Using Lead Free Solder - Mitsubishi Electric LT-37131 Service Manual

Pb Solder
The above symbol indicates Lead (Pb) Free solder was
used during the construction of PWBs. Only Lead Free
solder should be used when servicing these PWBs.
Solder must be compatible with that used by the manu-
facturer. Leaded solder can not be used on PWBs manu-
factured with Pb-free solder. The Mitsubishi standard for
service requires the use of Tin-Silver-Copper (Sn-96.5,
Ag-3.0, Cu-0.5). It can be obtained through the Parts
Department.
Order part number: PB FREE SOLDER
Lead Free solder has a higher melting point, and does
not "wet" as well as leaded solder. This means it does
not adhere as readily to the solder iron tip, and the sur-
face to be soldered. To counteract this, the flux used is
more corrosive.
The following cautions must be taken when using Pb
Free solder.
• Higher temperatures can cause the PWB to
warp, detaching surface mount components.
• Higher temperatures may
cause thermal damage to
components.
• Higher temperatures can cause
plastics, such as connectors,
relays, LEDs electrolytic
capacitors, etc. to melt or
warp.
• Higher temperatures can cause
surface oxidation resulting in
poor solder spread-ability and
wet-ability.
• The flux is more corrosive.
• The time required for a good
Pb-Free
Display
Figure 2: Pb-Free display on PWB
MODELS: LT-37131 / LT-37132 / LT-46131 / LT-46231

Using Lead Free Solder

Pb-Free
Phase
Phase-1 PCB's constructed using
Pb-free solder.
Phase-2 Solder, PCB surface
finishing and component
lead plating is Pb-free.
Components may have
internal Pb.
Phase-3 Solder, PCB surface
finishing and components
are Pb-free. (100% Pb-
free)
solder connection may take longer.
• Poor wet-ability can cause solder balls.
• Higher temperatures can cause flux spattering.
• Soldering iron tip life is shortened.
• Dull finish solder joints (not shiny) can appear to be
a "cold" solder joint.
In general a tip temperature of 700° F will usually provide good
results.
Displays used to indicate Pb-free
PCBs will be marked, indicating the level of Pb-free construc-
tion. Table 1 defines the levels by phase and shows the differ-
ent symbols that will be displayed on the PCB. Additionally, a
PCB constructed using Pb-free solder may be simply marked
LFS.
When possible, the indication will be placed close to the part
number that is screened onto the PCB (not the part label).
Figure 1 is an example of a PCB showing the display and its
location.
Definition Display
Pb Solder
Pb Joints
Pb PCA
Table 1: Pb-Free Phases and Symbols
Page 18
Short Display (When the
area is too small)
Pb S
Pb J
Pb P