LED packaging process, how to do a good job in sulfur prevention measures

In the LED packaging process, vulcanization mainly occurs in the process of solid crystal and dispensing. The vulcanization mainly occurs in the materials containing silver (silver plated bracket and conductive silver glue) and silicon rubber materials. When the material containing silver is vulcanized, it will form black silver sulfide, which causes the vulcanization area to turn yellow and black. Silicone rubber material is vulcanized will cause silicone "poisoning", leading to curing obstruction, can not be completely cured. Silica gel curing agent of poisoning: LED encapsulation using silicone curing agent containing platinum (pt) complex, and the platinum complex is very easy to poisoning, poisoning agent is any kind of nitrogen (N), phosphorus (P), sulfur (S) compounds, once the curing agent poisoning, organic silicon curing incomplete, can cause high linear expansion coefficient, stress increased.

Take the SMD lamp bead packaging process for example, the materials that LED may be vulcanized in the production process are:

1. During the solidification process, the silver-plated support is vulcanized, and the support turns yellow and black and loses luster, which will reduce the reliability;

2. During the solidification process, the silver glue will be vulcanized, and the silver glue will turn black and dim, which will lead to reliability reduction or failure;

3. During the solidification process, the solidification glue of silicon property is vulcanized, which results in obstruction of curing. It cannot be completely cured, which will lead to the decline of adhesion force or failure;

4. In the process of glue dispensing, powder dispensing and packaging, the silicon powder dispensing is vulcanized, which will result in the obstruction of curing and the failure of product.

5. During the powdering process, the phosphor contains sulfur, which will lead to obstruction of curing and product failure.

LED packaging factory, in the LED production process must pay great attention to the two links of vulcanization prevention, prevention methods are:

1. Avoid LED exposure to acidic (PH<7) workshop environment. An acidic gas containing nitrogen reacts with silver and then with sulfur/chlorine/bromine to produce black silver sulfide, silver chloride, or silver bromide.

2. for the purchase of other LED supporting materials, can provide the LED accessories require manufacturers to provide Jin Jian sulfur/bromine chloride test report, confirm whether sulfur, halogen, such as material, in order to prevent the chemical or physical reaction with the LED material, silver coating corrosion caused by the LED products, LED silicone, phosphor material properties change, leading to the failure of LED photoelectric properties.

3. Use desulfurization gloves, finger gloves and sulfur-free masks; Distinguish sulfur-free materials, box clamp jig; Use sulfur free cleaner; PCB board containing sulfur is cleaned and desulfurized before use; Set up a special sulfur free oven, use the product separately, bake independently.

4. Silicone "toxic" substances: containing N, P, S and other organic compounds; Sn, Pb, Hg, Sb, Bi, As and other heavy metal ion compounds; An organic compound containing an unsaturated group such as acetylene. Pay attention to the following materials:

Organic rubber: sulfuric rubber such as gloves

Epoxy resin, polyurethane resin: amine, isocyanate curing agent

Synthetic silicone RTV rubber: especially using Sn catalyst

Soft polyvinyl chloride: plasticizer, stabilizer

flux

Engineering plastics: flame retardant, heat - resisting agent, ultraviolet absorbing agent, etc

Silver-plated, gold-plated surface (electroplating bath during manufacture is the main reason)

Degasification generated by Solder register (caused by heating and curing of organic silicon)

Vulcanization is an irreversible chemical reaction. Once vulcanization occurs, the product will be scrapped and cannot be retrieved. Jin Jian test LED laboratory LED analysis as a professional third-party 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 quickly to LED encapsulation process may lead to sulfur / / bromine chloride in screening and identification of pollution sources, optimization scheme is given, for reducing the loss of millions of packaging manufacturer.