Precautions For Mounting; Precautions; Reflow Mounting; Recommended Conditions For Different Mounting Methods - Citizen CBM-202PC-04 User Manual

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9. PRECAUTIONS FOR MOUNTING

9.1

If a relative humidity drops, the LSI will be electrified with static electricity more easily. The

surface mounting package must be stored in a dry atmosphere to prevent humidity absorption,

but while it is being stored, it will not be electrified because it will not have friction, etc. When

handling or mounting it onto the PCB where friction or electric discharge may be expected, the

relative humidity is desired to be 45~75% from a viewpoint of prevention of electrification.

9.2

Using the screen printing method, etc., apply a constant amount of solder paste to the pattern

on the PCB, which was formed into the specified shape required for soldering the lead pins to a

package mounting section, and mount the package onto it. It will be temporarily fixed by the

surface tension of the solder paste. Then, if the solder is melted(reflow) again, the leads of the

package and the pattern of the PCB will be matched by a self-alignment effect through the

surface tension of the molten solder.

Although the lead joint pattern design values of the PCB depend on the solder paste material

used, reflow condition, etc., they should be preferably 1.1~1.3 times larger than a soldered lead

pin width.

9.3

The most common mounting methods employed for the surface mounting devices are the

infrared reflow method, vapor phase reflow method, and flow solder method.

mounting methods must heat the entire package and apply a strong thermal stress, they

require you to manage not only a temperature at the solder joints, but that on the package

surface, from a viewpoint of maintenance of reliability. Therefore, the recommended mounting

conditions are given in terms of the package surface temperature for the reflow method, and in

terms of solder temperature and immersion time for the flow solder method.

The following describes the concepts of the recommended conditions, using Fig. 9.1.

Fig. 9.1

CBM-202PC-04 User's Manual

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