Section 1: Repair Services
Applying UV three-proof coating to PCBs creates a strong bond between the adhesive film and the board surface. Carefully using a pointed tool to gradually damage the coating's edges is permissible, and the process can be conducted at allowed high temperatures without damaging the components. Solidifying adhesives are divided into two types: adhesive, which boasts high bonding strength, and covering, which, if used to replace the UV three-proof coating on PCBs, makes it nearly impossible to repair. This is because adhesive solidifying adhesives are difficult to repair both physically and chemically, and the adhesive film is bonded to each component on the PCB, so forceful removal will definitely damage the components.
II. Functional Aspects
The hardness of the curing adhesive ranges from 60 to 80 Shore D, while the UV coating's hardness is typically between 50 to 60 Shore D. This indicates that, for the same area and thickness, the UV coating has better flexibility compared to the curing adhesive. If the curing adhesive is to replace the coating in PCB applications, the dry film thickness is generally between 50 to 200 μm. The higher the hardness, the thinner the thickness, and the lower the flexibility. Under harsh conditions such as high temperature and humidity, or alternating temperatures, long-term use can easily lead to expansion and contraction of the adhesive film, simply causing cracking or delamination. Only by choosing a curing adhesive with appropriate flexibility and non-adhesive properties can the impact of environmental factors on flexibility be overcome. Of course, there are also other functional differences.
Section III: Technology Aspect
The common application process for light-curing adhesives is dot dispensing, with a few special processes involving brushing, dipping, or spraying; UV three-in-one varnishes typically use brushing, dipping, or spraying for application. Therefore, the application processes for light-curing adhesives and UV three-in-one varnishes are similar, primarily depending on viscosity. The viscosity range of light-curing adhesives at 25°C is from several hundred to tens of thousands of mPa.s, while the viscosity range of UV three-in-one varnishes at 25°C generally does not exceed 1000 mPa.s. Whether they can be substituted depends on the accuracy of the chosen viscosity of the light-curing adhesive.
