Ongoing communication between designers and fabricators heads off costly problems.
As printed circuit board technology continues to advance, board design challenges increase exponentially. By the time a design hits the fabrication line, it’s often difficult and costly to make a design change. Upfront and detailed communication between designers and fabricators can head off a lot of potential problems.
“It’s not so much that designers and fabricators are making life difficult for each other,” says Joseph O’Neil, president of Hunter Technologies, a PCB fabricator/board assembler in Santa Clara, California, USA. Sometimes, a board’s design and engineering rules are out of sync with the fabricator’s manufacturing guidelines. “We have one set of manufacturing guidelines, and our competitor down the street has another,” O’Neil says. “What may be a problem for one designer is not a problem for someone else.”
To avoid last-minute design changes and costly delays, designers should consider the following issues before engaging a fabricator.
Fabricator Capabilities
Not all fabricators are created equal. At the moment, the technology driving PCB fabrication and the solutions available are vast. Although there are standards for PCB fabrication, standardization of all of these options [technology] has not yet been achieved, so materials, processes and equipment vary, O’Neil says.
For example, Hunter is one of a limited number of U.S.-based manufacturers that use laser-direct imaging (LDI) systems. LDI enables designers to tighten feature sizes and tolerances, giving them more board real estate to work with. However, if the same techniques are used and the design is placed with a manufacturer who does not have LDI, the cost of the project is affected.
Price/performance Expectations
Even the latest fabrication technologies are not right for all product designs. High-density designs using finer line widths, tight spacing, smaller interconnect vias and tighter impedance increase board complexity and impact manufacturing costs. “Do you want to use the same fabrication techniques for a game board as a no-expense-spared, ruggedized, redundant and bulletproof computer board?” O’Neil says. “Game board designs have to consider cost.”
One sure way to drive costs up is to use multiple design techniques on the same board. “One good example would be a designer who designed in two laser vias,” O’Neil says. “If you are going to use high-density interconnect (HDI) techniques (LDI, laser drill), then use it throughout the board. The cost of running the micro via process is nearly the same for two holes or 1,000 holes.”
Bill-of-materials Management
Design tools and data sheets provide component information that doesn’t do much if a footprint is wrong or a device isn’t available. PCB fabricators typically check component footprints against the board layout and flag any deviation. “Most of the headaches are spacing issues: component-to-component or component-to-edge,” O’Neil says.
A fabricator that offers both design and assembly services will be able to troubleshoot component spacing issues, find substitute parts that fit a footprint (if the first choice isn’t available), and manage component lead times and material pipelines. The lack of a single device can hold production up for the entire board. “You can shave time off the design process and get the board to the fab in three days, only to jump through hoops waiting for the parts,” O’Neil says.
In general, designers should look for a fabricator that will work with them as early in the design process as possible. “There are cases in which we have a team working right alongside the customer,” O’Neil says. “That’s been a pretty successful strategy.”
