Placement Guide
===============

Pick and Place
--------------

.. figure:: ../images/concept/QFN-pick.jpg
   :figwidth: 40%
   :align: right
   :alt: QFN inspection

Each part picked is analysed by the vision system prior to placement to ensure that all programmed part dimensions match.  
It is important that each part is programmed with the correct tolerance parameters so that the machine can detect if an 
incorrect or mis-orientated part has been loaded and also that acceptable parts are not rejected. 

The outer contour of the QS module and the pads on the outer edge of the module are not suitable for this purpose.
Due to the manufacturing process, there are certain tolerances for milling the outer contour. As a result, the length 
of the pads along the outer contour is not always the same. 

Due to the panel construction and separation, there may be slight protrusions at the corners.

.. figure:: ../images/concept/QSLS.jpg
   :figwidth: 30%
   :align: center
   :alt: QS inspection

**The large square pads should be used for QS modules to determine the center point and alignment of the module.**

Pick offset
--------------

.. figure:: ../images/concept/pick-offset.png
   :figwidth: 40%
   :align: right
   :alt: Pick Offset

QS modules cannot be picked in the center. Depending on the QS module, an offset to a suitable surface must be determined.

Thermal Considerations
----------------------

.. figure:: ../images/concept/QSBASE3-ICK.png
   :figwidth: 50%
   :align: right
   :alt: QSXP-QSBASE3 Thermal

The QS module consume more than 1 W of DC power. In any application where high ambient 
temperatures for more than a few seconds can occur, it is important that a sufficient 
cooling surface is provided to dissipate the heat. The thermal pad at the bottom of 
the module must be connected to the application board ground planes by soldering. The 
application board should provide a number of vias under and around the pad to conduct 
the produced heat to the board ground planes, and preferably to a copper surface on the 
other side of the board in order to conduct and spread the heat. The module internal 
thermal resistance should in most cases be negligible compared to the thermal resistance 
from the module into air, and common equations for surface area required for cooling can 
be used to estimate the temperature rise of the module. Only copper planes on the circuit 
board surfaces with a solid thermal connection to the module ground pad will dissipate 
heat. For an application with high load the maximum allowed ambient temperature should 
be reduced due to inherent heating of the module, especially with small fully plastic 
enclosed applications where heat transfer to ambient air is low due to low thermal 
conductivity of plastic. The module measured on the evaluation board exhibits a 
temperature rise of about 20°C above ambient temperature. An insufficiently cooled 
module will rapidly heat beyond operating range in ambient room temperature.    

.. figure:: ../images/concept/QSBASE3-THERM.png
   :figwidth: 100%
   :align: left
   :alt: QSXM-QSBASE3 Thermal

The package thermal properties can be found in the processor's data sheet.
   
================= ============== ==============
**Processor**     R\ :sub:`θJB`\ R\ :sub:`θJC`\
================= ============== ==============
i.MX93                           6.4 °C/W
i.MX8M Mini       7.8 °C/W       4 °C/W
i.MX8M Nano       7.8 °C/W       4 °C/W
i.MX8M Plus                      0.24 °C/W
STM32MP1          20.5 °C/W      10 °C/W
================= ============== ==============