i. Alternative technique of soldering a low pin count SMD device

QUESTION:

I’m having troubles soldering SMD oscillator to the prototyping PCB. It keeps loosing contact. Is there an alternative way to firmly solder it to the circuit?

ANSWER:

There are different techniques of making your own PCB. But making closely spaced narrow contacts for SMD devices requires precision etching, which is difficult to achieve, if you are making etching mask by hand. If you decide to skip this part of the project and opt for a prototyping PCB with hundreds of equally spaced holes, you might find it difficult to solder an SMD device, because most of cheap prototyping PCB boards lack SMD adapters.

This is also the case with FOX924B crystal oscillator, which enables PIC32MX250F128B microcontroller to use USB 2.0 communication. Though there are many +3.3 V through whole crystal oscillators on the electronics market, they lack frequency stability compared to SMD devices.

Instead of soldering the oscillator directly to the PCB, you may solder it to soft wires, as shown in the photos bellow. Use tongs or tweezers to hold the oscillator in place while soldering the first contact. If you hold it by hand you may get burned, because the heat spreads quickly through the small ceramic casing. After soldering the first wire, it is much easier to hold the chip in place, if you hold it by the wire. It is advisable not cut the wires to the desired length and strip their insulation until all of them are soldered to the chip. You should also be quick not to overheat a wire and make it loose contact with the chip. Finally, place some electric insulation tape underneath the oscillator, if you are soldering it to the bottom side of the PCB. Alternatively you may solder the oscillator wires through PCB holes…

NOTE: Check each wire’s grip to the contact on the chip casing before you cut the wires to the length! It important to avoid a “cold” contacts that quickly loose grip, if slightly pulled by hand.

Here are some photos: