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

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Solder bridging after printing

#35165

Solder bridging after printing | 25 June, 2005

Hi all,

Recently I had problem with printing the lead free solder paste, almost every board has bridging especially on the fine pitch locations. Anyway this problem never happens when we use leaded solder paste. So I would like to ask if there are any special controls such as environment, viscosity, stencil design and printer parameters in order to achieve good printing for lead free solder paste.

Regards

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MSK

#35169

Solder bridging after printing | 25 June, 2005

What is stencil thickness & what is the pitch of your component.What is your cleaning processor for stencil.

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#35170

Solder bridging after printing | 25 June, 2005

Hi MSK,

Stencil thickness: 5mils with laser cut Smallest pitch: 20mils Underscreen cleaning frequency: 10 bds per cleaning

Note: We have decreased the cleaning frequency from 10 boards to 3 bds to reduce solder bridging after printing

Regards,

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RDR

#35180

Solder bridging after printing | 27 June, 2005

What is the viscosity of your lead free paste vs. your lead paste?

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MSK

#35201

Solder bridging after printing | 28 June, 2005

What is your stencil cleaning procesor.It sould not be wet after cleaning & what is room tempreture.?

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#35206

Solder bridging after printing | 28 June, 2005

Are you saying that increasing the frequency of cleaning to every 3 boards *reduced* bridging, or that it's just something you tried? I don't understand why that would help(in my experience it has reduced "insufficient solder" conditions but not bridging).

I would look at paste volume, i.e., stencil thickness, aperture size, or if you're printing off contact, and slumping (temperature or humidity).

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