Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

previous by date index next by date
previous in topic topic list next in topic

Subject: Re: starting with SMD

From: "eeks123" <eeks123@...>
Date: 2008-01-31

> Basically that is the idea, yes. But if you reflow with hot air
> instead of an oven this doesn't always work perfectly. Some part
> shapes tend to be pushed around by the air, like MELF diodes.

yes, air flow and small components are apparently a bad combination. i
suppose it's a try-and-try-again until you learn which distance is
best, taking care where you point with the gun at, how much time a
component can be exposed to that temperature, etc. you can solder a
lot faster than with an oven, but you need to learn how to work with
it. plus chances to damage something seem to be higher, when
learning/starting


> It also depends on the solderpaste used, some stays in shape when hot
> and some melts and forms large puddles on which the components swim
> around.

i didn't knew there are two types, i supposed all components would
swim, and that was also a reason to use soldermask -to avoid
solderpaste flowing away through tracks-. so the first one is better
but has a shorter shelf-life :( how do you know which type of
solderpaste you are buying? through composition?


> But you still need to observe some layout considerations for parts to
> stay put. Always think surface tension.

i've seen this explained on a webpage, it's important the way tracks
go to the component, and also if there any very near to it.



regards