TECHNET Archives

August 1998

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Paul Klasek <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 12 Aug 1998 16:57:18 +1000
Content-Type:
text/plain
Parts/Attachments:
text/plain (122 lines)
Hi Peter
Thanks God it's not a civil-aero , than I'd be worried .
Something must be forcing you to the epoxy (I wouldn't) .
And if you really insist on dragging SMD's through the wave :
I am sure Bob (is on copy) will tell you where you stand .
He's the author of the outrageous title :
"Wavesoldering Surface Mount PCB's With Zero Defect" ,
so blame him if you won't achieve the 100% pass :
[log in to unmask]

See you (wish you luck[you'll need more than that on class3])
Paul Klasek
http://www.resmed.com

PS
If you can not follow recommended manufacturers profile (may be
difficult on wave) , you know you're in the reliability gray zone .
The controlled cooling would help you on grain .
Details with Werner Engelmaier (he may be on the road) :
[log in to unmask]



> ----------
> From:         mudbugz[SMTP:[log in to unmask]]
> Sent:         Wednesday, 12 August 1998 12:37
> To:   [log in to unmask]
> Subject:      [TN] DFM guidelines
>
> I have a customer who is transitioning from 100% thru hole boards to
> designing boards with smt components.
>
> We gave them our basic DFM guidelines and they have laid out 2 boards
> following these guidelines.  When I saw the result of their first
> pass, I
> thought of two things.  1) we need to review our guidelines and 2) I
> need
> some advice from Technetters.
>
> The product is mil-aero building to IPC Class 3 using mil spec
> components.
>
> The assemblies are all laid out for a process flow of
> 1) reflow topside smt
> 2) epoxy bottomside smt
> 3) stuff thruhole
> 4) wave solder
>
> I have 2 questions:
>
> 1)  They have placed smt resistors as large as 2512's and capacitors
> up to
> 1812 on the bottomside.  I recall reading about problems with wave
> soldering large capacitors and having reliability problems.  Would
> this
> also apply to resistors?  What about the 1812 caps?
>
> 2)  They have also place 1206 resistors between the pins of .300 dips
> on
> the secondary side.  We had them orient the resistors parallel to the
> wave
> but unfortunately the dips are also oriented parallel to the wave (I
> need
> to check our DFM doc).  With this, they have positioned 6 1206's
> between
> the leads of a dip16 component and place 3 dip components in a row
> with 3
> 1206s between them.  ASCII art to follow.
>
> o - reps a dip lead
>
> [] - reps a 1206
> []
>
> <-----  conveyor direction
>
> o  []  []  o  []
> o  []  []  o  []
> o          o
> o  []  []  o  []    repeated 3 times in this direction
> o  []  []  o  []
> o          o
> o  []  []  o  []
> o  []  []  o  []
>
> Is anyone building anything like this successfully?  Volumes are less
> than
> 100/mo.
>
> Any input is appreciated.
>
> Peter Wong
> [log in to unmask]
>
> ################################################################
> TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services"
> section for additional information.
> For technical support contact Hugo Scaramuzza at [log in to unmask] or
> 847-509-9700 ext.312
> ################################################################
>

################################################################
TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################


ATOM RSS1 RSS2