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February 2001

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From:
Kathy Kuhlow <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 23 Feb 2001 15:32:44 -0600
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When I have completed FDA validations of wave soldering I accomplished acceptable profiles to the most delicate component on the board.  In general most caps/resistors could withstand 235C for 1-5 seconds.  Inductors were always a lot lower but very dependent on the material used.  I would take the bill of material and go to each component manufacturer and request maximum temp/time information.  

Kathy

>>> [log in to unmask] 02/23/01 03:05PM >>>

Hi Bob...
Wouldn't the ability to do thermal damage to components be a function of the dwell time in the heat source... there is a time factor, isn't there, that affects the equation? If components can have their leads raised to 500+ F for normal SN63 soldering without damage..then there must be a similar technique involved..
 
I believe the operator sets up a profile that soaks the assembly up to a given temp and then spikes the temperature to reflow temp for a few seconds as it passes that point in the oven... then it is immediately reduced in temp before the part bodies can actually absorb enough heat to raise the internal temperature high enough to do them damage.... I don't have all the details, I am just a PCB Designer... but I think that's how it's done... so setting a general limit would be impossible because there are more variations due to design and component location, and heat sinking, and thermal conductivity of the components and their susceptibility to thermal damage... I would guess your limit to be the most easily damaged part on the board... rather than an arbitrary general temp limit... Perhaps there is some more to it than I know, though...
Any one else?
 
 - Bill Brooks
 
-----Original Message-----
From: Bob Arciolla [mailto:[log in to unmask]]
Sent: Friday, February 23, 2001 11:09 AM
To: [log in to unmask]
Subject: [TN] temperature


Good Afternoon, 
 
I am looking for some input as far as what is the highest the top side temperature can be on a pcb going over the wave solder before there is damage (bonding) to components (ex: transistors, IC's etc). Any help would be appreciated. We are seeing around 254 degrees F
 
Thanks in advance,
 
Bob Arciolla   [log in to unmask]
 



<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META content="text/html; charset=iso-8859-1" http-equiv=Content-Type> <META content="MSHTML 5.00.2614.3500" name=GENERATOR></HEAD> <BODY style="FONT: 8pt Arial; MARGIN-LEFT: 2px; MARGIN-TOP: 2px"> <DIV><FONT size=1>When I have completed FDA validations of wave soldering I accomplished acceptable profiles to the most delicate component on the board.&nbsp; In general most caps/resistors could withstand 235C for 1-5 seconds.&nbsp; Inductors were always a lot lower but very dependent on the material used.&nbsp; I would take the bill of material and go to each component manufacturer and request maximum temp/time information.&nbsp; </FONT></DIV> <DIV>&nbsp;</DIV> <DIV><FONT size=1>Kathy</FONT><BR><BR>&gt;&gt;&gt; [log in to unmask] 02/23/01 03:05PM &gt;&gt;&gt;<BR></DIV> <DIV><FONT color=#0000ff face=Arial size=2><SPAN class=627024720-23022001>Hi Bob...</SPAN></FONT></DIV> <DIV><FONT color=#0000ff face=Arial size=2><SPAN class=627024720-23022001>Wouldn't the ability to do thermal damage to components be a function of the dwell time in the&nbsp;heat source... there is a time factor, isn't there, that affects the equation? If components can have their leads raised to 500+ F for normal&nbsp;SN63 soldering without damage..then there must be a similar technique involved..</SPAN></FONT></DIV> <DIV><FONT color=#0000ff face=Arial size=2><SPAN class=627024720-23022001></SPAN></FONT>&nbsp;</DIV> <DIV><FONT color=#0000ff face=Arial size=2><SPAN class=627024720-23022001>I believe the operator sets up a profile that soaks the assembly up to a given temp and then spikes the temperature to reflow temp for a few seconds as it passes that point&nbsp;in the oven... then it is immediately reduced in temp before the part bodies can actually absorb enough&nbsp;heat to raise the internal temperature high enough to do them damage.... I don't have all the details, I am just a PCB Designer... but I think that's how it's done... so&nbsp;setting a&nbsp;general limit would be impossible because there are more&nbsp;variations due to design and component location, and heat sinking, and thermal conductivity of the components and their susceptibility to thermal damage... I would guess your limit to be the most easily damaged part on the board... rather than an arbitrary general temp&nbsp;limit...</SPAN></FONT><FONT color=#0000ff face=Arial size=2><SPAN class=627024720-23022001> Perhaps there is some more to it than I know, though...</SPAN></FONT></DIV> <DIV><FONT color=#0000ff face=Arial size=2><SPAN class=627024720-23022001>Any one else?</SPAN></FONT></DIV> <DIV><FONT color=#0000ff face=Arial size=2><SPAN class=627024720-23022001>&nbsp;</SPAN></FONT></DIV> <DIV><FONT color=#0000ff face=Arial size=2><SPAN class=627024720-23022001>&nbsp;- Bill Brooks</SPAN></FONT></DIV> <DIV><FONT color=#0000ff face=Arial size=2><SPAN class=627024720-23022001></SPAN></FONT>&nbsp;</DIV> <BLOCKQUOTE style="MARGIN-RIGHT: 0px">   <DIV align=left class=OutlookMessageHeader dir=ltr><FONT face=Tahoma   size=2>-----Original Message-----<BR><B>From:</B> Bob Arciolla   [mailto:[log in to unmask]]<BR><B>Sent:</B> Friday, February 23, 2001   11:09 AM<BR><B>To:</B> [log in to unmask]<BR><B>Subject:</B> [TN]   temperature<BR><BR></DIV></FONT>   <DIV><FONT color=#000000 size=2>Good Afternoon, </FONT></DIV>   <DIV><FONT color=#000000 size=2></FONT>&nbsp;</DIV>   <DIV><FONT color=#000000 size=2>I am looking for some input as far as what is   the highest the top side temperature can be on a pcb going over the wave   solder before there is damage (bonding) to components (ex: transistors, IC's   etc). Any help would be appreciated. We are seeing around 254 degrees   F</FONT></DIV>   <DIV><FONT color=#000000 size=2></FONT>&nbsp;</DIV>   <DIV><FONT color=#000000 size=2>Thanks in advance,</FONT></DIV>   <DIV><FONT color=#000000 size=2></FONT>&nbsp;</DIV>   <DIV><FONT size=2>Bob Arciolla&nbsp;&nbsp; <A   href="mailto:[log in to unmask]">[log in to unmask]</A></FONT></DIV>   <DIV><FONT size=2></FONT>&nbsp;</DIV></BLOCKQUOTE></BODY></HTML>

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