Money Saving Tips for Printed Circuit Board Design

Raising the Top Line With Good Execution Will Make Up For The Additional Expense Of Expediting Development

There is a pretty simple equation when it comes to counting up profits. The fixed and overhead costs have to be less than the revenue number for there to be any profit. The first units out of the gate owe the company for all of the non-recurring engineering costs. The item will be in the red until all of that is paid back by the margin between unit cost and unit price.

In many sectors of the economy, particularly the commercial sector, the cost of goods sold (COGS) is pretty close to the selling price meaning that very little margin after overhead is considered. Note that PCB design is among the overhead costs. Many units must leave the factory and find a consumer before the project’s financials hit the break-even point. Product cycles are such that price erosion is putting the squeeze on margins right from the beginning. Consumer hardware is a tough game, no doubt.

Competition among the players keeps us on the path of continuous improvement. Sitting still while others strive to grab your market share is actually moving backwards so let’s take it for granted that we have to keep reinventing our products. Those new features, whatever they are, will likely add to the Bill of Materials which increases the variable costs. We can soften that blow with a few money saving methods.

Winning the Socket - Be First to Market With the Latest Technical Wonder

There is so much more margin to be had for the first mover. Nobody else gets that premium pricing advantage. There is always the risk of someone mirroring your company’s blueprint so that lead is perishable but definitely worth having and keeping. A design win can lead to more design wins but only if we execute on the new product introductions that follow. Winning creates enthusiasm.

I’m not here to think about losing so keep that energy going with your attitude and willingness to do what it takes as far as staying on schedule. By monitoring progress against expectations, you know if the product time-line is beginning to slip. Taking action before it gets out of hand is the best way to approach this ongoing concern.

The one thing you might know at the beginning is the expected end-date. Working from there back to now, milestones should be established for completion of library, schematic, placement, critical routing, simulation etc. Each of those milestones should conclude with a meeting where we can check off on all of the items needed to proceed to the next gate.

Just to keep it real, let’s say that the schematic-complete date is here but the schematic is not. Have that meeting anyway. Use that as a pivot point and figure out how you can pick up your coworker by getting a lot of quality board layout work done in a short period.

Some of these things can be done in parallel with additional design resources if your solo efforts are falling short. If you know that you will need help to get to the tape-out date, then it is up to you to get that help. The rate for a service bureau may seem high, likely more than your own rate.

The pay-back comes if everything falls into place as planned. The majority of the revenue comes before the copycats release their version. The first one in with a similar product might get away with it for a while and might even supplant the first mover. That’s not the norm. Be the original and stay the original by developing something better than the previous iteration. Spend money to make money or lag with a me-too product’s market share.

Let Someone Else Create the Library

Component footprints can be outsourced for a very reasonable price. Most of them are available off-the-shelf and if not, then soon after you place the order by providing a data sheet. Some library generators also do schematic symbols and include step models of the parts.

You know that the PCB cannot be any better than the underlying component footprints. It’s a wise designer who double-checks the new geometry prior to use. If you manage this correctly, you can retire from making footprints and just check them over before adding them to your library.

Tighten up the Loop Between the Product Designer’s Data and the PCB Data

We get mechanical data in different ways. Typically, there are a few layers with shapes that define route and component keep-in/keep-out regions. Sometimes, ok, most of the time, the Mechanical Engineer has a few glitches in the data they provide for the first go-round. The things I have seen and accepted over the years could make this a very long story.

So, here’s an example. The headroom under a shield was set to zero when it needs to be enough to allow parts that fit but flag parts that are too tall. Flagging all of the parts as too tall is not right but, hey, I can work with it. One way is to ignore the design rule checks. Another is to edit the properties so that the actual head room is enforced.

Figure 1. Image Credit: Author - Little did I know back then (2012) that Chromecast would sell tens of millions of units. Reducing the layer-count from eight to six helped enable a low price.

Both of those methods come with a risk. By pointing out the glitches as they happen, you can get to a better place where the mechanical data is correct by design. Experience has shown that a mechanical outline drawing is rarely available at the start. Some attributes may be in a state of TBD as in to-be-determined.

As these items are ironed out, keep feeding back your edits to their baseline form-factor. The goal here is to reduce the pain of having to capture a slightly different outline down the road. Time is money so try to streamline those occasions. The sooner you can get a handle on it, the lower the impact it will have. Schedule-wise, this goes hand-in-hand with cleaning up the schematic; early in the game.

You are not being a pest when your aim is to clean up the process. Frame the request as good for the design integrity rather than complying with the particulars of the ECAD tool. Setting aside the gate swapping, we don’t routinely alter the netlist. By the same token, we should not make a routine out of “fixing” the MCAD data. Every change can be an improvement but it’s even better if it doesn’t come with a self-inflicted setback. Dialog with that team pays dividends.

Use one side of the board

Say it again! Use one side of the board for components. This is probably the biggest favor you can do for your assembly house. If the form factor allows populating one side of the PCBA, you will come out ahead of the game over putting parts on the primary and secondary sides. Most MCUs will be able to function with this arrangement. Explore the possibility if it makes sense.

Single sided boards make one pass through the reflow oven. In order to solder both sides of a PCB, one side must be populated with the tiny parts only. The first soldering pass on a double sided board will use a higher temperature solder so that it doesn’t reflow again when the other side is soldered. Even then, heavier components on the secondary (downward facing) side may require glue to make sure they don’t come free.

Figure 2. Image Credit: Author - Placement is fine-tuned using robotic technology to align an array of lasers in this San Jose, CA factory

Limit the BOM to one type of technology. Again, we’re looking at reducing processes. Surface mount is the prevailing technology so that is your best bet for an end-to-end solution for your component picks. Mixing surface-mount and through-hole parts is a cost driver. The wave soldering process is trickier with surface mount included. Like oil and water, surface mount and through-hole do not mix well.

Avoid or Minimize High Density Interconnect

This one can be tricky too. It is difficult to fill out a Bill of Material without having a few Ball Grid Array (BGA) packages where the pin-pitch requires the use of micro-vias. These tiny vias are formed with a laser and the fab shop has to create them layer by layer. The result is that every layer of micro-vias involves a pass through the lamination press.

That’s time-consuming which is to say money-consuming. The press is a big, expensive machine that uses a lot of power. It can be the bottleneck of a smaller fabricator’s flow. Doesn’t matter how big they are, they all charge for sequential lamination because it’s so much more work.

Getting around all of that will have you shopping for chips that come in quad flat packs or other packages with perimeter pins only. Finding a second source will be another chore. Regarding the assembly line, they will still have to xray the board to find voids in the solder joint for the thermal pad in the middle of most of those packages. We’re often working with a system of boards where one of the distinctions between the boards is the required technology. Maximizing the use of the cheapest boards may help downsize the main PCB of the system.

Creativity and innovation pay off if the execution doesn’t get in the way. It’s often better to get a set of features into the field and work on yields and costs as you iterate down a list of desirable upgrades. So-called Agile development can help steer a product from concept to concrete with calculated steps. Feature creep is the point but it is fastened to market requirements so that you have the product to win the short game and evolve to the cost-competitive model as the market dictates.