Hi there, 

The following message was posted two weeks ago, without 
response. 
I'm trying it again only one more time. Thanks, and apologies 
for the bandwidth.

--------------------------------------------------------------------------------------------------
Sebastian Garcia wrote:

Hi listers,

I'm just starting the development of a small batch reflow oven and
it would be helpful to obtain some thoughts from those experienced
developers (both commercial oven users and those that have built
their own).

I've seen the good results obtained by the simplest approaches
(like the Seattle Robotics's "toaster oven" method) doing some kind
of on/off control (and therefore exponential temperature response)
on the oven.
Instead of that, i would like to guarantee some level of reliability
for prototyping and small production of boards, following the
manufacturer's (both of solder paste and IC's) guidelines, in order
to avoid the related problems (popcorns, cracks, delaminations,
etc).

For the oven, i'm thinking in a small electric ("cooking") one,
adapted. That is, convection heaters and small fans, forcing 
convection in the horizontal direction.
[Maybe i'll need the speed of an IR heater (only for a
moment), in order to achieve the profile's peak temperature
(though i'm aware of its dangerous side, regarding the black colour
of IC packages) ].
Probably, the plant's model would be a first order, delayed, system.
In fact, i have obtained the step response of a small electric oven
with a convection heater (sensing air temperature in two points with
thermocouples), and it fits well with a delayed exponential
function.

Hence, the idea is to implement some control law with a scheme to
tackle the delay (Smith predictor?) that guarantees the reflow
temperature profile (within some margins) in the pins and pads to be
soldered.

Any thoughts will be helpful and greatly appreciated.

Best regards,

S.-

--

/*
 Sebastian E. Garcia
 Embedded systems development  ~ sebasgarcia at gmail . com
&
 Embedded Applications Group ~ sgarcia at fi . uba . ar
 School of Engineering ~ University of Buenos Aires
*/
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