RoHS Compliant, Lead-Free, No Lead, Solder, Soldering, ZeroLead,
Lead-Free Soldering
Process and Mandate


Zephyrtronics Equipment
is Designed, Engineered, and Manufactured in the United States of America.


Through-Hole Brushes

Solder Wick

ZeroLead Soldering & Its Impact on PCB Manufacturing with Case Studies & Thermal Profiles

[TECH 1] [TECH 2] [TECH 3] [TECH 4] [TECH 5] [TECH 6]

Copyright  2008 - 2010, 2011 & 2012, 2017 by David Jacks

RoHS Compliance, Lead-Free, Solder

What is the 2006 Lead-Free Solder Mandate?

Several years back and motivated by environmental concerns, the European Union, following the lead of Japan, determined to reduce the amount of Lead in all manufactured products.


The governing regulatory body of the E.U. set a compliance deadline of July 1, 2006 for manufacturers to transition away from lead content on PC Boards to “Lead-Free” solder alloys.

What is RoHS? This E.U. mandate is the RoHS (Restriction on Hazardous Substances) Directive. As cut-off date looms, many manufacturers are rushing to comply with these new regulations. If your company intends to market and export into the E.U. then you use Lead-Free solders.

How Are Lead-Free Alloys Different From  63Sn/37Pb Solder? While there are many lead-free solder alloys, the greatest focus was finding a “drop-in” replacement for the traditional “eutectic” 63Sn/37Pb or 60Sn/40Pb solder alloys, both common staples in the electronic industry for over 50 years. Alas, all candidates had higher melting points impacting everything from high-volume production reflow ovens to lower volume bench-top soldering and desoldering.


Using Lead-free Solder Alloys requires a higher, final temperature applied in order to create quality solder joints. And, this can lead to understandable frustrations as the next section points out some of the reactions from struggling engineers and technicians around the globe.

A Tighter Soldering Window? Yes, soldering PCB's requires using solder alloys with higher liquidus temperatures -- while components become smaller, more fragile and temperature sensitive like. And to make it even worse, more substrates are packed with greater density of chips and onto higher and higher copper content substrates loaded with heavy ground planes creating more heat sinking which hinders solder melt reflow.


Does Its Make Soldering Difficult? This “window of opportunity” between how much temperature a PCBA can handle on the “low end” and the amount of temperature still needed to solder with lead-free alloys at the “high end” just got a lot tighter. Will it make it more difficult?

No and yes. No, it will not be more difficult if you are just willing to properly and effectively preheat your PCBA before attempting solder reflow. Yes, it will be much more difficult if you choose not to preheat your PCB.


   The Zephyrtronics AirBath Preheat Makes the RoHS Lead-Free Soldering Challenge a Breeze, Enhancing the High Quality of Solder Joints.

Six Key Thermal Parameters For Processing PCB's at Reflow
Regarding that "window of reflow opportunity," there are six critical
 parameters that impact and limit any reflow temperature profile when it
 comes to processing PCB assemblies:

 1.) The substrate’s glass transition temperature.
 2.) The plateau temperature where flux will activate;
 3.) The max temp ramp rate that a chip can handle during heat-up.
 4.) The amount of heat or thermal energy needed to bring a PCB
       up to where solder reflows between its pads and chip leads.
 5.) The maximum temperature and duration at that point that the
       die/chip itself can experience without being damaged;
 6.) The actual reflow temperature of the solder alloy itself, that is
       where the alloy transitions from solid to liquidus.
Six Limiting Soldering Parameters:

1.) The glass transition stage for most FR PC substrates is typically around 160C to 175C. Above these temperatures, a substrate becomes prone to unwanted warping, measling, discoloring and delamination. Therefore, the substrate can only be subjected to temperatures above its glass transition stage for a very limited, that is, short periods of time.  Importantly, the ever-popular “flex circuits” have even far lower transition stages and are even more prone to thermal damage. And BGA and CSP packages also have low tolerances to high temps.

Preheating the PCB assembly at 150C with a Zephyrtronics AirBath will be safely below the glass transitions stage of most all PCB’s where not warping, measling, discoloration or delamination can ever occur. And this is a good thing...and why Zephyrtronics pushed the concept so forcefully in the early 1990's.

2.) Flux activation temps used within most soldering processes have range between 120 to 135C. It is important that flux activation have its brief “moment” in order to clean away impurities, oxides, dirt, oils, surface films that impede and/or prevent good solder wetting and hence quality solder joints.

Preheating the PCB at 150 with a Zephyrtronics AirBath will activate your flux and helping prep the pad/lead interface for high quality solder joining.

3.) Industry Standard  Temp Ramp rate for PCB assemblies is between 2C and 4C. The trend today is toward miniaturization which makes chips very temperature sensitive. Most all SMD ceramic capacitors and glass diodes can not be heated faster than 2C to 4C as they crack or experience microscopic “fissuring”.


The Zephyrtronics AirBaths all have this built-in temperature ramp rate of 2-4 to prevent thermal shocking delicate components and chips.

How to Preheat Printed Circuit Boards

4.)  The energy required to heat up a populated/assembled PCB in order to bring it up to a temperature where solder reflow is possible is dependent upon various factors.
These factors include: the material of the substrate, the footprint and thickness of the substrate, the component density, the copper content and/or the amount of grounding planes, and finally the number and weight of heat sinking devices on the PCB assembly.

The “heavier” the board assembly, the more energy is required to achieve successful solder reflow. Preheating your PCB with a Zephyrtronics AirBath at 150C generously supplies the “extra energy” needed and  “stores thermal energy” right in the board itself helping overcoming the heat-sinking characteristics described above.

5.) The maximum temperature that an SMD die/chip can tolerate during reflow without damage is never greater than 260C! Indeed, there are many chips with even lower thresholds. Generally 260C (500F) is the maximum permitted by semiconductor manufacturers.

The late Dr. Charles Hutchins -- who founded the prestigious Surface Mount Technology Association -- wrote that IC's exposed to more than 260C for even five seconds can be irreparably damaged.


Because classic tin/lead solders are liquidus around 183C, they still left ample room in the “process thermal window” for success.  Even so, a PCB assembly that is preheated will achieve final solder reflow at far lower temps than without preheat.

Example: The very same solder joint that requires a 370C (700F) soldering iron can be made at only 226C (420F) if the assembly is briefly preheated for just seconds. That is a delta temp difference of a whopping 144C (280F)!

6.) With lead-free alloy, the actual reflow temps where solid state becomes liquidus are now higher than with the old traditional 63Sn/37Pb alloy. Whereas the traditional 63Sn/37Pb alloy had its liquidus at 183C, most all of the leading Lead-Free candidates that are replacing it have significantly higher reflow liquidus temperatures typically between 220C and 235C.

What is eyebrow raising to most engineers, electronic technicians and quality personnel is that there is now little room for “play” between the limiting maximum temperature threshold for chips at 260C and the liquidus ranges of these new Lead-Free alloys.

However, as described above, by preheating your PCB with a Zephyrtronics AirBath at only 150C for just seconds makes the nearly impossible to achieve with No-Lead solders a breeze.See the study below.

Video: Four Methods of Preheating Lead-Free Solder PC Boards

A Case Study with 4 Time/Temperature Profiles With Lead-Free & Traditional Soldering
With & Without Pre-heating as the Variable

Measure and record differences in thermal profiles when soldering thru-hole devices on a plated-through, FR substrate PCB assembly in four distinct tests.

Test 1: Generate a quality solder joint using 63Sn37Pb (traditional) solder alloy after a brief preheat (soak) of the PCB at 150C. Measure the minimum temperature required to achieve solder reflow for a quality solder joint.

Test 2: As with Test #1, generate a quality solder joint using 63Sn37Pb (traditional) solder alloy without the assistance of any preheating of the PCB. Measure the minimum temperature required to achieve solder reflow and to create the solder joint.



Test 3: Generate a quality solder joint using a Lead-Free (96.5Sn/3Ag) solder alloy (See ZeroLead Solder Paste) after a brief preheat (soak) of the PCB at 150C. Measure the minimum temperature required to achieve solder reflow and to create the solder joint.

Test 4: As with Test #3, generate a quality solder joint using a Lead-Free (96.5Sn/3Ag) solder alloy without the assistance of any preheating of the PCB. Measure the minimum temperature required to achieve solder reflow and to create the solder joint.


Result and Observations:

Achieving successful solder reflow with lead-free solder required higher temperature applications than those of traditional 63Sn/37Pb solder. Indeed, soldering lead-free without any preheating of the PCB assembly required the application of approximately 100C more temperature than when preheating was included into the controlled test sample. (See Figure 1).


 A Big Surprise Conclusion for Many. 

Perhaps, most notable and most encouraging was that soldering through-hole components with a plain soldering iron could be done at lower temperatures with Lead-Free solder than with traditional leaded-solder IF a preheating soak at only 150 was made prior to the attempt to reflow. That’s a headline in and of it self: You can solder with Lead-Free solders at lower temperatures, if you preheat first, than you can with traditional 63Sn/Pb solders.


Preheat With Lead-Free Solder Is Essential. So hotter soldering irons and desoldering tools are not a solution to transition to lead-free. Our customer service group receives calls from engineers who discover they can not desolder thru-hole connectors with their old desoldering tools when using lead-free alloys…that is until they slide a tried and true Zephyrtronics AirBath underneath their PCB and then, it’s a breeze.

 Let’s review:

1.) Zephyrtronics AirBaths™ preheat your PCB assembly BELOW the substrate' glass transition stage  so warping, discoloration, measling and delamination cannot occur!

2.) Zephyrtronics AirBaths™ preheat your PCB so your flux activates before reflow temp application and so culprits like dirt, oils, oxides and surface films are cleaned away to yield beautiful metal to metal solder joining!

3.)  Zephyrtronics AirBaths™ provide the long-established industry-recommended temperature ramping at 2 to 4C prevent thermal shock, and the best part is that the ramping is built right into your AirBath™!


4.) Zephyrtronics AirBaths™ preheat permits far lower final solder reflow temps and a shorter reflow dwell time, too! Soldering at HUNDREDS OF DEGREES LOWER than what is required if no preheat is there.

5.) A Zephyrtronics AirBath™ is your ally for your higher temp lead-free alloys. It’s on your side and makes your transition to lead-free as easy as calling us here at Zephyrtronics today at (909) 865-2595. We have a Zephyrtronics AirBath with your name on it and its just waiting to go to work for you! Give us a call!


David Jacks was Director of Engineering at three Fortune 500 corporations along with the two largest soldering equipment manufacturers on earth for 13 years before launching Zephyrtronics in 1994 with fellow engineer, Randy Walston.

David's professional design career stretches from the early 1970's. His original products have been spotlighted in feature articles in  both Popular Science and Popular Mechanics magazines and have ranged from commercial coffee brewers and radio frequency controlled residential garage door openers to hobby glue guns, professional heat gun paint strippers and sophisticated industrial soldering equipment.

He has designed products, tools and appliances marketed by Sears, Black & Decker, RadioShack, Motorola, Stanley Tools, Snap-On Tools, Rubbermaid, CooperTools, Weller, Hakko, Ungar, Farmer Brothers and Brewmatic.


Any electronics catalog of soldering equipment, tools and products today reflects David's long and enduring influence on the printed circuit board industry world-wide.

David holds many patents (both utility and design) in North America, the European Union, Japan and around the world. His patented inventions have been cited as prior art by firms from IBM to Mitsubishi. He has authored technical articles for international journals, and routinely speaks to electronic professional societies.

Now in his old age, David's keen interests is in encouraging inventors and designers to "stick with it" and never to surrender their dreams, and to "make the impossible possible" through science and technology.

-- Bio by Joe Guillen



1996 - 2011, 2012, 2013-2016, 2017, 2018, 2019, 2020, 2021 by Zephyrtronics. All rights reserved. The information, text, images, photographs, charts, graphs you receive online from Zephyrtronics are protected by the copyright laws of the United States. The copyright laws prohibit any copying, redistributing, retransmitting, or repurposing of any copyright-protected material. Zephyrtronics is the registered trademark property of JTI, Inc. "The Science of Zephyrtronics" and "Simplicity Through Innovation" and "Zephlux" and "ZeroLead" and "ZeroTouch" and "Zero Balling" and "Zero Residue" and "Post Cooling" and "Post Cooler" and "AirBath" and "SolderGlide" and "ZeroTouch" and "SolderMill" and "Just So Superior" are the protected trademark property of JTI, Inc. "Zephyrtronics" and "Low Melt" and "Air Fountain" and "Fountainhead" are the registered trademark properties of JTI Inc. *The above names are the registered property of their respective owners.


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Updated for February 17, 2021