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Toe Fillets


Toe Fillets | 8 January, 2004

It is my understanding that per IPC specs toe fillets are not required as they do not add any strength to a solder connection. Our thoughts were allways that proper toe fillets are a sign of a good process. What are some of your guidelines and thoughts for inspecting toe fillets. How much importance do you place on proper toe fillets and what do you consider a proper toe fillet? Thanks.

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Toe Fillets | 8 January, 2004

Toe fillets are not required per IPC. Toe fillets could be used as a process indicator, if you desire; I would not. Gull wing leads are typically cut off on the ends when manufactured; this exposes the non-plated material in the lead, typically copper. Toe fillets are dependant on the process variables and design, they are also dependant on the ability of the exposed non-plated material to wet. Being this is a variable we cannot typically control or understand, it is not worth the effort using it for anything. Even if you have a decent toe fillet it does very little for the integrity of the solder joint.

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Toe Fillets | 8 January, 2004

I agree 100%

The strength of the joint is contained at the interface.

Ever seen a fillet on a mail stamp?

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Toe Fillets | 9 January, 2004

DWZEEK-Nicely put. I agree. cal

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Paul F


Toe Fillets | 12 January, 2004

Is anyone having issues with fillet inspection on AOI machines due to poor toe fillets caused by exposed base metal? We're just getting into AOI now and QFP inspection is proving difficult.

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