Acceptability of Printed Circuit Board Assemblies

Transcription

1 Section No.: 12I.2.3, Sheet 1 of 9 Rev Level: 16 Additional Distribution: PCB Assembly Subcontractors 1.0 Purpose 2.0 Scope Acceptability of Printed Circuit Board Assemblies 1.1 The purpose of this standard is to provide a compilation of visual quality acceptability requirements for electronic assemblies manufactured by or for Magnetek. This standard is intended to be used by Engineering, Purchasing, Manufacturing, and Inspection in the process of designing, assembling, inspecting, or otherwise evaluating electronic assemblies. 2.1 This standard establishes acceptability criteria for the mounting and interconnection of electronic and mechanical components on rigid single sided, double sided, or multilayer printed circuit boards (PCBs) where through-hole and/or Surface Mount Technology (SMT) components are utilized. Acceptability criteria for flexible electronic circuitry, Chip on Board (COB), Tape Assisted Bonding (TAB), or other advanced assembly techniques are not included in this standard. In general, the acceptability criteria for Magnetek will conform to established industry standards as presented in: IPC-A-610; Acceptability of Electronic Assemblies. 2.2 Unless specified otherwise, the criteria defined in this standard will correspond to IPC Class 2: Dedicated Service Electronic Products. 3.0 Support Documentation 3.1 Decisions regarding acceptability must be based on applicable documentation such as contractual agreements, assembly or component drawings, customer or engineering specifications, and referenced documents or other standards. In the event of conflict, the following order of preference shall apply: The purchase order, work order, or other statement of customer specification The assembly drawings, Bill-of-Materials (BOMs), or other engineering specifications Visual inspection work instructions and/or test specifications (i.e. 96S procedures) This standard The latest revision of IPC-A Standard industry practice or other applicable documents. 3.2 This standard, and other support documentation, will reside with and be maintained by the Process Improvement Manager.

2 Section No.: 12I.2.3, Sheet 2 of 9 Rev Level: Acceptable Handling Procedures 4.1 The general specification for handling electronic assemblies is given in Section 3.0 of IPC- A-610. This specification includes basic concepts for physical handling of PCBs either with or without attached components. An electronic assembly will not be acceptable if physical damage in the form of cracked, chipped, or broken components and connectors, bent or broken terminals, or badly scratched/damaged board surfaces, traces, or pads are evident (Reference Sections 9 and 10.) Visual inspection will include evaluation of appearance criteria such as the presence of fingerprints, soldering residues, lead trimmings, or other contamination. It is required that workstations and packaging materials will provide the necessary protection against Electrical Overstress (EOS) and Electrostatic Discharge (ESD) damage. 5.0 Mechanical Assembly 5.1 This portion of the standard considers the mounting of electronic devices on a PCB, or other components by means of, but not limited to: screws, bolts, nuts, washers, fasteners, clips, component studs, adhesives, tie wraps, rivets, stand-offs, heat sinks, RF shields, and connector pins. Acceptability criteria for mechanical assembly focus on proper securing (tightness), as well as checking for physical damage to the devices, hardware, or the mounting surface that may have occurred during the assembly process. Screws used on printed circuit board assemblies to secure hardware to the circuit board assembly must be secured to the torque values in the following table unless otherwise noted on drawings or other Magnetek specifications. Thread size Into nylon lock nut, or with use of any thread locking compound With lock washer Installation Torque Into plastic (plastite type screws) M2.5 x in-lbs. 7 in-lbs 3 in-lbs. # in-lbs. 8 in-lbs 4 in-lbs. # in-lbs 12 in-lbs 6 in-lbs.

3 Section No.: 12I.2.3, Sheet 3 of 9 Rev Level: 16 Note: Compliance to torque requirements shall be verified as specified in assembly drawings or other Magnetek specifications. If torque verification is performed, the procedure shall ensure that no damage to the components or the assembly occurs. In general, the mechanical assembly portion of this standard conforms to Section 4.0 of IPC-A-610 and includes discussion of: Hardware Eyelets Mechanical Component Mounting Connectors, Handles, and Extractor Mounting Heatsink Mounting and Bonding Terminals Connector Pin Installation Wire Securing and Routing 5.2 In addition, the following special acceptability criteria shall apply as necessary All metal tabs, spring leads, etc., on snap-in parts which are intended for electrical connections to the conductive pattern on a PCB, shall be in contact with the conductive pattern to which they are to be soldered When screws and nuts are required to mount a bracket or component, the screw head should be on the bottom side of the PCB with a star washer, unless otherwise specified Parts that extend more than 1/8 inch above the bottom (solder) side of a PCB must be mounted after wave soldering Assemblies using the 05P and 05P relay with the 05P socket must have the retaining spring (01P ) properly attached to each such relay/socket combination Assemblies using a PCB terminal strip (05P typical) must have a properly installed keying plug (05P ) All re-drilled or additional holes used for component installation in double sided PCBs must have properly mounted eyelets. 6.0 Component Installation, Location, and Orientation

4 Section No.: 12I.2.3, Sheet 4 of 9 Rev Level: This portion of the standard discusses acceptability requirements for the installation, location, and orientation of components and wires as described in Sections 6.0 through 8.0 of IPC-A-610. The criteria in this section refer to direct mounting of components to PCB lands or pads as well as indirect mounting to terminals or connector pins. Where applicable, adhesive bonding as described in IPC-A610, sections and In addition, the following special acceptability criteria shall apply as necessary On double sided and multi layer boards, all capacitors with a diameter (or major dimension) larger than 3/4 inch or longer than 1-3/4 inches shall be bonded to the PCB with RTV as specified on the Bill of Material. On single sided boards all capacitors 1 inch or longer will be bonded to the PCB with RTV. Additional support may be provided by means of tie-wraps as specified on the assembly drawing When mounting 3 Watt or greater resistors with axial leads, the resistor body must have a 1/8 to 1/4 clearance off the board. Leads are to be bent to form a standard stress relief on both sides of the component When mounting 5 Watt or greater resistors, the components shall be bonded to the PCB with RTV as specified on the Bill of Material. The RTV shall contact the resistor for the first 1/4 on each end of the resistor Coated or sealed components that are to be vertically mounted shall have a maximum of in. from the top of the mounting hole to the end of the meniscus on the lead Special mounting procedures for transistors with TO-105 or TO-92 packages may be required in the case of older PCB layouts. Transistors with part numbers 5P , 0023, 0033, 0034, and 0053 may be supplied in either the TO-105 or TO-92 package. With the TO-105 package the transistor leads should be straight and mounted as shown on the PCB silk-screen or assembly drawing. For transistors with the TO-92 package, the leads will be bent and inserted into the plated through holes as shown in the Figure given below. Note that the line markings on the silkscreen denoting the flat on the case will not correspond with the flat on the TO-92 package.

5 Section No.: 12I.2.3, Sheet 5 of 9 Rev Level: 16 OLD ( TO-105 ) NEW ( TO-92 ) In those cases where a component lead or a bare conductor may come in contact with a trace, pad, or an un-insulated part of a component, the wire or lead in question shall be covered with an insulating plastic sleeve. The sleeving shall be specified in the assembly drawing or, preferably, in the BOM. 7.0 Soldering 7.1 This portion of the standard considers the acceptability requirements for soldered joints of all types except those usually associated with Surface Mount devices. The soldering of SMT components is reviewed in Section 14 of this standard. The discussion of soldering in this standard is based on Sections 6.0 and 7.0 of IPC-A Cleanliness 8.1 The acceptability requirements for circuit assembly cleanliness are outlined in Section 10.4 of IPC-A-610. Additionally the following is required: Magnetek requires the use of no clean solder flux for the purposes of wave and SMT soldering, and no clean flux in solder cores for manual component connection, rework, and solder joint touchup. Circuit board assemblies, which have been wave soldered, are not cleaned because the flux residue is not usually visible and is not chemically active. The residue from hand soldering is often visible but is not removed unless specified in appropriate process documentation If aqueous flux is used, a cleanliness level of a maximum of 1.56 Micrograms/cm 2 sodium chloride (NaCl) equivalent ionic or ionizable flux residue is specified. Cleanliness to be verified via solvent extract methods as specified in IPC-TM Production Lot Testing

6 Section No.: 12I.2.3, Sheet 6 of 9 Rev Level: All printed circuit board assemblies to be 100% electrically tested, unless specified or deviated otherwise. Test methodology, test coverage, and test electrical requirements to be mutually agreed upon between Magnetek and PCB supplier. 9.2 Upon successful completion of electrical test, assemblies to be marked with a Test stamp in accordance with Sec Marking 10.1 The general specifications for the acceptability of various markings are presented in Section 10.3 of IPC-A-610. Marking provides product and process identification, status, and traceability. At Magnetek, markings and labels have various formats and are utilized for many different purposes. Examples of markings addressed by this standard include, but are not limited to, the following: Magnetek and supplier logos on PCBs Assembly and PCB part numbers, date codes, and revision levels Component legends including reference designators and polarity indicators Inspection and test traceability labels Relevant regulatory agency (UL, etc.) logos and certifications Installation and user information The specification of a marking style and orientation, label material and size, and print formats shall be defined in appropriate BOMs and assembly drawings If a marking consists of a stamped number, it shall be applied to the PCB surface with a non-conductive, permanent ink (not soluble in water or alcohol,) and coated with clear varnish Unless otherwise specified, all labels will be clean white adhesive backed paper Unless specified otherwise, a marking shall not cover or disfigure another marking. For example, a test label or stamp shall not cover a PCB date code or part number The following PCB marking/labeling criteria are utilized: The sub-assembly BOM number shall be permanently affixed to the component side of the PCB. Some boards, which have a BOM number stamped or silkscreened onto the laminate surface, may be used for more than one assembly. It is required that the proper 46S BOM numbers appear on the PCB if the assembly BOM number is different from the permanent marking The PCB supplier shall provide a label on the PCB that indicates the latest change or revision number in an area adjacent to the BOM number. The change (revision)

7 Section No.: 12I.2.3, Sheet 7 of 9 Rev Level: 16 number label shall be placed so as not to interfere with or be considered as part of the BOM number. Note: Items and may be combined on a single label The manufacturer shall provide labels indicating that ATE, functional test, or visual inspection has been performed. Each manufactured PCB assembly shall have a unique serial number. Serial number labels shall specify the date code, production source, and serial number, in both a Code 3 of 9 bar code and human readable format. This data will appear in a coded format consisting of a seven (7) digit number structured as follows: First Digit - Year: 1990 E 1995 K 2000 Q 2005 V 2010 A 1991 F 1996 L 2001 R 2006 W 2011 B 1992 G 1997 M 2002 S 2007 X 2012 C 1993 H 1998 N 2003 T 2008 Y 2013 D 1994 J 1999 P 2004 U 2009 Z 2014 E Second Digit - Month: Jan A May E Sept J Feb B Jun F Oct K Mar C Jul G Nov L Apr D Aug H Dec M Third Digit - Manufacturing Code: The manufacturing code will consist of a singular alpha character. For confidentiality, the table containing the manufacturing codes is maintained in a separate document, document # MPS12I.2.3.A. The specific manufacturing code will be furnished to respective suppliers on the purchase order, in the Vendor Special Instructions area. This code will be furnished by the Process Engineering group and maintained in document MPS12I.2.3.A. The code shall be entered into the Magnetek vendor database by purchasing.

8 Section No.: 12I.2.3, Sheet 8 of 9 Rev Level: Fourth Through Seventh Digits: The last four digits of the serial number code shall be numerals beginning with Note: These digits restart at 0000 on the 1 st of each month All date code data for years prior to 1990 will reside with and be maintained by the Process Engineering Manager Coatings All field returns require an additional date code label. A three-character date code, as defined in , and , shall be applied as close as possible to the original serial number by the responsible party conducting the repair. This shall indicate that the PCB or assembly has been properly ECO updated and has passed all required electrical tests This portion of the standard considers the visual acceptability requirements for solder mask on PCBs and conformal coating of assembled boards as summarized in Section 10.5 of IPC-A Laminate and Component Condition Serial Number 0001 Made in Menomonee Falls Made in Month of November Made in This portion of the standard considers the visual acceptability requirements for the laminated PCB material as discussed in Sections 10.1, and 10.2 of ANSI/IPC-A Additional criteria, including acceptability criteria for traces, pads, lands, and through hole plating are specified in ANSI/IPC-RB-276 and IPC-6012B, Qualification and Performance Specification for Rigid Printed Boards Component condition shall be maintained at the acceptable as-received level as specified by Magnetek, Purchasing Specifications, or supplier documentation. In the event of conflict between these documents, the Magnetek Purchasing Specifications will take precedence.

9 Section No.: 12I.2.3, Sheet 9 of 9 Rev Level: Discrete Wiring Assembly 13.1 This portion of the standard provides acceptability criteria for the material, routing, surface bonding, and connection of discrete wires as discussed in Section 11.0 of IPC-A Surface Mount Assemblies 14.1 This portion of the standard provides acceptability criteria for the placement and interconnection of SMT components as discussed in Section 8 of IPC-A-610.