One component room temperature curing (RTV type) silicone rubber uses moisture in the air (- OH groups in water molecules) as a curing agent to achieve liquid crosslinking and curing! Due to the fact that this crosslinking curing reaction belongs to the condensation reaction of organic chemistry, this type of adhesive is also known as "condensation (reaction) type silicone rubber". The curing speed of this silicone rubber is relatively slow, usually requiring more than 24 hours for the curing of 3mm to 5mm coatings. The curing reaction rate after coating mainly depends on the temperature and humidity of the working environment, as well as the thickness of the adhesive layer. The higher the ambient temperature and humidity, the faster the curing reaction speed. But too fast a reaction speed can quickly form a "skinning" effect on the surface of the adhesive layer, that is, the rapidly solidified surface adhesive layer will block the channel for the bottom adhesive layer to continuously obtain moisture (water molecules), resulting in insufficient solidification (or even never solidification) of the bottom adhesive liquid, forming a "sugar core egg" curing effect, causing the colloid to lose its proper electrical insulation and bonding function of components. Therefore, the curing conditions for single component room temperature cured (RTV type) silicone rubber should be set at an ambient temperature of 20 ℃ to 35 ℃ and a relative humidity of 45% RH to 65% RH.

One characteristic of single component room temperature cured (RTV type) silicone rubber is that there will be a small amount of small (low) molecular weight liquid substances oozing out during its curing reaction, which is a normal (inevitable) phenomenon of this type of adhesive curing reaction. At present, the exudates of Nanda 703, 704, 705, and GD414 adhesives commonly used in the electronic product assembly industry are all low molecular weight alcohol compounds, and these liquid low compounds will not have any impact on the subsequent processing and performance of the product. The full precipitation of this low molecular weight compound also takes time. If the adhesive layer is too thick, or the curing environment temperature and humidity are too high, the curing reaction is too fast, and the "skinning" effect of the surface adhesive layer will prevent the effective and full precipitation of this low molecular weight liquid compound in the bottom adhesive liquid, forming a "residue". Sealing (residual) these low molecular weight compounds at the bottom of the adhesive layer will cause the colloid to exhibit the characteristic of never curing (referred to as the "retrogradation" phenomenon in the field of adhesive technology, and the retrogradation phenomenon of condensed silicone rubber is irreversible once formed), and any measures taken in the later stage will be of no help!