Some ICs only available in SMT packages
Working with SMD parts
Hobbyist SMD Soldering
Point Hand Iron
Sucker into Hot Air Rework type tool
Hot Air Solder Reworking Tools
Quakko 850D Hot Air SMD Rework Station
850D Air Flow
Application & Use
Printed Circuit Boards
eBay Clock Kit
Related Web Pages
SMT replaces through hole
Surface Mount Technology (SMT) is rapidly replacing through hole
technology as the preferred method of fabricating electronic
equipment. The reason for this is that a Printed Circuit
Board (PCB) that's populated with through hole components costs
more than an equivalent SMT PCB. There are a number of
reasons for this. For example SMT parts require much less
board drilling and SMT parts are much smaller allowing the board
area to be correspondingly smaller. Note a through hole
shows up on both sides of a board, but SMT parts only show up on
one side. It's common to have SMT ICs on both sides of a
board. The big bulky Tape & Reel that held axial
leaded through hole components has been replaced with "Tape"
holding SMT parts. "Tape" is based on various sizes of
movie film that has pockets and a cover tape. A reel of
tape SMT parts takes up much less space than a "Tape and Reel"
allowing many different "Tapes" to be mounted in a small space.
Surface Mount Device (SMD) is a related term that points to
devices rather than the broader concept of the technology.
Some ICs only available in SMT
Products that push the size envelope, like hand held
electronics, also push the IC manufacturers to down size their
products resulting in a number of the ICs now only being
available as Surface Mount Devices (SMD). This has been
the reason why I'm writing this web page. Parts that I
want to use are only available in fine pitch SMT packages.
Working with SMD parts
Stereo Zoom microscope with arm type base & illuminator.
Bausch & Lomb StereoZoom 4
Variable knob on top has range of 0.7 to 3.
Times 10X eyepiece equals magnification of 7x to 30x.
When I was working with microwave components (Radar Warning Receivers
) where the
modules made use of raw semiconductor dice we used Stereo Zoom
4 microscopes. I've seen a web page that said that these
should be called macroscopes because the magnification is
low. It turns out that your hand eye coordination gets a
gain boost by the magnification of the microscope
allowing you to do work down in the 1/1000 of an inch
area that would be impossible if done using normal (good) eye
I really like the swing arm type of stand on a heavy base for
the stereo zoom which allows you to get it over what's being
worked on. The classical microscope stand would be in
the way. I'm using the classical light bulb and optical
illuminator that sits in a holder that can be rotated around
about 3/4 of a circle on the microscope. A ring light
would be much better.
Although there is a zoom knob, it spends almost all it's time
on 0.7X. Combined with the 10X eyepieces, the power is
7X. It's properly called a macro-scope rather than a
micro-scope because of the low power.
Stereo vision is mandatory to have depth perception.
I've ordered from eBay "60LED Adjustable Ring Light
Illuminator Lamp For STEREO ZOOM Microscope" which should work
better than the existing lamp which often is not in the
Note: at the bottom of the macroscope there's a screw in
ring that's 40mm OD, 35mm ID and has what might be 38mm x
1.0mm threads and no optics. This would be the place to
mount the ring light.
60LED Adjustable Ring Light
Illuminator purchased from eBay seller jimshop268.
The old i
lluminator would cast shadows and to avoid
that required rotating the support, but that often pulled the
cord (it seems the supplied cord always seemed to short)
sometimes unplugging the lamp. This ring light casts no
shadows and is brighter and cooler than the old illuminator.
EEVblog #390 - Mantis
Elite Microscope Review -
|I removed the nose piece from the
microscope to adjust the pinch screws and it shows up
in the photographs.
|Top with LED ring light
Optical instrument and
optical element providing expanded exit pupil, Vision
Engineering Limited, Filed:
2000, Pub: Oct 17, 2006, 359/569
, 359/573 - good for 8 hr/day use.
I found one on eBay, but it was freight shipping since the
weight (without an objective lens) was 150 pounds.
The first thing that's very
apparent is that SMDs are very small. Some of the first
generation SMT resistors and capacitors had sizes like 1206
meaning the chip was 0.120 x 0.060 inches (3 x 1.5 mm) but
after a few generations of size reduction have now become more
like 0402. If you drop a 1206 part there's a chance of
finding it, but if you drop an 0402 don't' even bother
The common through hole Dual
Inline Package (DIP) has two parallel rows of pins that have a
pitch (distance between adjacent pins) of 0.1 inches and a
separation between the two rows of pins that's an integer
multiple of 0.1 inches (0.3" is the most common). So
most through hole PCBs have all the holes located on a 0.1 x
0.1 grid. SMT ICs are much smaller than through hole
parts and so have finer pitch. Some common pitches are
0.05" and 0.025" (i.e. 1/2 and 1/4 through hole pitch).
It's much more difficult to use a hand soldering iron on these
finer pitches than soldering a DIP package.
There are also metric pitch SMT packages, i.e. instead of
0.05" (1.27 mm) pitch a metric SMT would have 1.25 mm pitch
(0.0492"). If you use these be sure to use metric board
layout (or convert back to inches).
The commercial method of
assembling a SMT board uses Pick and Place automated machinery
to place the parts on a large PCB that will be later separated
into the actual product size boards). Prior to being
placed solder paste is applied to the board, maybe by means of
a silk screen or using an automated syringe to place
dots. This board is subjected to a heating cycle that
has a controlled temperature profile that melts the solder
paste. When the solder is a liquid it's surface tension
tends to pull the parts into alignment over the pads. A
common method is called vapor phase reflow, and another is an
Hobbyist SMD Soldering Methods
The PIC List has a web page
. So far I think there are two main problems
when using a hand held soldering iron on 0.025" pitch SMDs.
The first problem is that the soldering iron tip may be much
wider than the width of a single lead (about 0.012 inches) and
so solder gets on two or more leads causing a solder
bridge. It may be that a liberal application of flux
will reduce this tendency. Using a hot air rework tool
is good in that there is no iron tip to smear the solder where
it does not belong.
The second problem is that the surface tension of the solder
may be stronger than the weight of the SMD, in which case the
SMD may lift up when the soldering iron is lifted. Some
ways around this are:
- Use tape to hold down the SMD (Spark Fun method) - I
don't like tape because it's hard to adjust the part
- Use Elmer's yellow quick dry wood glue to glue down the
SMD (Electronic Goldmine method) - I've done this and it
works. You need to wait 15 to 20 minutes for the
glue to dry and rework is more difficult
- Use Tack n' Stick Reusable Adhesive (Black Box Camera
method) - Works with soldering iron, but not hot air.
Fine Point Hand Iron
Note that there are two factors relating to soldering iron
and what they can solder. One is the power rating
(Watts) of the iron and the other equally important is the
heat capacity (pretty much relates to the weight of the tip)
of the tip. Note that the WES50 is rated 60 Watts, but
it can not solder wire terminals on 12 AWG wire because the
wire acts as a heat sink and the small tip and not transfer
enough power to melt solder. The Weller SP-40, rated
at 40 Watts, can easily solder terminals to 12 AWG wire, but
not so easily to 10 AWG where the 200 Watt iron can do that
This works better than you might
think when a small tip is used.
|Weller WES50 with ET-S fine tip (60
Used for electronics.
|Example of SMT hand soldering. Battery Top Signal Generator
|Weller SP-40 40 Watt iron not suitable
for SMT work.
Used for soldering terminals to some wire when crimp is not used.
|Generic 200 Watt soldering iron totally
not suitable for SMT work.
Used for large wire (>= 10 AWG) terminals, like EC5.
5 May 2006 - When using a Weller WES-50 soldering iron with
the ET-S fine tip (this tip is maybe 10 times smaller than the
stock tip) and Kester wire solder that's 0.015 diameter
with 282 flux core I was easily able to hand solder the
SOIC-28 package onto a professionally built PCB that included
solder mask and silk screen layers. The board also has a
thin lead tin solder coating on the pads. I think the
four components that made this easy are :
(1) the stereo zoom microscope,
(2) the solder mask on the PCB,
(3) solder coating on the PCB
(4) solder coating on the IC leads. Prior to placing the
SOIC the PCB pads were wetted with RMA liquid solder flux and
the SOIC was held in place with Blu-Tak. This worked
better than the hot air iron because there was much better
control of the amount of solder. My solder paste
dispensing method is at fault and if fixed I expect that SMT
with the hot air tool will be a better method, but for now
this is the best by far.
Note that just by applying the iron to a single lead solder
reflow occurs, from both the lead and PCB. There is not
enough solder to get good fillets, but enough to hold the part
firmly allowing the Blu-Tak to be removed giving access to all
the leads. Applied a very small amount of solder to the
pad just in front of the lead foot and when it melted the
solder ran under the lead resulting in a nice fillet.
There was not a single case of solder bridging. Visual
inspection easily showed leads without a fillet at the foot of
the lead and they were easily fixed.
Note that the board being assembled only has a one SMD, the
SOIC-28, all the other parts are conventional through hole
There's about 3.5" inches between the tip of the Weller WES-50
to the tip of the ET-S. This is a problem when working
under magnification because the iron may be completely out of
your field of view and that's when you're likely to move it
into your skin (ask how I know this) Ouch.
I see that the Weller WSL Micro Soldering Station advertises
having the shortest tip to grip distance. Tthe WMP iron used
on this station has a tip to grip distance of 37 mm
(1.5"). That's good but it really should be a shorter
distance, more like 1/2". This may require forced air
cooling or some other fancy method, but for using a soldering
iron with a microscope the grip to tip distance should be very
Aug 2010 - I've used this method with great success for 1/2
and 1/4 pitch parts and don't see much need for the hot air
The attraction of the toaster
oven is that it uses heating elements that put out a lot of IR
and so is very similar to the commercial IR ovens.
Modifications are needed to control the temperature profile
for SMT soldering use. Some web pages on this: Seattle
. They are working with the 68332
processors in 132 pin fine pitch packages
Electric Fry Pan
Not as popular as the toaster
oven, but some have been able to get results this way.
The Harbor Freight 41592
is a hot air type. The manual says
up to 600 deg F. It includes a pressure regulator to be
connected to compressed air. So setting the pressure
sets the flow rate and effects the temperature. Might
make a hot air soldering iron. About $30.
The idea is to add some steel
wool near the tip to help heat the air and replace the sucking
rubber bulb with an aquarium air pump so that the exit air is
hot enough to melt solder. Trying to have a lower cost
version of commercial hot air SMT rework soldering
equipment. At the bottom of this web page the author
says he has now converted to using the $ 79 MPJA model 306
Hot Air soldering tool. This appears to
use the same nozzles as the Hakko hot air tool. It also
has a strong similarity to the Harbor Freight Heat gun.
The problem with the Harbor Freight heat gun is that is uses a
common small motor to turn a fan. The brushes wear out
in about a year of occasional use. The Hakko, Aoyue and
Quakko tools use a diaphragm type pump in the main box which
is quieter and longer lasting.
Commercial Hot Air Solder Reworking Tools
I think Hakko
in Japan pioneered
the hot air approach to SMT soldering. The Hakko units
are quite expensive. As of April 2006 there are a number
of Chinese copies (I can remember when Japan was know for
making copies) of the Hakko hot air solder rework stations
that are reasonably priced. The one I got is called the
Quakko 850D SMD Rework Station.
Quakko 850D Hot Air SMD Rework Station
850D photo is with the unit right out of the box with no
nozzle installed. When the switch is turned ON, the
blower comes on and the temperature is regulated to the
default value of 200 deg C. Only a low humming noise
from the air pump. When the switch is turned OFF,
nothing appears to happen, while the blower continues until
the air temperature goes below 100 C. then the blower shuts
off. A very nice feature that will extend the life of
the heating element. My first get aquatinted uses for
the 850D will be trying to use it where normally a hand type
soldering iron would be used.
The tip of my hot air gun is 21.6 mm O.D. and I understand
there is a standard size for all hot air soldering guns.
There are a few dozen different nozzles available. Some
have just a round outlet tube for single point heating.
One web page suggestgs that the single point tip hot air tool
may replace the standard soldering iron because it works
better. Other nozzles are matched to the SMD, such as
for different sizes of: SO or SOIC (Small Outline Inline
Circuit), QFP (Quad Flat Pack), PLCC (Plastic Leaded Chip
Carrier), BGA, CSP (Ball Grid Array), or SOJ (Small Outline
with "J" leads).
This might be a rebranded Aoyue
Hot Air Rework Station
although they don't offer the
850D, just the 850 and 850A.
Or more likley a knockoff Hakko
since the Hakko 850D is not obsolete, replaced by the FR-801,
or FR-803. These have a ball in tube air flow monitor
and the two higher numbered versions have a key lock on the
The manual says the main use of the 850D is for removing
SMDs. But when used for soldering to watch for solder
balls and bridges. The 850D can also be used for shirnk
There seems to be two styles of hot air irons. Those
that have the air supplied by a diaphram pump in the main box
and those that have a fan in the tool handle. I expect
that the fan in the tool type are very similar to the Harbor
Freight Heat Gun (see below) and will have a short fan motor
|Single hole nozzle
|Multi hole nozzle
Aug 2010 - I almost never use
this. For unsoldering just use solder wick and liquid
Pre Heaters are used to heat the
bottom side of the board. This is done to prevent the
board from distorting which causes a lot of problems with Ball
Grid Array (BGA) type of ICs. It's questionable if a pre
heater is needed for other types of SMD.
Harbor Freight Heat Gun
The $10 heat
gun (Harbor Freight Heat Gun 35776
used mainly for shrink tubing has a 35 mm diameter where it's
accessory nozzles fit. But when you buy the $20 heat gun
in the kit (47269
it comes with a reducing nozzle from 35 mm to 23 mm adapter
that's a little tight, but does accept the rework station
nozzles. The bad news is that without the adapter (just
the stock heat gun) it can not melt solder enough to ball up,
just turns dull gray color. With the adapter and nozzle
it will not melt solder at all. But there might be a
modification that would make the heat gun run hotter?
But even if you could make it run hotter the time until the
fan motor fails may be decreased from the stock 1 year to some
much shorter time.
first try I got Kester
R276SRSN63 The R276 is the no clean flux, SR is for
Syringe and SN63 is for old fashion Lead Tin. This is
a 35 gram (10 cc) size.
The shelf life is 6 months from the date of manufacture when
stored refrigerated between 0 to 10 deg C ( 32 to 50 deg F)
and so needs to be shipped using an overnight service in a
refrigerated box (the same styrofoam type box is used to
Paste is also available in a number of larger
containers. But for small runs the problem is that the
paste will exceed it's shelf life before it gets used, so
the smallest possible container is desirable.
A problem with solder paste is that most distributors no
longer carry it. Probably because of the short shelf
life. They will supply case quantities drop shipped,
but this is not practical for a small business. Techni-Tool
to carry both and will sell individual tubes.
R276 No-Clean is TT No. 488SO540 and the R500 Water-Soluble
is TT No. 488SO5603
The Mesh: -325/+500 means it's type 3 which is the stock
solder power. Type 4 is a special order finer powder.
Aug 2010 - not needed for 1/2 pitch parts. Just use
small diameter solder and a fine point iron.
Just as the SMT business borrowed the "tape" from the movie
industry, they borrowed Syringes from the medical
industry. Back in the 1950s medical syringes were made
of glass and the needles were all metal. The syringe
had a tapered outside diameter that attached to the
needle. Doctors were supposed to use an auto-clave to
sterilize them prior to the next use.
Modern medical syringes are called "Luer
" and are made out of plastic. They have a taper
(maybe the same one as used in the 1950s?) and in addition
there is a sleeve over the taper that has threads on the
inside. The needle has either "ears" or a male
thread. To attach the needle to the syringe you screw
In addition to the
syringe you also need a plunger to push out the paste and a
needle to form it into a small diameter. Commercial
practice is to use a pneumatic actuator that will put out a
controlled burst making a controlled dot of paste and the
fancy ones have a pull back.
Kester has sent a complementary plunger. I've seen on
the web plungers with a bigger diameter head that rests in
the palm of your hand. It would be easy to adapt a caulking
gun to work the solder paste tube. Once installed the
plunger may lock to the solder paste tube preventing
reuse. The plunger dies not lock and is a nice fit in
28 April 2006 - I've had an adapter made that fits a
standard caulking gun. It holds the syringe and when
the disk shaped normal caulking gun plunger is removed the
existing rod will fit the syringe. It is not needed
with the huge 14 ga needle. Will see how it works with
the Yellow finer ga needles. questionable if needed.
I have also seen kits that contain a plier type device
designed to give more leverage and maybe some metering of
the paste, but expensive.
needle diameter should be between the lead width and 1/2 of
the lead width (from another web page, but see the calculation
recommendation may have been for chip resistors or
capacitors that were much larger than SOIC or finer pitch
ICs?) Run a line of solder paste along all the pads
(solder paste will be between pads). Place part paying
attention to orientation or polarity. For the SOIC-28
package where the lead is 0.008 inches wide this suggests a
needle I.D. of 0.004 to 0.008 inches. Note that the
smallest needles are 30 ga or 0.006. In addition the
solder paste uses different solder powder sizes and these
are rated for 22 ga (0.020 inches) for the solder paste I
have. So it looks like the smallest needle that can be
used with this paste (there are other pastes that use a
finer solder powder called Type 4 that may have been a
better choice) may put down too much solder.
In a commercial setting the needle is held vertically and a
round "dot" of solder is applied. In this case the
important thing is the volume of solder for each
joint. For hand use the volume of solder for each
joint also needs to be correct. I'm thinking of ways
to get this right in a controlled manner.
One way may be to use a roller, like is used for inking a
printing press. I've seen small rollers offered for
this purpose. The roller is charged by rolling it on a
flat surface then transferring the solder paste to a single
row of pads.
The needles have an ID range of 0.006 (30 ga) to 0.069
(14 ga) inches. But a given solder paste typically has
a recommended minimum needle size.
medical type needle
(except no diagonal cutting edge,
just blunt) take more pressure to get the solder out.
are easier to use, but only come in 0.063 (14
ga) to 0.013 (24 ga). The 24 gauge may be just about
right for an SOIC-28 package with 0.008 lead widths.
Kahnetics makes SMT type needles.
See Luer Lock
above under Syringes
for how the
needle attaches to the syringe.
2006 - while at the doctors office I got a B-D
model 305155 needle
that's 22 ga by 1" long and a 25 ga by 5/8 long (B-D
5122). Both of these use the same Luer Lock system as
the needles sold by the SMT distys
But they have sharp points! There may be a way to
grind off the point and also make the tube much shorter,
like 1/2" or less long. The shorter the tube the
easier it should be to push out the solder paste. So I
now have a selection of needles from Techni-Tool
yellow), and Kester
(16x0.5), a disty I won't mention (16x0.5 violet), and the
medical needles (22x1 gray and 25x0.625 lt blue). 25
ga looks very small, like no solder paste is going to go
The medical needles have a safety shield over them so you
won't get poked. It does not come off using just your
hands. This idea is that when you screw the needle
onto the syringe the safety shield is loosened and can then
be safely removed.
Volume Calculation 24 May 2006
A first cut looks at two places that solder would
be. All dimensions in mills (1/1000 inch) Package is
1) an even layer on each PCB pad maybe 2 mills
thick. The pads are 14 x 80 mills so that's 2,240
2) a filet on the sides and both the end and the back of
the SMD foot which is 8.5 mils wide and the length of the
foot may be 65 mills for a total filet length of 150 mills
(rounding up). The filet looks like what's left if
you subtract a circle from a square and take 1/4 of that
where the square is 0.0085 on a side. So the area of
the filet is about 4 square mills for a filet volume of
600 cu mills.
Adding 2,240 and 600 gives 2,840 cu mills of solder for
Solder paste has about 87% solder by volume so the
calculated solder volume needs to be increased to paste
2800 / 0.87 = 3,264 cu mils of solder paste.
Since the pitch (distance between lead centers) is 25 we
can divide the volume by the pitch giving the area of a
3264 / 25 = 131 sq mills, or the ID of a round needle
would be SQRT(4*A/PI) = 13 mil ID or 25 ga, way too small
for this paste.
So a 20 ga needle (min size for this paste) with an ID of
25 mills is about 4 times the volume required and a 14 ga
needle (0.063 ID) with an area of 3,117 sq mils is
25 times too much solder!
If too much solder was on each pad then there would be
about a 1/2 cylinder on top of each pad. Since the
pad is 14 x 80 the cylinder volume would be 80 * PI * 14 *
14 / 4 = 12315 cu mils and half a cylinder would be 6157
cu mils of solder or 6157/0.87 = 7078 cu mils of
The paste bead area would be 7078 / 25 = 283 sq mils for a
needle ID of SQRT(4*283/PI) = 19 mils or 22 ga. So
it's clear that a 20 ga needle is way too big for laying
down a cylinder that's as long as the distance between the
end pads on each side.
This is consistent with the idea that the way needles are
used commercially is to put down round "dots". The
"dots" do not need to be inside the pads they just need to
touch the pads so capillary action can suck the solder to
On the next try with the Yellow 20 ga needle maybe putting
down a bead that is 1/4 the length of the side or about
14/4 = 3.5 pads long. Spread it out over the 14
pads. Then do the same for the other side.
Application & Use
Afternoon of 4 May 2006 - needles
arrived. They are 16 ga which is way too big to just
put down a bead and melt it. The result is to solder
bridge all the leads into one blob.
To fix that just soak solder wick in RMA flux
(probably the no clean
and the water soluble
flux would also work, it just has to be a liquid not a dry
powder) and using a normal soldering iron wick off the
excess solder. But now the part is not aligned with
the pads. So using the hot air iron with no tip melt
all the joints and move the chip from the pads. I then
used Blu-Tak to hold the chip in place and with the small
round tip on the air iron reflow the solder on most of the
pins. But there were still some pins not soldered (can
tell by poking them with a needle). To fixed those
used Weller WES-50 soldering iron with the ET-S fine tip and
Kester wire solder that's 0.015 diameter with 282 flux core.
The Blu-Tak leaves a gummy residue where it's been heated to
solder melting point so there's still a procedure to be
developed. It may be that just the normal soldering
iron would work, will know more on the next one. The
gumy residue makes for bad solder joints.
It's not necessary to try and apply the solder only to the
pads, but instead it can be applied in a row covering all
the adjacent pads and when it melts will move under the
leads leaving a space between leads. This may be more
true when there's a solder mask on the PCB, like in my case.
The problem is geting too much solder paste.
5 May 2006 - The 16 ga
needle supplied by the disty has more than 4 times the
area of the minimum size (20 ga) needle that would work
with this solder paste, so the bead I applied contained
more than 4 times the solder than it could have. Or
even less if Type 4 solder powder was in the paste.
So it looks like the easiest way to control the solder
volume is to use the correct size needle and just lay down
a line of solder (like putting toothpaste on a brush).
One of the web pages on soldering SMDs says to heat the
board from below, after the paste has been applied and the
part installed, until the flux activates and the solder
flows to the individual leads, then use a small pencil point
of hot air to reflow the solder to get wicking on the sides
of the leads (this done while the board is heated from
below). Other web pages say the same thing but suggest
using a hot plate or fry pan for the lower heat
source. These ideas are probably necessary when
working with Ball Grid Arrays or other packages that have
zero tolerance for board warping, but for SOIC or other
packages that are tolerant of board bending it's not
necessary to heat the board from below.
Another possible reason for doing this would be the case
where the board has a large difference in the total percent
of copper on one side when compared to the other side, for
example a microwave board where the back side is all copper
and the top side has almost no copper. This will make
the board bending worse, but still should be OK for leaded
It looks like the default 850D temperature of 200 C is on
the low end for Lead-Tin solders and the manual says to use
300 to 350 deg C.. The manual also says the air speed
depends on both the type of
nozzle and the temperature setting.
In the past I've had mixed
results when trying to use solder wick. It turns out
that the magic step is to wet the solder wick with liquid
flux. The secret is not so much the wetting action
of the flux but rather that the flux displaces air and
provides a good thermal path for the heat. Dry flux
will not act the same way. This makes a great
difference in how well solder wick works.
One way to apply solder
paste is to have a silk screen made. It's
processed using photo lithography methods. By
specifying the screen thickness the opening size for each
pad amount of solder paste can be controlled. This
may be a viable way to make a high volume of boards, but
for prototypes and short runs seems expensive and
Printed Circuit Boards
In order to work with SMDs you
need a PCB designed for them. Some of the features that
a PCB can have are:
- Simple board that just has the top copper layer with no
- Solder-Mask over Bare Copper ( SMOBC) typically a green
- Plating over copper, might be conventional solder or for
RoHS, tin or silver plate (in all cases the traces are
metalic silver in color not Cu colored)
- Silk screen (typically white ink over solder mask)
I think solder mask was developed to prevent solder bridges
when working with fine pitch surface mount devices. From
my limited experience it seems to work very well. It
would be interesting to compare the same board layout with and
without solder mask but as far as I know there's no simple way
to remove solder mask, only machanical abrasion which would
not be a good thing to do the fine pitch pads.
Boards that have solder plated on the copper will need less
solder to make a joint than will boards that do not have any
solder. I'm thinking about how to calculate
the amount of solder needed
and convert that into a
7 May 2006 - ExpressPCB is now
offering your choice of lead-in or RoHS compliant. For
the RoHS they are using a silver coating instead of the more
common tin coating. This way you can use either type of
solder. They recommend 96.5% tin, 3.0% silver, 0.5%
copper alloy, such as Kester 24-7068-7600 (Mouser part number
for RoHS compliance with their boards. But this is big
0.031 diameter wire solder. For a little more you can
that's 0.020 diameter, but that's still larger than the 0.015
solder I'm using.
It's more economical to have one board made with many circuits
on the board and cut them apart yourself. It's only been
since Feb 2010 that I've found the 12"
Bench Top Hand Shear
that will easily cut the 1/16" PCB
Surface Mount Devices come in
many different sizes and outlines. This page was started
because I wanted to work with a part (ICS525) that only cames
in the SOIC-28 package (0.008" wide leads on 0.025
pitch). There are a number of different sizes of
rectangular chips used for two terminal devices like
resistors, capacitors, inductors, diodes, LEDs, etc.
There are also a large variety of packages for transistors and
Some of the packages have gull wing or "J" leads and so after
being soldered there is some compliance between the part and
the board, so if the board flexes there is strain relief
(SOIC, SOT-23). But some of SMDs come in packages that
have no compliance like the Ball Grid Array or Quad Flat pack
(QFP). Working with the chip parts or parts with leads
is much easier than working with the no compliance parts.
) - Your
coordination improves with the magnification (up to some
point), so when working under the microscope (more properly
called a macroscope) you can do much better fine work.
The problem is as the magnification gets higher the field of
view gets smaller and you loose your frame of reference.
Magnifying Lamp with ring
(Harbor Freight model 31679
or model 34018
the later one looks like what I used to use.
Pin Vise with sewing needle
- good for moving small mechanical things and when a DMM probe
is slid down the hollow handle makes an excellent electrical
test probe. It will puncture conformal coating or sit on
an IC lead where a normal probe tip is way too big.
- Note these
tweezers have very thick (stiff) legs, unlike 99.99% of the
tweezers that have flexible legs. With these you can
pickup a delicate part and if your grip changes pressure the
legs do not deform. When your grip changes pressure when
holding the flexible type tweezers the legs bend and can
change from holding a part at the far corners to holding it at
the near corners, and then the tweezers launch the part into
the air never to be found again. They have been stamped
00c but I don't know where to get another pair. I've had
these for maybe 40+ years. They're great for bending
hookup wire for use in white plastic type proto boards and all
kinds of other things that small pliers might be used for, yet
they can do it to much smaller items. highly
Otto Frei - watch, clock & Jewerly supplies - Dumont
Made Style OO Tweezers
- Horotec Stainless
Steel Antimagnetic #00
without bolting down, which allows it to be rotated.
Also once a board has been clamped you can loosen the ball
joint clamp and flip the board over. The more I use it
the more I like it. No need to bolt it down, making it
much easier to position under the Magnifying Lamp with ring
- only for use
with conventional soldering iron, not hot air iron
use with flux pen
RMA flux pen
- use with
eBay Clock Kit
This LED clock kit uses a lot of surface mount parts, but
only cost $8 including shipping from China. May 2015
I'm using it as a test case for SMT assembly.
|Fig 1 Kit as received
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