I want to add some more...
- Direction of chip part is same as reflow direction (parallel instead of
perpendicular): Tombstone.
- Size of electrode in one end of part is bigger than the other side:
tombstone.
- Size of copper pads are different each other: tombstone
- For tiny part such as 0201": if too much N2: tombstone.
- Gradient of Profile NG: Tombstone.
- And ... 8-D
all for now,
Quoc
----- Original Message -----
From: "TDK" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, May 11, 2005 8:26 AM
Subject: Re: [TN] Tombstone
> Yes, very true. I have seen some fab docs actually have an arrow showing
the
> direction of the squeegee when applying the paste.
>
> Screen opening that are rectangular will get good paste if parallel to the
> squeegee flow but not so good if perpendicular. This is really for small
> openings such as 0.015" wide x 0.100" long. The 0.015" wide slot, if
> squeegeed perpendicular, gets very little paste.....
>
> I have that problem on a design now. After reflow, 1 part has to get
touched
> up by hand, which is bad for quality overall....
>
> Regards
> TDK
>
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Le Thanh Tung
> Sent: Tuesday, May 10, 2005 6:39 PM
> To: [log in to unmask]
> Subject: Re: [TN] Tombstone
>
> Following is one of reasons cause Tombstone:
> - Vertial shifted part: Mounting condition is NG
> - Not same solder paste volume at two sides of part: Printing
condition
> is NG.
> - Temperature at two electrodes of part is different: when PCBA going
> through reflow machine, one electrode
> of part will be heated and smell first -- > tombstone
> Best regard.
>
> ----- Original Message -----
> From: "Suganthi" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, May 10, 2005 2:51 PM
> Subject: [TN] Tombstone
>
>
>
> Dear All,
>
> What is called Tombstone effect ,please explain me , and tell me how to
> overcome this problem..
>
> Thanks and Regards
>
> ---------------------------------------------------
> 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
> -----------------------------------------------------
> Suganthi
>
> ---------------------------------------------------
> 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
> -----------------------------------------------------
>
---------------------------------------------------
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
-----------------------------------------------------
|
