Hand Soldering Guidelines

5.7 Moisture sensitivity level (MSL) classification


The Moisture Sensitivity Level of the DIL component is Level 3 according to the IPC/JEDEC JSTD-
020C. This means that the part is delivered in a dry pack bag and the manufacturing floor time
(out of bag) at the customer’s end is 168 hours.
Following instruction shall be followed:
1. Calculated shelf life in sealed bag: 12 months at < 40 °C and < 90% relative humidity (RH). 2. Maximum soldering peak temperature for the package is 250°C/40sec, measured from the package body. 3. After bag is opened, devices that will be subjected to reflow solder or other high temperature process must be a) Stored at <10% RH, or b) Mounted within 168 hours of factor conditions ≤30 °C/60%RH. Note: Do not re-store devices that have exposed >10% RH conditions.
4. Devices require bake, before mounting, if:
a) Humidity Indicator Card is > 10% when read at 23 ± 5 °C
b) 3a or 3b not met.
5. If baking is required, devices may be baked for 24 hours at 85°C.
Note: Also Tape&Reel materials are applicable for baking at 85°C
Note: Packing materials and procedures according to IPC/JEDEC J-STD-033
Note: Level and body temperature defined by IPC/JEDEC J-STD-020

5.8 Inspection


Optical and visual inspection of solder joints can be done easily, since the solder joints are clearly
seen. A visual inspection of the solder joints with conventional AOI (automatic optical inspection)
system can be used. Also X-ray inspection can be used.
Cross-sectional analysis is also an approved method to inspect how well solder has wetted the
pads of component. Cross-sectional analysis is not used for production inspection, but if required, it
can be used to establish and optimize the component assembly process parameters. Crosssectioning
is a destructive inspection method. An example of a DIL solder joint cross-section in
presented in Figure 9.


6 Hand Soldering Guidelines


For hand soldering of the DIL component, VTI recommends eutectic tin-lead solder due to the
lower melting point compared to lead-free solders. Key thing is that as soon as the solder flows the
soldering iron must be removed from the board. The package temperature should be kept under
280ºC (max 250ºC recommended) and all mechanical stresses in the pin should be minimized. It
should be noted, that also PCB material might damage if too much heat or force is used.
Generally the hand soldering of the DIL component can be done in two different ways:
Method A: Soldering of components with tin wire and soldering iron
Method B: Soldering by applying solder paste onto PCB land pads and then using reflow heating
or soldering iron to melt the paste and achieve the soldered joint.
METHOD A: Soldering of components with soldering iron
Use the tin wire and soldering iron to solder the component onto PCB. Do not touch the package
plastic body with the soldering iron, soldering iron should touch only the PCB pad and through that
the heat should be conducted to the tin wire and component lead. VTI has used 315ºC setting
temperature for component soldering. The temperature on the tip of the tool is 270…275ºC.
Soldering process takes only few seconds for each pin. For leaded soldering we have used
Multicore Sn60Pb40 and for lead-free soldering Almit KR-19SHrma flux-cored solder wire.


METHOD B: Soldering by applying solder paste and then using reflow heating or soldering
iron
1. Apply the solder paste onto the PCB land pads. The paste can be applied by two different
methods.
• Manual solder paste printing through a stencil with normal openings designed for the
DIL component. .
• Needle dispensing of solder paste manually onto the PCB pads. VTI recommends use
of a microscope in manual solder paste dispensing. Dispensing needle tip size can be
0.12″-0.16″.
2. Place the component gently on top of the solder paste. To avoid solder bridging, push only very
gently on top of the component.
Melt the solder paste by putting the part through reflow oven or by using soldering iron as mentioned
in the previous part.

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 normally +315ºC.
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.