Brother International HL 5030 Service Manual - Page 160
Guidelines For Lead Free Solder
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CHAPTER 4 DISASSEMBLY AND RE-ASSEMBLY 6. GUIDELINES FOR LEAD FREE SOLDER 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 Compositon Manufacture Origin Name Indication r 1 Sn/Ag/Cu Nihon Genma H only Sn/Ag/Cu Nihon Component- Genma side Japan Japan DHB-RMA3 NP303 DHB-RMA3 NP303 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.) Shrinkage cracks Figure 1 Shrinkage Cracks 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. 4-63