Miniaturization requires greater use of PC board relays with semiconductors instead of plug-in type relays. The penetration of solder flux into the relay operation. PC board relays can be affected by this problem unless they are sealed. To avoid problems, the following recommendations are offered.

A. Soldering

1. Hand soldering is recommended to avoid flux penetration.
2. Automatic soldering (dip-soldering)
   The sequence of automatic dip-soldering should be as shown in the diagram below.
   
   
   
3. Apply flux thinly and evenly to the portion to be soldered.
   Care should be taken to position the board properly to prevent flux overflow.
4. The use of a low-corrosive rosin flux is recommended to simplify cleaning of solder terminals.
5. Do not fail to preheat before dip-soldering. This will help to dry flux and prevent penetration as well as improve solderability.
6. Use a soldering tub which forms a convex surface, not a flat surface, of the melted solder. The PC board should just skim the surface .
7. Soldering must be done as quickly as possible, that is within 10 seconds at 250°C (482°F) solder temperature or 3 seconds at 350°C (662°F) solder temperature.
8. Example of flux penetration
   In Fig. 2, if the board is pressed down hard against the fluxsoaked sponge, the flux can easily penetrate the relay. This method should be avoided.
   
   

B. Cleaning

Avoid cleaning the relay after soldering to prevent the cover from being deformed and to prevent dregs of flux from remaining in the contact area. If cleaning must be done, it is recommended that a fluorinated hydrocarbon, Solvent 113 (CCi₂F-CCIF₂) or other alcoholic solvent be used.

Do not clean by "glass-shot method."