SMTA Great Lakes Chapter Meeting

Transcription

1 SMTA Great Lakes Chapter Meeting IPC-7711B/7721B Rework, Repair and Modification Presented By: Frank Honyotski Master IPC Trainer (MIT) STI Electronics, Inc.

2 1.1 Scope Procedure for rework/repair Aggregate of information (from many sources) Includes expanded Coverage for lead free processes Document does not limit the maximum number of rework, modifications or repair actions

3 1.2 Purpose Document prescribes Procedures Tools & Materials Methods Applicable to any type of electronic equipment Product flow down applies when invoked by contract Most Common equipment and processes covered Alternate equipment and processes can be used

4 1.2.1 Definition of Requirements Document is intended to be used as a guide No specific requirements or criteria unless separately and specifically called out Must, should, or need to be Used to stress an important point If not followed the end result may not be satisfactory

5 1.3 Background Manual is designed to help users repair, rework and modify electronic assemblies with minimum impact on end use function or reliability Procedures have been obtained from assemblers, printed board manufacturers and users Technique have been proven to be acceptable for the class of product indicated through testing and extended field functionality

6 1.4 Terms and Definitions Definitions marked with an *are from IPC-T-50 PCA Printed Circuit Assembly Rework Modification Repair

7 1.4.1 Class of Product Class 1 General Electronic Products Class 2 Dedicated Service Electronic Products Class 3 High Performance Electronic Products

8 1.4.2 Board Types Types of Printed Boards R Rigid Printed Boards and Assemblies F Flexible Printed boards and Assemblies W Discrete Wiring Boards C Ceramic Boards and Assemblies

9 1.6 Training Soldering Skills Personnel Selection Professional Training

10 1.7 Basic Considerations Approvals - Before proceeding Singular procedures - Combined procedures Quality - Should equal original Procedure selection - Optimum functionality Patience Do not rush the process Applying heat Excess heat is common cause of damage Removal of coatings Essential to remove before processing

11 Materials Materials listed are generic in nature Recommended that materials are available or approved by your company Use of certain materials includes some increased risk (fire, personnel safety, etc.) Should not be used unless appropriate safety precautions are enforced

12 Solder Procedures in this document are not specific to any alloy type Should be compatible with most commonly used tin-lead or leadfree alloys Newly manufactured assemblies Same alloy type needs to be used Repair of fielded assemblies Use drawings to determine alloy type Use alloy used in your facility, if unknown Standards used to identify solder alloys and coatings on the assembly IPC-1066 and JEDEC J-STD-609

13 Process Goals/Guidelines Component replacement involves three basic procedures Component removal Land preparation Component installation Note: Conformal coating removal and replacement may be required Nondestructive process No damage or degradation should occur to the board, adjacent components and the component to be installed or removed

14 Process Goals/Guidelines Controllable, reliable and repeatable process Process appropriate to particular application Operator friendly process Efficient process

15 Selecting a Process Advantages and Precautions Type of component Lead (termination) type Body composition Size of component Moisture sensitivity level of component Type of substrate (FR-4, ceramic, etc.) Component mounting site Thermal mass considerations Adjacent components Accessibility of component or joints

16 Selecting a Process (cont.) Advantages and Precautions Whether the component is being installed or removed Whether the component being removed must be salvaged Applicable workmanship specifications EOS/ESD control requirements

17 Time Temperature Profile (TTP) Steps to achieve an acceptable TTP Select a preheat temperature for both the component and the assembly Identify solder paste characteristics Viscosity, thixotropy, rheology, deposition thickness, drying time/temperature Identify flux cored solder characteristics Land prefill solder quantity and prefill coplanarity Define cleaning procedure Confirm through destructive physical examination or x-ray BGA attachment meets quality requirements Define accelerated cooling system, if used

18 1.9 Lead Free Rework of circuit boards assembled with lead free solders Similar to common alloys Procedures are not specific to any alloy type Tin/Lead alloys or soldering iron tips that have been used with solder containing lead Keep away from lead-free work areas

19 1.9 Lead Free Difference between lead free solders and common alloys Lead free Have higher Liquidous (or melting) temperature May require different dwell times and temperatures May require different fluxes and special cleaning procedures Wetting times are generally extended Solderability indicators will generally be different Wetting angles, joint appearance Higher temperatures and longer dwell time may increase oxidation

20 Solder Differences Lead-free (SAC305) 217 C Liquidous Tin lead (Sn63Pb37) 183 C Liquidous 34 C difference Liquidus

21 1.9 Lead Free (cont.) Difference between lead free solders and common alloys Lead free Component lead frames as well as circuit board finishes must be compatible with the solder alloy Alternative means of attachment may be advantageous due to temperature and other considerations Conductive epoxies For both conductive and convective Use of inert atmosphere (nitrogen) should be considered

22 Figure 1: Flux Component Tweezer Method

23 Gull Wing Removal-Bridge Fill, Surface Tension

24 Figure 1: Position Component Gull Wing Installation, Multi-Lead-Top of Lead

25 6.1.4 Removing Shorts Between Gull Wing, Respread

26 3.9.1 BGA Removal - Hot Gas Reflow System

27 5.7.3 BGA Reballing Procedure - Fixture

28 4.7.1 Surface Mount Pad Repair, Epoxy Method

29 4.7.1 Surface Mount Pad Repair, Epoxy Method

30 6.1 Jumper Wires

31 6.1 Jumper Wires

32 3.5.1 Base Material Repair, Epoxy Method

33 2.3.1 Conformal Coating Removal, Identification IPC-CC-830 Primary specification for printed circuit assembly conformal coating Types Type AR Acrylic resin (includes lacquers and varnishes) Type ER Epoxy resin Type SR Silicone resin Type UR Polyurethane resin Type XY Paraxylylene

34 2.3.1 Conformal Coating Identification

35 2.3.5 Coating Removal, Grinding/ Scraping Method

36 8.1.3 Hook Splice

37 Questions? Please check us out on the web at: Stielectronicsinc.com Phone:

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