Brochure

26
Technical Information – Relays
■
Automatic Mounting of Relay on PCB
THOUGH-HOLE MOUNTING
The following tables list the processes required for mounting a relay onto a PCB and the points to be noted in each process.
Process 1: Placement
Do not bend any terminal of the relay to use it as a self–clinching relay or the relay may malfunction.
It is recommended to use magazine-packaged self–clinching relays for placement onto the PCB.
Possibility of Automatic Placement
Process 2: Flux Application
To apply flux to a flux protection or fully sealed relay, a sponge soaked with flux can be used. Place the relay in the holes drilled in the
PCB and press the PCB (with the relay still mounted) firmly against the sponge. The flux will be pushed up the relay’s contact legs, and
through the PCB holes. This method must never be applied with an unsealed relay because the flux will penetrate into the relay.
The flux used with the sponge must be a non-corrosive resin-type flux.
For the flux solvent, use an alcohol–based solvent, which tends to be less chemically reactive.
Apply the flux sparingly and evenly to prevent penetration into the relay. When dipping the relay terminals into liquid flux, be sure to adjust
the flux level, so that the upper surface of the PCB is not flooded with flux.
Possibility of Dipping Method
Process 3: Transportation
When the PCB is transported, the relay mounted on the PCB may be lifted from the board surface due to vibration. This can be prevented
if the relay mounted on the PCB has self-clinching terminals.
Mounting Interval
When mounting multiple relays side by side on a PCB, pay
attention to the following points:
When many relays are mounted together, they may generate an
abnormally high heat due to the thermal interference between the
relays. Therefore, provide an adequate distance between the
relays to dissipate the heat. When using a relay, be sure to check
the minimum mounting interval.
Also, if multiple PCBs with relays are mounted to a rack, the
temperature may rise. In this case, preventive measures must be
taken so that the ambient temperature falls within the rated value.
PATTERN LAYOUT
Countermeasures Against Noise
The relay can be a noise source when viewed from a
semiconductor circuit. This must be taken into consideration
when designing the layout positioning of the relay and other
semiconductor components on the PCB.
Keep the relay away from semiconductor components as far away
as possible.
Locate the surge suppressor for the relay coil as close to the relay
as possible.
Do not route wiring for signals such as audio signals that are likely
to be affected by noise below the relay.
Design the shortest possible pattern.
One method for separating the power source and relay from other
electronic components is to use shielded patterns.
Coating
As is also the case in humid environments, coating the PCB is
recommended to prevent the insulation of its pattern form being
degraded by gases containing harmful substances. When coating
the PCB, however, care must be exercised not to allow the
coating agent to penetrate into the relays mounted on the PCB;
otherwise, faulty contact of the relay may occur due to sticking or
coating. Moreover, some coating agents may degrade or
adversely affect the relay. Select the coating agent carefully.
Type of Coating
Unsealed Flux protection Fully sealed
NO YES YES
Construction Unsealed Flux protection Fully sealed
Magazine-packaged relay NO YES YES
Self-clinching relays
Item Applicability Feature
to PCB with
relays mounted
Epoxy Good Good insulation. Performing this
coating is a little difficult, but has
no effect on relay contact.
Urethane Good Good insulation and easy to
coat. Be careful not to allow
the coating on the relay itself,
as thinner-based solvents are
often used with this coating.
Silicon Good Good insulation and easy to
coat. However, silicon gas may
cause faulty contact of relay.
Omron A5 Catalogue 2007 1-282 11/9/06 10:16 am Page 26