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December 2011

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Subject:
From:
Steven Creswick <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steven Creswick <[log in to unmask]>
Date:
Wed, 7 Dec 2011 11:26:12 -0500
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Steve,

I purchased the MU 1000-CK from AmScope.  A smidgen under 10 Mpixels, with 1.67 x 1.67µm pixels. Here is the link to the camera on their site  http://store.amscope.com/mu1000-ck.html

It is $315 with calibration slide, or $295 without.  The cal slide they provide is 1mm overall, with 0.01 mm smallest divisions.  Other cal slides are available for around $60.

It does both live video [w/frame capture] and still frame, although I have not worked with the live video aspects of it thus far.  Mostly the still frame, generic images.

Have been using it on my Wild microscope here at my desk, or with my B&L Sterozoom3 [solder 'squirt' pictures] downstairs.  Works on the eyepieces of both.

AmScope has updated software for the unit available on their site.  

Software is pretty intuitive, but manual suffers from normal translation ambiguities in spots.

My current focus is on getting the colors corrected when using my halogen lamp source on the Wild.

Service and support has been good from AmScope.  I can provide the link to the parent mfr if you like, but their web site is not completely functional.

Steve C

Disclaimer - I am not associated with AmScope in any way that I am aware of other than the purchase of a few items from them in the last 1.5 years



-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]] 
Sent: Wednesday, December 07, 2011 8:56 AM
To: 'TechNet E-Mail Forum'; 'Steven Creswick'
Subject: RE: [TN] NTC - Experimenting with new microscope camera

Steve,

What kind of camera do you have?

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: Wednesday, December 07, 2011 7:38 AM
To: [log in to unmask]
Subject: Re: [TN] NTC - Experimenting with new microscope camera

All,

Thanks for your inputs.

I am in alignment with Richard & Wayne in the comparison of FC solder extrusion into adjacent voids.  It does indeed happen that way!

In general, I have observed that if reflowable coatings are over-molded, glob-topped, or covered with a reasonably high modulus material and there exists a path to the 'outside', or to a cavity of some form, upon reflow everything expands and the liquid solder squirts/extrudes itself to the outside, or into the cavity [position of lower external pressure].  This even occurs below the liquidus of the solder with moderate temp cycle excursions - especially for FC's.

My perspective WRT plastic encapsulated devices such as this, is that it is NOT a good thing.  Also as Wayne says, a(nother) potential leak path. 


Getting pretty comfortable with the camera [video and still] and able to actively/accurately measure in various units.  Able to import/export the calibration file so as to be able to have a calibration file for each scope.  As usual, new software takes some getting used to, but is pretty intuitive.

Regards

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Thayer, Wayne - IIW
Sent: Tuesday, December 06, 2011 5:36 PM
To: [log in to unmask]
Subject: Re: [TN] NTC - Experimenting with new microscope camera

I think Richard's on the right track with the solder plated leads.  That's all you need to make this happen:  During reflow the molding compound puts pressure on molten solder on the lead, forcing the solder to "squirt" out onto the lead which has no flux on it, so the solder beads up on top of the oxides.

This phenomenon is the bane of flipchips: if the solder joints can find a void (such as may happen due to poor adhesion between underfill and the surface of the die or the surface of solder mask), then solder will "squirt" in causing shorts.

On your capacitor, it is probably no big deal except that you have an easier path for moisture to get in and do nasty things.

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Tuesday, December 06, 2011 2:28 PM
To: [log in to unmask]
Subject: Re: [TN] NTC - Experimenting with new microscope camera

Not necessarily the supplier, at least not directly.

That type of solder beading, for lack of a better term, shows up like that during tinning/plating processes. The reason for it is due to residues from the encapsulation or molding on the lead near the body that prevent solder wetting. Those may be droplets of non-wetted solder from tinning, not necessarily solder squeeze-out from under the molded package. If it was solder from under the molded package, why did it not wet out onto the lead?
But no matter the source of the solder, it showed up as an issue due to poor solderability in the area where the lead enters the package body.

Also consider the leads may have been stamped from a sheet of metal that had been pre-coated with solder, in which case the squeeze-out could occur during reflow soldering later.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Tuesday, December 06, 2011 11:48 AM
To: [log in to unmask]
Subject: Re: [TN] NTC - Experimenting with new microscope camera

I've seen this before as well on similar diode packages.  I don't think we were ever able to discover the actual root cause, though the supplier would almost certainly be the culprit.

Leland



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: Tuesday, December 06, 2011 12:20 PM
To: [log in to unmask]
Subject: [TN] NTC - Experimenting with new microscope camera

All,

I recently purchased a microscope camera and have been trying it out on various items.

Have placed two photos on the IPC website which I believe illustrate a tin [or solder plated] lead on which the plating has reflowed and squirted out from beneath the mold compound.

Have seen similar manifestations with improperly processed solder & glob-topped assemblies.

http://ipc-technet.groupsite.com/gallery/22093  filed alphabetically under folder name - Tin Plated Leads

Anyone else have other ideas?

Please keep in mind that this an old modem board of unknown chronological vintage that I had in my 'scrap bin'.  It just happened to be the subject of my scrutiny.

I see no evidence of solder balls, etc on the board.

Steve




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