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August 2004

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Subject:
From:
Steve Gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Mon, 16 Aug 2004 11:15:47 EDT
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Hi Pankaj!

I have a board like that here that we build, and at first it gave me the same
problems you face.

This might sound out of the ordinary, but you do what you have to do when you
are faced with a board that is unusually thick and has heavy copper planes in
it. I run the assembly twice through my wave machine. Once with the wave
pumps off to pre-heat it, then once again with the pumps on. You could accomplish
the same thing by pre-heating the board in a oven, but I don't have a oven
close by my wave machine, so I use the wave pre-heaters instead.

I also flux the topside of the board manually to help aid heat transfer a
little, and it seems to improve capillary action too. I also use both the rotary
and laminar wave pumps.

I have a Electrovert Electra machine with a Optiflux-1 spray fluxer. The
machine has three bottomside convection pre-heaters. I run my beltspeed at 3.5
feet per minute, and my pre-heaters are set at 270 F., 280 F., and 300 F. going
from the entrance to the solderpot. I use a Alpha 615-25 RMA flux. I leave the
fluxer on for both passes through the machine.

I use a fixture for the board that has solder dams around all four sides, so
I can run the board quite a bit deeper in the wave than normal.

As far as rework on the board I use a system from Zephrytronics
(http://www.zeph.com/) called a ZT-6 Hot Air Fountain. I was turned on to this system from
a Technetter named Steve Sauer. I couldn't rework anything on this board
without damaging pads, barrels, or the PCB itself until I got the ZT-6.

I put some pictures up on my web page a while back of me pulling a 96-pin
connector out of that board. Look at:

http://www.stevezeva.homestead.com/files/ZT6.jpg
http://www.stevezeva.homestead.com/files/TakingTemperature.jpg
http://www.stevezeva.homestead.com/files/JustAbout.jpg
http://www.stevezeva.homestead.com/files/ItsOut.jpg

There's a picture of the unit, me monitoring the temperature with a
hand-held, non-contact, I/R Thermometer, me getting ready to pull the connector out,
and then me finally pulling the connector out with a pair of tweezers...couldn't
be easier!

-Steve Gregory-

Dear Tecnetters " Hi "

we have a PCB of 12 layers with thickness of  3.2mm.

Problems we are facing are

1.Solder doesn't come top side and as the thickness is more than pre
established components lead lengths ,like DIP's  IC,connectors pins , it is
mandatory for us that a fully wetted solder is visible from primary side.

2.Many of the components are on the ground plane , so if any rework is
required we could not do so by soldering iron ( we tried weller 150 watts
iron with temp. 450 deg. C , but we could not remove an electrolytic cap.)

3.What IPC tells about the power connector lead protrusion and the top side
solder fill up for the same. As the IPC 610B states in components
installation 3.5.3.1/note: that lead protrusion may not be visible in more
than 2.3mm thick boards.How we interrelate it with soldering 4.1/vertical
fill of soldering 75 % in this case.

4.We are using AC by pass connector  "PICH47F400A1" with recommended PCB
hole dia 2.1mm for lead dia 1.6mm , Is it enough for 3.2mm thick PCB too.


Any body have the soldering experience of 3.2mm thickness PCB. what
parameters ( wave height/ pre heater temp ) of wave soldering M/c matter in
this case .Is chip wave is useful , Pls. share your exp. it will be highly
appreciated.

Thanks

BR
Pankaj Karnwal
Jr. Engineer QA

Barco Electronics System  (P) Ltd.
Plot no. A- 4 & 5, Sector- 5
G.B Nagar, Noida  - 201301
India
Tel .+91-120-2421651-660 Ext.211
Fax.+91-120-2421691
WWW.barco.com
mailto:[log in to unmask]

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