Guidelines For Lead Free Solder - Brother HL 5030 - B/W Laser Printer Service Manual

CHAPTER 4 DISASSEMBLY AND RE-ASSEMBLY

GUIDELINES FOR LEAD FREE SOLDER

6.
Information on Manually Repairing PCB Soldered with Lead-Free Solder
This document provides information on how to correctly make manual repairs to a printed circuit
board (PCB) soldered with lead-free solder.
1. Characteristics of lead-free solder
Melting point higher than that of conventional tin-lead solder
(Lead-free solder: approx. 220'C, Conventional tin-lead solder: approx. 180'C)
Relatively poor solder wettability and spread (difficult to wet and spread), and hard
Appearance (dull and grainy surface) different from that of conventional solder
Relatively poor wettability, rough surface (bumps are likely to be formed), and solder
dragging
Poor solder elevation
Poor thermal conductivity and heat resistant (difficult to melt)
2. Metal composition & wire solder
The metal composition of lead-free solder allowed for use on PCBs for Brother's products is
following.
LF
Indication
1
H
We use wire solder which is indicated by digit after LF indication on PCB.
Wire solder made in the contries except Japan are under investigation,and will be evaluated.
3. Appearance quality criteria
The appearance of the surface of portions soldered with lead-free solder is basically the
same as that for those soldered with conventional lead-tin solder, except for the following
points.
1) The surface of a portion soldered with lead-free solder is dull and not smooth.
2) Shrinkage cracks can be observed on the surface of a portion soldered with lead-free
solder. (They can be observed using a magnifying glass with approx. 10x
magnification.)
4. Identification of lead-free solder on PCBs
For PCBs that use lead-free solder, "LF" is indicated by silk-screen printing or attaching a
label. "LF" stands for lead free and indicates that the PCBs bearing such an indication have
been soldered with lead-free solder. A digit is given in a box following "LF" if produced by
silk-screen printing or follows "LF" without a box on an attached label, the digit indicating the
metal composition and wire solder.
Compositon
Sn/Ag/Cu
only Sn/Ag/Cu
Component-
side
Shrinkage
cracks
Figure 1 Shrinkage Cracks
Manufacture
r
Nihon
Genma
Nihon
Genma
4-63
Origin Name
Japan DHB-RMA3
NP303
Japan DHB-RMA3
NP303