Franklin

To the contrary, I originally became interested in this issue because the
peel strength of copper treated with brown oxide and laminated to a
substrate was generally a good deal less than that of black oxide. The
assembly and field performance on a whole was the same for the two
treatments; they both performed well.

When the same comparison was made using the T260 test similar results were
obtained. As I showed in my analysis, the T260 test only generates a shear
stress which is the case when the board or panel undergoes a free expansion
such as in reflow. The peel test always generates both a shear and a tensile
stress. As we all learned in our initial materials course, the shear rupture
strength of most any material is considerably different from the tensile
rupture strength. Consequently, it is very important to use a test that
produces the type of stress that will be encountered in the field.

Best regards

Lee

J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389


----- Original Message -----
From: "Franklin D Asbell" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, June 02, 2006 2:40 PM
Subject: Re: [IPC-600-6012] Bond Strength -vs- Peel Strength


> If I'm reading the 2 methods correctly, bond strength does not make any
> consideration for laminated foil (laminated by the pwb fabricator) and
> this
> test may often be performed on double or even single-sided product;
> whereas
> peel strength focuses on the foil laminated to the product by the pwb
> fabricator.
>
> Am I understanding the difference correctly?
>
> Franklin
>
> -----Original Message-----
> From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Lee parker
> Sent: Friday, June 02, 2006 11:04 AM
> To: [log in to unmask]
> Subject: Re: [IPC-600-6012] Bond Strength -vs- Peel Strength
>
> Chris
>
> In the paper referred to below I demonstrated that the shear component of
> the peel rupture is of the same order of magnitude as the tensile
> component
> and that both stress are dependent upon the local radius of curvature at
> the
> rupture point; which is not controlled. This paper also contained numerous
> examples of the inadequacy of the peel test to discriminate between
> acceptable and unacceptable bonding of copper foil to substrate. When
> failures occur due to thermal expansions etc The rupture stress is
> entirely
> shear ( again see the paper). What is needed is a test that simulates this
> condition. The T260 test is a good beginning, but has other issues.
>
> Best regards
>
> Lee
>
> J. Lee Parker, Ph.D.
> JLP Consultants LLC
> 804 779 3389
>
>
>
> ----- Original Message -----
> From: "Chris Mahanna" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Friday, June 02, 2006 11:43 AM
> Subject: Re: [IPC-600-6012] Bond Strength -vs- Peel Strength
>
>
> Of course one could and should separate tensile and shear properties.
> But,
> we as a standard body must think about the cost of testing and the return
> on
> that investment.  Essentially, the "bond strength" test (which is supposed
> to measure tensile only) is too expensive to be done properly.  Too many
> uncertainties and non-linearity (probably caused by not truly being able
> to
> separate tensile and shear).  That's why Susan called the method
> "Provisional".  And that's why Russ only does it as a "process indicator",
> or whatever you'd like to call it.
> The historical "rework/unsupported hole bond strength" testing is pretty
> good methodology because it controls many of the uncertainties through
> coaxial geometry.  This test vehicle could be mimicked on a new board
> designs, but I haven't seen it done.  Of course, it also incorporates the
> rework heat cycles.
>
> I would conjecture that:
> 1) there are people out there that understand this much better than I, and
> 2) they would say that while peel strength is a combination of tensile and
> shear, it is controlled by defining the bend radius (thickness of foil and
> no surface finish)
> 3) the peel methodology is capable of discriminating "good" foil
> laminating
> from "bad", pass/fail requirements are in place, and testing is already
> required.
>
> IMO, to add bond strength testing as a spec. req. one would need to show
> that peel methodology is not capable of discriminating "good" foil
> laminating from "bad".
>
> Chris
>
> Chris Mahanna
> Quality Manager
> Robisan Laboratory Inc.
> 6502 E 21st Street
> Indianapolis, Indiana 46219
> phone 317.353.6249
> fax 317.917.2379
>
>
> -----Original Message-----
> From: IPC-600-6012 [mailto:[log in to unmask]]On Behalf Of Lee parker
> Sent: Wednesday, May 31, 2006 10:29 AM
> To: [log in to unmask]
> Subject: Re: [IPC-600-6012] Bond Strength -vs- Peel Strength
>
>
> Franklin
>
> At the 2005 Expo I presented a paper that quantified both of these
> measurements in terms of the first principals tensile and shear stresses
> at
> the point of rupture. The peel test produces a simultaneous and
> essentially
> uncontrolled combination of both tensile and shear stresses. Ideally you
> would prefer only one of these stress to be present an the extent
> measurable. The thermal stress test produces only a shear stress between
> layers of materials. The drawback here is that the temperature is dynamic
> and consequently the stress changes until the entire package reaches
> thermal
> equilibrium. Of the two I prefer the thermal test, but the drawbacks can
> be
> signoficant.
>
> Best regards
>
> Lee
>
> J. Lee Parker, Ph.D.
> JLP Consultants LLC
> 804 779 3389
>