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| Date: | Wed, 13 Apr 2016 14:43:06 +0000 |
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The main source of my previous reply was from a seminar presented by Premier EDA Solutions in 2006 present by Alan Johnson.
The main notes for this section were:
"It is recommended that all laminates used in lead-free processes have a Tg value > 140C for all products"
"For products with more than 10 layers, >6:1 hole aspect ratio or containing BGAs a Tg value >165C is recommended"
"(source iNEMI)"
And,
"Time to delaminate T(299)"
"Materials which are sold as being compatible with lead-free processes should survice 260C for at least 30 minutes and 288C for at least 5 minutes".
Just after the seminar I spoke with Kerry Hewlett of Graphic who reinforced the Time to delaminate as being the critical factor rather than the Tg. He advised the Td should be in the region of 350C, and T260 should be at least 30 minutes.
Regards,
James
James Head BEng CID+ MIIE MIET
Senior PCB CAD Engineer
Crowcon Detection Instruments Limited
172 Brook Drive
Milton Park
OX14 4SD
Telephone: +44 (1235) 557700 ext. 7885
E-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson
Sent: 13 April 2016 15:09
To: [log in to unmask]
Subject: [TN] Material Tg for RoHS
Way back when we were making changes to meet RoHS requirements, we were advised to use bare board materials with 170 Tg or higher. So we changed our Fabrication Drawing Notes and everything has been fine.
But recently I've noticed that the default material for several different suppliers is around 155 Tg. Has the thinking "relaxed" in this regard? Or should I stick with my 170 ?
Jack
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