[6] Handling Guide
113
3.5.4
Flux Cleaning and Ultrasonic Cleaning
(1) When cleaning circuit boards to remove flux, make sure that no residual reactive ions such as Na
or Cl remain. Note that organic solvents react with water to generate hydrogen chloride and
other corrosive gases which can degrade device performance.
(2) Washing devices with water will not cause any problems. However, make sure that no reactive
ions such as sodium and chlorine are left as a residue. Also, be sure to dry devices sufficiently
after washing.
(3) Do not rub device markings with a brush or with your hand during cleaning or while the devices
are still wet from the cleaning agent. Doing so can rub off the markings.
(4) The dip cleaning, shower cleaning and steam cleaning processes all involve the chemical action of
a solvent. Use only recommended solvents for these cleaning methods. When immersing devices
in a solvent or steam bath, make sure that the temperature of the liquid is 50°C or below, and
that the circuit board is removed from the bath within one minute.
(5) Ultrasonic cleaning should not be used with hermetically-sealed ceramic packages such as a
leadless chip carrier (LCC), pin grid array (PGA) or charge-coupled device (CCD), because the
bonding wires can become disconnected due to resonance during the cleaning process. Even if a
device package allows ultrasonic cleaning, limit the duration of ultrasonic cleaning to as short a
time as possible, since long hours of ultrasonic cleaning degrade the adhesion between the mold
resin and the frame material. The following ultrasonic cleaning conditions are recommended:
Frequency: 27 kHz
∼
29 kHz
Ultrasonic output power: 300 W or less (0.25 W/cm
2
or less)
Cleaning time: 30 seconds or less
Suspend the circuit board in the solvent bath during ultrasonic cleaning in such a way that the
ultrasonic vibrator does not come into direct contact with the circuit board or the device.
