HB2LS_TE1_TestDesolderWick p1 / 4 print: 7.9.2003
DIPL.-ING. ERNEST SPIRIG
POBOX 1140 HOHLWEG 1
CH-8640 RAPPERSWIL
PHONE: (+41) 55 222 6900 FAX: 55 222 6969 INFO@SPIRIG.COM WWW.SPIRIG.COM
How to Test and Compare Desolder - Braids / Wicks?
prepared by and copyright for by Ernest Spirig
Introduction
DE-SOLDERING with a wick is actually SOLDERING the wick with the solder to be removed.
Solderability is therefore a reliable test to predict the desoldering "power" of a wick.
A desolder wick (or braid) is a copper mesh pre-coated with a flux of natural rosin or synthetic rosin based
chemicals.
Desolder wicks are available in various widths to fit the desoldering task area. The different wick width means
different thermal masses or different heat flow needed to bring the wick to the melting temperature of the
solder to be removed.
Desoldering Operation
The wick end is placed on top of the solder to be
removed. A hot soldering iron tip is pressed from top
onto the wick. The wick heats up and the highly heat
conductive copper braid of the wick conducts the heat
to the solder and melts the solder if heat supply is
sufficient.
The heat source must heat up the copper mass AND
the solder mass simultaneously.
The heat source must be able to quickly supply the
needed thermal calories to the job.
The heat source must therefore correspond to the
wick size.
The heat source is normally the heated tip of a
soldering iron.
TIP!
Desoldering a small area and having only a
large wick size on hand?
Cut the end of the wick with a scissor in an
angle, as seen to the left.
There it is your fine wick end tip!
It is also easier to guide and hold a wider
wick with a fine pointed end.
Quick and undelayed heat transfer stems from the heat stored in the thermal mass of the hot copper tip and
only secondary from the available continuous heating power (wattage) of the iron.
A geometric too small tip size compared to the wick width will be (even if set to an increased soldering
temperature level) immediately cooled below the melting temperature and this obviously means unsatisfactory desoldering action or no desoldering action at all.
Ideally, a soldering iron tip will have a chisel like shape and the tip width should be at least as wide as the
wick width. This rule is a good fit for almost any desoldering task. The soldering iron should be a thermostatic
or electronic temperature controlled unit. and the temperature set on the iron temperature control to 320 °C or
temperature code 8 on a Weller® TCP iron version.
HB2LS_TE1_TestDesolderWick p2 / 4 print: 7.9.2003
DIPL.-ING. ERNEST SPIRIG
POBOX 1140 HOHLWEG 1
CH-8640 RAPPERSWIL
PHONE: (+41) 55 222 6900 FAX: 55 222 6969 INFO@SPIRIG.COM WWW.SPIRIG.COM
TESTING a Desoldering Braid
Testing a desoldering braid with a soldering iron gives a quick and rough idea of its function (good / no good)
but will give no "measurable" results, or results which can be easily verified or repeated by the same test setup.
Spirig has used the Solderability definition in nearly 28 years (1968) of wick manufacture as its internal quality
control and audit instrument. (Due to the unavailability of a commercial solderability tester in the late 60's,
Spirig designed such a tester).
The Solderability Tester received a US patent 4,227,415.
Today solderability testers are available with similar or identical principle from leading vendors of solder or
flux materials. The solderability test is based on the solder dip principle.
Solderability Test of Desolder Braid
Spirig US patent 4,227,415 describes such a system that could even be built by an in-house mechanic-electric shop.
The wick specimen is clamped vertically in a holder. A thermostatic controlled solder bath (pot) is located
under the specimen.
The wick is slowly lowered down into the pot, enters the molten solder surface, and starts to absorb (draw up)
solder by capillary forces pulling the fluid solder into the wick mesh.
An electric circuit detects the mechanical contact of the wick to solder surface. This STARTS a timing cycle
for the dip/dwell time and calculates at given drive speed the time needed to reach the specified dip depth.
The picked up solder can be determined as the difference in weight before and after the wick sample test.
Pick-up weight will vary with wick sizes (volume within braid available) and be between a few mg (=1/1000
gram) for a very fine wick size and up to 100 mg for a large wick size.
It therefore should be measured on a precision balance (resolution 1/10 mg = 1/10'000 gram), eg a Mettler
Delta precision electronic scale.
From left to right:
A solder buoyancy tester, a high precision electronic
scale, a stereo microscope, an electronic digital
thermometer, some scissors and flux residues
cleaning solvents make up a basic test set.
Solder Buoyancy Tester:
see also
Spirig US-Patent No. 4,227,415 Oct 14, 1980.
Spirig started to manufacture Desolder Wick almost 30
years ago. Spirig had to develop and invent equipment to
manufacture and tools to test Desoldering braids.
Spirig US-Patent No. 4,081,575 Mar 28, 1978
Method of Flux Coating Metal Wick
Spirig US-Patent No. 4,078,714 Mar 14, 1978
Desoldering Method and Apparatus
Tare the wick specimen holder with wick specimen
attached to it before the test. The weight indicated
after dip test will then indicate the net amount of
solder absorbed into the wick.
Spirig US-Patent No. 4,164,606 Aug 14, 1979
The following test parameters have been used since
1968 to evaluate our wick and competitors wick solderability performance and have also been used as a
basic rule for discussions with customers and competitors to avoid errors in advertising messages.
Spirig US-Patent No. 4,416,408 Nov 22, 1983
Lowering speed:
Dip depth:
Dwell time:
Bath temperature:
5 mm / second
2 mm
2 second
260 °C
Tinned Copper Braids For Solder Removing
Spirig US-Patent No. 4,323,631 Apr 6, 1982
Solder Removing Device.
Solder Removing Device ("Open Mesh wick")
Spirig US-Patent No. Re32086 Feb 25, 1986
Solder Removing Device "Open Mesh wick"patent reissued without changes after a competitor challenged
the 4,416,408 in its validity.
Open Mesh Wicks are a Spirig invention.
HB2LS_TE1_TestDesolderWick p3 / 4 print: 18.9.1998
DIPL.-ING. ERNEST SPIRIG
POBOX 1140 HOHLWEG 1
CH-8640 RAPPERSWIL
PHONE: (+41) 55 222 6900 FAX: 55 222 6969 INFO@SPIRIG.COM WWW.SPIRIG.COM
Visual Evaluation during Dip Test
Upon impact with the molten solder surface the wick will indent the solder surface (negative). After a short
delay (time until wick is heated up enough from solder bath to start its own fluxing activity) the solder surface
will turn into an upwards positive curve.
The capillary forces of the wick now draw the solder into the wick and even lift the solder surface on the wick
sides upwards.
The flow of the solder into the wick can be easily seen. This gives a quick check and a good preview of the
performance.
Numerical Evaluation of a Dip Test
A wick specimen is clamped into holder. Holder is put on precision balance. Auto-tare puts weight to <0>.
Go through dip test and then put holder again on balance.
The weight displayed is the weight of solder absorbed.
Obviously only identical size wicks can be compared by the weight of the solder absorbed.
Potential Errors in Weight Results
The following factors can cause weight errors
(a)
The wick test end touching the solder surface must be cut-off in a 90 degrees angle. Otherwise not the full
cross section of the wick will be dipped. Dip depth still will be 2 mm, but the angle sized contact offers less
squarage for the heat flow into the wick and end of wick offers less volume for solder "storage".
In case of a flattened tubular braid construction (almost 95% of makes available) the flattened tubular end
may not be opened artificially as this creates extra absorption volume for solder in that end. In practice the
solder tip pressure against the wick will keep the tubular construction flattened at end!
(b)
A solder globule forms at the wick end by some irregularities, mostly caused from oxide layers not wiped off
from the solder bath surface before the dip test. A test wick specimen with a globule on end is not acceptable as regular test sample.
Before each dip test the molten solder surface must be wiped clean from oxides, eg using a piece of carton
or a thin blade of stainless steel (not wetted by solder). Too thick a metal blade would absorb heat and
temporarily cool the molten solder surface.
Comparison of Braids of Different Production
Solderability conservation of the fresh copper surfaces is an ongoing fight in the printed circuit board fabrication.
The desoldering braid is exposed exactly to the same problems. A braid starts to age from the moment it is
coated.
Spirig's patented "vacuumisation" coat process minimizes influences on solderability during flux coating of
the braids copper structure to an absolute minimum. Shelf life is accordingly high under regular storage
conditions and extends well into years. We have 25 years old specimen from our QC control storage still
performing surprisingly well.
A comparison test between braids of different makes should take aging into consideration. That means a
braid stored under bad conditions (high humidity) compared in a dip test with a fresh coated braid will be an
unfair comparison.
Comparison could be concentrated on fresh (up to a few months old) or on equally artificially aged (high
humidity and elevated temperature storage) braids.
Wick with a quick aging behavior might turn a valuable desolder braid stock with time into worthless copper
scrap.
Wick Manufacturing Procedures
Anybody in urgent need for a desoldering braid can easily create one for himself in an urgency. The braided
shielding of a high-frequency (coaxial) cable is stripped from insulation. The tubular structure is dipped into
liquid rosin flux, dried with hot air from a hot air gun and a piece of desoldering braid is born. How long it will
operate, how costly it's "production" is, that is another question. But in an emergency this makes a wick.
By the way this is not an inventive matter, it is an old plumbers trick. See also decisions in the US Court of
Customs and Patent Appeals, Washington, "Spirig vs Solder Removal Company / US International Trade
HB2LS_TE1_TestDesolderWick p4 / 4 print: 7.9.2003
DIPL.-ING. ERNEST SPIRIG
POBOX 1140 HOHLWEG 1
CH-8640 RAPPERSWIL
PHONE: (+41) 55 222 6900 FAX: 55 222 6969 INFO@SPIRIG.COM WWW.SPIRIG.COM
Commission".
A decision around 25 years ago was in favour of Spirig and Spirig's wick production technology did not
infringe on Solder Removal US patent at that time. The patent has in the meantime passed its life.
Now and then newcomers do and did get into the wick making business and also disappeared quickly. The
product "wick" seems to be a simple technical product open for almost everybody with access to copper
braid, a rosin flux bath and the intention to make a quick profit.
Practice then quickly shows the reality with consumer applications. To make a well absorbing wick the metoo manufacturer starts to increase the rosin flux content of activator content once his customers complain
on poor performance. The higher the activator content, the more the request for a perfect raw copper material diminishes.
The increased activator content of residues left on the desoldered area can and will cause corrosion on pc
board and will start to create electric conductivity paths. A situation on which a user has no influence, except
that he might clean his desoldered assembly very carefully to be sure to have removed any traces of flux
residues and activator contents.
Sooner or later (or never) the user is faced with problems on assemblies now contaminated with such activator residues. He might look for all type of sources for his troubles but not identifying a highly activated wick
as the source of trouble. He might never detect the reason if he is not a real professional. Professionals
prefer to use a desolder braid from an established long term wick manufacturer. Spirig has now close to 30
years experience in wick manufacture.
Standard Flux coating of a Wick
The bare copper braid is dipped or fed through a volatile solution of rosin (natural or synthetic) in a solvent.
Then the wet braid is dried in a hot air stream and bobbined. The solvent is evaporated and discharged into
the ambient. Solvents contain ozone depleting substances.
A solution of rosin at increased temperature has a rapidly increasing chemical activity (interaction) with the
braids copper. Copper starts to form complex chemical combinations with the activator. Drying the flux solution with hot air heats the flux solvent.
Spirig's Patented Flux coating of a Wick
Spirig's patented vacuumisation production process dries the wet flux coated braid structure under vacuum
and without heating. Therefore eliminating rise of chemical activity and interactions of the coating with the
copper surface. The solvents in the vacuum pump exhaust are recycled.
->-> Ozone depleting substances do not escape into nature.
->-> Minimal loss of expensive solvents is one of the reason for economic wick production.
Spirig's patented powder flux deposit production process does not use solvents at all. Costly solvents and
recycling is avoided completely. This is the ultimate economic approach to braid processing.
Ozone depleting substances do not exist at all in this patented flux coating process.
A listing of Spirig patents related to wick manufacture and desolder wick products:
SPIRIG PRODUCTS ARE COVERED INTERNATIONALLY BY ONE OR MORE OF 100+ PATENTS GRANTED TO ERNEST SPIRIG. USA Re 32,086
4,206,029 4,336,122 4,113,601 3,957,618 5,217,507 4,263,584 4,087,814 4,086,586 4,241,338 4,072,936 4,416,408 4,459,046 4,354,105 4,280,244
4,194,705 4,323,631 4,164,606 4,078,714 4,081,575 4,133,291 4,227,415 GREAT BRITAIN 2,094,692 2,082,952 1,513,496 1,546,601 1,546,602 2,020,697
2,081,743 2,119,403 2,020,872 2,020,871 1,548,771 1,154,880 2,020,872B 2,052,731 2,030,857 1,469,667 1,554,880 CANADA 1,123,377 1,177,013
1,090,199 1,088,811 1,513,496 1,546,601 1,092,546 EUROPE 1,921 5,597 9,860 9,891 45,583 47,579 102,426 131,173 620,604 623,764 GERMANY
2,346,839 2,716,452 2,747,895 2,754,668 2,960,924 3,174,929 3,176,277 2,202,739 AUSTRIA 357,066 FRANCE 7,732,616 7,713,003 5,597 45,583 131,173
AUSTRALIA 552,949 518,349 502,482 525,573 543,866 557,997 506,887 495,837 INDIA 146,997 JAPAN 1,608,603 1,548,156 1,350,196 1,346,246 1,260,197
1,592,223 BRAZIL 7,807,303 7,707,234 1,100,933 7,902,965 8,104,869 7,902,965 7,905,553 7,406,904 7,708,155 ARGENTINA 217,092 ITALY 5,597 45,583
131,173 1,100,933 NETHERLANDS 5,597 45,583 SPAIN 474,830 480,475 428,292 SWEDEN 79,300,737 SWITZERLAND 620,604 624,149 KOREA 14,394
TAIWAN 11,899 19,342 SINGAPORE 24,583 HONG KONG 41,783. SPIRIG TRADENAMES & MARKS ARE CELSISTRIP® CELSIDOT® CELSIPOINT®
CELSIMETER® CELSIPICK® ECOCLEAN® ECONOCLEAN® HUMIPICK® LIGHTPICK® PRESSPICK® VOLTPICK® SPIRFLAME® SPIRFLUX® SPIRIG30® STATIEX® STATIFRI® STOPSLIP® PTS® SPIRLIGHT® 3S-WICK® SMD-WICK® 6S-WICK® 3S-TIP® 3S-WATCH® PRESSMETER® SPIRAC® TFUSE® TORCHMATE® WRISTEX® X-HAND® X-PLATE®. LISTS ARE NOT COMPLETE.