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What should we pay attention to when using the LED dispenser? [Customizing non-standard equipment]
Precautions for dispensing machine operation: 1. Before starting the machine, check whether the automatic dispenser is clean and whether there is moisture and other problems that directly affect the normal operation of the machine; 2. It is not allowed to touch the rubber dispensing head, needle nozzle, guide chain and other moving parts with your hands under the working condition to prevent accidental pinching; 3. In case of special circumstances, press the red emergency button in front of the machine body to stop the machine immediately; 4. When it is necessary to move the equipment, the gas circuit and power supply must be cut off first; 5. Don't pile up too many articles beside the machine to avoid affecting the operation; 6. Gloves must be worn during operation. Try not to expose the skin to avoid glue sticking to the skin; 7. When using glue, be fully aware of glue. For example, the use of glue and how to use it correctly can better ensure the quality of dispensing; 8. Regularly
1. Wire drawing
The so-called wire drawing, that is, the glue patch is not broken when the dispensing machine is dispensing, and the glue patch is connected filamentous in the direction of the dispensing head. More wire connection, patch glue covered on the printed board pad, will cause poor welding. Especially when the size is larger, this phenomenon is more likely to occur when the point smears the mouth. The drawing properties of the patch adhesive are mainly affected by the drawing properties of its main component resin and the setting of point coating conditions.
The solution:
a. Increase the dispensing head stroke of the dispensing machine and reduce the moving speed of the manipulator, which will reduce the production beat.
b. The lower the viscosity and high shake solubility of the material, the smaller the tendency of drawing, so try to choose this kind of patch adhesive.
c. Set the temperature of the thermostat slightly higher, and compulsively adjust it into a patch adhesive with low viscosity and high shake to dissolve ratio. At this time, the storage period of the patch and the pressure of the dispensing head must be considered.
2. Thermal damage of components
In wave soldering process, in order to improve the production efficiency, even LED, aluminum electrolytic capacitor and other electronic components with poor heat resistance are also cured by the reflow welding furnace. At this time, such as adhesive curing temperature is higher. The above components will be damaged by exceeding their heat-resistant temperature.
At this time, our approach is either to install low-heat resistant components after installation, or choose low-temperature curing patch adhesive.
3. Empty spot, too much adhesive
The distribution of adhesive is unstable, too much or too little. Too little glue, there will be insufficient strength, resulting in wave soldering tin pot components fall off; On the contrary, the amount of adhesive patch is too much, especially for small components, if it is stuck on the pad, it will hinder the electrical connection. Therefore, when using the dispensing machine to dispense glue, the first parameter of the dispensing is adjusted.
Reasons and Countermeasures:
a. There are large clumps mixed in the glue, blocking the dispenser nozzle; Or there are bubbles in the glue and empty spots.
The solution is to use a film adhesive that removes large particles and bubbles.
b. When the film adhesive is not stable, the point coating is not stable.
Prevention method: Each time you use it, put it in a closed container to prevent condensation for about 1 hour, and then install the dispensing head on the dispensing machine. After the temperature of the point coating mouth is stable, you can start dispensing. Use if there is a thermostat better.
c. If the dispensing head is not used for a long time, the shaking solubility of the patch glue should be restored. There will be insufficient dispensing amount in the first few times of dispensing.
Therefore, each printed board, each dot smear mouth at the beginning of use, should be tested several times.
4. Components are offset
Component deviation is a common problem of high - speed SMT machine. One is the θ Angle offset that occurs when the component is pressed into the patch. The other is the deviation of the X-Y direction when the printed board moves at high speed. This phenomenon is easy to occur on the components with small patch adhesive coating area. The reason is that the adhesion is not in.
The corresponding measure is to choose the patch adhesive with high shaking solubility and high viscosity. It has been proved by experiments that if the patch speed is 0.1sec/piece, the acceleration on the component can reach 40m/S2. Therefore, the adhesion of the patch adhesive must be sufficient to achieve this.
5. Collapse
Excessive fluidity of the patch will cause collapse. There are two types of collapse, one is the point after the placement of too long caused by the collapse. If the patch glue is extended to the pad of the printed board, it will cause poor welding. Moreover, for those components with relatively high pins, the collapsed patch adhesive cannot contact the main body of the component, which will cause insufficient adhesion. Because the patch adhesive prone to collapse is difficult to predict its collapse rate, the initial setting of its point coating amount is also difficult.
In view of this, we have to choose those who are not easy to collapse, that is, shake solubilies relatively high patch adhesive. For the collapse caused by placing too long after the point coating, we can use a short time after the point coating to complete the mounting, curing to avoid.
6. Components fall into the crest solder groove
