Question:
If silicone is used for the power transistor, will it affect the relay?
Answer:
If silicone gas enters the relay, it may cause contact failure.
Explanation:
Mechanism of contact failure due to Silicone
- Use in a silicone gas atmosphere can cause contact failure.
- Silicone gas enters the relay through the relay case and fitting gap. (Gas can enter even in plastic-sealed type.)
- Organic silicon (Si) becomes silicon oxide (SiO2) and adheres to the contact due to the arc energy at the time of contact load switching.
- As the number of switches increases, silicon oxide deposits (the layer of film) increases and contact resistance increases, resulting in contact failure.
Use of silicone for power transistors
Silicone grease is sometimes used between the power transistor and the heat sink, but silicon gas is generated from the silicone grease due to heat generation from the power transistor (Tr).
Depending on the amount of silicone contained in the silicone grease and the size of the load that is switched by the relay, the length of time it takes to cause contact failure of the relay will vary.
In the case of micro load switching, the generated silicone coating cannot be destroyed, leading to contact failure at an early stage. In the case of power switching, the silicone coating is destroyed by the arc, taking a longer period of time to cause contact failure.
Regarding malfunction examples and countermeasures for relays, refer to The SOLUTIONS General-purpose Relay Edition.
Quick tips
Other than silicone grease, do not use any bonds containing organic silicon as well. Please use non-silicon products.
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Relays | Digi-Key Electronics
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