[hpsdr] PCB thermal issues

Sun May 6 17:17:36 PDT 2007

I'm not sure if any of you guys worried about balanced copper in the PCB stack up going form the middle out. We bang heads with the mechanical guys all the time at work because they want the solid planes distributed evenly throughout the stackup from the middle out so they don't warp or do other bad things in the wave. I know they try to keep them in sealed bags before use and want to bake them even before repairs or modifications. Sometimes it takes us 12 hours to get a board turned around for a modifiacation or repair. They usually want to bake a board for 4 house before they do anything. frank

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Today's Topics:

1. Re: OZY reflow blows up the board (Scott Cowling)
2. 2007/May/05 TeamSpeak audio (Mike Naruta)
3. Sl\older Reflow Problem (bstrick at n5brg.com)
4. HPSDR Files (Phil Harman)
5. Re: HPSDR Files (Eric Blossom)
6. Re: OZY reflow blows up the board (Chris Albertson)
7. Re: OZY reflow blows up the board (H. Gruchow)
8. OZY reflow blows up the board (Gerd Loch)
9. Re: OZY reflow blows up the board (Graham Haddock)

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Message: 1
Date: Sat, 05 May 2007 16:33:36 -0700
From: Scott Cowling 
Subject: Re: [hpsdr] OZY reflow blows up the board
To: hpsdr at lists.hpsdr.org
Message-ID: <6.1.2.0.2.20070505150809.0d1d44d0 at mail.tonks.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

Hi Horst,

I have asked our CM for the temperature profile that he uses to reflow the 
boards. I will get this from him on Monday and forward it to the list.

He says that they heat the board up gradually through 7 "zones", ranging 
from 100C in zone 1 through 190C-210C for zones 6-7 (the reflow zones). The 
board stays in the reflow zones for 30 to 60 seconds and then proceeds 
through three cool-down zones to bring it back down in temperature slowly.

In order to char the material the way you have done, I would guess that you 
would need over 100C hotter than 220C.

What are you using for your reflow oven? How do you determine that the 
temperature is 220C? Do you attach thermocouples to the board to determine 
the temperature profile? How long do you leave the PCB at the elevated 
temperature?

We have built hundreds of boards at 210C or a bit higher, and have seen 
nothing like what has happened to your board.

73,
Scotty WA2DFI

At 22:01 2007-05-05 +0200, you wrote:
>***** High Performance Software Defined Radio Discussion List *****
>
>Hi HPSDR DIYers
>look what happened to my OZY board during reflow.
>
>At about 195 degrees Celsius (383 F) the board started to pop and stink.
>Reflow temperature was 220 degrees Celsius (428 F).
>This is the result:
>Decoloration
>http://www.needles.de/HPSDR/decolor.jpg
>
>Delamination
>http://www.needles.de/HPSDR/delam.jpg
>
>Popcorn
>http://www.needles.de/HPSDR/pop.jpg
>
>Delamination side view
>http://www.needles.de/HPSDR/delam-side.jpg
>
>Here an example of a board treated exactly with the same temperature 
>profile about 10
>minutes after OZY:
>http://www.needles.de/HPSDR/compare.jpg
>
>Nothing happened here.
>
>Very disappointing. Anybody out there with a solution????????
>
>
>73
>Horst
>DL6KBF
>
>_______________________________________________
>HPSDR Discussion List
>To post msg: hpsdr at hpsdr.org
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------------------------------

Message: 2
Date: Sat, 05 May 2007 21:36:36 -0400
From: Mike Naruta 
Subject: [hpsdr] 2007/May/05 TeamSpeak audio
To: FlexRadio , HPSDR Reflector

Message-ID: <463D3124.6070503 at comcast.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

The 5/April Flex Radio TeamSpeak audio
***mp3*** file is available at:

< http://www.hamsdr.com/dnld.aspx?id=555 >

or

< http://www.hamsdr.com/dnld.aspx >

This session features Phil's unexpected
findings and future opportunities.

Mike - AA8K

------------------------------

Message: 3
Date: Sun, 06 May 2007 02:05:58 +0000
From: bstrick at n5brg.com
Subject: [hpsdr] Sl\older Reflow Problem
To: hpsdr at hpsdr.org
Message-ID: 
Content-Type: text/plain; charset="utf-8"

Hi Horst, DL6KBF

Your problem looks a little strange and I can offer a few comments:

It may be that your PCB was not dry and moisture was working its way out of the PCB and delaminating the solder mask material. The solder mask material may have also contained moisture or not been completely cured.

If this is the condition you have you may correct the problem by baking the PCB. The exact time and temperature needed may be determined by testing. I would start with a bake at 100 C for a minimum of 10 hours. This should dry out the moisture. You will need to solder the boards very soon after drying them or protect them from reabsorbing moisture.

The black material is more troubling. Could this material be something placed in the reflow furnace that should not have been there? Some low temperature plastic material that melted and found its way through the holes in the PCB. That is what it appears to be.

Double check the solder reflow profile temperatures. Be sure your furnace temperature is correct. The temperature you reported sounds low for a typical reflow profile but the results may indicate the temperature was much higher than you thought.

Your boards and components should have a JEDEC moisture sensitivity level (MSL) rating. This rating gives you information on how fast the parts absorb moisture. This is typically not as much of PCB problem as it is for the parts.

Hope this helps.

Bob, N5BRG

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Message: 4
Date: Sun, 6 May 2007 11:56:16 +0800
From: "Phil Harman" 

Subject: [hpsdr] HPSDR Files
To: "'High Performance Software Defined Radio Discussion List'"

Message-ID: <007101c78f92$7f556ad0$0301a8c0 at phil>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original

A number of folks have asked what files they need from SVN to bring up their 
home made Ozy and Janus boards.

Whilst you could download the entire directory be warned that there are some 
32,000 files there comprising about 1.1GB of data.

The HPSDR SVN URL is

< svn://206.216.146.154/svn/repos_sdr_hpsdr >

Note: this is not a web URL - you need a suitable program to read it e.g. 
TortoiseSVN (http://tortoisesvn.net/)

The directories of interest are:

\trunk\Janus-CPLDV2
\trunk\OzyV2-JanusV2
\trunk\KD5TFD\PowerSDR\HPSDR-1.6.3
\trunk\KD5TFD\OzyWrapTest
\trunk\KD5TFD\JanusTest

We need to document how to do this in a step-by-step manner and maintain it 
for the group - any one willing to volunteer please?

73's Phil....

------------------------------

Message: 5
Date: Sat, 5 May 2007 21:37:14 -0700
From: Eric Blossom 
Subject: Re: [hpsdr] HPSDR Files
To: Phil Harman 

Cc: 'High Performance Software Defined Radio Discussion List'

Message-ID: <20070506043714.GA17635 at comsec.com>
Content-Type: text/plain; charset=us-ascii

On Sun, May 06, 2007 at 11:56:16AM +0800, Phil Harman wrote:
> ***** High Performance Software Defined Radio Discussion List *****
> 
> A number of folks have asked what files they need from SVN to bring up their 
> home made Ozy and Janus boards.
> 
> Whilst you could download the entire directory be warned that there are some 
> 32,000 files there comprising about 1.1GB of data.
> 
> The HPSDR SVN URL is
> 
> < svn://206.216.146.154/svn/repos_sdr_hpsdr >
> 
> Note: this is not a web URL - you need a suitable program to read it e.g. 
> TortoiseSVN (http://tortoisesvn.net/)
> 
> The directories of interest are:
> 
> \trunk\Janus-CPLDV2
> \trunk\OzyV2-JanusV2
> \trunk\KD5TFD\PowerSDR\HPSDR-1.6.3
> \trunk\KD5TFD\OzyWrapTest
> \trunk\KD5TFD\JanusTest
> 
> We need to document how to do this in a step-by-step manner and maintain it 
> for the group - any one willing to volunteer please?
> 
> 73's Phil....
> 

Why don't you guys just create a tag that has copies of the
appropriate files/directories in it? Then folks could pull it down
with one command.

If this sounds like greek, see http://svnbook.red-bean.com ;)

73 Eric K7GNU

------------------------------

Message: 6
Date: Sat, 5 May 2007 22:47:39 -0700 (PDT)
From: Chris Albertson 
Subject: Re: [hpsdr] OZY reflow blows up the board
To: "H. Gruchow" , 'High Performance Software
Defined Radio Discussion List' 
Message-ID: <833185.91544.qm at web56510.mail.re3.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1

--- "H. Gruchow" wrote:
> > 
> Very disappointing. Anybody out there with a solution????????

I just was using a part tonight for something completely unrelated
and the data sheet had a warning that warned not to wave solder
the device unless it was first baked in an oven to remove water.

I think what happened was there was some humidity in the board
and your solder turned it into steam.
You may have to heat it for some hours before you solder it.

Chris Albertson
Home: 310-376-1029 chrisalbertson90278 at yahoo.com
Office: 310-336-5189 Christopher.J.Albertson at aero.org

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------------------------------

Message: 7
Date: Sun, 06 May 2007 08:16:33 +0200
From: "H. Gruchow" 
Subject: Re: [hpsdr] OZY reflow blows up the board
To: 'High Performance Software Defined Radio Discussion List'

Message-ID: <463D72C1.7060807 at needles.de>
Content-Type: text/plain; charset=ISO-8859-15; format=flowed

Hi all,
thanks very much for your input regarding the reflow failure of OZY.

One thing is for sure: I can trust my reflow oven. OZY was the 32nd board which I treated 
in the furnace. Mostly I use it for de-soldering boards in order to get the parts. But 
also soldering never failed so far.

The temperature profile I used for OZY was:

1. Preheat: 1?C/s from room temp to 110 ?C. Usually takes about 2 min.
2. Soak: 90s from 110?C to 150?C
3. Dwell: from 150?C to 180?C
4. Reflow: from 180?C to 220?C time 60s
5. Cooling in the oven with door open from 220?C down to 45?C before removing the board 
from the oven.
The max temp my oven can reach is about 270?C because above that it is switched of by a 
security thermo switch.
This all is controlled by a thermocouple and microcontroller.

I do not know what happened here. I have blisters all over the OZY board. My guess is 
moisture. But that does not explain the heavy de-coloration of the silk screen print into 
almost brownish color.

One thing is for sure: the other boards will be hand-soldered. I will not take another 
risk of loosing a board.
John, W9DDD, is there a spare OZY which I could order?

73
Horst
DL6KBF

------------------------------

Message: 8
Date: Sun, 6 May 2007 10:36:46 +0200
From: "Gerd Loch" 
Subject: [hpsdr] OZY reflow blows up the board
To: 
Message-ID: <000001c78fb9$aec953e0$1380a8c0 at pcglnt>
Content-Type: text/plain; charset="iso-8859-1"

Hi Horst,

if the board is manufactured properly (layer adhesion is according to
standards) there is the risk of delamination if there is too much humidity
incorporated in the board. This happens depending on relative humidity and
time of storage before soldering.

It is always a recommended procedure to bake the board at 120-130?C for
about 3 hours before assembling and soldering. Futhermore you should do the
same procedure with bga and other big chips because they could have a base
board of the same material and the same risk of delamination or popcorn
during the soldering process.

You should also be sure about the real (measured) temperture profile on your
board during the reflow process. It also depends on the amount of parts
assembled on the board and you have only assembled a few parts which could
result in a higher temperature.

If you have additional questions I will send you my tel.no. directly.

73 Gerd, DJ8AY

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Message: 9
Date: Sun, 06 May 2007 10:51:00 -0500
From: Graham Haddock 
Subject: Re: [hpsdr] OZY reflow blows up the board
Cc: 'High Performance Software Defined Radio Discussion List'

Message-ID: <463DF964.20904 at austin.rr.com>
Content-Type: text/plain; charset=ISO-8859-15; format=flowed

Horst:

In addition to an improperly cured PCB, and/or a board that contained
a lot of moisture, as the others have already discussed, I suspect that
you are using a oven where the thermal heating coils are directly
exposed to the PCB.

This adds another variable of infrared absorption to the surface heating
of the PCB.

In other words, if the infrared absorption of the particular materials and
dyes used in this board were higher than average, the surface temperatures
soldering this board could have been much higher than your other boards,
and all the oven settings were still the same. Your oven probably
measures air temperature, not the actual surface temperature of the board.

I suspect that the solder mask and possibly the screen printed legend
absorbed a lot more infrared energy than the boards you normally
solder, and contributed to much higher local temperatures than normal. 
If the main heat transfer method is hot air, and the PCB is blocked from
"seeing" the heating coils then the surface temperatures would be a lot
more uniform.

It could have still been an improperly cured PCB and/or excess
moisture in the PCB, also.

--- Graham / KE9H

==

H. Gruchow wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi all,
> thanks very much for your input regarding the reflow failure of OZY.
>
> One thing is for sure: I can trust my reflow oven. OZY was the 32nd board which I treated 
> in the furnace. Mostly I use it for de-soldering boards in order to get the parts. But 
> also soldering never failed so far.
>
> The temperature profile I used for OZY was:
>
> 1. Preheat: 1?C/s from room temp to 110 ?C. Usually takes about 2 min.
> 2. Soak: 90s from 110?C to 150?C
> 3. Dwell: from 150?C to 180?C
> 4. Reflow: from 180?C to 220?C time 60s
> 5. Cooling in the oven with door open from 220?C down to 45?C before removing the board 
> from the oven.
> The max temp my oven can reach is about 270?C because above that it is switched of by a 
> security thermo switch.
> This all is controlled by a thermocouple and microcontroller.
>
> I do not know what happened here. I have blisters all over the OZY board. My guess is 
> moisture. But that does not explain the heavy de-coloration of the silk screen print into 
> almost brownish color.
>
> One thing is for sure: the other boards will be hand-soldered. I will not take another 
> risk of loosing a board.
> John, W9DDD, is there a spare OZY which I could order?
>
> 73
> Horst
> DL6KBF
>
> _______________________________________________
> HPSDR Discussion List
> To post msg: hpsdr at hpsdr.org
> Subscription help: http://lists.hpsdr.org/listinfo.cgi/hpsdr-hpsdr.org
> HPSDR web page: http://hpsdr.org
> Archives: http://lists.hpsdr.org/pipermail/hpsdr-hpsdr.org/
>
>
> 

------------------------------

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