HSMS-280F datasheet(6/10 Pages) HP

6 / 10 page

TIME (seconds)

MAX

100

150

200

250

Preheat

Zone

Cool Down

Zone

Reflow

Zone

120

180

240

300

Figure 8. Surface Mount Assembly Profile.

SMT Assembly

Reliable assembly of surface

mount components is a complex

process that involves many

material, process, and equipment

factors, including: method of

heating (e.g., IR or vapor phase

reflow, wave soldering, etc.)

circuit board material, conductor

thickness and pattern, type of

solder alloy, and the thermal

conductivity and thermal mass of

components. Components with a

low mass, such as the SOT

package, will reach solder reflow

temperatures faster than those

with a greater mass.

Agilent’s SOT diodes have been

qualified to the time-temperature

profile shown in Figure 8. This

profile is representative of an IR

reflow type of surface mount

assembly process.

These parameters are typical for a

surface mount assembly process

for Agilent diodes. As a general

guideline, the circuit board and

components should be exposed

only to the minimum tempera-

tures and times necessary to

achieve a uniform reflow of

solder.

After ramping up from room

temperature, the circuit board

with components attached to it

(held in place with solder paste)

passes through one or more

preheat zones. The preheat zones

increase the temperature of the

board and components to prevent

thermal shock and begin evaporat-

ing solvents from the solder paste.

The reflow zone briefly elevates

the temperature sufficiently to

produce a reflow of the solder.

The rates of change of tempera-

ture for the ramp-up and cool-

down zones are chosen to be low

enough to not cause deformation

of the board or damage to compo-

nents due to thermal shock. The

maximum temperature in the

reflow zone (TMAX) should not

exceed 235

°C.

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