If the baking temperatures are too high for too long, potential thermal
degradation can occur which can impact both mechanical and electrical
properties. Additionally, the visual quality of the board can be
potentially impacted. Lastly, if an inert atmosphere is not used, the
solderability of the board can be impacted, especially on non-HASL boards.
For most mid-to-high Tg FR-4 boards, 130C and below for even fairly long
times (even longer than you are using) is acceptable with the potential
exception of the impact on solderability. But I think the point is, 140C
is not really buying you much, if anything over 105-125C, so why risk the
higher temps, especially on what appears to be a lower Tg FR-4?
Joel
Joel S. Peiffer
3M Electronic Solutions Division
3M Center, Building 201-1E-21
St. Paul, MN 55144
Tel: (651) 575-1464
Cell: (612) 327-1983
Fax: (651) 737-4601
[log in to unmask]
From: SARAVANAN R <[log in to unmask]>
To: <[log in to unmask]>
Date: 10/24/2013 06:17 PM
Subject: [TN] Fw: [TN] PCB BAKING DURING FABRICATION
Sent by: TechNet <[log in to unmask]>
Dear all ,
If the baking temperatures are high, what are the effects on the PCB ?.
regards,
R.Saravanan
On Thursday, 24 October 2013 11:23 PM, "Whittaker, Dewey (EHCOE)"
<[log in to unmask]> wrote:
Expecting good results using those higher than needed temperatures is Dicy
at best.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ramakrishnan Saravanan
Sent: Thursday, October 24, 2013 8:43 AM
To: [log in to unmask]
Subject: [TN] PCB BAKING DURING FABRICATION
We are using 170 deg C IPC 4101/24 material for making hi reliability
PCBs. The PCB coupons are subjected to 6X Solder Dip to access PTH
integrity & laminate integrity. 5X R/W also carried out.
to achieve this initial laminates(cores) are baked at 140 deg C for 4
hours.
after blak OXIDE baked at 140 deg C for 4 hours after MLB pressing baked
at 140 deg C for 4 hours after electroless copper plating baked at 140 deg
C for 4 hours prior to HASL baked at 140 deg C for 4 hours a total of 20
hours at 140 deg C baked during fabrication.
after PCB fabrication. the coupon is separated from PCB and the coupon is
baked for 12 hours at 120 deg C.
The coupon is subjected to 6X solder dip & 5x R/W simulation.
My doubts are
Q1. These extra long hours of baking will deteriorate the chemical &
mechanical properties of the laminates ?
if so , what are the properties are getting affected. The material
dicy cured FR4.
Q2. Whether Test coupon results will reflect the quality of PCBs ?.
R.Saravanan
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