TECHNET Archives

January 2016

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:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Wed, 20 Jan 2016 21:50:35 +0000
Content-Type:
text/plain
Parts/Attachments:
text/plain (64 lines)
And the re-forming or non-standard forming does not cause the component body to be up off of the PWB, assuming it is not designed to be mounted that way. If the board is normally conformal coated, not having the body flat to the PWB and thus captured in the coating could cause a reliability issue from vibration.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Wednesday, January 20, 2016 3:44 PM
To: [log in to unmask]
Subject: Re: [TN] Terminal Bent More than 10% Diameter

You do not state in which direction the leads were formed in order to meet all of the requirements listed in IPC-610 or J-STD-001, inwards, outwards, up, down, and in the case of round leads, sideways. Technet always strips all attachments, but Steve will probably post a link to your picture for us if you send it to him directly, along with a gift certificate to the local microbrewery. :) I'm betting he will do it in response to this posting however.
But after reviewing both standards, I cannot find anything that says an inward bend that is less than 90 degrees (where the heel is closer to component body than the knee is) is a reject condition. I know that you can form the leads such that the heel is further out from the body than the knee, or greater than 90 degrees. Not sure about inwards.
Flat leads cannot be bent sideways, but round leads can. All of that is pretty well covered, except for inward bends.
AS LONG AS;

*         The lead is not bent in any direction within one lead thickness from the point where it exits the body.

*         There is sufficient strain relief (the bend radius itself is at least one lead diameter or thickness, even though the general bend angle is less than 90 degrees).

*         There is no reduction of electrical clearance as a result of the re-forming.

*         There is no cracking of the lead as a result of the forming, nor are there any gouges or scratches exceeding the posted requirements in the standards.

*         All of the lead-to-pad placement and solder joint requirements are met.

*         No stress was applied to the lead at the point where it enters the body at any time during the forming or re-forming.
Then it should not pose any reliability issues. I would need to see a good picture to state this for certainty.

dean


From: Ricardo Moncaglieri [mailto:[log in to unmask]]
Sent: Wednesday, January 20, 2016 1:30 PM
To: Stadem, Richard D.; Steve Gregory
Subject: Env: [TN] Terminal Bent More than 10% Diameter

Steve, Richard,
Any feedback from your side? Is will be to much appreciated from my side....
brgds,Ricardo

>>> Ricardo Moncaglieri 
>>> <[log in to unmask]<mailto:[log in to unmask]>> 
>>> 19/01/2016 17:45 >>>
Colleagues,
We are considering in a space (IPC class 3) application assembly, a component similar to case T0 257 whose six gull wing terminals (three on each side and their seals are vitrified) had to be blent more than 10% (IPC J-STD-001 7.1.1) of their diameter (1 diameter) in order to be mounted due to a wrong gerber design The gull wing terminal zone shape well soldered on the pcb pad was not modified, terminal was bent on its straight zone. Vitrified seal was not affected at all. Thermal plane was fully soldered on thermal plane pad, cause of that rework desoldering component could be more complicated.  Pcb base material is FR4.
Could anyone make me know his/her consideration as per background experience on a case like this one about stress relief performance? Could it have been affected to cause a solder crack under manufacturer specified working conditions?
Matter here is that we have no enough time to run a stress analysis (ciclic stress simulation on three axes) and reworking as I said upper could be hazardous due to complexity of assembly.
Will appreciate too much your feedback/considerations.
Attached photo is x40 magnified.
Keep awaiting.
brgds,Ricardo

______________________________________________________________________
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]<mailto:[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