How to Choose Red Glue in SMT Processing
SMD adhesive is also known as red glue. SMD adhesive is mainly used for chip resistors, IC chips and capacitors in SMT processing. It is usually suitable for squeegee (printing) and dispensing. SMD adhesive is the bonding material necessary for surface mount components to pass the wave soldering process. Before the wave soldering, it is necessary to fix the mounted components to the corresponding positions of the PCB with the adhesive to prevent the components from falling into the tin pot during the wave soldering. The quality of SMT processing is not good? Mostly, because red glue is not selected properly.
The basic requirements for the choice of SMD adhesive for red plastic:
1. There are no impurities and air bubbles in the package, and the storage period is long and non-toxic.
2. The shape and volume of the glue spotare the same, the glue spot section is high, and there is no wire drawing. The glue spot profile is affected by the shake solubility, zero shear rate and other factors. The actual glue spot shape may be “pointed” hemispherical or conical. The definition of the glue spots profile is usually a non-stick parameter (such as the glue spot volume, the off-plate height, and the diameter of the dispensing needle). Typically, the width to height ratio of the glue spot is in the range of 1.5:1 to 5:1, depending on the parameters of the dispensing system and the level of the glue.
3. The color is easy to identify, which is convenient for manual and automated machines to check the quality of the gluespot.
4. The initial adhesive force is high, and the flow characteristics of the glue affect the formation of the shape of the glue spotand its shape and size.
5. High-speed curing, the curing temperature of the glue is low, and the curing time is short. When heat curing, the glue spotswill not collapse.
6. High strength and elasticity to withstand sudden temperaturechanges of wave soldering. Bond strength is the key to the performance of a glue and is determined by many factors, such as adhesion to the component and the PCB, the size of the glue spot, and the level of cure. The three most common causes of insufficient bond strength are insufficient cure, insufficient glue, and poor adhesion.
7.It has excellent electrical properties after curing and has good rework characteristics.
8.The gap of the glue is determined by the difference between the height of the PCB solder mask layer and the thickness of the terminal metal and the thickness of the component.
How to choose the suitable SMD glue to ensure the smooth progress of SMT processing is also the most concerned issue for FASTPCBA technologists. We will also continue to improve the craft to provide better service to our customers.
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