The Fine Detail



This course was developed from a five day course on Printed Circuit Board Assembly Technology (PBAT) and a two day course on Design for Surface Mount Technology (DSMT). It was found that in the DSMT course, attendees needed to know the physical options for component packages, which were much greater than with leaded technology, and their individual good and bad points from both the manufacturing and design points of view. Design for Manufacturability (DFM) should be a high priority for any designer. Also, the attendees needed to know about the solder paste process and its relationship to pad design as well as the correct characteristics of the final solder joints for all the different SMT packages and how this related to pad design. All of this was already being covered in the SMT section of the PBAT course.

As the use of SMT was increasing, it was decided to take the SMT section of the PBAT course, add to it the remaining sections from the DSMT course and call it "Manufacture & Design for Surface Mount Technology".

Design for Manufacturability (DFM)

Today, where "time to market pressures" are very great and your third party assembler may be on the other side of the world, you cannot afford, in time or money, to have several goes at getting the product right. You have to try very hard to "get it right the first time". All of the way through the MDSMT course, DFM issues are discussed with respect to the topic being covered: for example, the effect of the selection of certain component packages or types of PCB substrates on cost, yield and quality; the effect of certain design decisions on PCB manufacture and assembly.

Teaching Method

Because of the practical nature of this course and a strong belief in the saying "a picture is worth a thousand words", the course presenter uses many video tapes (indicated in the Course Content as V) and a great number (approx 200) of samples of the various materials, components and processes being discussed (indicated in the Course Content as S). These samples, the detail of many not being able to be seen with the naked eye, are shown to the attendees using a system with a fibre optic light source and a video camera with x60 magnification. This allows all the features of, for example, the cross section of a Ceramic Ball Grid Array (CBGA) mounted on a 10 layer PCB to be clearly seen, including the bumps on the silicon die and it's attachment to the ceramic carrier.

Course Content

Section 1 - PCB Manufacture (4 hours)

    1. The electrical and physical properties of the following substrates, how these apply to good SMT design and how this differs from leaded design:
Phenolic, glass epoxy, polyamide, ceramic, flex, teflon

Some of the very new substrates: BT epoxy, Thermount, IBM's Lignum (green)

    1. The manufacturing process for Single sided, PTH, Multilayer, Flexible and how certain aspects of PCB design can make this more or less difficult.
    2. Surface Finishes including a brief discussion of the Surface Mount Council's White Paper on this subject.
    3. Solder Masks including "damming" for Ball Grid Arrays (BGAs)
    4. PCB Costing - how it is done, cost breakpoints for track widths, spacing, annular ring, etc.
    5. Manufacturing defects - their causes, measures of severity, standards, relationship to PCB design, possible assembly problems for SMT caused by poor bare board manufacture, vendor selection guide
    6. Build-up Technology -
          1. an overwiew of the four main ways for the manufacture of micro vias and an overview of 18 ways that Build-up boards are being made
          2. indepth examinaton of IBMs Surface Laminar process (SLC) and HPs Dycostrate process
    7. IPC Standards (formally the Institute for Interconnecting and Packaging Electronic Circuits) for PCB manufacture including an explanation of Classes and Design Difficulity

Section 2 - General Manufacturing Issues (2 hours)

    1. Component selection - who should be involved, what the big companies do, how small, growing companies can "go off the rails", third party assembler input
    2. Component procurement - some of the pitfalls, relationship to design
    3. Component Storage and its possible effect on manufacturing, ESD prevention in the store
    4. Manufacturing philosophies - batch or push, pull, lot sizes, not making defects
    5. Just in Time - its benefits, HP Training Video

Section 3 - SMT Components (4 hours)

    1. Chip components - sizes (down to 0201), naming, labelling incl value, standardisation within an organisation to minimise purchasing, storage and possible mistakes
    2. Rectangular Plastic Components - tantalums, diodes, etc sizes, naming, labelling incl value, standardisation (or lack there of)
    3. MELFs incl MINI & MICROMELF - sizes, naming, labelling incl value, standardisation (or lack there of), introduction to Insertion Mount Technology (IMT)
    4. Small Outline Transistor Packages (SOT) incl D2- sizes, naming, labelling, mounting
    5. Small Outline IC Packages (SOIC) incl TSOP & TSSOP (thin), QSOP (quad) - sizes, pitch, naming, labelling, mounting, all the different widths, specials such as diode bridge, temp sensor
    6. Plastic Leaded Chip Carriers (PLCC) - sizes, pitch, naming, labelling, mounting, possible assembly problems
    7. Quad Fineline Packs (QFPs) - all the different sizes & pitch, naming, labelling, mounting, possible assembly problems
    8. Tape Automated Bonded (TAB) - all the different sizes & pitch, mounting, significant assembly changes & possible problems, hot bar soldering, relationship of this process to Flip Chip Attach
    9. Ball Grid Arrays - Ceramic & Plastic - sizes & pitch, IBMs C4 flip chip attach to the creamic carrier, mounting, assembly process, PCB design for BGAs, circuit operation benefits esp speed
    10. Flip Chip - sizes & pitch, PCB assembly steps, inverse stepped solder paste stencils
    11. Lead styles and assembly problems
    12. Component Packaging incl bulk cassette, feeders, packaging and feeder problems

Section 4 - SMT Assembly Processes (5 hours)

    1. The Reflow Process
      1. The variations on the Process for single and double sided attach, single reflow for double sided attach
      2. Soldering leaded components by reflow, paste printing rules
      3. The Chemistry of Soldering - phase diagram, intermetalic compounds
      4. Flux - its job, types, new flux standard, possible problems with low solids no clean fluxes, the difference of wave soldering (flux over whole board) to reflow (flux in paste)
      5. Solder alloys - some of the different types and their properties, where is the "lead free" debate, current legislation in some countries
      6. Solder Paste - specifications, manufacture, storage, intelligent use,
      7. Solder Paste Testing
      8. Paste Application - methods, the screen printing process, stencils
      9. Component Placement - evolvement of Pick & Place & Turret machines, the compromises, a typical SMT line
      10. Reflow - the actual process, the behaviour of the paste, IR, Convection, Hot Gas, Bar, Laser
      11. Oven Profiling - methods of attaching thermocouples, where and when to measure, effect of PCB design on reflow
      12. Solder Joint Defects and their causes
      13. Acceptability Criteria - IPC Standards
      14. Cleaning - is it required, if so how and what with
      15. Rework and Hand Assembly - good practices, some of the myths, suitable equipment
    2. The Wave Soldering Process
      1. Overview of the Process - some of the problems
      2. Glue - required properties, placement methods & equipment, dot size requirements, SPC
      3. Wave Soldering - single, dual, front nozzle pump, flux application, preheat requirements, profiling
Section 5 - PCB Design (5 hours)
    1. The Design Process - overview and how it can be improved
    2. CAD Systems - What the top end ones can do, some of the limitations of others
    3. Introduction to IPC782A - PCB Design Standard - how pad sizes were determined
    4. JDEC Package Rules
    5. Component Layout Guidelines - shadowing, layout for wave soldering, component spacing
    6. Mechanical Specifications for a sample of each SMT package style and how the variations impinge on pad design and the subsequent soldering processes
    7. CAD System Automation Algorithms - how they work, what they are intended to do
    8. Fiducial Marks - different types, when to use, methods of use, standards
Section 6 - Some Key Areas not covered in this Course (1 hours)
    1. Electrostatic Discharge, Electromagnetic Compatibility, Statistical Process Control, Testing, Quality
    2. How Selectron (third party assembler in the USA) won the highest quality award