Silicone is an inert material with low surface energy: in its raw state it does not fuse strongly with metal, plastic or PCBA boards. We use clean pre-treatment, a matched specialist primer and controlled-temperature press curing to solve delamination and cracking in dissimilar-material bonding.
Delamination, cracking and poor weathering resistance in overmolded parts look like molding problems, but the root cause usually lies in the state of the substrate beforehand: residual oil, dust and oxide on the surface, or the absence of surface activation, or a primer that does not match the substrate. Any of these leaves the interface bond weak from the start, and it only shows up under bending, temperature difference or damp heat.
So we standardise this stage: clean pre-treatment → matched specialist primer → controlled-temperature press curing. The treatment is matched to the substrate, the operating conditions and the weathering requirement, and the fix starts at the interface.
Step one
Every insert substrate (metal, plastic, PCBA) is cleaned and activated to a fixed standard before molding, removing the oil, dust and oxide that cause bond failures, in a closed and controllable sequence.
Removes oil, contamination, dust and oxide residue from the substrate surface, leaving a clean interface for activation.
Physical modification raises the surface energy of substrate and silicone, greatly improving interface bonding and preparing for primer and curing.
The specialist primer is selected by substrate material, instead of one additive covering every material.
Precise baking drives off volatiles and cures the active coating, laying the base for a high-strength heat-cure bond.
The whole line runs dry and clean, leaves no residue and does not corrode precision electronic components, which suits high-end electronics, medical and outdoor products. See surface finishing for the related surface routes.
Step two
No one-size-fits-all primer: the formulation is matched by substrate, molding process and operating environment, and each family answers a different requirement.
For overmolding stainless steel, aluminium alloy, iron, copper and other metal inserts. The additive contains metal-affinity active ingredients, with heat, damp-heat and ageing resistance that suits high-temperature compression curing.
For ABS, PC, nylon, PBT and similar substrates, with a formulation adjusted for plastics that tolerate little heat and crack easily.
A low-corrosion, low-volatiles, insulating formulation without chemistry that attacks traces, solder joints or SMD components, balancing bond performance with electrical insulation stability.
A one-component room-temperature curing formulation that needs no baking, for secondary operations such as double-sided tape, labels and lamination on silicone.
A clean, non-toxic formulation with no migration and no odour, and good biocompatibility that meets medical and food-contact safety standards.
Three things decide it: what the substrate is, which molding process is used, and where the product is used.
Step three
Once clean pre-treatment and primer activation are complete, molding temperature and pressure are set to suit the silicone (solid or liquid), the substrate and the part structure, and the integrated cure is completed under those controlled conditions.
Controlled temperature and steady pressure let silicone molecules cross-link and interlock with the activated substrate layer, forming a molecular-level composite rather than physical contact.
The bonded face is dense after molding, with water, shock, tensile and temperature cycling performance that reduces the risk of moisture ingress at the interface.
Temperature and pressure are not fixed values; they follow the silicone, the tolerance of the substrate and the structure, and become the basis for volume production once confirmed.
Pre-treatment, primer and curing are controlled as one system, which reduces the delamination, debonding and cracking that commonly affect composite parts.
Molding routes and tool systems are described under molding and tooling; interface strength can be verified through peel strength, thermal shock and related tests in the R&D and testing system.
FAQ
Silicone is an inert material with low surface energy, and in its raw state it does not fuse strongly with metal, plastic or PCBA substrates. Oil, dust and oxide on the substrate surface, together with the absence of surface activation and matched primer, leave the interface bond too weak, so delamination and cracking appear under bending, temperature difference or damp heat.
Ultrasonic deep cleaning, plasma surface activation, application of the primer matched to the substrate material, and then constant-temperature baking to cure. The whole line is dry and clean, leaves no residue and does not corrode precision electronic components.
It is not advisable. Substrates differ in surface characteristics, temperature tolerance and operating conditions. Metal, plastic, PCBA, room-temperature adhesive bonding and medical or food-grade applications each correspond to a different specialist primer formulation, matched to the substrate and the working conditions.
Ordinary lamination is physical contact held by an adhesive layer. Heat-cure molding completes an integrated cure under set temperature and pressure, so the silicone molecules cross-link and interlock with the activated layer of the substrate to form a molecular-level composite with a tight interface — water, shock, tensile and temperature cycling performance is more stable.
The whole pre-treatment line is dry and environmentally clean; plasma activation and constant-temperature baking are set to the tolerance of the components. For PCBA we use a low-corrosion, low-volatiles and insulating primer formulation that balances bond performance with electrical insulation stability.
Send us the substrate type, the operating environment and the failure you see. We will first establish whether it is an interface treatment issue or a process parameter issue, and then propose a fix.