Anti-sulfur measures to avoid millions of losses in LED packaging plants

The poisoning of the silica gel curing agent: the curing agent of the silicone for LED encapsulation contains a platinum (platinum) complex, and the platinum complex is very easily poisoned, and the poisoning agent is any nitrogen (N), phosphorus (P). ), a compound of sulfur (S), if the curing agent is poisoned, the curing of the silicone is incomplete, resulting in a high coefficient of linear expansion and an increase in stress. Vulcanization is an irreversible chemical reaction. Once vulcanization occurs, the product will be scrapped and cannot be recovered. As a professional third-party LED analysis and testing organization, Jinjian Testing LED Laboratory has a large number of professional microstructure detection and analysis equipment and a large number of LED sulfur emission case analysis experience, which can quickly bring sulfur/chlorine/bromine in the LED packaging process. The source of pollution is investigated and identified, and an optimization scheme is given to reduce the loss of millions for the packaging manufacturer.

For example, the patch lamp bead packaging process, the materials that the LED may be vulcanized during the production process are:

1. In the solid crystal process, the silver-plated stent is vulcanized, and the stent is yellowish and black and tarnished, which leads to a decrease in reliability;

2. In the solid crystal process, the silver glue is vulcanized, the silver glue is black, and the color is dim, which may result in reduced reliability or failure;

3. The solid crystal process, the silicon-based solid crystal glue is vulcanized, resulting in curing inhibition, unable to fully cure, resulting in decreased adhesion or failure;

4. Dispensing, powdering, and encapsulating processes, the silicon powder is vulcanized, which will cause curing failure, complete curing, and product failure;

5. The powdering process, the phosphor contains sulfur, which will cause curing inhibition and product failure.

In the LED production process, we must pay great attention to the prevention of vulcanization in these two links. The prevention methods are:

1. Avoid exposing the LED to a mildly acidic (PH<7) workshop environment. The nitrogen-containing acid gas is first reacted with silver and then replaced with sulfur/chlorine/bromine to form black silver sulfide, silver chloride or silver bromide.

2. For the other LED matching materials purchased, the manufacturer may be required to provide the LED auxiliary material sulfur/bromine/chlorine detection report provided by Jinjian to confirm whether it contains sulfur or halogen to prevent it from chemically reacting with the LED material. The physical reaction causes the corrosion of the silver plating layer of the LED product, the performance of the LED silica gel and the phosphor material to be mutated, resulting in the failure of the photoelectric performance of the LED.

3. Use desulfurization gloves, finger sleeves, sulfur-free masks; distinguish between sulfur-free materials and box clamps; use sulfur-free cleaning agents; use sulfur-containing PCBs for cleaning and desulfurization; set special sulfur-free ovens and use products separately. Independent baking.

4. The substances which are prone to "poisoning" of silica gel include: organic compounds containing N, P, S; heavy metal ion compounds such as Sn, Pb, Hg, Sb, Bi, As; and organic compounds containing unsaturated groups such as ethynyl groups. Pay attention to the following materials:

●Organic rubber: sulfur vulcanized rubber such as gloves

●Epoxy resin, polyurethane resin: amine, isocyanate curing agent

●Integrated silicone RTV rubber: especially using Sn-type catalyst

●Soft polycyanide: plasticizer, stabilizer

●Solder

Engineering plastics: flame retardants, heat-resistant agents, UV absorbers, etc.

Silver plated, gold-plated surface (the main reason for the plating solution at the time of manufacture)

Degassing by the Solder register (caused by silicone heat curing)