Here are some things that I would look for:
1. Good solder paste "Brick" on both pads of 805, if one is less in volume.
After reflow if component is missing then there should be solder bumps were pads are.
2. Is one side of 805 connected to large thermal mass area, meaning temperature on one side of compnent is liquifying faster
than other, causing the Tombstone.
3. I have seen some component especially resistors, loose or have their end metalization missing, this will not allow the
component end to solder.
4. Just check Reflow Profile, if #2 is suspected, place thermocouples at those points to measure the acutal temperatures.
5. Span or footprint of 805 may be issue, if 805 is just making connection, when Solder joint relows, then surface tension will pull
component to one pad or other.
Hope this may help if I think of some more I will send it your way
Tom B.
-----Original Message-----
From: Becerra Alejandro [SMTP:[log in to unmask]]
Sent: Wednesday, May 10, 2000 11:09 AM
To: [log in to unmask]
Subject: Re: [TN] Tombstoning and missing parts on 0805 Resistors
The problem is after reflow soldering
-----Original Message-----
From: Tom Braswell [mailto:[log in to unmask]]
Sent: Wednesday, May 10, 2000 3:15 PM
To: 'TechNet E-Mail Forum.'; Becerra Alejandro
Subject: RE: [TN] Tombstoning and missing parts on 0805 Resistors
Are components present or skewed prior to Reflow Soldering, Just after
palcement.
-----Original Message-----
From: Becerra Alejandro [SMTP:[log in to unmask]]
Sent: Wednesday, May 10, 2000 10:27 AM
To: [log in to unmask]
Subject: [TN] Tombstoning and missing parts on 0805 Resistors
Hi Technetters,
We are having some problems with tombstoning and missing parts on 0805
resistors.
We think that the problem is related to the component, since we only detect
the problem in some specific codes of the material.
Could you please tell me what can I look in the components?
Thanks in advance
Alejandro Becerra
MSC
Phone (915)841-8518, Fax (915)841-8401
[log in to unmask]
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