I also use a polyimide kapton tape. A good technique for attaching a TC
is to place it on a foil on the pwb and put the tape over the business
end (the weld) and then use SMT chipbonder about 1/2" behind the tape to
hold the TC firmly in place. The first time through the oven the epoxy
will lock up and hold the thermocouples. The Kapton tape directly over
the weld will reduce the reading by exactly 1 deg. C; it is almost
transparent to the heat. Press the tape firmly around the weld to hold
the weld in contact with the foil so you get a nice solid line in the
graph. If it is not in contact it will measure the air temperature
rather than the foil temperature, and the line in the graph will be
quite jumpy and erratic.
Be sure to put all of the TCs your profiler can load onto the pwb in a
widely distributed manner when profiling a new pwb, and see which
process provides you with an acceptable process window. Usually putting
the board on the chain conveyor gives you the most delta T (the smallest
process window) between the edges of the pwb and the center (sometimes
up to a 20 deg C difference), but this may be OK for smaller .062" pwbs,
the second worst process window is provided by placing the pwb directly
on the mesh or link conveyor, which robs a small amount of heat from the
bottom side, but is evenly distributed. This only works for single-sided
pwbs, of course. The widest process window is to put the pwb in a pallet
or carrier fixture that suspends the pwb with long narrow fingers
holding the pwb. This robs the least amount of heat, and provides the
best dispersion of heat over the entire pwb.
A good delta T to shoot for is a variation of no more than 5 deg. C
deviation from the mean over the entire pwb.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jeffrey Bush
Sent: Tuesday, March 21, 2006 9:18 AM
To: [log in to unmask]
Subject: Re: [TN] thermocouple attachment
We use a Polyimide Kapton tape.
Jeffrey Bush
Director, Quality Assurance and Technical Support VERMONT CIRCUITS
INCORPORATED
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302
Voice - 802.257.4571 ext 21
Fax - 802.257.0011
<http://www.vtcircuits.com/>
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dominic Boudreau
Sent: Tuesday, March 21, 2006 9:56 AM
To: [log in to unmask]
Subject: [TN] thermocouple attachment
Hello Techneter's,
I am searching for a non-destructive technique for attaching
thermocouples to a PCB for thermal profiling. I already know the
technique with Aluminum tape proposed by the study made by KIC but I
wanted a technique with some components installed on the PCB.
Thank you
Dominic
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e To
unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or
(re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing
per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at:
http://listserv.ipc.org/archives
Please visit IPC web site
http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100
ext.2815
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e To
unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or
(re-start) delivery of Technet send e-mail to [log in to unmask]: SET
Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the
posts: send e-mail to [log in to unmask]: SET Technet Digest Search the
archives of previous posts at: http://listserv.ipc.org/archives Please
visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for
additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
