Silicone over-molding has contributed a lot to the medical industry. It has allowed the medical device manufacturers to design and develop several parts and equipment for various health-based and therapeutic applications. Orthopedic handles, wire insulators for various implantable devices as a pacemaker, surgical blades, and many other products are developed with the help of silicone molding.
Silicone over-molding is a process in which silicon is bonded to a substance, typically any metal or plastic.
Overmolding protects the component from the electrical current passing through the insert. It shields the elements from mechanical wear and tears. What is more, it simplifies the design and assembly.
When a medical device manufacturer approaches the silicone molders, the two work in tandem with each other to make it sure that the bond strength must be able to fulfill the product requirements. They ensure biocompatibility as well.
Five major steps help ensure bond strength in silicone over-molding, and here are they. Look no further.
Comprehending the chemical reactions between silicone and substrate-
The silicone over-molding process to develop any device begins with the designing process. In this process, you must try to understand the potential chemical reactions between the silicon and the substrate in the process. If you understand the reactions, this will be easier for you to ensure the strong bond in the main products.
Since the process begins with the designing, you must focus on knowing the chemical process between the silicone and the substrate material that can result in a strong bond.
What substrate or inserts are used in the over-molding process, do you have any idea? Mostly, titanium alloys, engineered plastics, stainless steel alloys, peek thermoplastic, ceramics, and nylon.
Silicone with some certain inserts, creates a chemical bond, using a primer system. However, not all substrates react well without any third agent and give the desired results. For example, engineered plastics need bonding agents and additional surface treatments.
When any medical device is designed, biocompatibility is the thing that tops the list of requirements and expectations. Engineered plastics, steel, and titanium have been researched thoroughly and found to be biocompatible. So, most of the device manufacturers rely on these materials.
Preparing the insert material to bond ideally with the silicone–
Silicone molding engineers consider a number of methods to better the chemical bond quality, as designing and cleaning, mechanical abrading, chemical etching, and applying a bonding agent or adhesive.
The substrate material may have some chemicals, grease, or oil on it, so this is important to clean it so that it can become ready for the use. While cleaning the substrate, the silicon engineers ensure that the cleaning should not damage the material’s chemical composition or its biocompatibility.
The surface treatment of the insert material includes corona treatment that lowers down the free energy and improves bonding. This includes Plasma treatment as well in which proper surface tension is created by using an inert gas. This includes micro scaling of the surface too in which more surface area is created for bonding.
When we look at these treatment choices, then we find that plasma treatment is the priciest choice. It is the most expensive option because of the process requirements. When you talk to a silicon-molding expert, he can provide you with the best idea as per your requirement.
If you do not want a surface treatment, you have an alternative as well. You can use any adhesive that has been approved for medical usage by the FDA. If you ask about the alternative options, the silicone molder will provide you with another idea as per your needs.
Checking and curbing variability–
The variability must be checked and controlled because this can affect both the over-molded component and the production timing, thereby affecting the bond strength.
The handling of the over-molded element needs to be done with caution because this can cause damage to the surface of the insert or the silicone bond; moreover, to avoid any kind of contaminants.
When the plasma or corona treatment is begun, over-molding timing matters a lot because the surface energy is limited. If either of these treatments is done for cleaning purposes, the effect of the cleaning process on the material diminishes with time.
Inspecting the done part–
Overmolding silicone on any metal or plastic helps create a robust bond. However, some inspection and cleaning ways can harm the bond and make it weak. Therefore, it is a very important process that you cannot take for granted.
Some silicone molders say visual inspection to be the best inspection method; some say custom mechanical tests are the most effective ways to inspect a silicone-overmolded part.
Discuss this with your silicone molder, and he will let you know what will be the best way to inspect the finished part as well as to clean it.
Your silicone molder ensures that inspection and cleaning process must not affect the product quality.
Authenticating the manufacturing process-
Now, the final step is for validating the manufacturing process. Now, the medical device manufacturer has to check the product to validate its design and its usefulness for the requirements.
This process is highly important when it comes to the implantable devices.
The original equipment manufacturers or OEMs have custom methods to validate the manufacturing process and minimize the risk of the failure so that the best quality products can be delivered that can ensure that the applications in which they are used can perform well.
When you approach a silicone molding company to create specific parts for specific medical devices, the silicone molders can do a comprehensive discussion with you to understand your requirements, and then they make a plan for step 1-4. Once these are done, they send you the manufactured product for approval.