Soldering Materials, Process & Tools PDF

SOLDERING MATERIALS, PROCESS & TOOLS MANJESH KUMARA N S CENTRAL ELECTRONIC FABRICATION FACILITIES  UNIQUENESS OF SPACE MISSIONS Design Complexity  Multi-disciplinary  Weight, Volume, Power, Thermal constraints Technical  Single shot  Non repairable  Un attended operati...

SOLDERING MATERIALS, PROCESS & TOOLS MANJESH KUMARA N S CENTRAL ELECTRONIC FABRICATION FACILITIES  UNIQUENESS OF SPACE MISSIONS Design Complexity  Multi-disciplinary  Weight, Volume, Power, Thermal constraints Technical  Single shot  Non repairable  Un attended operations Environment  Vibration & shock during launch  Extreme Temperature in Space  Vacuum – Outgassing (TML & CVCM)  Radiation  Difference b/w Commercial & Space hardware  Space hardware has to withstand the harsh environmental conditions of space, including extreme temperatures, radiation, vacuum, shock and vibrations.  Space hardware has to be most reliable under extreme conditions.  Space hardware cannot be repaired Hence extreme care shall be taken during realization  QUALITY & RELIABILITY Quality Reliability is defined as degree to which is defined as the probability that a the product meets the product/ system will continue to specifications or the perform its intended function requirements of the customer adequately under stated operating at the start of its life. conditions over a specified period of time without failure.  SPACE MISSIONS  Space missions require highly reliable systems to deliver results and loss of mission will incur, huge loss in terms of money and trust as;  A matter of national pride  Entire world is watching the mission  Enormous investments (hundreds of crores per mission including spacecraft, launch vehicle and ground support equipment)  Un-interrupted service requirements  Large replacement time (Typically 18-24 months)  Single shot & non-repairable system, does not tolerate defects. Space missions to be defect free How Reliability of Space systems are ensured  Design with sufficient margins.  High reliable components & parts  Space proven materials & consumables  Controlled environment conditions  Qualified processes  Trained & High skilled workmanship  Carrying out performance tests under simulated environmental conditions expected during ground handling, launch & orbital operations to asses flight worthiness.  Through various reliability assessments.  Redundancy of critical subsystems.  RELIABILITY IN SPACE SYSTEMS Spacecraft Mission Launch Assembly Goal & performance Subsystems performance Launch & orbital Phase Subsystem Realization Processes Parts & Materials Design Quality – Every where Clearance Design Phase  SOLDER JOINT QUALITY & RELIABILITY CONTROLLED ENVIRONMENT CONDITIONS MATERIAL SELECTION AND CONTROL High Reliable parts Space proven materials PROCESS CONTROL Space qualified processes SOLDER JOINT DESIGN AND WORKMANSHIP Hi-skilled trained workmanship RESULTS IN ZERO DEFECTS  CONTROLLED ENVIRONMENT CONDITIONS CLEANLINESS: CLASS 100,000 TEMPERATURE: 22 ± 3 oC RELATIVE HUMIDITY: 55 ± 5% RH LIGHTING REQUIREMENTS: 1100 Lumen/sq. m ESD PROTECTION METHODS STORAGE, HANDLING & TRANSPORTATION  CLEANLINESS Purpose To avoid the foreign particles that would affect the quality, performance or reliability of the electronic assemblies. Specifications  CLASS 1,00,000 for ASSEMBLY & FABRICATION of Electronic Packages: < 1,00,000 particle of size > 0.5 µm/cubic feet  CLASS 10,000 for Satellite Level Clean Room Activities: < 10,000 particle of size > 0.5 µm/cubic feet  TEMPERATURE, HUMIDITY & LIGHTING TEMPERATURE purpose of temperature control is to avoid the possible corrosion of the metallic parts in the presence of humidity Specifications : 22 ± 3 ºC RELATIVE HUMIDITY Humidity control is essential to strike a balance between the problems associated with ESD & corrosion. Specifications: 55 to 60% RH LIGHTING REQUIREMENT Specifications: 1100 Lumens / sq. m  TYPES OF ESD FAILURES & ESD PRECAUTIONS 1 Catastrophic failures 1 Prevention of charge generation 2 Parametric failures 2 Dissipation of generated charge 3 Latent Failures 3 Neutralization of charge 4 Shielding  MATERIALS SELECTION AND CONTROL Heritage Material qualification Material certification Incoming inspection Traceability  PROCESS CONTROL Qualified Process Work instruction & PID Checklist Fabrication documents Measurement Inspection Evaluation & Control Defects NC management  DEFINITION OF SOLDERING Soldering is A process of joining two parent metals, by means of third material (filler) whose melting temperature is less than the parent metals. Soldering is a process of forming a metallurgical bond at temperature < 600 OF (315 OC). The bonding is primarily because of the inter-metallic compound formed between the parentmetal & the filler material.  SOLDER JOINT DESIGN AND WORKMANSHIP Solder joint should be properly designed to meet the following requirements Electrical conductivity Mechanical durability (strength) Heat dissipation Ease of manufacturing Simplicity of repair Visual inspectability THE BASIC DESIGN CONCEPTS TO ENSURE RELIABLE CONNECTIONS AND TO AVOID SOLDER JOINT FAILURE Stress relief Solder- joint reinforcement Minimum mismatch of thermal expansion coefficients Materials and processes which result in the formation of brittle intermetallic The assembled substrates are designed to allow inspection.  FABRICATION MATERIALS SOLDER ALLOY - MIL SPEC. QQ-S-571/ IPC J-STD-006 FLUX - MIL-F-14256/ IPC J-STD-004 BASE METAL - IPC-4101, MIL SPEC: MIL-PRF-55110 CLEANING SOLVENTS FABRICATION MATERIALS SOLDER ALLOY  TYPES OF SOLDER ALLOYS As per use – Bar solder - used for wave soldering and tinning – Solder wire – used for PCB & connector wiring – Solder paste - used for reflow soldering – Solder pellets – used for solderability test  TYPES OF SOLDER ALLOY AS PER COMPOSITION Soft solders Sn 63 - 37 Pb Melting Point 183 O C. Sn 62 - 2 Ag - 36 Pb Melting Point 179 O C Hard solders Eg. - HMP solder Pb 95.5 - 4.5 MELTING POINT 308 O C. As per flux core SINGLE CORE MULTICORE  PROPERTIES OF TIN & LEAD PROPERTIES TIN LEAD PHYSICAL Bright - silver white lustrous Bluish grey when fresh Resists corrosion when exposed Dull grey when exposed to air to atmosphere Do not react with oxygen & humidity MECHANICAL Malleability : Good Malleability : Good Ductility : Good Ductility : Good THERMAL Melting point: 231.9°C Melting point: 327°C FLUID Surface tension - Higher Surface tension - Moderate Viscosity - Less Viscosity - More Flow rate - Good Flow rate - Poor  EUTECTIC SOLDER ALLOY (SN63 PB37) Good Mechanical Strength : 140.5 kg/cm2 Tensile strength : 43.0 Mpa Shear strength : 37.0 Mpa Anneal at Room Temperature : 22 ºC CTE matches to that of Copper : ~ 24.5 ppm / ºC Low Resistance : 2-3 mΩ Low Melting Temperature : 183 ºC Soldering Time : 2-3 sec Quick Solidification : From 260 ºC to182 ºC in 2-3 sec Good Wetting Power : Excellent Affinity towards Copper Atoms Non Corrosive EUTECTIC SOLDER ALLOY (SN62 AG2 PB36) Good Mechanical Strength : 140.5 kg/cm2 Tensile strength : 48.3 Mpa Shear strength : 52.0 MPa Anneal at Room Temperature : 22 ºC CTE matches to that of Copper : ~ 27 ppm / ºC Low Resistance : 2-3 mΩ Low Melting Temperature : 179 ºC Soldering Time : 2-3 sec Quick Solidification : From 260 ºC to182 ºC in 2-3 sec Good Wetting Power : Excellent Affinity towards Copper Atoms Non Corrosive Reduces Silver leaching Higher Shear strength Better thermal fatigue resistance.  Solder alloy Comparison Property Sn63Pb37 Solder Alloy Sn62Ag2Pb36 Solder Alloy Tin (Sn): 63% Tin (Sn): 62% Composition (Percentage by Lead (Pb): 37% Silver (Ag): 2% Weight) Lead (Pb): 36% Melting Point (°C / °F) 183°C (361°F) 179 °C (354 °F) Density (g/cm³) 8.41 8.29 Thermal Conductivity (W/m·K) 50 51 Electrical Conductivity (% IACS) 12.4 10.3 Young's Modulus (GPa) 46 47 Tensile Strength (MPa) 55-65 70-85 Elongation (%) 10-25 10-30 Hardness (Brinell, HB) 14-16 15-20 Creep Resistance Moderate Improved due to silver Solderability Satisfactory Improved due to silver Corrosion Resistance Moderate Improved due to silver Thermal Fatigue Resistance Moderate Higher* Environmental Impact Not environmentally friendly Not environmentally friendly Appearance Bright & Shiny Brighter & Shinier  M PHASE DIAGRAM M TEMP M N M O N M N O N O o1 O o1 N O P P t t P t P t P t (a) 100% Pb (b) 90% Pb (c) 70% Pb (d) 50% Pb (e) 37% Pb (a) (b) (c) (d) (e) T1 T1 300- LIQUIDUS T2 T1 TEMP 0C LIQUID PASTY REGION 200- T1 = T2 183- T2 T2 SOLIDUS 100- SOLID 0 Pb 10 20 30 40 50 60 70 80 90 Sn TIN LEAD  Soldering iron Temperature selection guide THUMB RULE Soldering tip temp = Melting Point + Approx 60-1000 C = 240 - 280 0 C Recommended Temperature Range for good wetting LIQUIDUS 300- TEMP 0C 200- SOLIDUS 100- 0 Pb 10 20 30 40 50 60 70 80 90 Sn TIN LEAD FABRICATION MATERIALS FLUX  FLUX DEFINITION  A CHEMICALLY ACTIVE COMPOUND WHEN HEATED REMOVES SURFACE OXIDATION AND PROMOTES FORMATION OF INTER METALLIC LAYER BETWEEN SOLDER AND BASE METAL. FUNCTION OF FLUX  ACTS AS A CLEANING AGENT  ACTS AS A CATALYST TRIGGERS & PROMOTES A PROCESS WITHOUT ENTERING INTO THE END PRODUCT.  A VOIDS FURTHER OXIDATION OF THE BASE METALS  PROMOTES SOLDER WETTING  PROPERTIES OF FLUX THERMAL PROPERTIES WITHSTAND SOLDERING TEMPERATURE WITHOUT EVAPORATION OR BREAKDOWN. ACTIVATION TEMPERATURE (170 - 180 °C) THE TEMPERATURE AT WHICH THE FLUX MECHANISM IS TRIGGERED DEACTIVATION TEMPERATURE (330°C) THE TEMPERATURE AT WHICH THE ACTION OF FLUX IS COMPLETE & THE FLUX RESIDUES ARE CHEMICALLY INERT AND NON CORROSIVE. THE FLUX SHALL BE NON CORROSIVE RESIDUAL PRODUCTS SHALL BE EASILY REMOVABLE AFTER SOLDERING REDUCE THE SOLDERING TIME RAPIDLY  TYPES OF FLUXES SYNTHETIC (INORGANIC) NON-SYNTHETIC (ORGANIC) TYPES OF ORGANIC FLUXES WATER WHITE ROSIN FLUXES (R) ROSIN MILDLY ACTIVATED (RMA) ROSIN ACTIVATED (RA) CONSTITUENTS ABIATIC ACID VEHICLE ACTIVATOR FABRICATION MATERIALS BASE METAL  BASE METAL (PCB & COMPONENTS) PCB DESIGN PADS, PATTERNS AND GROUND GOOD SOLDERABILITY OF PCB PADS GOOD SOLDERABILITY OF COMPONENT LEADS FABRICATION MATERIALS CLEANING SOLVENTS TT-I-735  CLEANING SOLVENTS CLEANING AVOIDS ACCUMULATION OF DUST CORROSION SHORT CIRCUIT FINGER PRINTS & GREASE FLUX RESIDUES  FEATURES OF CLEANING SOLVENTS SHALL DISSOLVE OIL GREASE & DIRT SHALL DISSOLVE FLUX RESIDUES SHALL BE NON CORROSIVE SHALL CLEAN BOTH IONIC & NON IONIC CONTAMINATION SHALL VAPORISE AT ROOM TEMPERATURE SHALL NOT ERASE COMPONENT MARKING SHALL BE SAFE THERMALLY & CHEMICALLY  TYPES OF SOLVENTS POLAR SOLVENTS DEFINITION : POLAR SOLVENTS ARE THOSE WHICH DISSOLVES POLAR COMPOUNDS EXAMPLE- DISTILLED DE -IONISED WATER NON POLAR SOLVENTS DEFINITION : NON-POLAR SOLVENTS ARE THOSE WHICH DISSOLVES NON-POLAR COMPOUNDS. EXAMPLE- ISOPROPYLE ALCOHOL(EL GRADE)  TYPES OF SOLVENTS BIPOLAR SOLVENT DEFINITION: BIPOLAR SOLVENTS ARE THOSE WHICH CAN DISSOLVE BOTH POLAR AND NON- POLAR COMPOUNDS. EXAMPLE: FREON (TRI CHLORO TRI FLORO ETHANE) AZEOTROPIC SOLVENT DEFINITION: MIXTURE OF SOLVENTS WHICH VAPOURISES AND CONDENSES AT SAME PROPORTION. EXAMPLE: MIXTURE OF 50% IPA & 50% DI- WATER  SOLDER JOINT FORMATION- PICTORIAL PRESENTATION 39 VACUUM PURE BASE METAL Figure 5 SIMPLIFIED DIAGRAM EXPLAINING. Figure 6 SCHEMATIC OF METAL IN VACUUM SURFACE ENERGIES Figure 7 SCHEMATIC OF METAL IN AIR. Figure 8 SCHEMATIC OF TARNISHED METAL IN AIR AIR AIR TARNISH PURE BASE METAL PURE BASE METAL  SOLDER JOINT FORMATION- PICTORIAL PRESENTATION LIQUID FLUX LIQUID FLUX TARNISH PURE BASE METAL PURE BASE METAL Figure 9 TARNISHED METAL WET BY FLUX Figure 10 CLEAN METAL WET BY FLUX SOLDER SOLDER ALLOYED REGION PURE BASE METAL PURE BASE METAL Figure 11 CLEAN METAL WET BY LIQUID SOLDER. Figure 12 FORMATION OF INTER METALLICS  SOLDER JOINT FORMATION- PICTORIAL PRESENTATION AIR AIR SOLDER OXIDE SOLDER SOLDER Figure 13 SOLDER IN AIR. Figure 14 TARNISHED SOLDER IN AIR  WETTING The soldering process depends on molten solder flowing into all the microscopic surface imperfections of the metals to be soldered and even penetrating very slightly below the surface. In this process, a chemical reaction occurs in TOTAL WETTING & NON-WETTING which the solder alloy actually melts some of the parent metals & alloys with them resulting in a very strong bond between the solder & parent material. The process of surface penetration & alloying is known as Wetting. DEWETTING SCHEMATIC OF THERMODYNAMIC EQUILIBRIUM IN WETTING DIHEDRAL ANGLE METAL ‘A’ SOLDER METAL ‘B’  INTERFACE TWO METALS BONDED BY SOLDER TOTAL NON-WETTING ( = 1800) PLF VAPOUR OR FLUX LIQUID  PSF  PLS SOLID TOTAL WETTING ( = 0 TO 200) PSF = PLS + PLF COS   PARTIAL WETTING > 90  SOLDERING STATIONS MIL-STD-2000A ANSI/ESD S20.20-2021 Tip to Ground Point : < 5.0 ohms Tip to Ground Point : < 2.0 ohms Tip Voltage: < 2 mV RMS Tip Voltage: < 20 mV Tip Leakage: < 10 mA Tip Leakage: < 10 mA IMPORTANT SPECIFICATIONS OF SOLDERING STATIONS Sl. Specifications No. 1 Heater/Cartridge technology Cartridges with Integrated tip, heater and sensor 2 Temperature Range 100 ⁰C to 450 ⁰C or better 3 Temperature Stability ± 5 ⁰C or better 4 Display LED or LCD Tip to Ground Point : < 2.0 ohms EOS/ESD protection as per Tip Voltage: < 20 mV 5 ANSI/ESD S20.20-2021 Tip Leakage: < 10 mA ESD safe housing. Provision for setting standby Menu option provided to set standby time and 6 time and standby temperature standby temperature.  GENERAL PURPOSE TIPS Conical Conical Bent Chisel Chisel Bent Bevel Bevel Bent  COMPONENT SOLDERING Sn63 Pb37 solder - Eutectic alloy Melting temperature 183 0C Soldering time less than 3 s Contour of lead shall be visible, Concave fillet with dihedral angle 5-20o 100% wetting Step 1: Surface & Lead preparation Solder joint shall be bright and shiny, free Step 2: Component mounting/placement from defects such as Exposed base metal, Step 3: Apply heat Insufficient solder, Excess solder, Excess solder bridging / web, pin holes, Blow holes, Hot Step 4: Apply solder to the joint shear / shrink hole/cracked joint, De-wetted Step 5: Clean the joint joint, Non-wetted joint, Icicles, Over heated Step 6: Inspect the joint joint, Cold joint, Rosin joint, Disturbed joint  ADVANTAGES OF SOLDERING AT LOWER TEMPERATURE The tips last much longer because of reduced oxidation. This improves the wettability of the tip and therefore also the heat transfer efficiency. The flux does not burn directly on the tip, but is activated while soldering. In this way, the tip does not turn dark so quickly and its wettability is better. The risk of damaging components and PCB through excessive heat transfer is minimized. The process quality is optimized because there are less rework issues and scraps.  MAINTENANCE OF SOLDERING IRON Check the bit condition. If bad, replace Check for proper grounding of the bit Tip temperature range: 240 oC to 280 oC Preferred temperature 260 oC In any case the temperature should not exceed 320 oC Tin the bit & clean the hot tip using wet sponge/Metal wool During idling period of the soldering iron (non use of iron) 1) Wipe the bit using wet sponge/ metal 2) Apply small quantity of solder on the bit 3) Place the iron in the stand 4) Wipe the solder on the bit before next use  SMT ASSEMBLY PROCEDURE 50 1 1 Material preparation 2 Solder paste printing & Inspection using SPI Solder Paste Printer SPI 3 Comp Pick & place & Inspection using AOI 4 Reflow soldering & Cleaning Component Pick & Place AOI 5 Assembly Inspection using, AOI & X-ray systems 5 6 Rework activities, if any. Convection Reflow Oven X-ray Inspection Sl. No. Solder paste printer SMT Pick and place SMT Reflow oven X-ray Inspection SMT Rework station Incoming component inspection, 1 Stencil design Stacking, Components sorting & Thermal Profile setup Body soldered devices Profile setup kitting. Conveyor width set up Removing SMT 2 Stencil procurement Components XY data generation CCGAs and QFNs components/ devices Thermal Profile run & 3 Stencil Inspection Master data preparation SMD transistors Cleaning & Inspection verification Component loading & Value Reflow soldering 4 Solder paste preparation Micro-D connectors Solder paste dispensing measurement operation Components tray and component Post reflow Card RF Packages before cover Replacement of 5 Printer setup teaching to M/C Cleaning plate assembly components/ devices Reflow soldering Special investigation 6 Accessories cleaning Placement position verification Cleaning & Inspection inspection required from S/S or RQA 7 Solder paste inspection Comp verification - EVV Logging of checklists 8 Stencil cleaning Component placement Solder paste detail Component placement 9 logging verification Manual solder-paste 10 Logging of checklists dispensing  FACTORS AFFECTING REFLOW PROFILE Type of solder paste PCB material PCB thickness Number of layers Amount of copper within the PCB Number of surface mount components Type of surface mount components  SMT REFLOW PROFILE Profile can be divided into four zones: Pre-heat, Soak, Reflow, and Cool down  SMT REFLOW PROFILE Preheat – During this phase the components, PCB and solder are all heated to a specified soak. Heating too quickly can cause defects such as components to crack and the solder paste to splatter causing solder balls during reflow. Soak – The purpose of this phase is to ensure all components are up to the required temperature & Flux activation happens before entering the reflow stage. Reflow – This is the stage where the temperature within the reflow oven is increased above the melting point of the solder paste causing it to form a liquid. Cooling – This is simply the stage during which the assembly is cooled but it is important to not cool the assembly too rapidly - usually the recommended rate of cooling should not exceed 3ºC/second.  SOLDER JOINT INSPECTION Visual inspection Non destructive Testing X-ray Destructive testing Metallographic cross-section Bond pull test Environmental tests  SOLDER JOINTS INSPECTION  For `Detailed Inspection ' use 10x magnifier  For ' Referee Inspection ' use 25x to 50x  X-RAY INSPECTION SYSTEM  GOOD SOLDER JOINTS CHARACTERISTICS  Smooth bright and Shiny surface  Concave fillet  Correct amount of solder  Dihedral angle between 5-20º  Good wetting of surfaces  Visibility of conductor contour INSUFFICIENT SOLDER PREFERRED SOLDER MAX. SOLDER NOT ACCEPTABLE ACCEPTABLE  SOLDER FATIGUE THROUGH HOLE VS. SURFACE MOUNT THT SMT  DEFECTS IN THROUGH-HOLE SOLDERING PROCESS  Insufficient solder  Excess solder  Pin holes  Blow holes INSUFFICIENT SOLDER EXCESS SOLDER PIN HOLE BLOW HOLE  De-wetted joint  Non wetted joint  Icicles  Over heated joint  Cold joint NONWETTED JOINT DE-WETTING ICICLE COLD JOINT  Rosin joint  Disturbed joint  Cracked joint  Solder bridge DISTURBED JOINT CRACKED JOINT BRIDGING  DEFFECTS CAUSE, EFFECT & CORRECTION Sl. DEFECTS APPEARANCE PROBABLE CAUSE EFFECT CORRECTION No. INSUFFICIENT Insufficient solder Weak joint A) heat the joint until SOLDER applied to joint solder melts. Solder not covering B) introduce sufficient 1 the complete joint solder. EXCESS SOLDER Excess solder Joint cannot be Remove all the solder Contour of conductor allowed to flow inspected from the joint clean the completely covered into connection properly as parts and re-solder. 2 by solder. during soldering Wetting as well as operation contour is not visible. COLD SOLDER Insufficient heat Intermittent Remove all solder from JOINT applied to contact. joint clean the parts and A) Dull & grainy connection during re solder appearance soldering. 3 B) Solder has not wetted & adhered to surface.  DEFFECTS CAUSE, EFFECT & CORRECTION Sl. DEFECTS APPEARANCE PROBABLE CAUSE EFFECT CORRECTION No. DISTURBED SOLDER Relative movement Could fail in Re heat the joint A) Small cracks between parts during vibration and until solder flows. B) Rough (wrinkled) soldering. shock tests. Minimum amount of surface. flux and solder may 4 be added as required to achieve proper wetting BLOW HOLES Flux inclusion Intermittent Re heat connection Large depressions on resulting from contact. until solder flows surface or fillet inadequate heating freely and of joint or improper entrapped flux and application of solder, air escape. 5 large hole with small lead and trapped air trying to escape.  DEFFECTS CAUSE, EFFECT & CORRECTION Sl. DEFECTS APPEARANCE PROBABLE CAUSE EFFECT CORRECTION No. PIN HOLES Contamination of Intermittent contact. Remove solder Small holes in solder solder due to dirty and clean the parts, materials & surface. fillet 6 environment Re solder the connection. SOLDER SPIKES Contaminated This can result in Check soldering (ICICLES) soldering iron reduction of required iron for clearance between contamination and Spike protrude from adjacent connections properly tin the 7 fillet with possible arcing soldering iron tip. and corona discharge Re heat solder until it flows and forms into a proper fillet. DE-WETTED JOINT contaminated solder Intermittent contact Assure parts are Irregulary-shaped side of bare copper poor mechanical clean. reduce dwell solder deposits board, mainly due to strength time during heat separated by areas tin-plating process application & 8 resolder covered by a thin solder film  DEFFECTS CAUSE, EFFECT & CORRECTION Sl. PROBABLE DEFECTS APPEARANCE EFFECT CORRECTION No. CAUSE NON -WETTED Presence of Intermittent Assure parts are clean. JOINT contamination contact poor reduce dwell time during Base metal is on the surface mechanical heat application & resolder 9 visible to be soldered strength OVER HEATED Due to excessive Intermittent Remove all solder from the JOINT heat applied contact poor joint and re solder the Dull and grey during soldering mechanical connection 10 appearance strength BRIDGING Due to Electrical short Remove all the excess solder Formation of inadequate PCB circuit in the bridging area conductive path design spacing 11 between between conductors conductors  DEFECTS IN SMT SOLDERING PROCESS Solder Balls around SMD Components Poor Solderability Cracked SMD Capacitor Head-in-Pillow (HIP) Open BGA Joint Tombstone Components Poor Solderability Component "Popcorning" Solder Voids under Components Billboard Parts Insufficient or No Solder  DEFFECTS: CAUSE, EFFECT & CORRECTION Sl. DEFECTS APPEARANCE PROBABLE CAUSE EFFECT No. Solder Balls Heating rate of reflow profile Reduce heating rate of reflow around SMD too high causing flux within profile to no more than Components solder paste to splatter 2ºC/second 1 Poor Poor PCB quality or surface New PCB supplier, alternate PCB Solderability finish quality surface finish, or storage procedure for PCBs 2 Cracked SMD Heating rate of reflow profile Store components within Capacitor set too high causing moisture humidity cabinet or pre-bake trapped within component to before use, reduce heating rate 3 expand during soldering within reflow profile.  DEFFECTS: CAUSE, EFFECT & CORRECTION Sl. No. DEFECTS APPEARANCE PROBABLE CAUSE EFFECT Head-in-Pillow (HIP) Excessive heat during Reduce time and/or preheat and soak causing temperature during preheat flux to become and soak stage of profile, 4 exhausted before consider using nitrogen or entering reflow stage, higher activity solder paste oxidized solder connections Open BGA Joint Insufficient solder paste Check height and volume of applied, poor PCB paste deposit using 3D SPI surface finish, before component component defect, PCB placement, check PCB 5 warped. solderability, check quality of component, check PCB for bow and twist. Tombstone Components Thermal imbalance due Balance copper in PCB to copper design. Revise reflow profile difference/component to reduce change in temp. 6 misplacement Improve accuracy of placement  DEFFECTS: CAUSE, EFFECT & CORRECTION Sl. DEFECTS APPEARANCE PROBABLE CAUSE EFFECT No. Poor Solderability Poor PCB quality or New PCB supplier, alternate PCB surface finish quality surface finish, or storage procedure for PCBs 7 Component Entrapped moisture Storage of components in humidity "Popcorning" within components cabinets or pre-bake prior to usage which expands / 8 outgasses during reflow Solder Voids Volatile elements from Increase time during reflow stage for under solder paste entrapped volatile elements to escape. Revise Components by component or vias stencil design to all volatiles to escape. 9 within pads creating air Use low-voiding past and plug vias pockets  DEFFECTS: CAUSE, EFFECT & CORRECTION Sl. DEFECTS APPEARANCE PROBABLE CAUSE EFFECT No. Billboard Parts Pickup error during Check feeders on component component placement placement machine are process quite often caused indexing smoothly so parts are by feeder problems not flipped onto their side, adjust vision system on 10 placement machine library to detect parts picked up on their side and reject Insufficient or No Error during solder paste Ensure enough solder paste is Solder printing process caused by applied to the stencil and is insufficient solder paste on frequently replenished, set the stencil or blocked printer to clean stencil with aperture appropriate chemical and 11 vacuum, inspect solder paste print before placement. GOOD SOLDER JOINTS CHARACTERISTICS  Smooth bright and Shiny surface  Concave fillet  Correct amount of solder  Dihedral angle between 5-20º  Good wetting of surfaces CLEANING PROCESS  MANUAL CLEANING METHOD Dip to first tray Dip the assembly in IPA for 10 to 15 minutes Move to second tray Clean the card using medium stiff hog hair brush Move to third tray Clean the card using medium stiff hog hair brush Pour fresh IPA while taking out Drain out IPA from the PWB's using cold air blower Inspection of assembly and rework if any Reclining of card by ensuring no flux residues/oil/grease/finger prints/ wax etc., on PWB  VAPOUR DEGREASING CLEANING METHOD To clean the highly dense wired PCBs Cleaner Solvent: IPA (EL Grade) Test Process  Dip in Cold sump for 2 minutes  Place the assembly in Vapour zone for 3 minutes  Repeat cold & Hot cycles 4 times.  IONIC CONTAMINATION TEST To assess cleanliness of electronic assembly  After SMT process.  Prior to Functional testing of Cards mounted with CQFPs.  Prior to conformal-coating of Cards mounted with CQFPs. Method: Resistivity/Conductivity of Solvent Extracted (ROSE/SEC) Solvent: Mixture (vol. %) of 75 % IPA (EL Grade) & 25% DI water (Resistivity: 18 MΩ) Equipment Calibration Calibration after test solution replacement – Manual method, using calibration fluid (as per OEM recommendation)  IONIC CONTAMINATION TEST PROCEDURE 1. PCB Surface Area Calculation: ~ Length x Width x 2 (multiplication factor varies according to card density, ~ 2 to 3) 2. Machine Solvent Regeneration (Cleaning the solvent up to the 150 Meg-ohm cleanliness level prior to immersion of electronic assembly) 3. PCB immersion into test chamber after regeneration. 4. Test Report Generation: Graphical test data, summary with Pass/Fail decision 5. Test Duration: 3 -10 min. (depends on card density/surface area) 6. Acceptance Limit: Equipment Defined < 1.55 µg / cm2 NaCl equivalent 7. Test Cycles: 1 no. (2 cycles max.), second test cycle required very rarely 8. Rinsing: El-grade IPA, 5 minutes typical 9. Baking: 55°C, 1 Hrs  APPLICABLE DOCUMENTS Doc. No. Title Workmanship Standards for the Fabrication of ISRO – PAX - 300 Electronic Packages Design Requirements for Printed Circuit Board ISRO – PAX - 301 Layout Artwork ISRO – PAX - 304 Test specification for Printed Circuit Boards Storage, Handling & Transportation Requirements for ISRO – PAS - 207 Electronic Hardware Non-conformance Control Requirements for ISRO ISRO – PAS - 100 Projects THANK YOU