ROBOTIC HOT SOLDER DIP (RHSD)

ROBOTIC HOT SOLDER DIP (RHSD)
ELIMINATION OF LEAD-FREE RISK BY ROBOTIC HOT SOLDER DIP (RHSD) Don Tyler Corfin Industries LLC 7-B Raymond Avenue Salem, NH USA Tel: 1+(603) Fax: 1+(603) 10 September 2018 © Corfin Industries LLC. All rights reserved.

© Corfin Industries LLC. All rights reserved.
The Pb-free Problem In response to RoHS, Commercial Off the Shelf (COTS) devices in established BOM have changed from tin-lead finish to pure tin or Pb-free alloy finish, often without sufficient advance notice. 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 RoHS Manufacturers of high-reliability electronic systems are having increasing difficulty in obtaining electronic components termination finishes that meet their needs. Defense, space, and RoHS-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. 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 tin-lead. © Corfin Industries LLC. All rights reserved. 10 September 2018

Tin (Sn) Whiskers The Problem Tin Whiskers are conductive tin crystals that “grow or extrude” from plated pure tin finishes Whiskers create shorts to adjacent conductors No reliable test for whisker development exists 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 Fusing Floating Debris High impedance short circuit © Corfin Industries LLC. All rights reserved. 10 September 2018

Tin Whiskers Reliability Issues
Whiskers can grow up to 10mm in length in hours or years and may cause stable or transient short circuits by connecting with neighboring terminations (often less than 1mm away; see photo below) or by breaking off and bridging other conductive surfaces. © Corfin Industries LLC. All rights reserved. 9/10/2018

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

Conformal Coat Cannot Cover All Exposures and Can Be Penetrated
© Corfin Industries LLC. All rights reserved. 10 September 2018

Mixed Assembly results in weakened solder joints
"Photos courtesy of The Aerospace Corporation © Corfin Industries LLC. All rights reserved. 10 September 2018

Gold Plating A Durable Finish under the correct conditions: Adequate Thickness to Prevent Corrosion “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.” [TE Connectivity webpage] 9 9 9 © Corfin Industries LLC. All rights reserved. 10 September 2018

Gold Plating A Durable Finish under the correct conditions (cont.): Minimum Thickness necessary to prevent corrosion 1.27 µm (50 µinches) (see MIL-PRF-38535) Gold Flash is typically about 0.6 µm (25 µinches) 10 10 10 © Corfin Industries LLC. All rights reserved. 10 September 2018

Gold Plating A Durable Finish under the correct conditions (cont.): Devices and connectors with non-compliant coating are permitted “…provided they are subsequently hot solder dipped…” (MIL-PRF-38535) 12 12 12 © Corfin Industries LLC. All rights reserved. 10 September 2018

Gold Embrittlement Photo of SMT feet that “fell off the PCB” due to Gold Embrittlement. Beyond the issue of tin whiskers, there is continuous discussion about if, how, and when to integrate Pb-free with SnPb metallurgy in the overall electronics industry. However, many in the aerospace and defense industries consider mixing the two chemistries on assemblies to present an unacceptable level of risk, especially as regards BGAs. When building an SnPb assembly with lead-free BGAs, to properly assemble with the two different metals you would have to consistently combine the volume of the dissimilar metals in say SAC 305 BGA spheres and board tin-lead solder paste. That combination can be practically impossible to guarantee especially with the increasingly wide variety of BGAs on a board. Thankfully, if you wish to build an SnPb assembly and all that is available to you are Pb-free BGAs there is an alternative to placing those Pb-free BGAs onto SnPb paste. __________________________________________ That’s as opposed to merely mixing SnPb board paste with a relatively thin tin lead finish if you’re so inclined to do so and address tin whisker mitigation in another fashion or ignore that risk. For those assemblers and engineers who do not wish to mix Pb-fee BGAs and SnPb paste, if mixing metallurgies was easily avoidable, they’d do that through specification and purchasing control. © Corfin Industries LLC. All rights reserved. 10 September 2018

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: 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 thickness and all through-hole leads that will be hand soldered regardless of gold thickness. From 95% of all surfaces to be soldered of surface mount components regardless of gold thickness. 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. 14 14 14 © Corfin Industries LLC. All rights reserved. 10 September 2018

Insufficient Soldering Process Dwell Time are not defined.
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 to dissolve throughout the entire solder joint.” Low Solder Volume and Insufficient Soldering Process Dwell Time are not defined. 15 15 15 © Corfin Industries LLC. All rights reserved. 10 September 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 Beyond the issue of tin whiskers, there is continuous discussion about if, how, and when to integrate Pb-free with SnPb metallurgy in the overall electronics industry. However, many in the aerospace and defense industries consider mixing the two chemistries on assemblies to present an unacceptable level of risk, especially as regards BGAs. When building an SnPb assembly with lead-free BGAs, to properly assemble with the two different metals you would have to consistently combine the volume of the dissimilar metals in say SAC 305 BGA spheres and board tin-lead solder paste. That combination can be practically impossible to guarantee especially with the increasingly wide variety of BGAs on a board. Thankfully, if you wish to build an SnPb assembly and all that is available to you are Pb-free BGAs there is an alternative to placing those Pb-free BGAs onto SnPb paste. __________________________________________ That’s as opposed to merely mixing SnPb board paste with a relatively thin tin lead finish if you’re so inclined to do so and address tin whisker mitigation in another fashion or ignore that risk. For those assemblers and engineers who do not wish to mix Pb-fee BGAs and SnPb paste, if mixing metallurgies was easily avoidable, they’d do that through specification and purchasing control. © Corfin Industries LLC. All rights reserved. 10 September 2018

Hot Solder Dip Traditional Hot Solder Dipping with Sn63Pb37 can replace these finishes, but hand-held processes are unreliable: Under-/over-coverage Thermal controls Handling damage Cleaning © Corfin Industries LLC. All rights reserved.

10 September 2018

Robotic Processing Equipment
Tight Controls: Dwells Flux SpG Rates of Immersion Cleaning My goal is to introduce the services Corfin offers and help identify places where Corfin can work together to meet a customers needs. In-line Robotic Trim, Form, and Tin < 50 volts ESD Throughout Entire Process © Corfin Industries LLC. All rights reserved.

Flux Application Superior SuperSafe ® No. 30 Organic-Acid, Water-soluble Flux 3 gallon pot w/ dynamic wave Constant SpG controls Full Lead Depth seconds per side © Corfin Industries LLC. All rights reserved.

Solder Dip Full Termination Depth (to body) for seconds 245°+1 C Sn63Pb37 replaces existing finish Nitrogen blanket ~275 lbs of alloy to avoid rapid contaminant accumulation or alloy balance drift © Corfin Industries LLC. All rights reserved.

Robotic Hot Solder Dip (RHSD)

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. 10 September 2018

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

Tin/lead Plating After Dipping
Original alloy has been completely replaced. © Corfin Industries LLC. All rights reserved.

The 23 TMTI Packages SOT 23 CERDIP-14 (A) SOIC-28 CERDIP-14 (B) TSSOP 16 SOIC-8 TQFP-32 SOD-123 208 PQFP PDIP 14 100 TQFP PDIP 20 PLASTIC, LCC-28 SOP-8 PLASTIC, LCC-32 TO-92 CERAMIC, LCC-20 CERDIP-16 (A) SOP-14 CERDIP-16 (B) TO-220 (3 lead) CERDIP-16 (C) Many more processed since Shows the wide range or packages processed in TMTI. Highlights that no parts were damaged. “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 © 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.” © Corfin Industries LLC. All rights reserved. 10 September 2018

10 September 2018

Selected Changes to Rev A
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. 10 September 2018

10 September 2018

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. Beyond the issue of tin whiskers, there is continuous discussion about if, how, and when to integrate Pb-free with SnPb metallurgy in the overall electronics industry. However, many in the aerospace and defense industries consider mixing the two chemistries on assemblies to present an unacceptable level of risk, especially as regards BGAs. When building an SnPb assembly with lead-free BGAs, to properly assemble with the two different metals you would have to consistently combine the volume of the dissimilar metals in say SAC 305 BGA spheres and board tin-lead solder paste. That combination can be practically impossible to guarantee especially with the increasingly wide variety of BGAs on a board. Thankfully, if you wish to build an SnPb assembly and all that is available to you are Pb-free BGAs there is an alternative to placing those Pb-free BGAs onto SnPb paste. __________________________________________ That’s as opposed to merely mixing SnPb board paste with a relatively thin tin lead finish if you’re so inclined to do so and address tin whisker mitigation in another fashion or ignore that risk. For those assemblers and engineers who do not wish to mix Pb-fee BGAs and SnPb paste, if mixing metallurgies was easily avoidable, they’d do that through specification and purchasing control. © Corfin Industries LLC. All rights reserved.

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. How many people here have reballed components. Reballing has be going on for 20 years or so. There has been a good deal of review, most of it on a company by company level. It has been demonstrated to be a safe process. For example a recent paper by DFR Solutions and BAE in 2010 “BGA REBALLING FROM PB-FREE TO SN-PB METALLURGY” by S. J. Meschter, BAE Systems, Johnson City, NY, USA and J. Arnold,DFR Solutions, College Park, MD, USA. With that said, in order to do right, there have to be proper controls in place. For example, some of the problems that may dog the process and that the 0015 is replacing are REFER to SLIDE. Additionally, contact with BGA bottom with wick or hand held desolderer may damage mask, substrate or even remove the pads themselves. © Corfin Industries LLC. All rights reserved.

Classic Hand Wicked or Vacuum Desoldered Pads
Hand wicking or solder sucking (vacuum desoldering) can be useful in the lab or in the field but are not appropriate for high volume or high reliability applications. Beyond the consistent and complete removal of the existing alloy, damage to the BGA is all too likely. 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. © Corfin Industries LLC. All rights reserved.

Beyond the complete removal of the existing alloy, other issues seen may be, (REFER TO SLIDE) AND lifted pads, disintegrated pads, intermetallic only left on the pad (tough to solder), lifted mask on mask defined pads. That’s what you can see. Today, many BGAs have via in pad technology. Damage at those connections is impossible to detect by the visual inspection. Examples of damage © Corfin Industries LLC. All rights reserved.

Pb-Free Solder Sphere Removal
Let’s take a look at the process. Most common conversion is removal of SAC balls of one sort or another and replacement with tin lead. Show the XILINX BGA spec sheet again. Prior to going into the process, the components are visually inspected for ball and component body condition. In addition a sampling of parts is inspected with an optical comparator to establish incoming sphere size and height off the base of the BGA. An XRF reading may be required by the customer. The data sheet is also examined to establish if any of the temperatures or chemicals may have to be altered to adjust to the particular characteristics of the part. This can be interesting, as in my experience, BGA spec sheets are notoriously inaccurate regarding physical dimensions. Additionally, the 0015 will have other test steps – for example pre SAM – that may have to be accomplished prior to processing. We’ll look at the testing at the end of this presentation. © Corfin Industries LLC. All rights reserved.

Flux is Applied Prior to Preheat
First process step is flux application. In this case, we’re using a water soluble flux: Superior 30, a J-STD-004 ORM1 rated flux. The component can be completely immersed, or, if required, touched to a flux saturated pad to minimize flux spread for components that either have sensitive coatings or areas of the BGA that cannot be immersed (vents or top coating). The most sensitive parts can be protected by flexible and removable mask application. © Corfin Industries LLC. All rights reserved.

Preheat by Forced Hot Air
The flux is dried and activated with a convection air heater. The dehydration further reduces splatter and the activation contributes to the consistency of the finish. That consistent finish is a shining attribute of the process and allows further cost saving in the later re-balling step. One of the lessons learned from the TMTI study and numerous GEIA 0006 processed parts is that components can be reliably moved from ambient through a mild pre-heat and directly into the wave reflow without damage to the component structure. Extended pre-heat and cool down can be provided to reduce the temperature slopes, but that can vastly increase time and cost of process. And in the vast majority of cases, that is not necessary. © Corfin Industries LLC. All rights reserved.

SnPb Flush of Existing Pb-Free Alloy in an Inert Environment (N2)
Once the flux is activated, the BGA is brought to the edge of the nitrogen blanketed wave (see corner picture) where it is lovingly caressed by solder. Each BGA will have it’s own thermal profile. In addition, different BGAs have different pad, mask and heat absorbing characteristics. For example a fingernail sized 50 ball BGA with non-mask defined pads (the pad surface protrudes above the BGA surface) can be brought over the wave relatively quickly. On the other hand, a 1 inch square BGA - or conversion LGA with mask defined pads –that are sunk deep in the mask- requires a slower process. Time in wave, depth of immersion, approach angle, movement speed and temperature control are adjusted as appropriate to the BGA. In most cases, unlike the typical tin mitigation process, the nitrogen inerted wave is at 215 C. © Corfin Industries LLC. All rights reserved.

Prompt Inline Cleaning for Flux Removal
Post solder dip the component can be paused for as long as might be necessary for cool down, then the component is immersed in ultra filtered flowing hot water (60 degrees C) and agitated to remove the water soluble flux. The cleaning process can be checked for cleanliness by ROSE or Ionic Chromatography testing as required. 5 micron filters changed out monthly or as required. © Corfin Industries LLC. All rights reserved.

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. Benefits of the robotic system are as listed. Evaluate component size, and sensitivity. Determine dissolution rate and program robot for solder sphere removal. Maintain solder chemistry controls per J-STD-001, 002 and Flux per J-STD 004. © Corfin Industries LLC. All rights reserved.

Post Robotic Hot Solder Dip (RHSD) Process Appearance
Note consistent surface. This is representative and what you strive to achieve. That consistent finish wouldn’t be necessary, if you were to further wick the surface, but it is if you plan on placing spheres directly onto the pads. Cross sectioning and SEM EDX examination will reveal the complete removal of PB free material and replacement with, in this case, Sn63 Pb37 solder. © Corfin Industries LLC. All rights reserved.

Reballing with SnPb Spheres
Once Pb-Free solder is removed and replaced with SnPb 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 Nice consistent finish, but we’re only halfway there. A BGA without balls is useless. © Corfin Industries LLC. All rights reserved.

Part Specific Process Controls
Compare recommended flux and component reflow profile to ensure they are compatible. Observe mechanical, thermal and liquid restrictions such as caps, vents, cavities and easily damaged surfaces. Mask as required. Bake MSL rated devices when required by J-STD-033 for proper moisture removal. Testing of BGA mechanical and electrical characteristics pre and post process as required by company protocol or industry standard (pending.) There are two basic steps remaining. The first is putting spheres onto the pads and the second is reflowing the spheres in place. As BGAs have become more prevalent, in general they have become more durable, but package variety and complexity has increased as well. Each package has to be evaluated for MSL level baking requirements, thermal sensitivity, exposed vents, coating sensitivity to solvents etc. © Corfin Industries LLC. All rights reserved.

Steps of Reballing This will be an example of mobile platform reballing. It’s called mobile platform because the BGA is initially placed into a nesting fixture and remains in that fixture throughout the reballing process. This is a way to reduce hand contact with the BGA and to keep spheres in place during the reflow process. Otherwise spheres have a tendency to migrate when the paste flux becomes liquid causing bridges and un-balled pads. Once in the nest, paste flux can be applied through a screen or directly brushed onto the surface © Corfin Industries LLC. All rights reserved.

Stencil Individually designed and designated stencils and nests are used for each component and cataloged in customer specifications. Based on the size of the original ball / sphere a replacement sphere size is chose. Some customers or manufacturers will specify the exact staring ball size so there is no guess work involved. Others will only provide the finished dimension which is typically wider than tall and the reballing faility will have to make a choice as to which starting sphere size will produce a resultant ball that falls within the dimensional tolerance. Most times that’s easy enough to do. Certain rules of thumb can be used. For example the new ball will get inches wider and inches shorter once reflowed. On ocassion, you get an unusual application. For example a resultant “ball” inch wide ball that is inches high. That is more a bump that a ball. Whatever starting ball size is chosen, the spheres, certified for size and purity and as being from conflict free regions, are then placed onto the BGA pads using the stencil to position. 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.

Qualification Test Steps

Optional Qualification Test Steps

Production Lot Test Steps

Process Monitoring Option

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

Words of Caution 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 Experience with the process Verify controls are in place Qualification of same or similar packages TMTI Project can be downloaded at © Corfin Industries LLC. All rights reserved. 2 May 2007

ROBOTIC HOT SOLDER DIP (RHSD)

Similar presentations

Presentation on theme: "ROBOTIC HOT SOLDER DIP (RHSD)"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

ROBOTIC HOT SOLDER DIP (RHSD)

Similar presentations

Presentation on theme: "ROBOTIC HOT SOLDER DIP (RHSD)"— Presentation transcript:

Similar presentations

About project

Feedback