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September 2014

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Subject:
From:
Wayne Thayer <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wayne Thayer <[log in to unmask]>
Date:
Tue, 30 Sep 2014 13:19:30 +0000
Content-Type:
text/plain
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text/plain (159 lines)
I have quite a bit of experience with press fits, but I'm certainly prepared
to learn something new. Are you saying that you've seen press-fit pins where
the pin and package are so strong that despite the tremendous side forces
during pressing which are forcing the pin to be centered in the hole, they
end up where the package aligns them?

I'd like to see such a connector. Could you provide a part number for this?
All of the press-fits I've dealt with have deliberately sloppy fits in the
package so that they will self-align easily into the holes which will
hopefully make them less susceptible to buckling on insertion.

Wayne

-----Original Message-----
From: Tan Geok Ang [mailto:[log in to unmask]] 
Sent: Monday, September 29, 2014 11:12 PM
To: TechNet E-Mail Forum; Wayne Thayer
Subject: RE: [TN] FW: [TN] DIMM Socket press-fit Misalignment

There are tolerances in PTH drill positions, holes size, connector pins
alignment, etc. I am not surprised with the alignment in the picture. Can't
really see there are pins protrusion to the bottom side of the board. The
"eye" of the pin v.s. hole dimension is very important.

________________________________________
From: TechNet [[log in to unmask]] on behalf of Wayne Thayer [[log in to unmask]
COM]
Sent: Monday, 29 September, 2014 7:36:47 PM
To: [log in to unmask]
Subject: Re: [TN] FW: [TN] DIMM Socket press-fit Misalignment

Lyon-

The pictures do not look good--the defect cited is a "process indicator",
and demands closer inspection. I am not aware of any IPC standards
applicable in this case because analyzing press-fit from a visual
perspective(or any non-destructive technique) is too limiting.

The press fitting process assures that all pins end up exactly centered in
the holes because the point is supposed to be in the middle, and the sides
of the pin are supposed to collapse evenly. If the pin is off center, there
are very high corrective forces induced which push it back on center.

Examine the pins before pressing and make sure the splitting process was
done correctly. Measure the insertion/extraction force on a single pin and
verify you are within the stated range. Carefully measure the hole diameter
and make sure it is within the press-fit manufacturer's specifications.

The most likely scenario is that the holes are too big, so the pins are
barely scraping as inserted. If that's the case, you should be able to pull
off the entire connector without much effort. The pins need to be
considerably deformed as they swage into the through-hole plating.

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: Wednesday, September 24, 2014 1:34 PM
To: [log in to unmask]
Subject: Re: [TN] FW: [TN] DIMM Socket press-fit Misalignment

To my understanding there is no correlation between the centering of the
Press Fit Pin on the exit PTH versus the location of the contact wipe pin.

Victor,

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Wednesday, September 24, 2014 8:56 AM
To: [log in to unmask]
Subject: Re: [TN] FW: [TN] DIMM Socket press-fit Misaiming

Hi Lyon!

Your picture is posted. The link is here:

http://stevezeva.homestead.com/DIMM_Pins.jpg

Steve

On Wed, Sep 24, 2014 at 7:29 AM, Lyon Yuan wrote:

> Hi Steve,
>
> Please help to post picture.
>
> Lyon Yuan
>
> -----Original Message-----
> From: [log in to unmask] [mailto:[log in to unmask]] On Behalf 
> Of Louis Hart
> Sent: Wednesday, September 24, 2014 8:53 PM
> To: [log in to unmask]
> Subject: Re: [TN] DIMM Socket press-fit Misaiming
>
> Lyon, TechNet had a place to put pictures at one time. I used it. But 
> now, I do not see on the IPC a mechanism for posting pictures for all 
> to see.
>
> People have been using Steve Gregory's 'service', as you may have noticed.
> But the IPC depository was a place TechNetters could use directly.
> Has something changed at IPC so we can no longer post pictures?????
> Louis Hart
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Lyon
> Sent: Wednesday, September 24, 2014 7:34 AM
> To: [log in to unmask]
> Subject: Re: [TN] DIMM Socket press-fit Misaiming
>
> who should I send picture to ? so you can see it? Lyon Yuan 发自 Android
> 网易邮箱 On 2014-09-24 19:27 , Lyon Wrote: Folks, Recently,Customer 
> reported that found a field return unit with DIMM socket press fit pin 
> seems misaligned. you can see that some pins at the edge were 
> misaligned to one side and potentially caused contact issue. But i see 
> all of boards with same misalignment pin in production line.My 
> customer question us how do you think this is acceptable? Any IPC 
> standand mention it? How did it happen on this misalignment? Lyon Yuan
> 发自 Android 网易邮箱
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