Assembly Instructions for SCA6x0 and SCA10x0 series
TN71
VTI Technologies Oy
10/12
www.vti.fi Rev.1.0
7 Rework
Guidelines
If it becomes necessary to rework a SCA6x0/SCA10x0 series
component, the preferred way to remove the component is by hot
air. Use of a hot air rework station with a vacuum chuck, is the
preferred method. A key issue in using hot-air is preventing
thermal damage to the component or adjacent components.
If hot air rework station is not available, rework with thermal
tweezers is also an acceptable alternative. This method is used at
VTI e.g. for failure analysis purposes. This technical note
describes VTI's rework procedure.
Removing of the component with hot iron only is difficult as it is easy to get the part too hot and
destroy it. It is not recommend method if failure analysis or re-use of the component is desired.
7.1 Instructions for desoldering and removing of component
Soldering Station (Pace SensaTemp ST25E-PS90) and thermal
tweezers (Pace Thermotweez) with Pace 1121-0416-P1 tool head are
used for de-soldering and removing of the component.
Figure
11.
Thermal tweezers, Pace Thermotweez
Figure 12:
Tool head, Pace 1121-0416-P1
The plastic molding compound on the component is LCP (liquid crystal polymer) which withstands
very high temperatures and is good material for Pb-free assembly. LCP's melting point is 335ºC.
However, the mechanical properties start to change already near 280ºC. If the pins are heated too
long the plastic around pin will be softened and if there at the same time is some stress on the pin
there is a risk that pin might move and cause increased reliability or wirebond break inside housing.
In order to melt all pins simultaneously, tweezers are recommended for de-soldering of the
component. Also with tweezers, special care must be taken if failure analysis or re-use of the
component is desired.
In the component removal process, the temperature setting in soldering station is no315ºC.
The temperature on the tip of the tool is 270...275ºC. Tool is pressed against pins only for few
seconds. Same temperature is used both for Pb-free and SnPb-solder joints, even though SnPb
solders melt already below 200ºC. Some temperature adjustment might be needed. Especially if
tool head is old and 'dirty' temperature needs to be increased.
