Re: Chip pad

Hans Summers <Hans.Summers@...>
 

I was wondering how to make a pad for the chip then thought
use a piece of PCB with a cut through the copper in the centre
and then additional cross cuts of the copper to make the lands
for the holder.
That's what I do too, when I need to. I use firm pressure on one of those
cheap orange plastic "craft" knives. You can produce a nice thin cut with
this method. The LM386 in the BITX20 I just mounted "ugly" though, with no
pads. I tend to use the knife method if I need to use surface mount IC's.

The pinnacle of the art came when I found I had to connect a 24-pin Analogue
to Digital converter chip, in a TSSOP package. Pin spacing was a mere
0.65mm. In other words, 4 times denser than your BITX20 LM386. To do this I
cut 2 columns of 6 pads on either side of the IC (24 pads total). I glued
the IC to the board. The even-numbered pins (2, 4, 6 etc) were bent upwards
away from the board. Odd-numbered pins (1, 3, 5 etc) were soldered direct
onto the pads. The even-numbered pins were then connected to the outer
columns of pads using the hair-thin individual strands of copper from
ordinary lighting cable. You can find a picture of the result about 2/3 down
on the left hand side of this page
http://www.hanssummers.com/electronics/equipment/spectrumanalyser2/index.htm


People who work with SMD talk of special soldering irons & bits, special
solder, magnifying glass, flux, special lights etc etc. I used none of this.
Just my ordinary 18W Antex CS iron with 1mm bit and ordinary 22swg solder.
Just goes to show that the patient homebrewer can accomplish a lot even
without specialist equipment.

72/3 de Hans G0UPL

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