfur-containing substance in the reflow process LED inside, lead to silver sulfide, lead to product failure.

the LED application products SMT production process

for example, Jin Jian detection from many cases happened in the past the MCPCB plank in composition analysis, production of many plates are on the market have different content of residual sulfur, although MCPCB manufacturer will clean sheet in the process, to eliminate sulfur and acid solvent residual, but ordinary production process difficult to completely eliminate clean. In view of the sulfur in high temperature environment is more active, when SMT homework, can in advance before SMT will MCPCB board had a high temperature reflow furnace ( 230 degrees) To clean surface treatment ( The available medical alcohol, etc. ) , to reduce the sulfur content of MCPCB welding plate and surface layer. If the process does not allow, can be directly in front of the SMT PCB surface cleaning, back even after the completion of the product on a clean surface, by cleaning the plate and welding points to reduce the risk of LED sulfide, when cleaning need to choose do not contain sulfur and excluding other acidic cleaner.

it is important to pay special attention to the solder paste here. Solder paste is a complex system, is made up of solder powder, flux and other additives mixture of paste. Solder paste in the welding of high temperature, the solvent will evaporate and part of the additive, the solvent will penetrates through LED lamp bead crack or silica gel pores. Flux of solder paste composition is complicated, the activator components usually contain a few halogen or organic acid composition, its function can quickly eliminate by oxide film on the surface of the weld metal, reduce the surface tension of solder, the solder rapidly spreading in the weld metal surface. Usually use chlorine and bromine and halogen. And the existence of chlorine and bromine to make the lamp bead chloride, bromide, and chemical incompatibility problems.

so, detect Jin Jian advice LED lighting factory regularly to the PCB board, solder, and other supporting material incoming inspection, avoid substance sulfur residue on the PCB. PCB after completion of reflow soldering, through to the solder joint position cleaning, eliminate or reduce the surface residue. Detergent to avoid acidic sulfur glue, solvent.

in addition, in the process of SMT homework, to prevent the use of materials containing sulfur vulcanization on the LED. LED, for example, in the process of welding and processing, please do not use containing sulfur or halogen materials such as rubber gloves, rubber finger sets, rubber band, rubber anti-static cloth, fill glue, glass glue, hot melt adhesive and so on contact with the LED; Prevent the use of sulfureted clamp fixture and machine; It is best to establish a separate sulphur-free SMT production line or production workshop, ensure doing the LED products in the process of SMT products from sulfide pollution; Regularly clean reflow furnace and dehumidification of oven; And control the LED or LED component in welding workshop, processing and application environment, to reduce or even eliminate sulfur or halogen to LED the risk of harm.

Jin Jian detection as a professional third party LED LED quality laboratory analysis inspection agencies, has a large number of professional analysis of the microstructure test equipment and a large number of leds sulfur case analysis experience, can undertake major lighting factory incoming inspection, and quickly LED application products in SMT production process may lead to sulfur / / bromine chloride screening and identification of pollution sources, optimization scheme is given, for reducing the loss of millions of lighting manufacturer.

Lemon

LED quality laboratory