Hi Ofer:
Another approach is to build the board without covering the secondary side with a prepeg and build it as a regular boards is built. Cutting the connector leads as close as possible to the board before soldering, then, encapsulate the leads.
The material to repair board surface can be used for that purpose.
Regards,
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Ofer Cohen
Sent: Monday, December 13, 2004 11:41 AM
To: [log in to unmask]
Subject: [TN] Fastening a connector
Hi to all,
Well, Christmas is still far away, so far away, so many problems can arise till then... for example:
One of our designers gave a solution to a safety problem: Since his board carries high voltage (>72V) and is close to a metal sheet, he covered the secondary side with a ply of prepreg.
OK, we overcame the bow and twist problems that were observed during the SnPb reflow soldering, caused by the non-balanced stack up (we are looking forward to the coming LF soldering experiments). However, there is another problem: the power connector is through hole (the other components are SMT). The connector (Molex 15-24-9104, or A-42404-10B1) has 10 male contacts, with the following distribution:
* 3 are cut, to allow access to the internal legs;
* 3 are carrying 5A each; and
* 4 are small signal lines.
The diameter of the holes in the 62 mils-thick (or 80 mils, in another variant) PCB are 0.071", but they are not through, but plugged by the prepreg ply, that has a 10 mils hole for the out gassing. This is not unsupported holes, since the hole is coated. however, the legs are not supported from the other side. there are also plastic pins
I made two decisions:
1. Make a shear test to a sample of every production batch. This should be simulated by a pull test.
2. The test is destructive, and the sample should be scrapped even if the module has passed the test.
The mechanical designer, whom I asked for a simple shear/pull tester, does not think it is necessary. I decided to consult the forum. Thank you for your inputs.
Regards
Ofer Cohen
Manager
Quality Assurance, Reliability and Production Technologies
Seabridge Ltd. - A Siemens Company
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