Red Glue is a polyolefin compound, a special adhesive used for fixing and protecting electronic components in the surface mount (SMT) process.
Property Characteristics
Viscosity fluidity, temperature characteristics and wettability. By the characteristics so decided to red glue in smt chip processing in the role is to make the parts firmly affixed to the PCB surface, to prevent falling off.
It has the following characteristics:
- High viscosity: SMT chip red glue has high adhesion properties, can be firmly bonded to electronic components and PCB substrate, to prevent it from loosening or falling off in the process of transportation and use.
- High temperature resistance: SMT chip red adhesive usually has good high temperature resistance, can withstand high temperatures in the welding process, will not melt or deformation.
- Chemical resistance: SMT SMD red adhesive has good resistance to general chemicals, not easy to be corroded or discolored.
- High viscosity: SMT SMD red adhesive usually has a high viscosity, can keep the position of the electronic components in the placement process is stable, to prevent its offset in the placement process.
- Fast curing: SMT SMD red adhesive can be cured quickly after heat curing or UV irradiation to speed up production.
The purpose of SMT SMD adhesive
① Prevent components from falling off in wave soldering (wave soldering process). When wave soldering is used, the components are fixed on the printed board to prevent them from falling off when the board passes through the solder bath.
②Preventing components from falling off on the other side in reflow soldering (double-sided reflow process). Double-sided reflow soldering process, in order to prevent large devices on the side that has been soldered because the solder is melted by heat and fall off, to make the SMT patch adhesive.
③Prevent the displacement of components and stand (reflow soldering process, pre-coating process). Used in the reflow soldering process and pre-coating process to prevent the displacement of the mounting and standing piece.
④Marking (wave soldering, reflow soldering, pre-coating). In addition, the printed circuit board and component batch change, the patch adhesive for marking.
SMT SMD adhesive according to the use of classification
(a) Scraping type: through the stencil printing and scraping way for sizing. This way is the most widely used, can be used directly on the solder paste printing machine. Stencil openings should be based on the type of parts, the performance of the substrate to determine the thickness and the size and shape of the hole. The advantages are high speed, high efficiency and low cost.
(b) dispensing type: through the dispensing equipment in the printed circuit board sizing. Specialized dispensing equipment is required, the cost is higher. Dispensing equipment is the use of compressed air, the red glue through a special dispensing head point to the substrate, the size of the glue point, how much, by the time, the diameter of the pressure tube and other parameters to control the dispensing machine has a flexible function. For different parts, we can use different dispensing head, set the parameters to change, but also can change the shape and number of glue dots, in order to achieve the effect, the advantage is convenient, flexible, stable. The disadvantage is easy to have pulling and bubbles, etc. We can adjust the operating parameters, speed, time, air pressure, temperature to minimize these disadvantages.
SMT patch adhesive management
Due to the red glue affected by temperature with its own viscosity, fluidity, wetting and other characteristics, so there should be certain conditions of use and standardized management.
1) To have a specific flow number, according to the number of feed, date, type to number.
2)It should be stored in the refrigerator at 2～8℃ to prevent the characteristics from being affected due to temperature change.
3)Re-warming requirement is 4 hours at room temperature, and use in the order of first-in-first-out.
4)For dispensing operation, the hose red glue should be defoamed, for one-time unused red glue should be put back to the refrigerator for storage, old glue and new glue can not be mixed.
5) To accurately fill out the temperature record sheet, the temperature and the time to return to the temperature, the user needs to confirm the completion of the return to the temperature before use. Usually, the red glue can not be used after the expiration date.
Application in SMT
Cost saving
One of the advantages of using SMT red glue process is that when wave soldering, there is no need to make fixtures, thus reducing the cost of making fixtures. Therefore, in order to save costs, some customers who place small orders usually ask PCBA processors to adopt the red adhesive process. However, as a relatively backward soldering process, PCBA processors are usually reluctant to use red glue process. This is because the red glue process needs to meet specific conditions to be adopted, and the quality of soldering is not as good as solder paste soldering process.
Larger component sizes and wider spacing
When wave soldering, generally choose the side of the surface mounted components over the wave, and the side of the plug-in on the top. If the surface mount component size is too small, the spacing is too narrow, then in the wave crest on the tin, will cause the solder paste connected, resulting in a short circuit. Therefore, when using the red glue process, you must ensure that the component size is large enough and the pitch should not be too small.
SMT SMD red glue plays a vital role in the fixing and protection of electronic components. Its high viscosity, high temperature resistance, chemical resistance and other features to ensure the stability and reliability of electronic components in the production and application process
