Ahmed,
What the IPC specs don't say is that for automatic insertion, the hole size
may need to be larger than the IPC maximum spec (IPC-2222, Section
9.2.1.1). In the IPC Certification study guide, it says that clearances up
to 0.7mm can be used. Anything over that will typically cause problems.
Also be aware that clearance values larger than 0.5mm can cause problems
when soldering, such as skips and voids. Leaded insertion machines
typically need a clearance anywhere from 0.4mm to 0.7mm, depending on the
manufacturer and the part being inserted.
I would suggest that you get IPC-2221 and IPC-2222 for future reference;
they superceded D-275 three years ago.
The spec for unclinched leads is IPC-2221, section 8.3.1, but it doesn't
give any clearance data.
Hope it helps,
Roger M. Stoops, C.I.D., PCB Designer
Trimble
Engineering and Construction Division
5475 Kellenburger Rd.
Dayton, OH 45424-1099 USA
Ph: +01 937.233.8921 or +01 937.233.4574 ext 288
Fax: +01 937.233.7511
Ahmed
El-Sanhoury To: [log in to unmask]
<[log in to unmask] cc:
AHGAT.COM> Subject: [DC] Diameter of Unsupported Hole
Sent by:
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Please respond
to Ahmed
El-Sanhoury
All
I would like to verify about the clearance value-0.5 mm-that should be
between the Unsupported Hole and the lead diameter of component as
IPC-D-275
said at (Page 70 Sec. 5.4.6.1 Diameter of Unsupported Holes),
is this practical value?,In fact it seems to our assembler a small value to
insure that the Automatic Insertion Machine insert the components properly,
i wonder if he is right or there is somthing error on his process
(such as the Hole location determination, the accuracy of the machine or
somthing else),Moreover, in case of clinched component what the clearance
value should to be? (as IPC-D-275 in Sec. 5.4.6.1 refer to it but it does
not continue the information "....., Unless it is clinched"), Thanks in
advance.
A. Sunhoury
PCB Designer (Electronic Engineer)
www.bahgat.com
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