|
All Zephyrtronics Equipment is Designed, Engineered,
and Manufactured in the United States of America.
1994
The "early days" of the company as David Jacks &
Randy Walston lay ground work, engineer, R&D, test &
evaluate & apply for patents on their new, milestone
low temp approach to benchtop soldering & rework.
1995
The Company introduces world’s first stand-alone,
bottom-side preheating system, The AirBath™.
1996
Zephyrtronics awarded the "Vision Award" for Best
New Product of the Year at the Surface Mount Int'l
Expo in Silicon Valley.
1997
SMT Magazine's editorial staff calls Zephyrtronics
one of the three most innovative companies that
year. Boeing chooses our AirBaths for the
International Space Station Project.
1998
U.S. Department of Defense selects Zephyrtronics as
supplier. Boeing tests & approves Zephyrtronics AirBath™
& DeSolder for
SMD removal
1999
Raytheon recommends Zephyrtronics in written
report. National Semiconductor recommends
Zephyrtronics
in published paper
for
BGA rework
2000
Zephyrtronics continues
3-year string as fastest
growing soldering equipment manufacturer in the
U.S.A. Also: Introduction of
dispensing product
line.
2001
Zephyrtronics saves Raytheon
$1 Million in rework scrap after Six Sigma Study.
2002
Our ZT-7-MIL is selected by The J.P.L. Mars Rover
Project for BGA tasks.
2003
International Rectifier recommends
Zephyrtronics
for BGA rework.
2004
After smashing success of the Mars Rovers, NASA
issues 39-page touting Zephyrtronics for making
"mounting & removal of thru-hole and SMT/BGA easier
than routine bench methods"
2005
Zephyrtronics expands its leadership in preheating
with our
MegaGrid™
AirBath.
2006
Introduction of ZeroLead® branded lead-free solder paste and ZeroLead® LowMelt® DeSolder Wire.
both
are RoHS Compliant.
2007
Zephyrtronics launches
e-commerce site for the
convenience of
our customers
all over the world.
|
|
|
|
|
|
INTRODUCTION — THE PRINCIPLE ADVANTAGE OF THRU-HOLE OVER SMT:
In spite of the many benefits that surface mount technology (SMT) has proven to have in favor over the older, traditional through-hole technology (THT
and Thru-Hole), there still remains at least one easily recognizable advantage of the thru-hole PCB assembly: strength in the solder joint. Typically, in a through-hole assembly, the leads of a component first penetrate through the substrate, and in many cases are even clinched on the other side, and afterwards, the lead is wetted with solder. In the case of a plated through PCB assembly, the solder wets inside of the plated hole in addition to the pad/lead interface. It is easy to appreciate how this scenario provides multiple mechanical attachments resulting in high expectations for reliability (Figure 1)
|
|
|
| |
|
 |
|
|
|
|
|
|
|
| |
In the case of SMT, only the tiny solder
joint alone on top of the substrate's
surface must provide all of the mechanical
connection in addition to the electrical
connection. Therefore, the nature and
quality of the solder joint within surface
mount assemblies is far more critical than
that of the traditional through-hole type
joint. Accordingly, greater care and
attention must be given to the correct
process parameters when surface mount
soldering. |
|
| |
DOUBLE STANDARD -- QUALITY JOINTS EXPECTED IN THE PRODUCTION PROCESS WHILE MARGINAL JOINTS EXCUSED AT THE BENCH:
To insure integrity and strength of each solder joint, it is imperative that the leads of the SMD always have fillets at the toe, the heel and on the sides. This is true whether the soldering is made within the initial production assembly or later in rework. Unfortunately, while such fillet criteria has long been standard in all production processes, it is, for the most part, still universally ignored at the benchtop where prototyping and rework with SMT is performed.
The two principle reasons for inferior SMT solder joints at the benchtop are both explained as residual fallout from hangover processes long used with THT: a.) the continued use of solder wire rather than solder paste; and b.) the use of contact soldering irons rather than non-contact hot air.
Consider this simple truth: today there is not a single high volume soldering process for SMT reflow that utilizes solder wire. Either the widely popular use of solder paste with reflow ovens or molten solder as with wave soldering are the proven and established norm. So what about solder wire?
Historically, the use of solder wire (typically cored with flux) was a staple with THT for decades. Where wave soldering was not feasible or affordable, the long assembly line of personnel outfitted with soldering irons initially, and later temperature-controlled soldering stations/irons was the status quo for decades in electronic production. With each soldering iron there was always the ubiquitous spool of solder wire. And so it followed that the individual rework bench was a mere snapshot of the assembly line: soldering iron, spool of solder wire, wick, bottle of flux, etc.
|
|
| |
 |
The advent of SMT translated into a nearly proportional decline in the traditional THT assembly and with it the contact soldering iron and solder wire. This trend is irreversible. Try reflowing a BGA with an iron and solder wire if you disagree.
Curiously, as solder wire and the traditional conductive soldering iron were together transcending into history at the production level, they were still surviving at the rework bench, albeit not without lots of problems. (Figure 2)
Some of the more notable problems related to the use of contact irons and solder wire with SMT were: lack of solder fillets at the toe, heel and sides
on both J-leaded and gull wing devices; inducing pad damage and co-planarity problems due to hand pressure from the iron while contacting the components leads; and cracking ceramic devices due to sudden application of direct conductive heat
by soldering irons to the leads of these delicate devices.
Necessity became the mother of invention with the
hot
air pencil. |
|
|
|
|
|
|
|
|
|
|
| |
SOLDER PASTE IS IDEAL FOR SMT AT THE BENCH:
First,
solder paste has proven to be a near perfect compliment to high volume SMT production reflow. Paste is dispensed or screened to the substrate; components seated into the paste at pick and place sequence; preheating at first tunnel of oven activates the flux within the paste (and warms the board); reflow in last tunnel where the paste wicks up the SMD's leads and yields premium solder joints replete with fillets as required.
While it is somewhat new to the rework bench (there were some early converts years ago), solder paste is now rapidly gaining favor over the use of
solder wire when reworking SMT assemblies. When used with a
convective preheating device, generically known as an
Airbath™, under the board assembly, solder paste can be reflowed with a hot air pencil from above yielding solder joints that rival those from the conveyor oven. With this simple method, the paste reflows at the lead yielding fillets at the toe, heel, and sides of the device right at the bench. (Figure 3) In fact, the use of paste can even forgive some co-planarity problems as the solder wicks up the lead from the pad. Pre-heating during rework at the bench is just as integral to the reflow process as it is in initial production. Remember, the activation of the flux during pre-heating cleans and enhances the wetting process resulting in smooth and shiny joints that will feather out to the a thin edge.
|
|
|
| |
"These basic processes have the advantage that they are simple, require minimal training and virtually never cause damage to the assembly," Jerry Green, a senior manufacturing and quality engineer in San Diego points out, "you can actually see the solder reflow and become shiny" as the
AirPencil passes over the leads. Green emphasizes that it is critical that the SMD sit flat on the pads, that the paste be non-rigid, that the SMD not be moved once the preheating has begun, and that proper inspection be made after reflow.
Solder paste, like in high-volume production processes, instead of solder
wire? Right at the bench? You bet.
Forced convection from a hot air pencil like in high-volume production
processes, instead of contact, soldering irons? Right at the bench? You bet.
Ramping at 2°C to 4°C as in production? Preheating the PCB allowing flux
activation before final reflow as in production? All at the bench? You bet. |
|
 |
|
|
|
 |
|
Some Final Thoughts: The use of solder paste coupled with a hot air pencil and a warm air bath at the rework bench is rapidly gaining favor due to the many evident advantages over solder wire and the contact soldering iron. Here are a few points to remember: 1.) It is not advisable to use solder paste with a soldering iron as it gets very messy; 2.) Generally speaking, hot air pencils are not very effective without pre-heating and Green stresses that the "preheating cannot be rushed"; 3.) Only select a hot air pencil that features an extremely low velocity of hot air so as not to blow solder paste/balls across your board; 4.) And one last critical distinction: The hot air pencil is not to be confused with the larger hand-held hot air jets which have much larger, focusing nozzles that enclose the entire component. The air pencil provides only pin-pointed hot air to one lead at a time.
Finally, for a step-by-step, color pictorial presentation of how to solder smd's with solder paste and a hot air pencil, please visit our helpful primer at this direct link:
"SMD Soldering Made Easy at the Bench". |
|
|
|
ABOUT THE
AUTHOR:
David Jacks was
Director of Engineering with the two largest
soldering equipment manufacturers in the world for
nearly 13 years before founding the Zephyrtronics
company in 1994 with his business partner, fellow
engineer and great friend, Randy Walston.
David's professional
design career stretches from the early 1970's. His
designed products have been spotlighted in feature
articles in both Popular Science®
and Popular Mechanics®
magazines. He has designed products, tools and
appliances marketed by Sears®,
Black & Decker®,
RadioShack®,
Motorola®,
Snap-On Tools®,
Rubbermaid®,
CooperTools®,
Farmer Brothers®
and Brewmatic®.
David holds multiple patents (utility and design)
for his many inventions; has authored technical
articles for national journals, and routinely speaks
to electronic professional societies. |
|
|
