The process will stop once the material reaches the "Temperature of
Degradation", which in the case of standard FR4 is around 320oC. At this
point, the bonds irreversibly break down, or decompose.
----- Original Message -----
From: michael <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, July 13, 2000 3:15 AM
Subject: Re: [TN] Glass Transition Temperature (Tg) Questions
> Epoxies are thermosetting. Surely this process is not indefinitely
two-way? Or
> should I say: beyond what temperature is the process no longer two-way
(and what
> is the technical term for this temp.)?
>
> Michael Fennema
>
> -----原始郵件-----
> 寄件者: Mike Fenner <[log in to unmask]>
> 收件者: [log in to unmask] <[log in to unmask]>
> 日期: Thursday, July 13, 2000 05:58
> 主旨: Re: [TN] Glass Transition Temperature (Tg) Questions
>
>
> |Just for completeness, thet Tg is two way:
> |When ever the polymer is at a higher temperature than the Tg, the
> |chemical bonds are relaxed and the material is relatively floppy. When
> |the polymer goes back below the Tg the chemical bonds tighten back up
> |and the material reverts to its hard state. The transition from hard
> |to soft (or soft to hard) is a repeatable process in either direction.
> |
> |Mike
> |
> |----- Original Message -----
> |From: "Alain Savard" <[log in to unmask]>
> |To: <[log in to unmask]>
> |Sent: Wednesday, July 12, 2000 5:35 PM
> |Subject: Re: [TN] Glass Transition Temperature (Tg) Questions
> |
> |
> |> My answers marked with 2 asterisks (**) below.
> |>
> |> Alain Savard, B.Sc.
> |> Chemical Process Analyst
> |> CAE Electronics Ltd.
> |> e-mail: [log in to unmask]
> |>
> |> -----Original Message-----
> |> From: Hiteshew, Michael [mailto:[log in to unmask]]
> |> Sent: July 12, 2000 12:06 PM
> |> To: [log in to unmask]
> |> Subject: [TN] Glass Transition Temperature (Tg) Questions
> |>
> |> Hi,
> |> I've been reading up on laminate materials and have some
> |questions
> |> that I hope some-one can help me with:
> |>
> |> 1. What is the "glass transition" ? What is the glass transitioning
> |from and
> |> to? I'm guessing it's the plastic stage that occurs in a material
> |just
> |> before it melts.
> |>
> |> ** Temperature at which the laminate turns from a relatively hard
> |and
> |> potentially brittle state, to a vicious, semi-liquid stage. Epoxy
> |used in
> |> the boards is more likely to decompose or burn than it is of ever
> |melting.
> |>
> |> 2. What is gained by a higher Tg in tetrafunctional and
> |multifunctional
> |> epoxy-glass?
> |>
> |> ** Higher Tg means that you have a better resistance to heat from
> |any
> |> source. Your board is more likely to keep it's shape during heat
> |related
> |> fabrication process or during use if it has a higher Tg.
> |>
> |> 3. What is meant by the prefixes "tetra" and "multi" as they're
> |applied
> |> here? Is it a reference to the number on bonds in the chemical
> |structure of
> |> the epoxy or glass?
> |>
> |> ** It refers to the number of linkage sites of the epoxy prepolymer.
> |>
> |> Thanks in advance,
> |>
> |> Michael Hiteshew
> |> Lockheed Martin NE&SS-Baltimore
> |> [log in to unmask]
> |> (410) 682-1259
> |>
> |> ##############################################################
> |> TechNet Mail List provided as a free service by IPC using LISTSERV
> |1.8c
> |> ##############################################################
> |> To subscribe/unsubscribe, send a message to [log in to unmask] with
> |following text in
> |> the body:
> |> To subscribe: SUBSCRIBE TECHNET <your full name>
> |> To unsubscribe: SIGNOFF TECHNET
> |> ##############################################################
> |> Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
> |additional
> |> information.
> |> If you need assistance - contact Keach Sasamori at [log in to unmask] or
> |> 847-509-9700 ext.5315
> |> ##############################################################
> |>
> |
> |##############################################################
> |TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> |##############################################################
> |To subscribe/unsubscribe, send a message to [log in to unmask] with
following
> text in
> |the body:
> |To subscribe: SUBSCRIBE TECHNET <your full name>
> |To unsubscribe: SIGNOFF TECHNET
> |##############################################################
> |Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
> |information.
> |If you need assistance - contact Keach Sasamori at [log in to unmask] or
> |847-509-9700 ext.5315
> |##############################################################
>
> ##############################################################
> TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> ##############################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with
following text in
> the body:
> To subscribe: SUBSCRIBE TECHNET <your full name>
> To unsubscribe: SIGNOFF TECHNET
> ##############################################################
> Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
> information.
> If you need assistance - contact Keach Sasamori at [log in to unmask] or
> 847-509-9700 ext.5315
> ##############################################################
>
##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe: SUBSCRIBE TECHNET <your full name>
To unsubscribe: SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################
|