Posts Tagged ‘smt’

Soldering a wire to fine pitch (0.3mm) SMT devices

In this tutorial I will describe a technique for soldering to fine pitch SMD pads. Using this approach I was able to solder a wire to a 0.3mm (~ 12mil ) pad.

1) Start by tinning the pads:

– place liquid flux on the pads

– take a "ball" of solder on the soldering iron tip and gently touch the pads, if you get to much solder connecting the pads, just "wipe it off" with a clean soldering iron

– the pads that have fresh flux will attract the solder

– the tinned pads should have small "pillows" of solder on top of them.

2) The wire should be thinner than the pad. You can get a thin wire by separating a thicker stranded wire. Tin the wire the same way as you tinned the pads

– first place liquid flux on the wire

– next touch the wire with a soldering tip that has some solder on it

3) This is the main step, the main idea is to mask the pad being soldered with 3 pieces of temperature resistant tape (Kapton tape).

The setup looks "dirty" when magnified, because of the sticky flux, you clean it up usually at the end with alcohol.

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Reverse Surface Mounting of Small Leadless SMT Components

This method of surface mounting is unconventional and is not recommended for production projects. If you plan to use the device in a mobile project make sure you seal it.

It's a know fact that the surface mount devices are becoming more and more popular leaving behind the traditional through-hole mounting method. While for the electronics industry surface mounting brings a lot of benefits (one of them being the ability to pack more components per square inch) for the regular hobyst surface mount devices are often times a "show stopper".

This tutorial is for those of you who absolutely need to mount a small surface mount device for prototyping purposes and do not have the means or time to perfom a traditional surface mount. There's obviously a "correct" way to mount a SMT component and I highly recommend reading the Surface Mount Soldering guide at Curious Inventor first before attempting this method. However it's always good to know that there's an alternative method that does not require any investments in expensive SMT equipment or materials.

In this tutorial I'll describe how to mount an analog LIS244AL accelerometer (data sheet), that comes in a tiny leadless LGA-16 package. The size of the component is 4x4x1.5mm. It has 16 solder pads, each is 0.3×0.4mm. This is the tinest component that I ever have to deal with. When I first saw this device my first thought was that there's now way I can mount this little device without creating a custom PCB and using the traditional surface mounting method.

After several trials and errors I came up with an interesting method that uses masking tape in order to create bridges from the device pads to the pcb regular "through-hole" pads. I also made my work easier by bringing the device pads to the same surface as the PCB hole pads.

No custom PCB is required for this tutorial, we'll use a regular proto-board that you can find in any electronics shop. However you can create a custom PCB to minimize the distance between the device and the external pads.

First mark the desired size on the board that you'll use for your breakout board. We'll use a piece that has 4×4 holes (two pieces are marked on the picture below).

proto board

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