SMD Neck down (ширина пада к ширине проводника), "школьный" вопрос Опции

[Serbo]

Где-то я упустил в своем образовании - в альтиуме встретил правило SMD Neck down, которое ответственно за соотношение ширины пада к ширине подведенного проводника.
Скажите, пожалуйста, где и зачем учитывается эта вещь? Ну теплопередача, это понятно, а еще?
В каких случаях проводник должен быть тоньше/равен/толще пада?

[Владимир]

The width of the conductor should be as uniform as possible
over its length; however, it may be necessary because
of design restraints to ‘‘neck down’’ a conductor to allow it
to be routed between restricted areas, e.g., between two
plated-through holes. The use of ‘‘necking down’’ such as
that shown in Figure 10-1, can also be viewed as ‘‘beefing
up.’’ Single width, having a thin conductor throughout the board, as opposed to the thin/thick approach is less desirable
from a manufacturing point of view as the larger width
conductor is less rejectable due to edge defects rated as a
percentage of the total width.
In any event, if the conductor width change is used, the
basic design requirements defined herein shall not be violated
at the necking down location.

Тамже картинка это из IPC2221

В IPC 782 пункт 3.6.2.2 тоже сказано