STPCATLAS datasheet(74/111 Pages) STMICROELECTRONICS

74 / 111 page

MECHANICAL DATA

74/111

Issue 1.0 - July 24, 2002

5.3. SOLDERING RECOMMENDATIONS

High

quality,

low

defect

soldering

requires

identifying the optimum temperature profile for

reflowing the solder paste, therefore optimizing

the process. The heating and cooling rise rates

must be compatible with the solder paste and

components. A typical profile consists of a

preheat, dryout, reflow and cooling sections.

The most critical parameter in the preheat

section is to minimize the rate of temperature rise

to less than

2°C / second, in order to minimize

thermal

shock

the

semi-conductor

components.

Dryout section is used primarily to ensure that

the solder paste is fully dried before hitting reflow

temperatures.

Solder reflow is accomplished in the reflow zone,

where

the

solder

paste

elevated

temperature greater than the melting point of the

solder. Melting temperature must be exceeded by

approximately 20

°C to ensure quality reflow.

In reality the profile is not a line, but rather a range

of temperatures

all solder joints must be

exposed. The total temperature deviation from

component thermal mismatch, oven loading and

oven uniformity must be within the band.

Figure 5-7. Reflow soldering temperature range

Temperature (

°C )

Time ( s )

PREHEAT

DRYOUT

REFLOW

COOLING

240

250

200

150

100

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