Critical Link is often asked to help cost-out the differences between a single-board chip-down solution and a solution that incorporates a som. It’s well known that HDI (high density interconnect) and layer count increase the cost of a bare board, but just how much? We were surprised to find out.
Our customers generally expect board size to be a driver of board cost, double the size of the board and the cost of the board generally doubles. Pretty straight forward. HDI and 10-12 layers are known to increase the cost, but by how much?
In order to check it out Critical Link asked different PCB suppliers to quote a fictitious 12-layer HDI board and a non-HDI, same-sized design using only 6 layers. We were trying to analyze the difference in cost between board designs that used BGAs and required HDI and additional layers to perform the escape routing and those that didn’t. In the latter case we were thinking those designs leveraged a som such as our MitySOM-5CSx or others from the Single Board Computers resource guide.
Across multiple PCB suppliers we were shocked to find the cost of a 12-layer HDI board is roughly 5 to 6 times the cost of a 6-layer board. The actual size of the board was irrelevant; whether 2”x5” or 8”x5”, the multiplier remained consistent. Ouch.
To give you a better idea, here’s a pricing example from one PCB supplier. The actual prices were different from each supplier, but the multipliers were surprisingly similar.
Base board price comparison, based on number of layers:
(All figures based on a quantity of 1,000)
Board size
Six-layer board
Twelve-layer HDI board
Delta
Multiplier
2x5
$ 6.75
$ 39.00
$ 32.25
5.8
4x5
$ 13.50
$ 63.00
$ 49.50
4.7
6x5
$ 22.50
$ 105.00
$ 82.50
8x5
$ 25.00
$ 117.50
$ 92.50
In addition to the pure base board cost savings, incorporating a som like the MitySOM-5CSx typically allows for a smaller form-factor, meaning an even lower base board cost. (E.g., if you were able to reduce the board size from 6x5 to 4x5, the price decreases further to $13.50 and the multiplier jumps to over 7.5x.)
Reducing the number of layers and technology doesn’t come for “free,” of course. The BGA components that would have forced the extra layers have to go somewhere, and that’s on the som. Obviously there are costs associated with the som -- and in a later post, we will discuss Total Cost of Ownership of a chip-down approach vs. incorporating a som but we know designers find it interesting that a reduction in the number of layers produces such dramatic cost savings for the bare board.