I stand corrected. Peer is right, a side fillet is also required. A toe
fillet is not.

-----Original Message-----
From: P. Langeveld [mailto:[log in to unmask]] 
Sent: Friday, August 10, 2007 6:10 AM
To: TechNet E-Mail Forum; Stadem, Richard D.
Subject: Re: [TN] Minimum toe fillet for SOT23-3 land pattern

In addition to the heel fillet, also a meniscus untill at least half
lead thickness is required at the side of the lead feet as far as it has
a protuding width of solder land underneath. If there is no protruding
solder land, it is difficult to see if the full length of the feet is
wetted.
As a rule, the total leadframe must be wettable but, the tip of the toe
is cut off after moulding. It has a clean surface that most of the time
will be wetted, but it has no wetting requirement.

Peer Langeveld
Consultant Soft Soldering Processes
The Netherlands



2007/8/9, Stadem, Richard D. <[log in to unmask]>:
> The requirement is for a heel fillet only. Side and to fillets are 
> formed to exposed basis metals. While nice to have, they are not 
> required. Heel fillets are required and the specs are listed in 
> IPC-A-610D and J-STD-001D for Class 1, 2 and 3. The focus is on 
> aquiring a good heel fillet, as that is the part of the solder joint 
> that is formed with the finished surface of the lead. Side fillets and

> toe fillets are suspect, at best, as the solder is forming an 
> intermetallic with oxidized basis metal.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of James Verrette
> Sent: Thursday, August 09, 2007 11:54 AM
> To: [log in to unmask]
> Subject: [TN] Minimum toe fillet for SOT23-3 land pattern
>
> What should be the goal toe fillet for an IPC 7351 land pattern with 
> density level C for a SOT 23 - 3 pin package?  (least protrusion, 
> highest density)
>
>
>
>
>
> Jim Verrette
>
> Electrical Engineer
>
>
>
>
>
>
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