Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


lead coalescence in solder joint

Sergio Vito - Alan Patrick - Cristiano Dick

#18746

lead coalescence in solder joint | 29 January, 2002

Dear sirs,

We are experiencing problems with lines of lead formed inside the solder joint. In others words, there is a problem with the formation of the solder joint, after analyses on a microscope we can see the lead grouped in some positions. This problem is supposed to cause poor contact between the component and the PCB.

We will apreciate your help!

thank you very much!

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#18748

lead coalescence in solder joint | 29 January, 2002

Over-time lead separates from the tin in solder by force of nature [diffusion], but I assume that is not what you are talking about.

Please help us understand your question better. Are you saying that the solder does not attach properly to the component termination or the conductive pad on the board? Please describe the problem in more detail by telling us about: * Type of solder you are using. * Soldering method. * Distribution of the problem across this product [ie, all solder connections, some connections, etc.]. * Distribution of the problem across all products. * Component where you observe this problem [ie, type, size, lead type, solderable finish, etc.] * Board where you observe this problem [ie, type, solderable finish, etc.]

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seto

#18754

lead coalescence in solder joint | 30 January, 2002

Hello Dave,

Mechanically the conection between the component pad and PCB pad is good (the solder joint is very strong). The problem is associated with poor contact after the use by the customer (vibration, temperature, etc). You can see the pictures of the analisys in the following address: http://br.geocities.com/apatrick77/.

answering your questions:

1) I am using cobix solder paste (AIM) Sn63/Pb37; 2) The soldering method is convection air reflow; 3) All the points tested are with this problem ( we tested only one PCB)

We made this analisys in only one PCB.

Thank you very much for your help. If you want, I can send to you the thermal profile of the reflow oven.

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#18764

lead coalescence in solder joint | 30 January, 2002

Oooo, pix, coo!!!

Yes, that solder connection has been beat-up. It is very �old�. So, your customer is seeing failures, correct? I can believe it. I want to say the solder in your connections doesn�t stand a chance, but lack experience in this area.

Very smart people to contact are: * Dave S Steinberg, Steinberg & Associates, 818-889-3636, steinbergassoc@netscape.net

* Dr. Cemel Basaran, SUNY Buffalo, 716-645-2114 X2429, cjb@eng.buffalo.edu

[Please post the answer, if you get responses from off-SMTnet. Tks]

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Reflow Oven

PCB X-Ray Inspection