8
Motorola TMOS Power MOSFET Transistor Device Data
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 and D2PAK
packages. If one uses a 1:1 opening to screen 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 17 shows a typical stencil for the DPAK and D2PAK
packages. The 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
D2PAK Packages
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.
Always preheat the device.
The delta temperature between the preheat and soldering
should be 100
°
C or less.*
When preheating and soldering, the temperature of the
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.
The soldering temperature and time shall not exceed
260
°
C for more than 10 seconds.
When shifting from preheating to soldering, the maximum
temperature gradient shall be 5
°
C or less.
After soldering has been completed, the device should 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.
Mechanical stress or shock should not be applied during
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 to
incorporate other surface mount components, the D2PAK is
not recommended for wave soldering.