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Wave soldering SMT component spacing

#21349

Wave soldering SMT component spacing | 28 August, 2002

Hi,

Does anyone have guidelines on minimum SMT component spacing for bottom sided wave soldering?

I am looking for general rule of thumb in wave soldering bottom side SOTs, 0805 & 0603s.

How about minimum through-hole lead to pad distance?

Peter

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#21365

Wave soldering SMT component spacing | 29 August, 2002

Many people use the same spacing [and pad designs] as they use for primary side SMT. We don�t.

DOWN STREAM SMT-TO-SMT SPACING: In addition to proper orientation, components cannot be immediately upstream of terminations that are to be soldered or bridges, starved and missing solder joints will result. A small component cannot be in the shadow of a larger one without defects. A gap of 150-200� between potential shadow components is enough to eliminate those problems.

SIDE-TO-SIDE SMT-TO-SMT PAD SPACING: We like to see 0.040� between secondary side SMT pads.

SIDE-TO-SIDE SMT PAD-TO-PTH HOLE SPACING: First, there needs to adequate keepout for the PTH clinch head, but that varies according to PTH insertion machine and component type. For instance, we need 0.15� side-to-side keepout for DIP. That aside, we like to see 0.060� between pad and PTH annulus.

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#21369

Wave soldering SMT component spacing | 29 August, 2002

> A gap of 150-200� between potential shadow components is enough to eliminate those problems.

Dave,

Can you clarify? Do you mean 0.015 to 0.02??

Peter

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#21383

Wave soldering SMT component spacing | 30 August, 2002

Ooops, sorry Peter. [Those pesky decimal points.] I meant to say �150-200 thou�. There is a fair amount of 'Kentucky Windage' in this due to: * Height of the component and the down-stream spacing. * Chip wave capabilities.

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#21516

Wave soldering SMT component spacing | 12 September, 2002

PTH to SMT spacing should be 80-100 thous. any closer will result in bridging. Scott

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