How much do you know about dispensing process technology
1. Various technical process parameters that affect the quality of dispensing
Process defects that easily occur in product dispensing include: unqualified glue dot size, wire drawing, glue soaking, poor curing strength and easy to drop. To solve these problems, various technical process parameters should be studied as a whole to find a solution to the problem.
1. The size of the dispensing volume
According to work experience, the size of the glue dot diameter should be half of the product spacing. In this way, it is possible to ensure that there is sufficient glue to bond the components and avoid excessive glue. The amount of glue to be dispensed is determined by the length of time. In practice, the dispensing time should be selected according to the production situation (room temperature, viscosity of the glue, etc.).
2. Dispensing pressure
The dispensing equipment provides a certain pressure to the needle tube (glue gun) to ensure the supply of glue. The pressure determines the amount of glue supplied and the speed of glue outflow. Too much pressure can easily cause glue overflow and excessive amount of glue; too little pressure will cause intermittent glue dispensing and leaks, which will lead to product defects. The pressure should be selected according to the nature of the glue and the temperature of the working environment. High ambient temperature will reduce the viscosity of the glue and improve its fluidity. At this time, the pressure value needs to be lowered, and vice versa.
3. Needle size
In practice, the inner diameter of the needle should be about 1/2 of the diameter of the dispensing dot. During the dispensing process, the dispensing needle should be selected according to the size of the product. Different needles should be selected for products with very different sizes, which can not only ensure the quality of glue dots, but also improve production efficiency.
4. The distance between the needle and the working surface
Different dispensers use different needles, and some needles have a certain degree of stop. The distance between the needle and the working surface should be calibrated before the start of each work, that is, the height of the Z axis should be calibrated.
5. The viscosity of glue
The viscosity of the glue directly affects the quality of the glue. If the viscosity is large, the glue point will become smaller, or even drawing; if the viscosity is small, the glue point will become larger, and the product may bleed. During the dispensing process, choose a reasonable pressure and dispensing speed for glues of different viscosities.
6. Glue temperature
Generally, epoxy resin glue should be stored in a refrigerator at 0～5℃, and taken out half an hour before use, so that the temperature of the glue is consistent with the working environment. The use temperature of the glue should be 23℃～25℃; the ambient temperature has a great influence on the viscosity of the glue, the viscosity increases when the temperature decreases, the glue flow rate decreases correspondingly, and the wire drawing phenomenon is more likely to occur. When other conditions are the same, the environmental temperature difference is 5℃, which will cause a 50% change in the amount of glue, so the environmental temperature should be controlled. At the same time, the temperature of the environment should also be ensured. If the temperature is too high, the glue dots are easy to dry and affect the adhesion.
7. Curing temperature curve
For the curing of glue, the general manufacturer has given a temperature curve. In practice, it should be possible to use a higher temperature to cure, so that the glue has sufficient strength after curing.
8. Bubbles
The glue must not have bubbles. A small air bubble will cause many products to have no glue; every time the hose is replaced in the middle, the air at the connection should be evacuated to prevent the phenomenon of runaway.
9. Fluids that need special settings
Instant glue: Use safety pistons and Teflon-lined metal needles for water-based instant glues, use tapered slanted needles for thick instant glues, and use PP needles if flexibility is required.
UV glue: Use amber syringes, white pistons and oblique needles (which can shield ultraviolet rays). If you use other types of needles, please order needles that can shield ultraviolet rays.
Light curing glue: use black opaque syringe to avoid light exposure.
Anaerobic glue: Use 10CC syringe and white PE universal piston.
Second, the application and classification of the dispenser
Applicable liquid materials:
1. Adhesive, chemical reagent, flux, brazing flux, solidified covering agent, solder resist, ultraviolet light adhesive, solvent, brazing flux, chemical reagent, dripping solvent, screw fixing agent.
2. Add epoxy glue, anaerobic glue, white glue, eni glue, 502 glue, add epoxy glue, adhesive conductive silica gel, UV glue, silicon, EPOXY, red glue, silver glue, AB glue, COB vinyl , Conductive glue, heat-dissipating aluminum paste, instant glue, anaerobic glue, SMT red glue, yellow glue, silicon glue, screw locking glue, silica gel, white latex, crystal glue, insulating glue, organic silica gel, epoxy glue, EMI conductive glue, sealant, hot glue, quick-drying glue and other glues.
3. Ink paint, fiber paint, transparent paint, tin paste, electrolyte, damping oil, adhesive conductivity, silicone grease, methyl ethyl acetone, solder paste, grease, solder resist adhesive, damping oil, grease, thermal paste , Anti-solder paste, epoxy resin, damping oil, heat dissipation paste, lubricating oil, silicone oil, butter, alcohol, oil, etc.
Applicable products: automotive electrical appliances, packaging, household appliances, bearings, circuit boards, electronic components, pharmaceuticals, electrical components, capacitors, instruments, jewelry, quartz crystals, integrated circuits, lighting, mobile phones, radio equipment, wire connectors, semiconductor packaging , PCB electronic parts fixing and protection, LED glass machine board packaging and bonding, mobile phone board coating or button dispensing, speaker dispensing, TV box dispensing and sealing, auto parts coating, hardware parts coating and bonding, Quantitative gas, liquid filling coating, chip bonding, etc.
The purpose of glue dispensing: bonding, pouring, coating, sealing, filling, dripping, linear/arc/circular gluing, etc. in the product process.
The use of glue: First of all, the amount of glue is usually considered that the diameter of the glue dot should be half of the product spacing, so as to ensure that there is sufficient glue to bond the components and avoid excessive glue. The amount of glue to be dispensed is determined by the length of time. In practice, the dispensing time should be selected according to the temperature and the characteristics of the glue. Secondly, in terms of dispensing pressure, usually too much pressure will cause the glue to overflow and the amount of glue; if the pressure is too low, there will be intermittent dispensing and leakage, which will lead to product defects, so it needs to be based on factors such as ambient temperature and glue viscosity. Make adjustments. Moreover, the needle of the dispenser usually needs to select a needle with the inner diameter of the needle about 1/2 of the diameter of the dispensing dot. During the dispensing process, the dispensing needle should be selected according to the size of the product. There is also the distance between the needle and the working surface. Different dispensers use different needles. Some needles have a certain degree of stop. Therefore, it is necessary to grasp the dispensing distance, and even the needle and the working surface should be made before each work starts. Calibration of distance, namely Z-axis height calibration.
Except for the factors of the dispenser itself, the viscosity of the glue directly affects the quality of the glue. If the viscosity is large, the glue point will become smaller, or even draw the wire; if the viscosity is small, the glue point will become larger, which may stain the product, and the glue temperature should It is 23℃～25℃; the environment temperature affects the viscosity of the glue, the viscosity increases when the temperature decreases, the glue flow rate decreases accordingly, and the wire drawing phenomenon is more likely to occur. The glue curing temperature curve has been given by the manufacturer. In practice, it should be cured at a higher temperature as much as possible to make the glue have sufficient strength after curing.
In addition, the glue must not have bubbles. A small air bubble will cause many products to have no glue; every time the hose is replaced in the middle, the air at the connection should be evacuated to prevent the phenomenon of runaway.
Glue difference, instant glue: use safety piston and Teflon lined metal needle for water-based instant glue, use tapered slanted needle for thick instant glue, use PP needle if flexibility is needed; UV glue: use amber Colored syringes, white pistons and oblique needles (can be shielded from ultraviolet rays). If you use other types of needles, please order needles that can shield against ultraviolet rays; light curing glue: use black opaque syringes to avoid light exposure; anaerobic glue: use 10CC needles Tube and white PE universal piston; sealant and paste-like fluid: If the white piston rebounds severely, please switch to the safe type and use the oblique needle; for the adjustment of various parameters, you should follow the point and surface method , The change of any one parameter will affect other aspects. At the same time, the occurrence of defects may be caused by multiple aspects. The possible factors should be checked item by item.
Classification of dispensing equipment
1. According to the classification of the operation mode, it can be divided into manual dispensing equipment, semi-automatic dispensing equipment, and fully automatic dispensing equipment.
2. According to the glue, it can be divided into single-liquid dispensing equipment, double-liquid dispensing equipment, multi-component dispensing equipment, etc.
3. According to the classification of use, it can be divided into thread dispensing equipment, speaker dispensing equipment, mobile phone security key dispensing equipment, patch dispensing equipment, wiper and so on.
4. According to the characteristics of glue, it can be divided into silica gel dispensing equipment, UV glue dispensing equipment, SMT red glue dispensing equipment.
Semi-automatic dispenser
Semi-automatic glue dispensing can be set to manual and foot pedal two modes, can quantitatively discharge the glue, each time the glue volume is the same, the operation is simple, and has a vacuum suction function. The negative pressure can be adjusted to 0.6 kg to ensure a low concentration of glue. There is no dripping phenomenon, and it can also prevent the stringing phenomenon of the glue with a higher concentration.