With the rapid development of technology, more and more fields of dispensing application, more common is the field of mechanical hardware, automotive and parts, electronics and 3c manufacturing and so on. Among them, the application in the field of mobile phone can be said to be accompanied by the development of smart phones at the historic moment. Next, we will introduce in detail how to apply glue in the mobile phone industry!
Dispensing, also known as sizing, gluing, gluing, gluing, dripping, etc., can make the product play the role of sticking, sealing, insulation, fixing, smooth surface, etc., in the production and processing process of mobile phone and supporting parts, dispensing technology and dispensing technology is very important.
Lead component through-hole insertion (THT) and surface insertion (SMT) co-exist, is one of the most common assembly methods in the production of electronic products. In the whole production process, one of the components of the printed circuit board (PCB) from the beginning of the dispensing curing, to the final wave welding welding, for product quality control requirements on the analysis, because this period of time interval is longer, and more other processes, so the curing of components is particularly important. Because of the rapid development of current science and technology, the integration of electronic components is getting higher and higher, the volume is getting smaller and smaller, and the requirements of processing technology are getting higher and higher, so the research and analysis of dispensing technology is very important
I. SMT Patch processing glue and its technical requirements:
The glue used in SMT is mainly used in the wave soldering process of chip components, SOTs, SOics and other surface mounted devices. The purpose of using glue to fix the surface mounted components on the PCB is to avoid the removal or displacement of the components which may be caused by the impact of high temperature crest. The general production of epoxy resin thermal curing glue, rather than acrylic acid glue (UV irradiation curing).
II. Requirements for SMT glue:
1. Glue should have good thixotropic characteristics;
2. No wire drawing;
3. High wet strength;
4. No bubbles;
5. Low curing temperature and short curing time of glue;
6. Sufficient curing strength;
7. Low hygroscopicity;
8. Good repair characteristics;
9. No toxicity;
10 color is easy to identify, easy to check the quality of the glue point;
11. Packing. The packaging type shall be convenient for the use of the equipment.
III. in the process of dispensing process control plays a very important role.
The following process defects are likely to occur in the production: unqualified glue point size, wire drawing, glue dye pad, poor curing strength and easy to fall off pieces. To solve these problems, we should study the technical parameters as a whole, so as to find the solution to the problem.
1. The size of the dispensing amount
According to work experience, the size of the glue point diameter should be half of the pad spacing, and the glue point diameter should be 1.5 times of the glue point diameter after the patch. This ensures that there is plenty of glue to bond the components and avoids overwetting the pad with glue. The amount of glue is determined by the length of rotation time of the screw pump. In practice, the rotation time of the pump should be selected according to the production situation (room temperature, glue viscosity, etc.).
2. Dispensing pressure (back pressure)
At present, the dispensing machine uses a screw pump to supply the dispensing needle hose to take a pressure to ensure that enough glue to supply the screw pump. Back pressure is too large easy to cause glue overflow, glue amount is too much; If the pressure is too small, there will be intermittent phenomenon of dispensing, leakage point, resulting in defects. The pressure should be selected according to the glue of the same quality and the temperature of the working environment. High ambient temperature will make the glue viscosity smaller, better liquidity, then need to lower the back pressure to ensure the supply of glue, and vice versa.
3. The size of a pinhead
In practice, the inner diameter of the needle should be 1/2 of the diameter of the dispensing point. In the dispensing process, the dispensing needle should be selected according to the size of the welding pad on the PCB: If the size of the pads of 0805 and 1206 is not very different, the same needle can be selected, but different needles should be selected for the pads with a big difference, which can not only ensure the quality of the glue point, but also improve production efficiency.
4. Distance between needle and PCB board
Different dispensing machines use different needles, some needles have A certain degree of stop (such as CAM/A LOT 5000). Calibration of the distance between the needle and PCB should be done at the beginning of each work, that is, Z-axis height calibration.
5. Glue temperature
Generally, epoxy resin glue should be kept in the 0-50C refrigerator, and should be taken out 1/2 hour in advance when used, so that the glue is fully in line with the working temperature. The use temperature of glue should be 230C--250C; The ambient temperature has a great influence on the viscosity of glue. If the temperature is too low, the glue point will become smaller and the phenomenon of wire drawing will occur. Ambient temperature difference 50C, will cause 50% dispensing amount change. Therefore, the ambient temperature should be controlled. At the same time, the temperature of the environment should also be guaranteed. Small humidity points are easy to dry, affecting the adhesion.
6. Viscosity of glue
The viscosity of glue directly affects the quality of dispensing. Large viscosity, the glue point will become smaller, even drawing; Small viscosity, the glue point will become larger, and may stain the pad. Dispensing process, to deal with different viscosity of the glue, select a reasonable back pressure and dispensing speed.
7. Curing temperature curve
For glue curing, the general manufacturer has given the temperature curve. In practice, high temperature should be used as far as possible to cure, so that the glue after curing sufficient strength.
8. Bubbles
Glue must not have bubbles. A small gas will cause many pads without glue; Every time the rubber hose is replaced midway, the air at the joint should be emptied to prevent the phenomenon of empty play.
For the adjustment of the above parameters, should be according to the point and surface of the way, any parameter change will affect other aspects, at the same time, the generation of defects, may be caused by a number of aspects, to deal with the possible factors item by item inspection, and then exclude. In short, in the production should be according to the actual situation to adjust the parameters, not only to ensure production quality, but also to improve production efficiency.