Handling SMTs

 
The PHYSICAL SIZE of SMT components demands the use of TWEEZERS. However SMT components are VERY FRAGILE and thus a BLUNT NOSE Type is essential. Sharp tweezers can easily damage SMT resistors.

The resistive film on SMT resistors for example is VERY THIN and damage could either CHANGE the value or even make it completely OPEN CIRCUIT!


Resistors come in various physical sizes:
  • 1206 – 0.12” by 0.06” – This size is the easiest to handle
  • 0603 – 0.06” by 0.03”
  • 0402 – 0.04” by 0.02” – This size will blow away if breathed on!
The component value is printed on them in the form:
  • 1K5 1500 Ohm
  • 390R 390 Ohm
  • 1M8 1,800,000 Ohm

 
Capacitors are available in the same sizes as above but
have NO IDENTIFICATION marks on them AT ALL!

So DON'T MIX THEM UP!

 
It's important that you use the largest of the
SMT components available, for ease of handling.

Some devices are so small and light that just BREATHING ON THEM will send them flying away! The smaller devices may damage more easily as described.

The pads on SMT components are pre-tinned and SEALED in airtight packaging. This is to prevent the pads OXIDISING. They also have use-by dates similar to food stuffs. Therefore:

 ONLY OPEN THE PACKAGING JUST BEFORE USE

The use of CAROUSELS to hold lots of UNPACKED SMTs is NOT ADVISED for the above reasons.

ALL SMT components MUST ONLY be touched with TWEEZERS!Fingers will CONTAMINATE them with grease, which will be very difficult to remove and subsequently DIFFICULT to solder.

 
ELECTROSTATIC DAMAGE can occur when CMOS inputs are
exposed to high voltages as low as 60 Volts. However it’s
more likely to be KVolts.

The use of WRIST STRAPS and EARTH MATS are essential while handling any CMOS device.

When handling devices away from the electrostatic-free area ALWAYS:

Hold the device tightly in the palm of your hand,
keeping its pins discharged through your damp skin.