Components on the back side

Tim Wescott schrieb:

Hello,

if you have the passives on one side and the ICs on the other, you will need two vias for nearly each passive component. The vias will consume extra space on your board. Traces are much smaller than normal vias, but micro vias are more expensive.

Bye

I stepped on one while barefoot :-( ...Jim Thompson

-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

Common but EXPENSIVE. Any cost advantage goes out the window.

...or the design spec changes. You must live in a perfect world.

I don't believe it, Jim. You mean to tell us that you actually take off your jack boots from time to time? ;-)

production

to

going

Our purchase/kit/placement cost is a *lot* more than the cost of one of these, much less four separate resistors.

I don't understand those numbers. Did you meen feet?

Yes. Some of our VME boards get down around $40 for 6 layers, in better quantity. But we'd rather pay a bit more fro boards from a house that's consistantly good, which is rare.

Yup.

Our stuff wouldn't work on 2 layers. Occasionally we can get away with

1. BGAs need 6 or 8.

Yeah, but you've always been on the progressive side :) I worked with multilayers at the time but the thru hole components were on one side only. (Except from a piece of the wires that is.)

Don't know how to explain "accustomed". Maybe it's a Britisch rather the an American word.

petrus bitbyter

I stepped on a TO3 while barefoot. it went in far enough to stick, but the subject line is "on the backside" not "underfoot".

Could have been worse with a 68000 DIP.

No, those were all soldered to PC boards. :)

I flipped one I was holding tightly between two fingers (one, a thumb), and it put a row of pins into my thumb.

Can't remember what I was doing. I noticed different makers had different "points" on their respective lead frames.

Some could pierce you with the slightest of pressure.

I remember more the cuts I used to get on the back of my hands from pulling non-trimmed PCB cards out of ISA PC slots, full of other, non-trimmed PCB cards. Those years were a pain in the ass for PC oriented folks, which were far fewer at that time than now.

And now folks do not peer under the hood as much if at all any more. It is funny how many other engineers call me to investigate or fix a problem with PCs because they know my past saw a lot of legacy hands on utilization.

And I do cars and engines. And I do windows and dishes and gardening and horticulture. Machine tools and metal joinery of a wide variety.

and jewelry and watchmaking.

and fishing lures and lightning rods... and Jacob's ladders and Tesla coils and coin shrinkers!

And black powder cannons and other ballistic 'devices'.

),

I've done that more than once, being dumb enough to think I could pull a dil out of a socket. It always ends up letting go at one end first flipping right at the moment you pinch it the hardest

-Lasse

that cheap

than

resistors. That

Thank you John, for making usefully clear some of your cost issues relative to BOM.

?-)

limitation,

one of

the

the past,

pricing out

(board

in

to a

whole

reflow

Prescuse me, but that sounds insanely dense.

?-)

How about 121 BGAs (direct chip attach) on a 4" substrate?

limitation,

past,

out

Yikes, that sounds like a years-long project.

How do you cool a thing like that? Or get the signals on and out?

limitation,

past,

out

With 100 wiring layers in the substrate, and spring loaded pillars for cooling...as in an IBM 3090 thermal conduction module (TCM). IIRC the

Cheers

Phil Hobbs