Seal: Potting and flat tape in switches and relays

More ways to create airtight seals in electronic devices

Last time, we talked about the importance of vacuum sealing glass to metal sealing in electronic products. Similarly, a method called encapsulation (also known as encapsulation) is commonly used to create tightly sealed packages for electronic switching devices, including flat strips in semiconductors used in solid-state relays.

What is potting?

In potting, electronic components or assemblies are fully encapsulated in solid or gelatinous compounds that provide shock and vibration resistance, as well as protection from dust and other contaminants, as well as moisture and corrosion agents. The method typically involves immersing or injecting electronic components into a liquid dielectric (such as silicone, epoxy or polyurethane) and curing them. For void-free potting, the product can be placed in a vacuum chamber while the resin remains liquid; The vacuum is pulled and maintained to draw air out of the cavity and resin, and then released so that atmospheric pressure collapses the voids and forces the liquid resin into very corners and cracks.

Dielectric potting is widely used for electronic properties and to protect solid-state electronic components from environmental and mechanical damage; As an added bonus, potting often provides the structure to hold the components together.

Flat strips and Semiconductors: The power behind solid state relays

Many switching applications today use solid-state relays (SSR) to control and complete the power circuitry -- using a power semiconductor device on a flat ribbon to switch current up to about 100 amperes. SSR is faster than electromechanical relay; In addition, because there are no moving parts to wear out and no contacts to cause dents or carbon deposits, SSR has a longer service life and constant output resistance regardless of usage.

Power semiconductors consist of separate discrete devices or usually integrated circuits arranged on flat bands that are used as switches or rectifiers for high current or high voltage applications such as switching mode power supplies. Some common power devices include power diodes, thyristors, MOSFEts, and insulated gate bipolar transistors (IGBT).

Radiators and heat removal from semiconductors

Since semiconductors do not perform well at high temperatures, power devices in SSR require radiators to eliminate heat generated by high temperatures and thermal cycles. Packaging provides a means of removing heat from semiconductor devices by conducting it to the external environment. Connecting the power supply unit to the radiator also eliminates heat from operating losses. In addition, encapsulation helps make semiconductor devices less sensitive to factors such as mechanical shock, vibration, humidity, and external magnetic fields.

Potting is commonly used to create packages for semiconductor components, including those that use flat strip components. Seal encapsulation can also be achieved by positioning the semiconductor chip in the cavity of the package and pulling the vacuum. It is then sealed with a ceramic or metal lid.

As with glass-to-metal seals, it is important to ensure that the thermal expansion of the packaging material is compatible with that of silicon semiconductor devices. It is also critical to ensure that the flat carbon strip is free of cracks, cracks, or other surface conditions that could compromise the integrity of the sealed package. Careful visual inspection and eddy current testing (ECT) can be performed on the flat band to ensure it is free of surface and sub-surface defects. (You can read more about ECT in our previous blog - or better yet, call a metal cutting company!

In addition, if posing resin is injected directly into electronic components, it is important to ensure that precision manufacturing equipment is properly programmed to provide the right proportion of materials and form a gas-tight package without damaging the delicate semiconductor devices inside.

Seal the envelope with a mercury switch

Another type of electronic device that is usually poached is a mercury switch. As the name suggests, mercury switches use a small amount of liquid mercury to turn circuits on and off. Because even a drop of mercury is very sensitive to gravity, mercury provides unique sensing capabilities for simple low-force switching mechanisms.

The mercury switch consists of a set of electrical contacts with a sealed glass case containing a mercury bead; The envelope may also contain air, inert gases, or vacuum. When the switch is tilted, the mercury switch completes or disconnects the circuit, causing mercury to come into contact with or away from a set of contacts. Switches can contain multiple sets of contacts that close different contacts at different angles to sense movement in different directions.

Because mercury is a toxic metal, its use and disposal are strictly regulated and have replaced many previous applications for mercury switches over the years. For example, their use in new cars -- for things like lighting controls and antilock braking systems -- was discontinued in the United States more than a decade ago. However, mercury switches still play a valuable role in safety devices, such as tilt switches used to warn construction equipment of rollops or rollops. On airplanes, electric attitude indicators (aka artificial horizons) still use mercury switches to keep the gyroscope axis perpendicular. Mercury switches are also used as tilt alarms in some vending machines, activating switches to sound an alarm when the machine shakes or tilts.

Air tight bottom line

Whether we're talking about glass bonded to metal in light bulbs, semiconductor encapsulation with flat strips in solid-state relays, or the envelope in mercury switches, ensuring sealing is essential for air tightness. Working with the right partners helps ensure that these key electronic components and processes are tested in the supply chain to produce the desired end results.

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