Data Preparation: Front End Engineering
Printed Circuit Board fabricators all have a Front End Engineering group. How the group is organized and what they are called differs from manufacturer to manufacturer. The task remains the same. They are tasked with taking in customer designs and converting them into tooling for use by the manufacturing plant to build the customer’s design. Front End Engineering of a printed circuit board manufacturer consists of at least three core disciplines…
- Planning (AKA Methods)
- CAM (AKA Computer Aided Manufacturing)
- Photo (AKA Graphics)
Planning is the beginning of the process. The information supplied to build the pcb is reviewed by an Engineer. Information provided should consist of the following…
- Fabrication Drawing This is a must have. If you don’t provide one don’t be surprised if you don’t get the design you are looking for.
- Electronic Data In the old days we used to get tape masters or film. When CAM came about some fabricators would scan the film into RS-274-X format. Electronic data is now common place. We do occasionally have film or a tape master thrown our way. Its alway fun to get an old tape master from the early 70s with missing Bishop pads.
- Customer Manufacturing Specification. If one is not provided a manufacturer shall tend to default to the IPC standards.
- Reference images. As of today reference pcb artwork images are provided by designers in pdf format. Hard copies either printed on paper of plotted on film were common in the 90s. These are not generally provided now but are nice to have. In the event of a data error or question the fabricator can refer to the images that are typically generated directly from the designer’s system.
- A sample pcb. This is not a requirement but it is greatly appreciated. This is also very handy when the design is unique or contains cutting edge technology. It never hurts to give a physical reference for a manufacturer to refer to.
The Engineer shall review all of the information and plan the operations required to build the supplied design. The supplied information is reviewed for all starting and finished requirements. The Engineer shall generate work instructions to be followed by CAM and Photo groups informing them of what they need to do to provide shop floor tooling. The Engineer also generates work instructions for the shop floor. Shop floor instructions vary from manufacturer to manufacturer but are commonly referred to as the batch card. The batch card is the unique set of work instructions that define the process operations and requirements to be met by the shop floor to build the customer design.
CAM is the second phase of the operation. A CAM Operator shall load the customer design into CAM software. The CAM Operator needs to define what the data all means to the system. Letter screen markings, solder masks, circuity layers, drill, etc… need to be identified to allow the system to properly interpret the data. Once the data is loaded and defined the layers are reviewed and inspected by a series of automated functions. These are commonly referred to as Design Rule Checks (DRC). The CAM Operator is tasked with interpreting the results. Conflicts between the design and the manufacturing operation are identified and resolved.
The CAM Operator then prepares the data for the manufacturing operation by employing Design For Manufacturing (DFM) tools and automated functions. DFM operations include but are not limited to etch factors, scale factors, fillets, plating thief and non-functional pad removal. The printed circuit board fabrication process is a series of additive and subtractive operations. The design as supplied is what the board should finish as after the manufacturing process. Some of the DFM operations are required to increase circuitry features so that at the end of the manufacturing process the design intent is met. Other DFM operations are employed to improve manufacturing yields.
Once DRC and DFM operations are completed the design is prepared for mass production. The CAM Operator defines the process panel and places multiple copies of the customer design up on the process panel. This is an operation commonly referred to as panelization. This is typically an automated process that either consists of frame sets or program scripts. The process panel consists of equipment tooling unique to the printed circuit manufacturer. It varies from manufacturer to manufacturer.
Once the design has been panelized the data is exported from the CAM system into the various equipment formats used by the manufacturer. The formats depend on what type of equipment is used. The equipment ranges from a Laser Photo Plotter, LDI, AOI, CNC Drill, CNC Rout, V-Score, ink jet printer, electrical test, etc…
Photo is the third core discipline of Front End Engineering. Photo-tools using Silver plotted images, diazo duplicates or Lithography are still common to the industry. These tools need to be created, inspected and stored for re-use on follow up orders. This is the main function of the Photo Technician. The Photo Tech plots the film on the laser plotter and maintains the film processor. They inspect the films and generate duplicates. The Photo Tech also maintains the film archives. The room Photo is located in is typically temperature and humidity controlled.
As the industry progresses the reliance on a Photo department becomes less and less. Photo was the key operation in the days of tape masters, film reductions and before low cost photo-plotters became available. Manufacturing with Laser Direct Imaging and ink jets are relatively new to the industry. As the cost to own this type of manufacturing technology decreases the need for a photo department shall become less and less. However, I think it shall be a while till we see the traditional photo department go the way of tape masters and bishop pads.