The balls are manufactured separately by SPRAYING MOLTEN SOLDER through an ORIFICE at HIGH PRESSURE. This molten spray is cooled to produce the balls. The SIZE of the balls is controlled by the DIAMETER of the orifice.

Various GRADES of solder paste are available. Solder paste with SMALL BALLS for instance, are required for use with FINE PITCH Surface Mount (SMT) Components to reduce BRIDGING across the PCB's tiny ADJACENT pads.

Solder paste has a SHORT LIFE SPAN of only a FEW MONTHS and during that time MUST be kept in an REFRIGERATOR when not in use. After a while the flux within the paste EVAPORATES so making it unusable.

Solder paste's high VISCOSITY enables manufacturers to minimise PCB ASSEMBLY COSTS by shipping PCBs with solder paste already mounted on their pads to EASTERN COUNTIES where the labour is cheap. The components are then placed on the STICKY solder pads BY HAND.

The AMAZING THING is that the PCBs and their COMPONENTS manage to SURVIVE the return journey BACK to the manufacturer for soldering.

The components don't even need to be placed very accurately on the pads as the SURFACE TENSION of the solder paste is so great that it SELF-CENTRES the components AUTOMATICALLY.

There are ALTERNATIVE METHODS for soldering SMT Components that DON'T use solder paste. These techniques are particularly useful for PROTOTYPE PCBs where costly manufacturing is inappropriate.

I've created a FREE EMAIL COURSE discussing all aspects of PCB ASSEMBLY including HAND SOLDERING techniques of SMT COMPONENTS.

The WEB PAGE at:

describes the COURSE CONTENTS and how to ENROL.

Finding the task of "PRINTING" 100's of PCBs with Solder Paste VERY SLOW the lad decided to THIN DOWN the thick solder paste with WATER to make the job easier.

It cost the company 1000's in LOST surface mount components as the error wasn't detected until AFTER the components had been placed on the boards.