Patch glue type: in the SMT process, generally USES the thermosetting type patch glue stick components on the PCB circuit board, the main application of the material for epoxy resin, polypropylene, nitrile propionic acid ester and polyester and so on.There are two kinds of commonly used patch adhesive, epoxy resin patch adhesive and acrylic adhesive.
1, epoxy resin patch glue, epoxy resin adhesive patch is one of the most commonly used in SMT processing patch glue, its composition is mainly epoxy resin, curing agent, filler and other additives, curing of epoxy resin adhesive patch method is given priority to with the thermal curing.Epoxy resin is a thermosetting type, high viscosity, the binder can be made into liquid, paste, thin films and powders, and other forms, thermosetting adhesives solidified before heating will not soften, not to establish connection.The thermosetting property can be divided into single component and double component.
2. Acrylic adhesive.Acrylic laminating adhesive is another kind of laminating adhesive commonly used in SMT lamination processing. Its composition mainly includes acrylic resin, photocuring agent and filler.Acrylic resins are also thermosetting adhesives, commonly used as a single system.Is characterized by stable performance, short curing time and curing, easy to control process conditions, deposit for the room temperature away from light storage conditions, time of year, single bond strength and electrical properties as high epoxy type.
Curing.The curing methods of adhesive include heat curing and light curing.Photothermal double curing and ultrasonic curing, in which light curing is rarely used alone.Ultrasonic scraping is usually used as a binder with a mothball curing agent.The most commonly used curing methods in Smt patch processing are thermal curing, uv/thermal curing.
1. Heat curing.Thermal curing usually used oven intermittent thermal curing and infrared furnace continuous thermal curing two forms.
2. Uv/thermal curing.The uv/thermal curing system USES both uv irradiation and heating to cure the adhesive very quickly on a continuous production line.
Selection of rubber patch: how to select the appropriate patch glue, to ensure the SMT production run smoothly, is the most concern of the electronic product craft, the usual practice is to patch glue list of performance indicators, see table, according to the table in each of the selected test and compare several patch glue, choose the good varieties.
The selection method of patch adhesive is as follows:
(1) currently, thermosetting lamination adhesive is widely used, and the equipment and process requirements are relatively simple.Due to the sufficient curing and high bonding fastness of the light-solid lamination adhesive, the light-solid lamination adhesive should be chosen for the larger components.
(2) the pre-curing performance, curing performance and post-curing performance should be considered to meet the requirements of surface assembly process for laminating adhesive.
(3) the lamination adhesive with low curing temperature and short curing time should be optimized. At present, the curing condition of the better lamination adhesive is generally less than 3min at 150 degrees.