Microscope Mods

Modding a cheap microscope to solder small parts

@Work, we have a nice professional stereo microscope – with SMD parts getting smaller every year, this is a must-have for rework and inspection of PCB prototypes. At home, I mainly use a head loupe, but for really small parts, a microscope that has enough space to allow soldering would be nice.

A post in the newsgroup de.sci-electronics pointed me to a cheap stereo microscope available at Reichelt (“Mikroskop Junior”, ca. 30 EUR in 2013) – that looked like an affordable risk, so I ordered one.

The first impression is mixed:

The lenses seem to be OK – magnification is fixed at 20x, perfect for fixing messed-up pins  on TQFP packages, or soldering 0.4mm pitch parts. There is enough working distance (ca. 70mm).

Vertical adjusting range is 40mm – OK to focus, but not enough when working on thicker objects.

The illumination is a joke: a single white LED, powered by two AA batteries via a single resistor, barely works when supplied by fresh batteries. When the batteries drain, the light quickly fades – and don’t even think about using rechargeable NiMH cells. On my unit, the mounting bracket for the LED was slightly rusty.

The pedestal is solid, but absolutely not suitable to work on PCBs – it would only work for very small PCBs, the top is not flat, and on PCBs with more than 5cm, the vertical riser gets in the way.

Okay – let’s get to work: I did not buy this for the sophisticated illumination, so let’s take that off and use a Ikea “Jansjö” (3W LED lamp with flexible neck, 10 EUR) instead.

After a trip to the hardware store, the vertical riser is flipped to the top so that the microscope hangs down from it, and cut to the range useable for height adjustment. A piece of 20mm square aluminium profile and 8mm threaded rod and a piece of scrap wood complete the construction:

The butterfly nuts allow for coarse adjustment outside the range offered by the microscope mount, in case I need to work on thicker objects (like the bottom side of a PCB with thick parts on top):

The old bottom plate is used as a drill guide for the holes:

The result is quite nice for the money: 7cm working distance and enough space to work on bigger PCBs:

That board is one of my designs – 21cm*25cm, 8 layers

After taking the photos, I added rubber doorstops to the top ends of the threaded rods to avoid injuries.

2013-11-24 by rincewind