"Given the lack of responses on this question I guess I have to
>continue my search elsewhere. Ah well, TechNet can't answer
>everything... "
(what you pay is what you get...it already went very far for
"free"..sometimes, too far...)...
jk ;-)
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]]On Behalf Of Graham Collins
>Sent: Wednesday, September 11, 2002 7:27 AM
>To: [log in to unmask]
>Subject: Re: [TN] BGA Under fill
>
>
>Hi Victor
>I see a misinterpretation of my original question and premise here.
>
>1) we are still in the theoretical area here, we have built boards
>but not yet underfilled. The BGA joints look perfect in both
>Ersascope inspection and X-Ray. There are no failing parts.
>
>2) We are about to start shipping product. This product goes into
>a vehicle, hence the vibration / shock surviveability requirement.
>
>3) what I'm looking for opinions on is simply how much voiding in
>an underfill material is expected / acceptable.
>
>Given the lack of responses on this question I guess I have to
>continue my search elsewhere. Ah well, TechNet can't answer
>everything...
>
>A good day to all.
>
>regards,
>
>Graham Collins
>Process Engineer,
>Northrop Grumman Canada
>Atlantic Facility
>(902) 873-2000 ext 6215
>
>>>> <[log in to unmask]> 09/10/02 03:51PM >>>
>Graham,
>
> Is the " VIBRATION " test within the expected evaluation or do
>you have a
>" MARGINAL " BGA joint, interface, to begin with. What do cross
>section of
>the failing BGA look like especially the Intermetallic Compound, IMC,
>region. Is this region smooth or evidence of some large nodules at 1000x
>after copper etchant application. Are the failing BGA at random or
>location sensitive. How many REFLOW temperatures did this PCBA received.
>BGA are ROBUST interfaces.
>
>victor,
>
>-----Original Message-----
>From: Graham Collins [mailto:[log in to unmask]]
>Sent: Tuesday, September 10, 2002 11:51 AM
>To: [log in to unmask]
>Subject: Re: [TN] BGA Under fill
>
>
>Victor
>1) TCE is compatable with the board and bga. Not sure why that would
>influence an answer concerning voids...
>2) main purpose is to provide support to solder joints (vibration
>resistance).
>3) I "hope" to fill the entire gap (100% fill) - but realistically some
>voids are likely to occur. What % of voids are reasonable and
>acceptable is
>the question.
>4&5) Loctite 3568 is applied to 2 sides of the component in accordance with
>the manufacturer's instructions, the board and part are preheated to 100C
>and following application the cure is 15 minutes at 150C.
>
>regards,
>
>Graham Collins
>Process Engineer,
>Northrop Grumman Canada
>Atlantic Facility
>(902) 873-2000 ext 6215
>
>>>> [log in to unmask] 09/10/02 10:17AM >>>
>Graham,
>
> Have you considered the thermal properties, TCE, of the Locite 3568
>product.
>Is this compatible with the TCE of the PCB and device carrier.
>
> What is the main PURPOSE of the proposed UNDER FILL application?
> How far into the device carrier to you HOPE to FILL?
> Will the LOCITE have to be cured?
> Is the PCB Pre Heated?
>
>
>Victor,
>
>-----Original Message-----
>From: Graham Collins [mailto:[log in to unmask]]
>Sent: Tuesday, September 10, 2002 6:09 AM
>To: [log in to unmask]
>Subject: [TN] BGA Underfill
>
>
>Good day TechNet!
>A question for the BGA / Underfill guru's out there (hopefully we have some
>of those online).
>
>Using a capillary flow underfill on a BGA, say a .050 pitch 26x26 array,
>what is a reasonable result to expect with respect to voiding? Should this
>process result in no voids, some voids, lots of voids? Given the size of
>this part (1.38" square), is it reasonable to expect a void free underfill?
>
>The particulars: I'm using Loctite 3568 underfill, applied using a syringe
>along two edges (L pattern). Product is on a hotplate at 100C.
>
>Thanks all!
>
>regards
>
>Graham Collins
>Process Engineer,
>Northrop Grumman
>Atlantic Facility of Litton Systems Canada
>(902) 873-2000 ext 6215
>
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