[sdiy] components, smd and pcb

[Tony Clark]

> Does that mean, not carefull soldering causes resistor's parameters
> to derate? Does its resistance change, or does it influence reliability?
> Actually, yesterday I experienced for the first time how 0603 resistor
> can be broken, but I thought it was just bad quality component.
> How soldering with iron (not hot-air & paste) influences SMD part?

   No, I'm not suggesting that normal soldering will cause resistor 
parameters to change.  What I'm suggesting is that someone who doesn't 
have good steady hands will probably be frustrated trying to solder super 
small parts like 0603's.
   Yes, you can damage SMT parts with a soldering iron.  The difference 
between using an iron and using a reflow oven are very great!  A 
soldering iron has a very high temperature, higher than a reflow oven.  
The trick is to keep the iron on the SMT part for as short of a time as 
possible.
   Heating a SMT chip up too far will cause the contacts to separate from 
the ceramic carrier thereby ruining the part.  Sometimes it can be hard 
to spot a damaged resistor since the separation can be very small, but 
enough to ruin the part.
   In general, all SMT parts are much smaller than an equivilant 
thru-hole components, and that means less mass in which to dissapate heat 
through.
   It is good advice to purchase a 500 or 600 degree tip for your 
soldering iron if you are just starting out with SMT.  The lower 
temperature will help prevent thermal damage to SMT parts.

> I saw many times markings on capacitors - a letter and one digit.
> Letter was for prefix, and digit was number of zeros. Now either my eyes
> are too bad, or they simply stopped marking them...

   You are right, there are letters/numbers, but I haven't really 
correlated that to a value.  And typically, those markings are really 
hard to read anyway as capacitors usually print grey on brown, which 
doesn't show up nearly as well as white on black (resistors).

   Cheers,

   Tony

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