Prevention of Tin Whiskers and Weak Solder Joints from Pb-free Components by Robotic Hot Solder Dip Don Tyler

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Corey Doyle
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4 Pre-Bake Time and Temperature per J-STD-033 4

6 RHSD Process Steps Pick Up Solder Dip Flux Wash Flux Blowoff Preheat Return to Tray 6

7 Hands-free Pickup No contact with terminations Vacuum or mechanical w/ titanium fingers 7

8 Flux Application Superior No. 30 Organic- Acid, Watersoluble Flux 3 gallon pot w/ dynamic wave Constant SpG controls Full Lead Depth seconds per side 8

9 Excess Flux Blowoff Forced Air removes excess flux to reduce spatter and waste 9

Preheat 150 +3 C Forced Hot Air for 4.0 +0.

10 Preheat C Forced Hot Air for seconds Activates Flux Dehydrates flux to reduce spatter 10

11 Solder Dip Full Termination Depth (to body) for seconds C Sn63Pb37 replaces existing finish Nitrogen blanket ~275 lbs of alloy to avoid rapid contaminant accumulation or alloy balance drift 11

Hot Water Wash Full Package with back and forth motion 60 +3

12 Hot Water Wash Full Package with back and forth motion C Filtered Water is emptied and replaced between each cycle 12

13 Drop Off Return to Tray 13

14 Putting It All Together 14

Original Tin Plating Inter-metallic 15 Corfin

Tin/lead Plating After Dipping Original alloy has been completely

17 The 23 TMTI Packages SOT 23 CERDIP-14 (A) SOIC-28 CERDIP-14 (B) TSSOP 16 SOIC-8 TQFP-32 SOD PQFP PDIP TQFP PDIP 20 PLASTIC, LCC-28 SOP-8 PLASTIC, LCC-32 TO-92 CERAMIC, LCC PQFP CERDIP-16 (A) SOP-14 CERDIP-16 (B) TO-220 (3 lead) CERDIP-16 (C) 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 Transformational Manufacturing Technology Initiative (TMTI) project sponsored by the Office of Naval Research (ONR) Manufacturing Technology (ManTech) Program 17

18 18 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. Corfin Industries LLC. All rights reserved. 15 October 2013

Dipping of the Entire Lead Is Necessary 19 "Photos courtesy of NASA Goddard Space Flight

20 Low Risk of Thermal Damage with RHSD Internal Temperature of 160 PQFP processed to TMTI Parameters Temperature in C Time in 0.1 seconds 20

23 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. 15 October 2013

24 Gold Embrittlement Photo of SMT feet that fell off the PCB due to Gold Embrittlement. Corfin s flowing Dynamic Solder Wave completely flushes Gold and replaces it with SnPb. Corfin Industries LLC. All rights reserved. 15 October 2013

26 Pb-Free Ball Grid Arrays Pb-free Ball Grid Arrays present an unacceptable reliability risk for defense and space programs. SnPb options are diminishing Pb-free components require higher reflow temperature, exposing PCBs and other components designed for SnPb reflow to potential thermal damage. Mismatched metallurgy also results in significantly weaker solder joints. Corfin Industries LLC. All rights reserved. 15 October 2013

27 Reballing Techniques for Maintaining Existing Alloy Reballing of BGAs has long been performed to replace damaged balls, but in low volume and without the requirement to completely remove original alloy. Traditional methods of removing Pb-free spheres are often poorly controlled: solder wicking braid, vacuum desoldering, and solder pot immersion. 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 SnPb pad on the board.

Classic Hand Wicked or Vacuum Desoldered

28 Classic Hand Wicked or Vacuum Desoldered Pads Incomplete removal of existing Pb-free solder results in alloy combinations and unreliable interfaces with new SnPb alloy. High-temperature and Pressure from Hand-Held tools damage pads, mask, and substrate.

29 Pb-Free Solder Sphere Removal

30 Flux is Applied Prior to Preheat

31 Preheat by Forced Hot Air

32 SnPb Flush of Existing Pb-Free Alloy in an Inert Environment (N2)

33 Prompt Cleaning for Flux Removal Does Not Allow for Flux to Solidify

34 Robotic System Controls: Immersion depth, temperature and times of dwell at that temperature, rate of movement over wave Other features are dynamic wave, nitrogen blanket, variable angles of approach to edge of wave Provides smooth and consistent pad height. Corfin Industries LLC. All rights reserved. 15 October 2013

35 Post Robotic Hot Solder Dip (RHSD) Process Appearance

36 Steps of Reballing

37 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.

38 Platform

39 Ball / Sphere Placement

40 Programmable Convection Oven Reflow

41 Cleaning

42 Pb-Free to SnPb Conversion Complete

43 Robotic Hot Solder Dip Provides the option of SnPb-finished components when only Pb-free is available from the manufacturer, eliminating the risk associated with obtaining SnPb components from non-franchised sources. Is a proven and mature technique that uses tight processing controls to ensure reliable and safe conversion Corfin Industries LLC. All rights reserved. 15 October 2013

Re tinning Components for Hi Rel Assembly

Hi rel Soldering Re tinning Components for Hi Rel Assembly Alan Cable, President, ACE Production Technologies Lead tinning has experienced a surge in popularity recently for a number of reasons, even though