Ok, I'll take a stab at this and make some suggestions.
Factors to consider:
1. What is the diameter of the component wire?
On your drill (or master) drawing, you'll want to specify the "finished" hole size. It is then the function of the fabricator to make sure that's what you get.
This information is generated within the NCDrill report from your PCB CAM file. The NCDrill will also have the XY locations of all your component holes.
The component vendor will often have a data sheet that will give you recommended finished hole sizes for the components. These usually work just fine.
2. What type of copper are you specifying for the outside layers?
While you don't have to take this into account for the finished hole, the fabricator will. It's important to specify somewhere in your documentation or order that you want 1/2oz, 1oz, or more. Your fabricator and assembly house can give the pro's and con's of the different weights of copper. (FYI: 1/2oz=.0007inches & 1oz-.0014inches thick.) 1oz. is common on outside layers with 1/2oz. being common on inside layers.
3. What class are you building to?
To quote the CID study guide, "Selection of class should be based on minimum need, recognizing that less sophisticated classes require more coordination and communication between user and vendor."
4. What are your tolerances?
This may take some research on your part. Check with your fabricator and assembly house to see what works best for them. Looser tolerances mean larger holes and pads for your design, but may result in less expensive boards.
I would suggest you get a copy of IPC-2221. Refer to section 9.0 "Holes/Interconnections" to get a full discussion of what's involved. I use the 2220 Series all the time as a reference. I also find the 6011 Series very useful. Also, find a Designers Council in your area and get connected.
Good luck!
Cherie Litson, CID
President, IPC Cascade Chapter DC
PCB Designer/Librarian, Sonosite, Inc.
(425)951-1306 wk
(206)619-8844 cell
-----Original Message-----
From: Balasubramanian Krishnan [mailto:[log in to unmask]]
Sent: Sunday, December 22, 2002 8:09 PM
To: [log in to unmask]
Subject: [DC] PTH diameter and plating thickness
Dear DC members,
What are all the factors to be considered in determining the wall
thickness and diameter of different PTHs in a multi layer PCB? The PCB is a
4 layered with one Vcc plane and one ground plane.
Awaiting valuable information from experts.
Thanking you all in anticipation
K.Balasubramanian
Sr.Engineer, Hardware,
SCM Microsystems Pvt. Ltd.
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