[sdiy] SMT in a toaster oven

[mark verbos]

On Feb 26, 2010, at 5:41 PM, Eric Brombaugh wrote:

> On 02/26/2010 03:17 PM, mark verbos wrote:
>> I just tried using a small convection toaster oven to reflow some SMT
>> parts.
>>
>> Woah! It work perfectly.
>>
>> This circuit board is about 6" x 8" and FILLED with discrete parts.
>> Soldering it by hand takes me about 20 hours of labor and looks like
>> shit.
>
> How many parts are on that board? I find that hand soldering
> SMT with tweezers & a fine tip is slightly faster than through-hole  
> (less board flipping, no clipping), but I typically don't have more  
> than 50-60 parts on a board. If it's taking you 20 hours to solder  
> then you must have some serious number of parts.

80 discrete transistors, 9 chips, hundreds of 1206 resistors and  
capacitors. I have been using through hole diodes, because I didn't  
see a SMT one that looked appealing. I don't want to use one as big as  
the transistors. There are 120 diodes on this board, so it would help  
(just cutting the leads is a PITA). What do you use?



>
>> I stenciled solder paste on it and placed all the parts by hand in
>> about an hour and a half, reflowed it in 90 seconds. It looks like a
>> machine did it.
>
> The neat thing about reflow is that surface tension on the solder  
> pulls the parts into almost exact alignment, and the fillets/ 
> meniscuses (meniscii?) are gorgeous.

exactly. I can't believe how nice it looks.


>
>> Do all of you SMT guys do this?
>
> I've used a hot plate to reflow parts with leads that I can't reach  
> with an iron (SD card slot with pins underneath, chip-scale  
> packages,  etc). This works nicely, but generally all other SMT  
> stuff is done by hand. The stencil cost is mainly what keeps me away  
> from this, particularly since I'm only doing onesy-twosy quantities  
> for personal use.


One wabsite I read suggested using a seringe to apply the paste to the  
board, no stencil. Could work in small enough quantity. For me, $100  
was a small price to pay for the time savings. I can build 5 of these  
in a day instead of one in 5 days.

Mark