Robert said:
I have in the past hand soldered SOIC packages for prototypes using a microscope
and a soldering pencil. But now I am faced with a chip that is only available
in an LCC package - the kind with the contacts under the chip. It only has 8
pins. Is there any hope that I can solder this chip using hobbyist's tools?
Robert Scott
Ypsilanti, Michigan
I'm soldering a QFN68 pin package by hand:
1. By keeping the component stored in a jar with lots of silica gel and
a moisture indicator, the first samples I was sent made no mention of
the "pop-corning" effect caused by absorbed moisture turning to steam
and cracking the package.
2. Using a 400W stove element hooked to a temperature controller to warm
the board to 120 deg C to preheat the board and dry the component. This
also provides a slowly cooling base to reduce thermal stresses.
3. I made a spring steel clip attached to holes drilled into the edge of
a sheet aluminium base: the clip holds the component in position while
you tack solder a corner and the aluminium base transfers heat from the
hotplate to the board.
4. After a corner has been tacked down with solder and while the board's
still on the hotplate I run a small iron around the edges of the
component drawing a blob of solder as I go to leave a clean join on each
pad.
5. After soldering the hotplate gets turned off to allow cooling down of
the board with a thermocouple monitoring the component temp.
I'm playing around with IR reflow using a toaster oven but I need to get
some extra flux to add to the solder paste as it doesn't seem to flow
too well and lots of small balls of unflowed solder paste show under the
microscope. The IR oven shows promise but always needs reworking at present.