1、 JSC-66491 Revision: Baseline July 2013 Standard for JSC Lead-Free Control Plans (LFCP) Engineering Directorate Avionic Systems Division Verify this is the correct version before use Compliance is Mandatory July 2013 Baseline National Aeronautics and Space Administration Lyndon B. Johnson Space Cent
2、er Houston, Texas 77058-3696 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-JSC-66491 Revision: Baseline July 2013 Change Record Rev. Date Originator A
3、pprovals Description Baseline July 2013 Baseline Verify correct version before use at http:/server-mpo.arc.nasa.gov/Services/CDMSDocs/Centers/JSC/Home.tml. 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-JSC-66491 Revision: Baseline July 2013 TABLE
4、 OF CONTENTS 1 GENERAL REQUIREMENTS . 5 1.1 SCOPE . 5 1.1.1 AUTHORITY . 5 1.2 PURPOSE 5 1.3 APPLICABILITY . 5 1.4 ORDER OF PRECEDENCE 5 1.5 APPROVAL OF DEPARTURES FROM THIS DOCUMENT . 5 1.6 ROLES AND RESPONSIBILITIES 6 2 APPLICABLE DOCUMENTS . 8 2.1 JSC DOCUMENTS 8 2.2 NASA STANDARDS AND DIRECTIVES
5、8 2.3 MILITARY STANDARDS . 8 2.4 INDUSTRIAL STANDARDS 8 2.5 REFERENCE DOCUMENTS 9 3 LEAD-FREE CONTROL PLAN (LFCP) . 10 3.1 PROJECT LEAD FREE CONTROL PLAN (LFCP) REQUIREMENTS . 10 3.1.1 LEAD-FREE CONTROL LEVEL DESIGNATION 11 3.1.2 LEAD-FREE TIN IDENTIFICATION AND REPORTING 11 3.1.3 TIN WHISKER RISK D
6、OCUMENTATION . 11 3.1.4 TIN WHISKER MITIGATION 11 3.1.4.1 DESIGN . 11 3.1.4.2 HOT SOLDER DIP (HSD) 11 3.1.4.2.1. PRETINNING (PARTIAL HSD MITIGATION) . 12 3.1.4.3 CONFORMAL COATING . 12 3.1.4.4 EMBEDMENT / ENCAPSULATION . 13 3.1.5 SURVEILLANCE (INSPECTION and, applicable documents, and approved / una
7、pproved engineering documentation in the order indicated: a. Program Requirements b. This Document c. Engineering Documentation (i.e. : Approved Drawing) 1.5 APPROVAL OF DEPARTURES FROM THIS DOCUMENT Any changes, revisions, or deviations to the requirements of this document shall require technical e
8、valuation and approval by the JSC Lead Free Control Board (LFCB) with the programs having waiver authority. Verify correct version before use at http:/server-mpo.arc.nasa.gov/Services/CDMSDocs/Centers/JSC/Home.tml. 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without licens
9、e from IHS-,-,-JSC-66491 Revision: Baseline July 2013 a. Use of alternate control plans, documents, or processes shall require review and approval of the JSC Lead Free Control Board (LFCB) b. Less stringent control plans, documents, or processes meeting Level “2B“ are allowed in exceptional cases wi
10、th the review and recommendation of the EEE Parts Control Board (EEE-PCB) and approval of the Lead Free Control Board (LFCB). c. Requests for relief from requirements in this document shall be documented and adjudicated in accordance with NASA-STD-8709.20, Management of Safety and Mission Assurance
11、Technical Authority (SMATA) Requirements as implemented by the programs. 1.6 ROLES AND RESPONSIBILITIES a. Project Function. Project shall generate a Lead-Free Control Plan (LFCP) in compliance with the requirements of this document. Reference Appendix A, Project LFCP Template, as the minimum conten
12、t required for a Lead-Free Control Plan (LFCP). b. Lead-Free Control Board (LFCB). The Lead-Free Control Board (LFCB) outlined in Figure 1 and co-chaired by Avionic Systems Division (JSC-EV) Process Engineering (JSC-EV5) and Special Processes (JSC-NT), shall be convened on an as needed basis as a de
13、cision-making forum for the technical review and approval of requests for: (1) changes, revisions, or deviations to the requirements of this document (2) use of alternate control plans, documents, or processes The LFCB is the controlling authority for establishing the configuration baseline for all
14、Lead-Free Control Plans (LFCPs). The co-chairs of the LFCB are permanent members of the EEE Parts Control Board (EEE-PCB) and the LFCB is part of the EEE-PCB. c. EEE Parts Control Board (EEE-PCB). Reference JSC 64182 for the Charter for the Avionic Systems Division Government Furnished Equipment (GF
15、E) Electrical, Electronic and Electromechanical (EEE) Parts Control Board (PCB). (1): Or designated alternate Figure 1: Lead-Free Control Board (LFCB) LEAD-FREE CONTROL BOARD (LFCB) CO-CHAIR EV Process Engineer (JSC-EV5) CO-CHAIR Special Processes (JSC-NT) EEE Parts Lead (1)(JSC-EV5) Materials or, o
16、n internal cavity surfaces of EEE components (i.e.: hybrid, relay crystal cans, MEMS etc.). Lead-free Tin (Sn) solder alloys containing less than 3 percent lead (3% Pb) by weight as an alloying constituent. Exception: Sn96.3Ag3.7 Wiring technology (i.e.: wire, cable, connectors, terminators, clamps,
17、 braid / over-braid shield, etc.) composed of, or coated / plated with metallic Tin (Sn) containing less than 3 percent lead (3% Pb) by weight as an alloying constituent. Any EEE components, electrical / electronic assembly, printed wiring assembly (PWAs), cable assembly, and/or wire harness assembl
18、y assembled with lead-free tin solder alloy except high temperature solder alloy Sn96.3Ag3.7 (Sn96A). Note: Sn96.3Ag3.7 shall only be used where specifically indicated by approved drawings. 3.2 Project Lead Free Control Plan (LFCP) Requirements The use of lead-free Tin (Sn) technology shall be prohi
19、bited unless documented and controlled through a JSC-approved Lead Free Control Plan (LFCP). The use of lead-free Tin (Sn) technology in applications with exposure to temperatures at or below -30C (-22F) shall be prohibited unless controlled through mitigation (see 3.1.6). The LFCP shall be in confo
20、rmance with Control Level 2C requirements of GEIA-STD-0005-2, or as directed by the Program, and reviewed and approved by the LFCB prior to implementation. At a minimum, the project LFCP shall: a. Avoid the use of lead-free Tin (Sn) technology whenever possible. b. Document every incidence of lead-f
21、ree tin technology and prevent its use without prior review and approval of the LFCB. The documentation shall include a list of each individual piece part with a Pb-free tin-finished surface and a description of the finish composition, and a list of what applications will include that piece part. c.
22、 Incorporate a minimum of two (2) mitigation measures when the lead-free tin finish is not completely replaced through a replating or hot solder dip (HSD) process. d. Include any special design requirements, mitigation measures, test and qualification requirements, quality inspection and screening,
23、marking and identification, maintenance, and repair processes. Verify correct version before use at http:/server-mpo.arc.nasa.gov/Services/CDMSDocs/Centers/JSC/Home.tml. 10 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-JSC-66491 Revision: Baseline
24、July 2013 3.2.1 LEAD-FREE CONTROL LEVEL DESIGNATION The lead-free control level shall be set when all other project requirements are being determined. The default lead-free control level shall be 2C. 3.2.2 LEAD-FREE TIN IDENTIFICATION AND REPORTING For control levels 2C (or higher), the LFCP shall r
25、equire X-ray fluorescence (XRF) or similar testing of all parts with external surfaces that appear similar to tin in color and texture (i.e. matte nickel, silver, etc.). 3.2.3 TIN WHISKER RISK DOCUMENTATION The LFCP shall require an assessment of risk consistent with GEIA-STD-0005-2. 3.2.4 TIN WHISK
26、ER MITIGATION Lead-free Tin (Sn) technology, which by package design or engineering decision prevents / prohibits protection by SnPb replating or Hot Solder Dip (HSD), shall be protected by at least two (2) process or design mitigation techniques to reduce or eliminate the risks created by metallic
27、whisker formation and/or tin pest in the expected end-use application / environment. Mitigation is a systematic engineering approach to the control of risk. When considering any mitigation strategy, the engineering function must assess the applicability, strengths and weaknesses of the specific tech
28、nique being employed. Use of mitigation techniques shall require technical review and approval by the LFCB prior to implementation. 3.2.4.1 DESIGN An evaluation of the relative risk of actively mitigating metallic whisker growth must be part of the design process when the availability of components
29、is limited to lead-free tin finishes. This shall include an analysis to determine if the risk of whisker development is partially mitigated by the design and topography of the hardware, spacing between electrically uncommon conductive surfaces, or choice of finish. a. Design and Topography. Componen
30、ts, sub-assemblies, assemblies, and mechanical hardware identified as having a lead-free tin finish shall be physically positioned or mechanically isolated by board strengtheners, brackets, or other non-conductive components / structures to ensure the growth of conductive whiskers does not adversely
31、 affect hardware performance or reliability. b. Spacing. Direct line-of-sight spacing between electrically uncommon conductive surfaces shall be sufficient to ensure whisker growth rates (1mm/yr. nominal) over the life of the mission do not violate minimum electrical spacing requirements. c. Finish
32、- Adjacent Surfaces. Surfaces adjacent to components, sub-assemblies, assemblies, and mechanical hardware identified as having a lead-free tin finish shall be finished with a non-electrically conductive coating. 3.2.4.2 HOT SOLDER DIP (HSD) The Hot Solder-Dipping (HSD) process for tin whisker and ti
33、n pest mitigation differs from the solder tinning process for solderability in that all exposed surfaces of the lead-free tin plated conductors - up to the body-lead seal are replated with tin-lead (SnPb) solder alloy. Because the HSD process exposes components to significant thermal stress, the pro
34、cess shall be repeatable, controlled, not introduce immediate or latent damage, or degrade the performance of the component. Verify correct version before use at http:/server-mpo.arc.nasa.gov/Services/CDMSDocs/Centers/JSC/Home.tml. 11 Provided by IHSNot for ResaleNo reproduction or networking permit
35、ted without license from IHS-,-,-JSC-66491 Revision: Baseline July 2013 A device shall no longer be considered to be lead-free tin finished if all lead-free tin finishes are replaced through a replating or hot solder-dipping (HSD) process with a SnPb alloy having a minimum of 3% lead (Pb) by weight.
36、 The HSD process shall wet and replace all exposed surfaces of the conductors with a tin-lead (SnPb) alloy having a minimum of 3% lead (Pb) by weight. This will involve immersion plating up to the body lead seal, and will require verification that the process is controlled and does not introduce imm
37、ediate or latent damage, or degrade the performance of the component. 1. HSD solder alloy shall be Sn60Pb40, Sn62Pb36Ag02 or Sn63Pb37. Other alloys may be used with prior approval from the procuring NASA activity. 2. Flux chemistry shall be ROL0 (R) or ROL1 (RMA). ROL2 (RA) or other chemistries may
38、be used with demonstration of process control, cleanability, and prior approval from the procuring NASA activity. 3. Components shall be preheated prior to solder immersion to minimize thermal shock. Thermal ramp rates shall not exceed the following, unless specified by engineering documentation: a.
39、 Ramp-up: Not greater than +4C / sec. (+7.2F / sec.) b. Ramp-down: Not greater than -6C / sec. (-10.8F / sec.) 4. Solder immersion of conductors, terminations, or leads shall not exceed 5 seconds duration. Duration of molten solder contact with the body-lead seal shall be minimized but shall be suff
40、icient to ensure full and complete wetting of the entire conductor / termination / lead surface (generally less than 3 seconds maximum). 5. All components shall be properly cleaned, visually inspected per J-STD-001ES 4.2.3 and 11.2.2, and demoisturized per IPC-1601, J-STD-020D, J-STD-033C, or other
41、demoisturization schedule approved by EV5. 3.2.4.2.1. PRETINNING (PARTIAL HSD MITIGATION) The pretinning process used to comply with solderability requirements (ref.: J-STD-001E 4.3, NASA-STD-8739.2 7.2, NASA-STD-8739.3 7.2.5) is recommended as an alternative to Hot Solder Dip (HSD) only in cases wh
42、ere the hardware design prohibits implementation of Hot Solder Dip (HSD). It is considered a partial mitigation because only the portions of the lead-free tin-finished surfaces designated to be part of the completed solder termination are replaced with SnPb alloy. The remaining exposed lead-free tin
43、 finish between the pretinned section of the component lead and the body-lead seal has the potential for whisker development and shall be protected by an additional mitigation, such as conformal coating, embedment / encapsulation, or surveillance (inspection, functional test, etc.). 3.2.4.3 CONFORMA
44、L COATING External surfaces, platings, metallization, etc., with a lead-free Tin (Sn) finish shall be fully coated with conformal coating with a total cured finish thickness of not less than 100 m 0.004 in for silicone (SR) and urethane (UR), and not less than 50 m 0.002 in for paraxylene coatings.
45、Total cured finish thicknesses specified SHALL take precedence over requirements imposed by NASA-STD-8739.1A Table 10-1, or other user-approved conformal coating / polymeric standard. a. Spray or Brush Application Spray-applied or hand-brush-applied conformal coating is viewed as a significant mitig
46、ation tool as it increases environmental resistance, retards the development and propagation of whiskers, and serves Verify correct version before use at http:/server-mpo.arc.nasa.gov/Services/CDMSDocs/Centers/JSC/Home.tml. 12 Provided by IHSNot for ResaleNo reproduction or networking permitted with
47、out license from IHS-,-,-JSC-66491 Revision: Baseline July 2013 as an insulative barrier to Foreign Object Debris (FOD). However, spray or hand-brush application may only be capable of achieving partial coverage for complex PWA designs, as the spray and hand-brush processes only coat the visibly exp
48、osed surfaces, with some minor capillary flow under component bodies. This leaves the most whisker prone areas of the assembly exposed, such as the backside of component leads and leads located completely underneath component bodies (i.e.: BGA, flip chip, etc.). b. Dip Coating Dip coating, if perfor
49、med correctly, will ensure the polymer flows under and around all package types and terminations, producing a coating that wets all surfaces. Using a low viscosity material and a slow submersion rate at a 30 45 degree angle will reduce the incidence of voiding (bubbles). Although there is always some bridging of fine p
