Design timelines, sourcing schedules, production schedules, and assembly delivery schedules can all get set back due to a relatively small number of factors. PCB projects are very linear, and a team must go through a specific process to develop a new product and make it ready for production. When delays occur during development, a production schedule can get pushed back or reset completely.
As it turns out, for most design teams, there is a relatively small number of factors that can be the biggest drivers of design and production schedule resets. All of these problems are related to schedule resets in a company's design and development process. So when your company is developing a process for completing new designs, make sure it addresses these points to avoid schedule resets.
Top 4 Reasons For PCB Project Resets
PCB designers, your manufacturer, and your clients all hate it when a project schedule gets reset. Here are some of the most common causes of these scheduled resets.
1. Changing Engineering Requirements
By far the biggest reason for schedule resets and production delays is a change in engineering requirements. Whenever the engineering requirements change, it forces a reset of part of the design, almost always originating somewhere in the schematic. However, engineering changes can force a change in the core circuitry or PCB build requirement, which then requires adjustments in the PCB layout.
Engineering changes can be benign, basically amounting to compatible part swaps in the schematic and no PCB layout updates. Engineering changes could also be quite major, essentially leading to deletion of large blocks of circuitry. This then forces major changes to the PCB layout.
Circuit changes: These can be handled quickly as long as parts are pin-for-pin compatible.
Functional block changes: A change to channel blocks inevitably means pCB layout shifts.
Placement changes: If these are started after routing, a significant portion of the routing may have to be recreated.
The moral of the story is: anytime there is an engineering change, it will be more difficult to deal with the change after the PCB layout has started. This underscores the need for a thorough engineering schematic review before starting the PCB layout.
2. Main Parts Went obsolete or Out-of-Stock
This is a form of engineering change that can be quite difficult to predict. Instead of the case where an engineer took a second look at the schematic and decided to move things around, the supply chain forced you to make a change that you could not anticipate. This will most commonly arise when reusing old circuitry or when working off of the company library.
For designers working off the company library, this is where continuous reevaluation of lifecycle will be very time consuming, but it is really the only way to determine when a part swap is needed. The best time to check is at the beginning of the PCB layout by uploading the preliminary BOM to a distributor website.
3. Manufacturing Files Were Not Reviewed
When you send your manufacturing files into a fabrication house, the CAM operator will do some level of review while they prepare tooling and stencils so they can build your board. During the review, they may find mistakes or problems in your manufacturing files, and that generates questions for the designer prior to production.
If the manufacturing files are incorrect, this leads to questions and emails back and forth that will delay your production date. Each of these emails is a huge time suck that requires investigation by the designer, and often demands regenerating files for re-inspection. Production cannot start until all of those questions are resolved and any defects in the files are corrected. This is one of the major reasons for production delays that every designer has had to deal with.
4. Incomplete Parts Kit
One of the biggest reasons for an assembly delay will be an incomplete parts kit. Some companies prefer to source all of their own electronic components, and the received parts will be held in internal inventory. This is typical for the most important parts in a design, such as processors or primary ASICs. The company will then consign those parts to an assembler after creating an order.
Whenever parts kits are delayed or incomplete, this will push back the date for the assembly run. As each new package is received, it must be inventoried against the BOM to ensure all parts are received and ready for placement in assembly. This is the only way to make sure that all parts are present before a board is put through mounting and soldering.
When you’re ready to avoid these common delays, make sure you use the best PCB design features in OrCAD from Cadence. If you’re ready to take even more control over net logic and board layout, you can graduate to Allegro PCB Designer for a more advanced toolset and additional simulation options for systems analysis. Only Cadence offers a comprehensive set of circuit, IC, and PCB design tools for any application and any level of complexity.