HSMS-285P datasheet(9/13 Pages) HP

9 / 13 page

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

packages, will reach solder

reflow temperatures faster than

those with a greater mass.

Agilent’s diodes have been

qualified to the time-temperature

profile shown in Figure 17. This

profile is representative of an IR

reflow type of surface mount

assembly process.

TIME (seconds)

MAX

100

150

200

250

Preheat

Zone

Cool Down

Zone

Reflow

Zone

120

180

240

300

Figure 17. Surface Mount Assembly Profile.

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 evapo-

rating solvents from the solder

paste. The reflow zone briefly

elevates the temperature suffi-

ciently 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.

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 temperatures

and times necessary to achieve a

uniform reflow of solder.

HSMS-285P Datasheet(PDF) 9 Page - Agilent(Hewlett-Packard)

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