TECHNET Archives

March 2014

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:
Mike Fenner <[log in to unmask]>
Reply To:
Date:
Sat, 1 Mar 2014 12:08:47 +0000
Content-Type:
text/plain
Parts/Attachments:
text/plain (205 lines)
Well you can solder Aluminium without flux. Three ways, some of which
probably are capable of being used here, alone or in combination.
1) Scrubbing with Sn/Zn solder. Sn/Zn intermetallics are very hard and will
abrade the Al2O3 oxide, if done on point of melting you can achieve a solder
joint.
2) Ultrasonics can do the same thing with less skill involved
3) Use a reactive solder
Possibly some combination of these could be made to work by
- plugging the holes and reflowing
- inserting wires and soldering them
- using a sort of rivet and soldering heads
Off the wall: People who make power modules have similar problems.
In Google images search "DBC die wire bonds" and you will see quite thick
wires and ribbons stitching die - some on multi levels. Also spring clip
things bonded for vertical connections, might give you some ideas.

Regards 
 
Mike


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Jackson
Sent: Friday, February 28, 2014 6:43 PM
To: [log in to unmask]
Subject: Re: [TN] Aluminum fine-line PCB

Thanks Syed and Pat,

Our challenge is making the connection between layers. We have used 
zincating to apply an Immersion White Tin finish to the boards and it 
works well, where there is aluminum. The trouble is with connectivity 
across the FR4/PI material sandwiched between the aluminum outer layers 
on vias and edge plating. Even though the dielectric is usually only 
0.0021" thick (before pressing) the zincating doesn't adhere.

We have a solder flux combo which does work well with the solder wick 
braid via solution we use today but we would dearly love to find a more 
elegant solution.

- Paul

On 2/28/14 8:58 AM, Ahmad, Syed wrote:
> Electroless Ni after zincate over device Al pads is commonly used as under
bump metallurgy (UBM) for flip chips for solder ball attach/formation.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Patrick Goodyear
> Sent: Friday, February 28, 2014 10:50 AM
> To: [log in to unmask]
> Subject: Re: [TN] Aluminum fine-line PCB
>
> Paul,
>
> You can plate aluminum with zinc then nickel then copper.   The zinc
> keeps the aluminum from oxidizing the nickel replaces the zinc and the
> copper over plates the nickel.    I worked at a power plant, they use
> various products to decrease the oxide layers on buss work not sure what
works on aluminum but they use Cool Amp (dry silver plate solution)
> De-Ox-It a conductive grease and some other products.    I think there
> are some solders that will work with aluminum or low temp brazing rod, I
think it is all about the flux, Aluminum overlays an oxide layer almost
immediately and that is a dang good insulator.  TIG or MIG welding aluminum
is about the cover gas keeping the air out of the molten metal, my step dad
could weld aluminum with a Oxy acetylene torch, not a clue
> how he did it.      If you marry it with a dissimilar metal it will
> cause major galvanic corrosion, I deal with it on a daily basis, using
> stainless steel bolting in anodized aluminum mounting brackets.    It
> takes about 2 weeks and the stainless and aluminum become one large
> white ceramic mess faster if the anodizing is disturbed.    Look around
> in the Utility industry since they use aluminum buss work all of the time,
and bolt it to copper.
>
> Pat Goodyear
>
>
> On Fri, Feb 28, 2014 at 7:39 AM, Paul Jackson wrote:
>
>> Hi Wayne,
>>
>> Thanks for the ideas. The sputtering is one we really hadn't
>> considered and I am very interested into looking into it more.
>>
>> I'll send you the guide directly and if you are interested in seeing
>> what the boards look like they are on the cover of Time magazine, Feb
>> 17, 2014 edition.
>>
>> - Paul
>>
>> On 2/27/14 2:51 PM, Wayne Thayer wrote:
>>> Hi Paul-
>>>
>>> A fascinating application!
>>>
>>> When plating copper into vias is not possible, or is inconvenient,
>>> "macro-scale" designs use eyelets.  You can't attach to inner layers
>>> reliably with them, and I always found the external contacts to be
>>> unreliable as well, so we made sure they were soldered on both sides.
>>> But they can look a lot more professional than braid, and lend
>>> themselves to automation.  I presume that your application would be
>>> much tinier than any commercial eyelets and tooling sets could
>>> handle, but theoretically you could probably come up with something
>>> like that.
>>>
>>> Another possibility might be an organo-metallic paste like ORMET
>>> sells, or perhaps some kind of sintering nano-metals.  But either of
>>> these options would probably have trouble getting through the
>>> aluminum oxide to make a connection without some kind of assistance
>>> from a suitable flux.  Probably a lot of risky development would be
>>> required for this path, but it has the potential to be scalable down
>>> to your preferred geometry.
>>>
>>> Yet another possibility is that aluminum is commonly sputtered onto
>>> silicon wafers, so why not get it deposited into the holes?
>>> Activation and masking problems, but the prettiest and easily
>>> scalable to tiny geometries.
>>>
>>> I don't understand your process (I'd like to get the little guide
>>> available on your company's website, but for some reason it either
>>> isn't sending out the email or my spam filter is eating it).  But
>>> another way people build interesting boards is to put the vias in
>>> before the outer metal goes on.
>>>
>>> Wayne
>>>
>>> -----Original Message-----
>>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Jackson
>>> Sent: Thursday, February 27, 2014 2:31 PM To:[log in to unmask]
>>> Subject: [TN] Aluminum fine-line PCB
>>>
>>> Hi All,
>>>
>>> I'm new here to Technet so I'll ask you to be gentle, at least at
>>> first.
>>> We are manufacturing fine-line aluminum trace PCBs and our customers
>>> are mainly wirebonding chips directly on the aluminum and attaching
>>> components on selective copper pads. We are trying to find a more
>>> elegant way to achieve through-hole connectivity than our current
>>> method of filling vias with solder wick braid and aluminum solder
>>> paste. It works but it's "fugly". The aluminum is 30µm and the
>>> dielectric is typically 2.1mil. Any ideas would be greatly
>>> appreciated.
>>>
>>> Paul Jackson
>>> Omni Circuit Boards
>>> (855) 798 9717
>>> *w*ww.omnicircuitboards.com
>>>
>>>
>>>
>>> _____________________________________________________________________
>>> _ This email has been scanned by the Symantec Email Security.cloud
>>> service.
>>> For more information please contact helpdesk at x2960
>>> [log in to unmask]
>>> _____________________________________________________________________
>>> _
>>>
>>>
>>> _____________________________________________________________________
>>> _ This email has been scanned by the Symantec Email Security.cloud
>>> service.
>>> For more information please contact helpdesk at x2960
>>> [log in to unmask]
>>> _____________________________________________________________________
>>> _
>>>
>>
>> --
>> Omni Circuit Boards Ltd.
>> 3-12760 Bathgate Way
>> Richmond, B.C.
>> Canada V6V 1Z4
>>
>> Tel. 604.276.9717
>> www.omnicircuitboards.com
>>
>>
>> ______________________________________________________________________
>> This email has been scanned by the Symantec Email Security.cloud
>> service.
>> For more information please contact helpdesk at x2960 or
>> [log in to unmask]
>> ______________________________________________________________________
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________

______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________

ATOM RSS1 RSS2