MTV32N25E

http://onsemi.com

9

SOLDER STENCIL GUIDELINES

Prior to placing surface mount components onto a printed

circuit board, solder paste must be applied to the pads.

Solder stencils are used to screen the optimum amount.

These stencils are typically 0.008 inches thick and may be

made of brass or stainless steel. For packages such as the

SC−59, SC−70/SOT−323, SOD−123, SOT−23, SOT−143,

SOT−223, SO−8, SO−14, SO−16, and SMB/SMC diode

packages, the stencil opening should be the same as the pad

size or a 1:1 registration. This is not the case with the DPAK

solder onto the drain pad, misalignment and/or

“tombstoning” may occur due to an excess of solder. For

these two packages, the opening in the stencil for the paste

should be approximately 50% of the tab area. The opening

for the leads is still a 1:1 registration. Figure 16 shows a

pattern of the opening in the stencil for the drain pad is not

critical as long as it allows approximately 50% of the pad to

be covered with paste.

Figure 17. Typical Stencil for DPAK and

SOLDER PASTE

OPENINGS

STENCIL

SOLDERING PRECAUTIONS

The melting temperature of solder is higher than the rated

temperature of the device. When the entire device is heated

to a high temperature, failure to complete soldering within a

short time could result in device failure. Therefore, the

following items should always be observed in order to

minimize the thermal stress to which the devices are

subjected.

soldering should be 100°C or less.*

leads and the case must not exceed the maximum

temperature ratings as shown on the data sheet. When

using infrared heating with the reflow soldering method,

the difference shall be a maximum of 10°C.

260°C for more than 10 seconds.

maximum temperature gradient shall be 5°C or less.

be allowed to cool naturally for at least three minutes.

Gradual cooling should be used as the use of forced

cooling will increase the temperature gradient and result

in latent failure due to mechanical stress.

cooling.

* Soldering a device without preheating can cause

excessive thermal shock and stress which can result in

damage to the device.

* Due to shadowing and the inability to set the wave height

is not recommended for wave soldering.