solder flows through the plated through holes. The usual method for replacing a part on a double sided board
involves cutting all the legs of the component and desoldering the pins one at a time, using a solder sucker. This
minimizes possible board damage due to excess heat. Needless to say, since you will be destroying the component,
you want to get things right before you solder!
•If you make a mistake or are missing a part and need a replacement component, please e-mail us. Include your
order invoice number and name.
•If you have not soldered a double sided board before, be aware that solder will flow through the plated board holes
and out onto the opposite pad. Use only as much solder as required to make the connection look good on both
sides of the board. A little care now will insure a long lasting reliable module.
•Do your assembly work on a soft towel or a few layers of paper towel. This will protect components from impact
and make picking up small parts easier. Be careful when opening part bags (use scissors) as small parts can fly off a
considerable distance!
Tools
•You will need a 15 to 25 watt soldering iron with a fine pointed tip.
•There are several choices for solder. ACID CORE SOLDER IS NOT ONE OF THEM! Use a standard fine gauge
(.031) rosin core, aqueous core, or a “no clean” type. We very highly recommend Kester 331 as this can be
cleaned up with warm water and solders very nicely. Connections off the board or to the board that are
inconvenient to clean may best be made with a “no clean” solder such as Kester 245. Rosin core solder can be
used but is really somewhat old fashioned and flux removal can involve harmful chemicals. We build our boards
with the 331 and 245 products and cannot guarantee results with rosin core solders.
•You will also need a lead bender, needle nose pliers, side cutters, and a nut driver set or pliers. A DMM will be
necessary for checking voltages.
Inserting Parts
Take a look at the PCBs. All the parts are mounted on the silkscreened side of the board. Be sure to follow directions. Use
the “ref des” column on the Parts List to locate components. (The Type and Value fields will often have the part
marking in “xx”.)
We advise inserting components in groups according to type, checking them and then soldering the group. This will
help avoid errors. Solder one leg of components first, then come back and do the other leg later. This practice avoids
disturbing the solder joint on the first pin as it is setting up. Some items are heat sensitive and will benefit from this
practice.
PCB Assembly
You can assemble the complete board matrix or snap apart the sections, which is a bit easier. After separating the boards
and removing the tabs, take a small file to even out the area where the tabs were. This should only require a pass or two and
is only necessary where the board will rest against the front panel.
331 type solder should be used for these operations.
Resistors:
•Insert all the resistors, bending the legs at 30 degrees. Check the values. Did you have any left over? Then solder in
place. The resistor can be inserted in either direction, although a good practice is to orient the color code so that it
can be read from left to right along with the PCB silkscreen. This simplifies checking the values and later
troubleshooting/repairs. Don’t get confused over similar color codes.
•The color code chart shows how to identify resistor values. The exact hue of the colors can vary a bit, so be sure
that you pick the right value. Using the parts list and putting the resistors into groups of the same value can help
clear up any confusion. The suffix “K” is used to denote thousand and “M” stands for million. A 56K resistor is
thus 56,000 ohms. The 1% resistors are blue in color and have 5 color bands, with the right one always being
brown, indicating “1” % tolerance. The rest of the color bands are read in the same fashion as the 5% resistors
with there being one more digit to consider. For example, a 75K 1% resistor reads from left to right: violet (7),
green (5), black (0), red (2 zeros) or 75000. A possible problem with this system comes when the first digit is 1
(brown). Since the tolerance is also brown, make sure that you don’t read the resistor the wrong way!