Challenge

In some semi-conductor applications the small amount of electromagnetic interference (EMI) emitted by step motors disrupted precision instruments. To eliminate the EMI, the stators needed to be grounded to the housings.

Conductive tape, soldering a wire to the stator and electrically conductive adhesives were evaluated as potential solutions. The conductive tape was difficult to apply and often fell off during assembly leaving a high potential for assembly errors. Soldering a wire to the stator and the housing was time consuming and did not prove to be effective at eliminating the interference.

Solution

After extensive testing, Lin Engineering found that Loctite® 3888™, a two-part electrically conductive epoxy adhesive, was selected as the optimum solution.

To apply the adhesive, the epoxy is mixed in a pre-packaged twin pack. The mixed adhesive is then applied to the interior of the housing with an applicator stick (See Figure 2).

Finally, the stator is inserted in the housing and allowed to cure at ambient conditions (Figure 3).

Results

Loctite® 3888™ completely eliminated the EMI with the added benefit that it also structurally reinforced the motor. This has allowed Lin Engineering step motors to be used in sensitive semi-conductor applications.