Sun. Nov 28th, 2021

Silver is a metallic generally utilized in many electronics and microelectronic functions together with hybrid electronics, microelectronic elements and membrane switches. Silver is a really enticing metallic to make use of as a result of it has good conductivity, sturdiness and comparatively low prices. It’s a lot much less inclined to oxidation than naked copper and in reality silver oxide is definitely extra conductive than the silver itself. It has been utilized in polymer thick movie membrane switches for over 30 years. Silver primarily based conductive compositions are often display printed to type the conductive traces in membrane switches.

One of many issues related to silver is a phenomenon referred to as dendrite development or silver migration. Silver migration is the ionic motion of metallic, often between two conductive traces the place an electrical potential exists. Given sufficient motion, the migration will trigger a brief between two traces and render the digital machine ineffective. As a result of silver has a free ion it tends to be extra lively than different metals, thus extra inclined to the dendrite development.

Silver migration will happen if there’s moisture current between two traces with a possible. The speed of migration relies on the quantity of moisture, the temperature and the voltage. Silver migration may be created in a check lab by making use of a droplet of water between traces with a voltage potential. The migration will occur inside seconds.

Membrane switches which can be uncovered to excessive humidity or moisture circumstances usually tend to expertise silver migration. I’m personally conscious of a serious silver migration discipline failure concern that occurred in a microwave oven. This was again within the early 1980’s and the applying was range high microwave oven. Boiling water on the range created the moisture circumstances. Moreover the configuration of the meeting made this significantly inclined to moisture assortment. The “pig tail” was crimped to the primary physique of the membrane swap, which really shaped pure assortment factors for moisture. A easy design change really eradicated the crimps and the sphere failure dropped to close zero.

The next are some widespread methods used to scale back or remove silver migration.

  1. There are a number of new polymer thick movie pastes obtainable that comprise palladium, which has been demonstrated to considerably cut back (however not remove) the tendency of silver emigrate. Value and efficiency could also be a commerce off with these pastes.
  2. Defending the traces with a carbon coating or dielectric may be efficient if the correct materials is satisfactorily utilized. Some supplies are typically porous and are inclined to small “air gaps” that permit moisture to penetrate.
  3. Rising the conductor spacing between traces which have a voltage potential will lower the chance of silver migration.
  4. Holding moisture from penetrating the membrane swap may be efficient in stopping migration. There are a number of strategies and supplies obtainable that may successfully seal a membrane swap from its setting.

Silver migration is a possible drawback that must be addressed within the design and manufacturing course of.

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