1、 ITAA ENGINEERING BULLETIN GEIA-HB-0005-3 Rework/Repair Handbook to Address the Implications of Lead-Free Electronics and Mixed Assemblies in Aerospace and High Performance lectronic Systems EGEIA-HB-0005-3 September 2008 INFORMATION TECHNOLOGY ASSOCIATION OF AMERCIA Copyright Government Electronics
2、 ” February 2004, ver. 1.0 Altera Corporation Application Note 353, “Reflow Soldering Guidelines for Lead-Free Packages,” July 2004, ver.1.0 Peter Biocca (Kester) White Paper, “Lead-free hand-soldering - ending the nightmares,” http:/ Altera Corporation Application Note 81, “Reflow Soldering Guideli
3、nes for Surface-Mount Devices,” June 2002, ver. 4 3.0 Terms and Definitions For purposes of this document, the following terms and definitions apply: Alloy Composition is stated as weight in percent. For instance 63Sn-37Pb corresponds to a mixture of 63% by weight of Tin (Sn) and 37% by weight of Le
4、ad (Pb). Assemblies are electronic items that require electrical attachments, including soldering of wires or piece part terminations; examples include circuit cards and wire harnesses. 2 Copyright Government Electronics in this process, plating stops when the surface of the base metal is completely
5、 covered, thus only a limited coating thickness can be obtained through the immersion process. The control of the kinetics associated with both processes is vital to plating results. 3 Copyright Government Electronics repair of printed circuit boards, software maintenance, and fabrication or manufac
6、ture of repair parts, assemblies, piece parts. Intermediate maintenance consists of repair of aircraft and engine components, WRAs, and LRUs forwarded to the Intermediate level Navy (AIMD) or USAF Back Shops by the organizational level flight-line activities. WRA and LRU repair is accomplished by th
7、e removal, troubleshooting, and replacement of faulty SRA and SRU, pieces, and parts within the WRA/LRU. Lead (Pb) in this document, if the element “Lead” is implied, it will be stated as either Pb or as Lead (Pb). Lead-Free (Pb-free) is defined as less than 0.1% by weight of Pb in accordance with W
8、aste Electrical and Electronic Equipment (WEEE) guidelines. Lead-Free Control Plan (LFCP) refers to an aerospace or military system suppliers document that defines the processes that assure the plan owners, their customers, and all other stakeholders that aerospace and high performance high-reliabil
9、ity electronics systems containing Pb-free solder will continue to be reliable, safe, producible, affordable, and supportable. Technical guidance for a LFCP can be found in GEIA-HB-0005-1. Line Replaceable Unit (LRU) is a black box of electronics removed and replaced at the flight-line level. Liquid
10、us is the minimum temperature at which all components of a mixture (such as an alloy) can be in a liquid state. Below liquidus, the mixture will be partly or entirely solid. Measling is a condition that occurs in laminated base material in which internal glass fibers are separated from the resin at
11、the weave intersection. This condition manifests itself in the form of discrete white spots or “crosses” that are below the surface of the base material. Organic Solderability Preservative (OSP) is a thin organic compound that selectively bonds with Copper (Cu) used to preserve the solderability of
12、bare Cu on printed wiring boards (PWBs). Organizational Level Maintenance (O) is maintenance normally performed by an operating unit on a day-to-day basis in support of its own operations. Organizational-level maintenance typically includes “inspections,“ “servicing,“ “handling,“ and “preventive mai
13、ntenance” and is limited to the replacement of electronics assemblies at the WRA and LRU (black box) level of 4 Copyright Government Electronics e1 Tin-Copper; e2 Tin-Copper-Nickel “Stabilized”; e2 Other alloys containing Bismuth; e6 Tin-Silver-Copper-Bismuth (SACB); e6 Solders containing Indium; e7
14、 Melting temperature is less than 302F (150C) Other Pb-free alloys Currently over 200 different formulations exist 6.1.2 Solder Forms Pb-free solder is available in many of the same forms as SnPb solder including wire, paste, spheres, ribbon or foil, ingot or bar, and preforms. Pb-free solders may n
15、ot be easily distinguishable from SnPb solders or other Pb-free alloys so it is important for technicians to keep all solder alloy materials clearly marked in the manufacturers original packaging. Wire solder or solder paste with missing labels may render the material unidentifiable without testing.
16、 It is especially important to maintain 100% control of solders where multiple alloys are present at the rework/repair station and cross contamination could occur if mixed. 6.1.2.1 Solder Wire A wide range of solid and flux-cored Pb-free solder wire is commercially available. The diameters for rewor
17、k/repair have not changed with standard sizes between 0.062” and 0.015” 11 Copyright Government Electronics Marking and Labeling of Components, PCBs and PCBAs to Identify Lead (Pb), Pb-Free and other Attributes identifies an industry approved marking and labeling method to identify materials (lamina
18、te material, CCA surface finish, solder alloy (Pb-free or SnPb solder) and conformal coating family used in the manufacturing process. IPC/JEDEC J-STD-609 also identifies a marking system for individual piece parts termination finish identification and a labeling system for piece parts packaging. Th
19、e use of IPC/JEDEC J-STD-609 whether invoked voluntarily or by contract, can aid in the rework/repair process by providing valuable information on: The laminate material used in the CCA construction per IPC-4101 CCA laminate material Halogen content CCA surface finish Solder alloy or alloys (Pb or P
20、b-free) used in reflow, wave or other soldering process The conformal coating type applied during the assembly process Piece parts termination finishes when assembled parts are marked Piece parts termination finish when identified on exterior label of replacement component packaging The maximum piec
21、e part temperature rating when identified on exterior label of replacement component packaging Table 1 provides a guide to the IPC/JEDEC J-STD-609 assembly and piece part marking methods used to identify laminate type, Halogen presence, CCA surface finish, solder(s), and conformal coating. Refer to IPC/JEDEC J-STD-609 for additional information on board marking and labeling requirements. 22 Copyright Government Electronics & Information Technology Association Provided by IHS under license with GEIA Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-
