Prototyping Arduino Shields with Surface Mount Technology
This post takes a look at using a SchmartBoard Arduino prototyping shield with 1.27 mm pitch SOIC devices.
Having decided that a high-resolution ADC shield would make a useful addition to my Arduino toolbox, I searched online and found a web page describing how to interface the 24-bit LTC2400. This comes in a 1.27mm SOIC-8 package and provided the opportunity to try out one of the new prototyping shields from SchmartBoard.
SchmartBoard provide prototyping shields for use with SOIC devices in pitches of 0.5mm, 0.65mm and 1.27mm, and are supplied as the board only or as a kit with headers and other useful parts.
The shields make use of a system which has been dubbed SchmartBoard|ez, whereby solder mask is higher than component pads and creates “canals” which are filled with solder. This removes the need to apply solder and makes it much easier to hand solder devices down to 0.4mm pitch.
The first step is to position the device and to tape it down at one side, before applying flux across the device leads on the opposite side.
The soldering iron tip is then put into each canal (pad) and pushed towards the lead, with the solder flowing up to the lead and making a bond. When the first side is completed the tape is removed and the process repeated for the other side.
The shield can accommodate up to a 28 lead SOIC, however, this particular project called for 2 x SOIC-8s: the ADC and a precision voltage reference. For some reason I decided to leave a gap of one pin between the two devices.
The shield also includes space for a SOT23-6 along with plenty of plated-through holes, and on the underside there are pairs of pads with one side of each routed to a SOIC/SOT23 lead and the other to GND. These can either be fitted with an SMT decoupling capacitor or a small wire bridge if you want to tie an IC pin to GND.
The image below shows 3 x 0.1uF 0603 decoupling capacitors fitted and circled in red.
With the surface mount devices done it was time to then solder the headers along with the other through-hole components and hook-up wire.
The SchmartBoard|ez system made light work of hand soldering the SOIC devices and comes highly recommended to anyone who is uncertain of working with surface mount technology. And the shields high quality finish and neat results it achieves may also appeal to those who are experienced in hand soldering SOIC devices.
Top image: the completed shield.