TECHNET Archives

January 2006

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:
Mon, 30 Jan 2006 12:55:54 -0600
Content-Type:
text/plain
Parts/Attachments:
text/plain (62 lines)
The inspector was correct to reject the small amount of birdcaging, as he/she has no other criteria to go on except what is listed in IPC 610, both for the strand separation issues and the wetting issues.
The magnet wire varnish should be stripped off chemically by the component vendor, and he should be providing the component pre-formed without any birdcaging. 
Unless there is something on the component print that allows some separation in the bend, the inspector has nothing to hang his hat on.
I would get an ECO for the component print to define: 
1. The length of the "foot".
2. The foot to be coplanar with the bottom of the component (+-.005")
2. The portion of the lead from the end up past the bend about .080" to be free of varnish. Pre-tin this portion, and when the component is soldered to the assembly the bend will be filled with solder, making the birdcage a redundant issue.  

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stephen Gregory
Sent: Monday, January 30, 2006 10:28 AM
To: [log in to unmask]
Subject: [TN] Prepping Stranded Litz wire for soldering...

Mornin' All!

I hope you all had a good weekend! We finally got some rain here, it was only a half inch, but it was better than nothing...

My question has to do with Litz wire. We're building an assembly that has an inductor that we bond to the core, then hand solder the two stranded Litz wires to surface mount pads on the board. You can see some photos here:

http://www.stevezeva.homestead.com/files/Coil_Solder_Joints.jpg

http://www.stevezeva.homestead.com/files/Coil_Solder_Joints_2.jpg

The solder joint appearance hasn't pleased the source inspector, he's been rejecting these. We've been having a hell of a time getting decent looking joints because of the residue from the insulation on these wires.

The manufacturer of the part says all they do to prep the ends of the wires is dip them in a solder pot to melt the insulation and tin the ends. But that doesn't get all the insulation off. Residue from the melted insulation winds-up migrating up through the joint when we're trying to solder them to the pads on the board. You'll see voids, and non-wetting on some of the strands. That's what the source inspector is rejecting them for.

In the photos, those are just about the best we could get. I know they look really excessive. In one photo you can see where the source inspector was rejecting for "strand separation".

I'm looking for some suggestions on how best to prep the ends of this wire so that we can solder it to this board. 

I was thinking about crimping some sort of small diameter copper tubing over the ends (after it was tinned as best as we could), then forming a "foot" to solder to the pad?

Is there a better way to prep this wire? I did a search and found that there are all kinds of different suggestions for prepping this wire, from using a blow torch, to paint remover, to dipping it in molten aspirin...yes that's right, molten aspirin!

I've asked for a sample of the stranded wire from the inductor manufacturer and I'll be doing some experimentation on it.

All I know is that I'm getting a headache over this wire....
 
Stephen Gregory
Senior Process Engineer
LaBarge Incorporated      
Tulsa, OK 74146
(918) 459-2285
(918) 459-2350 FAX
  

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------

ATOM RSS1 RSS2