DocID14016 Rev 4

5/15

AN2639

SMD presentation

3

SMD presentation

Unlike through hole technology where leads are inserted into the printed circuit board, SMD

(surface mount device) package is attached directly onto mounting pads of the substrate.

SMT is extensively used in electronic applications because it has the following advantages:

•

Packages are smaller and support higher pin counts

•

Packages are light and compact, thus reducing system sizes

•

Mounting can be done on either side of the PCB

•

No cost for drilling holes into the PCB

Surface mount technology also comes along with a few disadvantages:

•

Increased sensitivity to soldering heat because of their thinner dimension

•

Soldering conditions harder to determine (use of finer structures and higher pin count)

3.1

Handling SMDs

Though the intrinsic reliability of SMD packages is now excellent, the use of inappropriate

techniques or unsuitable tools during mechanical handling can affect the long term reliability

of the device, or even destroy it.

When handling a SMD package, it is strongly recommended to use adapted tools such as

vacuum pipes to avoid touching the pins as much as possible. Manual handling could affect

lead coplanarity and cause lead contamination or scratches that could generate solderability

problems. It is also not allowed to widen the interval between two consecutive pins.