ELIMINATION OF LEAD-FREE RISK BY ROBOTIC HOT SOLDER

ELIMINATION OF LEAD-FREE RISK BY ROBOTIC HOT SOLDER DIP (RHSD) Don Tyler Corfin Industries LLC 7 -B Raymond Avenue Salem, NH 03079 USA Tel: 1+(603) 893 -9900 Fax: 1+(603) 893 -6800 3/19/2018 © Corfin Industries LLC. All rights reserved.

The Pb-free Problem l In response to Ro. HS, Commercial Off the Shelf (COTS) devices in established BOM have changed from tin-lead finish to pure tin or Pbfree alloy finish, often without sufficient advance notice. l Alternative parts with tin-lead finish are not available or only offered at excessive cost, delivery, and minimum order quantity. © Corfin Industries LLC. All rights reserved.

Defense, Space, Implantable Medical, and Transportation products are Excluded from Ro. HS Manufacturers of high-reliability electronic systems are having increasing difficulty in obtaining electronic components termination finishes that meet their needs. Defense, space, and Ro. HS-excluded users demand a minimum of 3% lead (Pb) in the termination finish to prevent tin whisker growth and provide the confidence of the proven strength of homogenous tin-lead solder joints. 3 Robotic Hot Solder Dip (RHSD) provides the solution by using tightly-controlled robotic process steps to remove all of the existing finish and replace it with tinlead. © Corfin Industries LLC. All rights reserved. 3/19/2018

Tin (Sn) Whiskers l The Problem – Tin Whiskers are conductive tin crystals that “grow or extrude” from plated pure tin finishes l – No reliable test for whisker development exists l l Multiple variables contribute to development Inconsistent results in test for whisker growth propensity Risk of failure is real and unpredictable Failure Modes – – Hard short circuit Intermittent short circuit l l – 4 Whiskers create shorts to adjacent conductors Fusing Floating Debris High impedance short circuit © Corfin Industries LLC. All rights reserved. 3/19/2018

Tin Whiskers Reliability Issues l 5 Whiskers can grow up to 10 mm in length in hours or years and may cause stable or transient short circuits by connecting with neighboring terminations (often less than 1 mm away; see photo below) or by breaking off and bridging other conductive surfaces. © Corfin Industries LLC. All rights reserved. 3/19/2018

Whiskers Do Cause Failures Over 10 Billion Dollars of Lost Hardware (per ONR) l. Military l. Space –F-15 Radar –Satellites – Complete losses –Missile programs l. Galaxy IIIR l. Phoenix l. GALAXY IV l. Patriot Missile II l. Galaxy VII l. Solidaridad I l. Automotive l. Space Shuttle –Toyota Unintended l. Card Guides Acceleration l. Medical Devices – l. Industrial Control Implantable Pacemaker External Defibrillators Crystal “can” http: //www. fda. gov/ora/inspect_ref/itg 42. html 6 –Nuclear Power plant l. Control Relay l. Diode to PWB trace l. Variable resistor in Solid State Protection System © Corfin Industries LLC. All rights reserved. 3/19/2018

Conformal Coat Cannot Cover All Exposures and Can Be Penetrated 7 © Corfin Industries

Mixed Assembly results in weakened solder joints "Photos courtesy of The Aerospace Corporation 8

Gold Plating A Durable Finish under the correct conditions: l Adequate Thickness to Prevent Corrosion 9 “Because gold is a noble metal and because thin gold platings tend to be porous, gold coatings are susceptible to the creep of base metal corrosion products across the surface of the gold after formation at pore sites and edge boundaries. ” http: //www. te. com/documentation/whitepapers/pdf/aurulrep. pdf [TE Connectivity webpage] 9 © Corfin Industries LLC. All rights reserved. 3/19/2018

Gold Plating A Durable Finish under the correct conditions (cont. ): l Minimum Thickness necessary to prevent corrosion 1. 27 µm (50 µinches) (see MIL-PRF-38535) 10 Gold Flash is typically about 0. 6 µm (25 µinches) 10 © Corfin Industries LLC. All rights reserved. 3/19/2018

Gold Plating A Durable Finish under the correct conditions (cont. ): l Must have

Gold Plating A Durable Finish under the correct conditions (cont. ): l Devices and connectors with non -compliant coating are permitted 12 “…provided they are subsequently hot solder dipped…” (MIL-PRF-38535) 12 © Corfin Industries LLC. All rights reserved. 3/19/2018

Gold Embrittlement Photo of SMT feet that “fell off the PCB” due to Gold

Gold Plating Gold Removal Must be Performed on the Surfaces to be Soldered: (excerpts from J-STD-001) Gold removal is performed to reduce the risk of failure associated with embrittled solder. Gold shall be removed: l From at least 95% of the surfaces to be soldered of the through -hole component leads with >2. 54 µm [100 µin] or more of gold 14 thickness and all through-hole leads that will be hand soldered regardless of gold thickness. l From 95% of all surfaces to be soldered of surface mount components regardless of gold thickness. l From the surfaces to be soldered of solder terminals plated with >2. 54 µm [100 µin] or more of gold thickness and from all solder cup terminals, regardless of gold thickness. l 14 © Corfin Industries LLC. All rights reserved. 3/19/2018

Gold Plating Gold Removal Must be Performed on the Surfaces to be Soldered: (excerpts from J-STD-001) (cont. ) From J-STD-001 “Note: Gold embrittled solder connections can occur regardless of gold thickness when solder volume is low or the soldering process dwell time is not sufficient to allow the gold 15 to dissolve throughout the entire solder joint. ” Low Solder Volume and Insufficient Soldering Process Dwell Time are not defined. 15 © Corfin Industries LLC. All rights reserved. 3/19/2018

Gold Embrittlement J-STD-001 requires removal of gold (any thickness) from areas to be soldered to prevent Gold Embrittlement. Failure of BGA at ENIG interface © Corfin Industries LLC. All rights reserved. 3/19/2018

Hot Solder Dip l Traditional Hot Solder Dipping with Sn 63 Pb 37 can replace these finishes, but hand-held processes are unreliable: – – Under-/over-coverage Thermal controls Handling damage Cleaning © Corfin Industries LLC. All rights reserved.

Risk Elimination © Corfin Industries LLC. All rights reserved. 3/19/2018

© Corfin Industries LLC. All rights reserved. 3/19/2018

Robotic Processing Equipment Tight Controls: • Dwells • Flux Sp. G • Rates of Immersion • Cleaning In-line Robotic Trim, Form, and Tin < 50 volts ESD Throughout Entire Process © Corfin Industries LLC. All rights reserved.

RHSD Process Steps l Pick Up l Flux • Solder Dip • Wash l

Hands-free Pickup l l No contact with terminations Vacuum or mechanical w/ titanium fingers

Flux Application l l l © Corfin Industries LLC. All rights reserved. Superior Super. Safe ® No. 30 Organic -Acid, Watersoluble Flux 3 gallon pot w/ dynamic wave Constant Sp. G controls Full Lead Depth 1. 0 +0. 1 seconds per side

Excess Flux Blowoff l © Corfin Industries LLC. All rights reserved. Forced Air removes

Preheat l l l © Corfin Industries LLC. All rights reserved. 150° +3 C

Solder Dip l l © Corfin Industries LLC. All rights reserved. Full Termination Depth (to body) for 3. 0 +0. 1 seconds 245°+1 C Sn 63 Pb 37 replaces existing finish Nitrogen blanket ~275 lbs of alloy to avoid rapid contaminant accumulation or alloy balance drift

Hot Water Wash l l © Corfin Industries LLC. All rights reserved. Full Package

Drop Off l © Corfin Industries LLC. All rights reserved. Return to Tray

Robotic Hot Solder Dip (RHSD) © Corfin Industries LLC. All rights reserved. 3/19/2018

Leadless Devices Hot Nitrogen Leveling integrated into Robotic Hot Solder Dip results in thin solder coverage on large pads of leadless devices after Gold or Pb-free removal. © Corfin Industries LLC. All rights reserved. 3/19/2018

Original Tin Plating Inter-metallic 31 © Corfin Industries LLC. All rights reserved.

Tin/lead Plating After Dipping Original alloy has been completely replaced. 32 © Corfin Industries

The 23 TMTI Packages SOT 23 SOIC-28 TSSOP 16 TQFP-32 208 PQFP 100 TQFP PLASTIC, LCC-28 PLASTIC, LCC-32 CERAMIC, LCC-20 CERDIP-16 (A) CERDIP-16 (B) CERDIP-16 (C) CERDIP-14 (A) CERDIP-14 (B) SOIC-8 SOD-123 PDIP 14 PDIP 20 SOP-8 TO-92 208 PQFP SOP-14 TO-220 (3 lead) Many more processed since “None of the 23 [package types] evaluated displayed evidence of damage or degradation directly attributable to the robotic solder dip process itself. ” 1 1 33 Transformational Manufacturing Technology Initiative (TMTI) project sponsored by the Office of Naval Research (ONR) Manufacturing Technology (Man. Tech) Program © Corfin Industries LLC. All rights reserved.

Report Highlights “The selected parts were subjected to a rigorous series of pre-dip electrical and environmental tests to ensure that they were ‘good’ parts. ” “The parts were subsequently retested and a number were subjected to destructive physical analysis (DPA) to look for damage, if any, resulting from the dipping process. ” “The results on these parts indicate that robotic solder dip introduced no deleterious effects. ” “No electrical anomalies were induced as a result of the robotic solder dip process. ” 34 © Corfin Industries LLC. All rights reserved. 3/19/2018

Selected Changes to Rev A l l l Remove “magnetic” as an acceptable means of robotic pick up Addition of Compliance Checklist and Requirements for Service Form Removal of Semi-automated Option Change “Piece Part Category” to “Piece Part Type” to avoid confusion with “Process Category” Add non-ceramic passives to Piece Part Type 2, formerly grouped into Piece Part Type 3. © Corfin Industries LLC. All rights reserved. 3/19/2018

Pb-Free Ball Grid Arrays l l Pb-free Ball Grid Arrays present an unacceptable reliability risk for defense and space programs. Sn. Pb options are diminishing. --------------------------Pb-free components require higher reflow temperature, exposing PCBs and other components designed for Sn. Pb reflow to potential thermal damage. Mismatched metallurgy also results in significantly weaker solder joints. © Corfin Industries LLC. All rights reserved.

Reballing Techniques for Maintaining Existing Alloy l Reballing of BGAs has long been performed to replace damaged balls, but in low volume and without the requirement to completely remove original alloy. l Traditional methods of removing Pb-free spheres are often poorly controlled: solder wicking braid, vacuum desoldering, and solder pot immersion. l Complete alloy removal at the pad level is not accomplished. The residue of the original alloy will result in the same joint weakness as using a Pb-free sphere placed onto Sn. Pb pad on the board. © Corfin Industries LLC. All rights reserved.

Classic Hand Wicked or Vacuum Desoldered Pads l Incomplete removal of existing Pb-free solder results in alloy combinations and unreliable interfaces with new Sn. Pb alloy. l High-temperature and Pressure from Hand-Held tools damage pads, mask, and substrate. © Corfin Industries LLC. All rights reserved.

Examples of damage © Corfin Industries LLC. All rights reserved.

Pb-Free Solder Sphere Removal © Corfin Industries LLC. All rights reserved.

Flux is Applied Prior to Preheat © Corfin Industries LLC. All rights reserved.

Preheat by Forced Hot Air © Corfin Industries LLC. All rights reserved.

Sn. Pb Flush of Existing Pb-Free Alloy in an Inert Environment (N 2) ©

Prompt Inline Cleaning for Flux Removal © Corfin Industries LLC. All rights reserved.

Robotic System l Controls: Immersion depth, temperature and times of dwell at that temperature, rate of movement over wave l Other features are dynamic wave, nitrogen blanket, variable angles of approach to edge of wave l Provides smooth and consistent pad height. © Corfin Industries LLC. All rights reserved.

Post Robotic Hot Solder Dip (RHSD) Process Appearance © Corfin Industries LLC. All rights

Reballing with Sn. Pb Spheres l Once Pb-Free solder is removed and replaced with Sn. Pb finish, multiple approaches are available for ball replacement: – – – Multiple part reflow with balls dropped on pads and maintained in place by stencil to prevent shorting Use of preforms Single component system with balls dropped on pads, reflowed with no support © Corfin Industries LLC. All rights reserved.

Part Specific Process Controls l Compare recommended flux and component reflow profile to ensure they are compatible. l Observe mechanical, thermal and liquid restrictions such as caps, vents, cavities and easily damaged surfaces. Mask as required. l Bake MSL rated devices when required by J-STD-033 for proper moisture removal. l Testing of BGA mechanical and electrical characteristics pre and post process as required by company protocol or industry standard (pending. ) © Corfin Industries LLC. All rights reserved.

Steps of Reballing © Corfin Industries LLC. All rights reserved.

Stencil Laser etched stencil secured to mobile platform. Spheres corralled perfectly to pad centers though the reflow process. Process speed can be easily increased by the ability to scale platform as desired to reball multiple units simultaneously. © Corfin Industries LLC. All rights reserved.

Platform © Corfin Industries LLC. All rights reserved.

Ball / Sphere Placement © Corfin Industries LLC. All rights reserved.

BGA Re-balling BGA Reballing 56 © Corfin Industries LLC. All rights reserved. 3/19/2018

Reballing Standard Draft Anticipated Release mid-2015 By INTERNATIONAL ELECTROTECHNICAL COMMISSION 57 © Corfin Industries

Qualification Test Steps © 2001 -2010 Corfin Industries LLC. All rights reserved. 3/19/2018

Optional Qualification Test Steps © 2001 -2010 Corfin Industries LLC. All rights reserved. 3/19/2018

Production Lot Test Steps © 2001 -2010 Corfin Industries LLC. All rights reserved. 3/19/2018

Process Monitoring Option © 2001 -2010 Corfin Industries LLC. All rights reserved. 3/19/2018

© 2001 -2010 Corfin Industries LLC. All rights reserved. 3/19/2018

Robotic Hot Solder Dip (RHSD) Benefits l Prevents pure tin whisker growth l Provides outstanding solderability l Controlled, repeatable, proven l Increases storage life of termination finish Disadvantages l Components with packages that surround tinplated surfaces can prevent solder contact with these surfaces (i. e. radial can) l Small leadless devices present handling challenges l Existing delamination may propagate 2 May 2007

NAVY TMTI process parameters must be followed "Photos courtesy of NASA Goddard Space Flight

Robotic Hot Solder Dip (RHSD) Words of Caution l Tight robotic controls are necessary to ensure the pure tin is completely removed over the full plated surface area and to prevent excessive thermal stress to the package. Selecting the Right RHSD Service Provider l Experience with the process l Verify controls are in place l Qualification of same or similar packages TMTI Project can be downloaded at http: //www. bmpcoe. org/news/bmpnews/tinwhisker_report. pdf © Corfin Industries LLC. All rights reserved. 2 May 2007