Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

question about vias on PCB

Status
Not open for further replies.

jayleung

Member level 5
Joined
Nov 29, 2005
Messages
82
Helped
8
Reputation
16
Reaction score
7
Trophy points
1,288
Activity points
1,962
Hi, everyone. I have a simple question about the PCB fabrication.

I am now working on a project with 3 layer PCB. And I am wondering can I drill some vias between the bottom layer and the middle one, but not going through to the top layer.

If yes, do I need to pay more for this kind of drilling if I ask the PCB company to make it? Any information will be appreciated, thanks in advance.
 

House_Cat

Advanced Member level 4
Joined
Feb 21, 2002
Messages
1,371
Helped
406
Reputation
812
Reaction score
98
Trophy points
1,328
Location
USA
Activity points
16,422
What you are describing is call a blind via. With current technology, they are limited to 1:1 aspect ratio because of plating difficulty in a blind hole. The 1:1 ratio severly limits the practical depth of a blind via.

Mechanically drilled blind vias are not generally done because of the difficulty in controlling the depth, difficulty in cleaning the hole for plating, and the fragile nature of the fine drills that would be required. The smallest drill size that a mechanically drilled blind via can practically use is about 20mils, which results in a finished size of about 15mils (which also means a max depth of 15mils). If you want a smaller via, then laser drilling is the only alternative.

Yes... blind vias will cost you much more than thru-hole vias. The reason for the extra cost is the greater number of steps added to the board production, and the decreased yield in finished boards.

See the following for a description: http://www.ccee.co.uk/blindBuried.php
 

    jayleung

    points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top