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3 General Safety Precautions and Usage Considerations

3-14

less in order to prevent thermal stress in the device.

• Figure 5 shows an example of a recommended temperature profile for surface-mount packages

using solder flow.

5 s

or less

60-120 s

(°C)

250

160

140

Time (s)

Figure 5 Sample temperature profile for solder flow

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/cm2 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.

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