Transcript Document
Advanced Skills Soldering Class Instructor: Ted Markson Lecture Goals Learn about Surface Mount Technology Become familiar with more-complex soldering techniques View demonstrations of common SMT procedures Hands-on assembly with a SMD kit 2 Basic Skills Soldering Class 7/7/2015 Surface Mount Technology 3 Basic Skills Soldering Class 7/7/2015 What is SMT? Acronym for ‘Surface Mount Technology’ Method for assembling components onto a PCB surface The leading circuit board assembly practice 4 Basic Skills Soldering Class 7/7/2015 SMT Compared to Thru-hole Technology Smaller component size, i.e. smaller land pattern Higher density components, i.e. more connections to the board Less solder used in assembly 5 Basic Skills Soldering Class 7/7/2015 SMT Advantages Smallest and most-dense component packages Simplified setup for automated assembly Quick assembly Automatic physical error correction Reliably repeatable end-products Lower cost in general, per unit (components, assembly, setup, tooling) Highest performance of end-product 6 RF signal effects Lowered inductance via pin-to-pad connection Basic Skills Soldering Class 7/7/2015 SMT Disadvantages Difficult single-unit assembly or repair Difficult QA and inspection SMDs are prototyping-prohibitive 7 Basic Skills Soldering Class 7/7/2015 SMT Component Packages Refer to Electronic Industry Alliance for latest specifications 8 Basic Skills Soldering Class 7/7/2015 2-pin Packages Numeric Outlines The component size is a reference to actual dimensions Generally passive components such as resistors and capacitors For example, 1206 (3216 metric) is 0.126 x 0.063 in (3.2 x 1.6mm) Small Outline Diode (SOD) 9 For example, SOD-123 is 3.68 x 1.17 x 1.60mm Basic Skills Soldering Class 7/7/2015 Few-pin Packages Small Outline Transistors (SOT) Usually in 3, 5, or 6-pin packages Common components are transistors and voltage regulators For example, SOT-23 is usually 2.9 x 1.3mm Discrete Packaging (DPAK, D2PAK, D3PAK) 10 Common components are voltage regulators and MOSFETS D2PAK is a common equivalent to TO-220 Basic Skills Soldering Class 7/7/2015 Multi-pin Packages, Dual In-line Acronym Name Description Small-outline Integrated Circuit 8+ pins Gull-wing lead form 1.27 mm lead pitch J-leaded Small-outline Like SOIC with J-leads TSOP Thin Small-outline Package Thinner than SOIC 0.5 mm lead pitch SSOP Shrink Small-outline Package 0.635 or 0.8 lead pitch TSSOP Thin Shrink Small-outline Package Lead pitch varies QSOP Quarter-size Small-outline Package 0.635 mm lead pitch VSOP Very Small Outline Package 0.4, 0.5, or 0.65 mm lead pitch DFN Dual Flat No-lead SOIC SOJ 11 Basic Skills Soldering Class 7/7/2015 Multi-pin Packages, Quad In-line Acronym PLCC Name Description Plastic Leaded Chip Carrier Square QFP Quad Flat Package LQFP Low-profile Quad Flat Package 1.4 mm height PQFP Plastic Quad Flat-pack 44+ leads CQFP Ceramic Quad Flat-pack MQFP Metric Quad Flat-pack Metric lead pitch TQFP Thin Quad Flat-pack Thinner version of PQFP QFN Quad Flat No-lead LCC Leadless Chip Carrier Contacts are vertically recessed MLP Micro Lead-frame Package 0.5 mm lead pitch, no pins PQFN Power Quad Flat No-lead Exposed die pads for heat-sinking 12 Basic Skills Soldering Class 7/7/2015 Multi-pin Packages, Grid Arrays Acronym Name Description BGA Ball Grid Array Rectangular array of solder balls, 1.27 mm typical pitch LGA Land Grid Array Mates with on-board socket FBGA Fine Pitch Grid Array Pitch less than 1.27 mm LFBGA Low Profile Fine Pitch Ball Grid Array 0.8 mm typical pitch TFBGA Thin Fine Pitch Ball Grid Array 0.8 mm typical pitch Column Grid Array Rectangular array of solder cylinders or columns CCGA Ceramic Column Grid Array Ceramic bodied CGA µBGA Micro BGA Ball pitch less than 1 mm Lead-less Package 0.5 mm typical ball pitch CGA LLP 13 Basic Skills Soldering Class 7/7/2015 Soldering Specifics 14 Basic Skills Soldering Class 7/7/2015 SMT Production Assembly Techniques Manual Placement Human using a soldering station to assemble components Speed per item is comparable to thru-hole assembly, though the time per pin is much greater QA is usually done with automated processes, such as X-ray examination, Ultrasonic testing, and/or Electrode testing Automated Placement 15 Solder paste is applied via stencil and screen print process Components placed onto board with pick-and-place machine Soldering procedure is completed in-batch using Infrared or Hot gas methods QA is usually done with automated processes Basic Skills Soldering Class 7/7/2015 Land Patterns Used to describe the arrangement of pads on a PCB While there are package standards, some components use package variants with different land patterns Proper patterns can always be found in datasheet or by contacting manufacturer Guideline: verify land patterns with component specs if pattern has not been tested in one month. Pay attention to easily-varied details: lead pitch and pad size 16 Basic Skills Soldering Class 7/7/2015 Joints Good mechanical connection when possible – let the pad contact the PCB pad before soldering Clean the pads before placing the component Proper heat transfer from iron to target: Tip the tip! Avoid ‘cold’ and ‘mounding’ joints Mis-aligned components are more common in SMT Tack-down multi-pin components Still be weary of pad stress from re-heating and lifting PCB pads 17 Basic Skills Soldering Class 7/7/2015 Soldering Techniques - Intro Inside to outside Smallest to largest 18 Basic Skills Soldering Class 7/7/2015 Soldering Techniques - Heat-and-slide For ‘2-pin’ or ‘few-pin’ packages 1. Use conical tip 2. Clean area with isopropyl alcohol or liquid flux 3. Grab component with tweezers 4. Heat single pad, then slide component into land pattern 5. Remove iron from single pad 6. Verify proper component alignment to land pattern 7. Connect other pads 8. Clean area with alcohol and let dry 19 Basic Skills Soldering Class 7/7/2015 Soldering Techniques - Sweep For all package types 1. Use hoof, blade, or chisel tip 2. Clean area with isopropyl alcohol or liquid flux 3. Apply flux to target pads 4. Hold component to board with tape or by tacking 5. Melt solder onto tip 6. Slide tip with solder into joint(s), wait for solder flow into pads, slide tip away 7. Repeat sliding procedure until all pads connected 8. Clean area with alcohol and let dry 20 Basic Skills Soldering Class 7/7/2015 Soldering Techniques - Drag For all package types 1. Use hoof or conical tip 2. Clean area with isopropyl alcohol or liquid flux 3. Apply flux to target pads 4. Hold component to board with tape or by tacking 5. Melt solder onto tip 6. Drag tip with solder along pads parallel to IC edge, with sufficient force to allow solder to connect pin and pad 7. Verify heel, side, and toe fillet joints 8. Clean area with alcohol and let dry 21 Basic Skills Soldering Class 7/7/2015 Demonstration http://www.youtube.com/watch?v=5uiroWBkdFY 22 Basic Skills Soldering Class 7/7/2015 Questions? 23 Basic Skills Soldering Class 7/7/2015 Build Your Kit! 24 Basic Skills Soldering Class 7/7/2015