Time Estimation for a Project

[nsreekanth9724]

Dear Eperts,

Can anybody suggest how can we stmate a rough time-period needed for a project.
For eg:- I have a design with 8 layers,2 BGAs 100x150mm size.Total components are around 800.Total connections are around 2000.

If such information is given from the Product Management Department, How can we estmate a time? Is there any formulas or thumb rules available??


Regards,
Sreeanth Nampoothiri

[cadpro2k]

2 weeks (10 calendar days) total. Send quote.

[randychase]

Back around 1981, I wrote a basic program to estimate actual board design costs for service bureaus. Mainly just because it was fun and I wanted to do something on my new Osborne computer.

The thing is, there are many variables that will affect pricing and time. You can define many of these variables. But some are hard to define.

For example, you mention 8 layers. Well, that can make the board a lot easier/faster, specially if it autorouted. Maybe it will choke on 6 layers? But it takes more time to set up and process more layers too.

What is track width and spacing requirement?

Any (or all) hand routing? Critical nets? High speed? Analog stuff? Video? Power supply sections? Keep outs? Connectors? Odd shapes?

My method was to start with a multiplier. Just take the total number of component pins... used or not, and multiply by a factor. If the board had a lot of replicated circuits, good for me. If it had a lot of easy to route stuff, good for me. If it had high pin counts, but lower connection counts, good for me. If the engineer required 96 pin connectors and only brought in 4 signals.. good for me.

On the other hand, certain boards would go the other way and you have to develop some experience and skill in telling those apart.

Odd shapes or long/skinny boards can be a lot more difficult.

Large components can have few pins and take more time (like in power supply circuitry).

Sensitive analog stuff or RF, can be 3 to 5 times as time consuming.

Laying out single layer production boards can take a long time, so I only bid on those after I finished them. :)

The factor I started with, was T= 1.62 * P, where P= component pins and T = time for layout. The factor would go as high as 3.8 and as low as .5


Using this crude formula, assuming your board has about 3000 pins, it would take 4860 minutes or 81 hours, which is 2 weeks or 10 calendar days. Just like he said.
:)

[nsreekanth9724]

Thanks ! I was looking for a general solution.How did u decide 1.62 factor?

[randychase]

Thanks ! I was looking for a general solution.How did u decide 1.62 factor?

The service burueau industry used to commonly quote on printed circuit layout jobs by multiplying component pin counts by a factor of $$. Back in the day, we used to bid $2.25 per pin.

My goal back then was to charge $85.00 per hour, which is 37.7 pins per hour. So each hour should take 60 minutes divided into 37.7 pins, or roughly 1.6 minutes per pin. Then you can use your own local labor rates and overhead.

[Skip Yutkus]

800 components? hmmm. I'd quote a little more time than that unless they are all caps an resistors, what about diff pairs, skew and length considerations - spacing constraints - ad infinitum, I guess my point is the info is far too sparse to quote anything but a generous lead time and still hope you get lucky, I've had some crazy customers with really odd requirements - one I remember vividly was the requirement to route the equivalent of a .400 wide trace to one pin in a 2 mm connector - for a possible 35 amp surge - my reply was if you have a 35 amp surge you won't have a pin anymore - they still wouldn't back off.

Skip

[randychase]

I mentioned a lot of those variables in my post Skip. You can only derive a starting point, and then modify it based on the variables. Back in the day... the last step of a quote was to just look at the total schematic and requirements and ask myself what my gut was telling me how long it was going to take. :)

As far as discretes, with 2000 connections and 800 components, two of which are BGAs, it might be a fair guess that most of those parts are discretes.

Been there and done that a few times on the very high current stuff. Or designing agency approved high voltage boards where the AC line comes in or goes to a 0.100" pin spacing IDC connector. Hello?

[Skip Yutkus]

Same deal - EN60950 - 2.5 mm spacing requirement - goes thru a resistor to a .05 pitch IC - the party line was it was no longer primary on the other side of the resistor, OK! then it violates the rules simply being attached to the resistor as primary on one end and SELV on the other (0603). Go figger.

Skip

[mirka_ha]

Hello all,
well I am curious, did you build the board.
What was your estimate and was the estimate correct?
Let us know

[nigelwright7557]

Dear Eperts,

Can anybody suggest how can we stmate a rough time-period needed for a project.
For eg:- I have a design with 8 layers,2 BGAs 100x150mm size.Total components are around 800.Total connections are around 2000.

If such information is given from the Product Management Department, How can we estmate a time? Is there any formulas or thumb rules available??


Regards,
Sreeanth Nampoothiri


Just guess at a time then double it to be safe.

Nigel.

[James Jackson]

Well... I know that I am checking in late on this, but I just want to tell those that are interested that I have a proram that I wrote that will assist in creating an estimate for doing PCB layouts (and Schematic Capture, too).

It is called PCB2Est.

http://joj.home.texas.net/53000.html

It is not free - but the low cost of the program will more than pay for itself the first few times that it is used.

It has several user-selectable options which add to the flexibility of the program, and allow for more accurately generated time-estimates.

I have been using this program for a few years now, and it is pretty much 'on' with its' estimates.

Regards,

James Jackson
Oztronics

[r_canor]

Dear Eperts,

Can anybody suggest how can we stmate a rough time-period needed for a project.
For eg:- I have a design with 8 layers,2 BGAs 100x150mm size.Total components are around 800.Total connections are around 2000.

If such information is given from the Product Management Department, How can we estmate a time? Is there any formulas or thumb rules available??


Regards,
Sreeanth Nampoothiri

Consider the factor of experience. If it so happens that you already encountered the same or similar design so you would not have hard time estimating. But then you ask so I assume the factor is not considered.

When you are working with Analog and Digital design in one, this may add difficulty.

The 10 man-days is a little too long it this design is just as simple as click and connect.

What is the function of your design?
By telling us what function it does we will have an overview of how many considerations should be done on your board.
Those # of connections, # of pins are more or less a lesser factor to deal.

I have a design more than that # of connections but the way I see it is not on how many they are but how complex they should be treated.

I short , I have no answer. :)