----------
From: John Guy[SMTP:[log in to unmask]]
Sent: Thursday, September 12, 1996 8:08 AM
To: 'Jerry Cupples'
Subject: RE: Vapor Phase Reflow
Jerry ,
I agree with everything you said here, but feel the need to add one major point.
When using a Vapor Phase system, the need to profile for a new assembly is almost nonexistent. As you said, the heating is very efficient and even across the assembly.
When using a Convective system, you get the added control and ability to profile, but only at a price. The need to profile for different assemblies is required. The Convective systems are very robust, but I wouldn't say that one profile will serve all your needs.
This means that time is required setting the oven up for a new product, however, this shouldn't take any more time that to program your pick and place equipment.
:)
John Guy
EMPF
[log in to unmask]
----------
From: Jerry Cupples[SMTP:[log in to unmask]]
Sent: Wednesday, September 11, 1996 9:05 AM
To: [log in to unmask]
Cc: [log in to unmask]
Subject: re: Vapor Phase Reflow
[log in to unmask] asked:
>I have attended a few training sessions and vapor phase reflow has been
>discussed, but how much is this process used in production these days?
>Isn't the convection reflow process better, more cost efficient, etc.?
>Inquiring minds wish to know?
Makes a good foil to throw in for a minute to dazzle the audience.
It _is_ a "good process" in that it will provide consistent results and it
can heat a lot of work fairly quickly. The work cannot heat past the fluid
boiling point, so the max temp is restricted.
There are unique advantages - some "tank" type VP systems are gigantic, and
you simply lower the work (like an entire assembly the size of your desk)
into the vapor zone, wait a few seconds, and pull it back out.
Trouble is, the heating is very rapid. The fluid (typically a
perfluorinated FC) is boiled to a vapor, then when the work enters the
chamber, it condenses on the work, then drips back to the boiling liquid at
the bottom of the chamber. The phase change transfers the heat pretty
evenly to any surface contacting the vapor.
Some VP furnaces have two vapor zones (one with a lower boiling fluid), or
some other type of pre-heating to reduce the thermal shock to the work.
It is difficult to get the type of "profile" with VP which IR or convection
furnaces can provide. Typically, the conveyor rate is much slower, as the
vapor zone is pretty short.
The fluids are _very_ expensive, and there is some drag-out or unwanted
evaporation in most systems.
To answer your question, it seems to me that most of the industry has gone
away from it in favor of the convection furnace. I'd say cost, some
environmental concerns (greenhouse effect), ability to "profile", and
throughput are the main reasons.
regards,
Jerry Cupples - [log in to unmask]
Interphase Corporation
13800 Senlac Dr.
Dallas TX 75234
(214) 654-5150
(214) 654-5500 FAX
***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to: *
* [log in to unmask] with <subject: unsubscribe> and no text. *
***************************************************************************
***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to: *
* [log in to unmask] with <subject: unsubscribe> and no text. *
***************************************************************************
|
