Subject: | |
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Reply To: | TechNet E-Mail Forum. |
Date: | Thu, 4 Feb 1999 12:12:30 GMT |
Content-Type: | text/plain |
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The electronics companies who swear by DOE and Taguchi arrays are
many. There's the classic example of the Wave solder matrix, two types
of flux, two pre heat settings, two conveyor speeds and two bath
temperatures. The wonders of this experimental method are praised
through out the electronics manufacturing world. Yet nobody ever
enters the parameter "Pad dimensions". As far as I'm concerned the
experiment is a pile of rubbish without this. The Array doesn't tell
us what parameters to enter. Anyway, enough ranting.......
Don't worry about the semantics regarding the occurence of bridging
between the new and old oven. Don't consider DOE or Taguchi.
Convection ovens are the standard, going from IR to Convection is a
good choice.
Pad geometry and stencil apertures will have a much more significant
impact. Establish the dimensions used and we can comment. If their
geometries aren't suitable then no oven will change the defects due to
bridging. Not all is being told here. The profile will have an
influence on bridging, but small compared to the effect of pad
geometry.
Establish what flux is being used in the paste.
Let us know the details and we'll sort you out.
Regards
Edward Brunker
PSION COMPUTERS
GREENFORD
LONDON
______________________________ Reply Separator
_________________________________ Subject: [TN] Solder Bridging
Author: "TechNet E-Mail Forum." <[log in to unmask]> Energy
Technology Systems <[log in to unmask]> at INTERNET
Date: 03/02/99 10:58
I have a customer who recently replaced a very old IR reflow oven with
a brand new convection one. Since the new oven has been installed they
are noticing an increase in solder bridging on some very fine pitch
components. Even the customer says that they do not suspect the reflow
oven but they cannot place a finger on it. Being the manufacturer of
this oven I want to help prove that it is not the problem as none of
our other customers have ever complained about solder bridging and
from my experiences solder bridging has been reduced dramatically when
switching from IR to Convection. Can anyone suggest additional places
to look.
The area I am most suspect of is the conveyor just prior to reflow.
The reflow has an edge conveyor and the linking conveyor just prior to
reflow is "power loading" the boards. By power loading I mean the
upline conveyor is running considerably faster so that the boards
slide a ways onto the conveyor prior to slowing to match the reflow
conveyor speed. I have heard that boards can crash into the conveyor
pins, other boards, etc. when power loaded and cause components to
shift. Could this be the case?
I know it can not be related to the energy transfer as the delta on
their boards was reduced from 40 degrees C to less than 15 (actually 8
- 15 degrees depending on the board) by switching from IR to
convection.
Comments?
Brian
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