Working successfully with your service providers: organization--your own--is the name of the game, when dealing with design, fabrication and assembly service providers.

As the downsizing trend continues, the drive to use outside resources is also increasing, and many internal design departments are shrinking--in some cases, disappearing altogether. At some point in time, most electronics companies will have the need to outsource some, if not all, of their PCB development work.

Some of these companies may hesitate to use outside resources because they fear the line of communication between their engineering departments and the designer or service provider will be severed. This may happen in certain cases; sometimes this may be the result of an intentional act to prove to management that outsourcing is not a positive progression. But for companies who want to form a good working relationship with outside service providers, there are a number of steps that can be followed during each phase of the development cycle to ensure success every time. This article will focus on the three major areas of PCB development and discuss some very simple ways to clear some of the obstacles associated with outsourcing.

PCB Design

Design is the first and probably most critical step in creating a successful product. It can have the greatest downstream impact on every other step in the development chain. A poor design package can and will wreak havoc on the fabrication and assembly processes to follow. A well-organized design package can provide peace of mind and clear sailing from start to finish.

Vendor selection. The first item to consider in the development cycle is which vendor will complete the design work. When selecting a vendor for PCB design activity, pick one who best suits your needs. If your designs are very simple, say, single- or double-sided boards, your moonlighting brother-in-law may be all you need. If your designs tend to be on the more complex end of the spectrum, pick a vendor who can design the project exactly to your specifications. Software compatibility may be a concern when searching for a service provider. However, rather than just looking for a vendor who uses the same software package that you use, also look for one with the expertise to complete the job. Budget and scheduling will also be criteria for your search, but be careful when selecting a vendor strictly based on a low price.

Remember these three simple formulas when shopping for domestic design vendors:

* Cheap plus fast does not necessarily equal high quality.

* High quality plus fast does not necessarily equal cheap.

* Cheap plus high quality does not necessarily equal fast.

If a vendor offers cheap, fast and high quality, design services, chances are he's probably using offshore resources to complete the design work. Be sure to check out some of his customer references. I know of a few design firms on the West Coast who do all of the front-end work in the U.S., but ship out the bulk of their workload to be completed in various Asian countries using low-cost labor resources. If you don't mind sending your money (or American jobs) overseas, suit yourself. Your out-of-work friends and neighbors may be thanking you some day real soon.

Input package. Organization is the key to a good input package. A concise input package (in hard and soft copies) should include at least the following items:

BOM. The bill of materials should include item numbers, quantities, reference designators, part manufacturer, manufacturer's part number, and part or package description.

Schematic. A hard and soft copy of the schematic is always preferred. Soft copies can be either an Adobe (.pdf) format or the native CAD database format if that is acceptable to the vendor. Be sure the schematic is readable and includes device numbers, part values, reference designators and signal names.

Netlist. A netlist should be provided in the vendor's preferred format. Although a specific format may be preferred, most vendors should be able to convert any machine-readable netlist into the format of their choice.

Mechanical drawing(s). The mechanical drawing should include a dimensioned board outline showing all mounting and tooling holes, critical component locations and restricted areas for clearances and/or hardware. Hard and soft copies should be provided. Soft copies can be either an Adobe (.pdf) format or a machine-readable format such as AutoCad DXF.

Data sheets. A manufacturer's data sheet should be provided for each component/package type on the board. Most discrete components such as caps and resistors may be exempt from this requirement as long as the package code (i.e., 0805, 0603, etc.) is clearly stated on the BOM for each part. There is no such thing as a standard IC package! Always include as much part information as possible for unique component packages.

Project notes. Notes can be a vital part in conveying specific design details from the engineer to the designer. Notes can be very general in nature or very detailed. Hard and soft copies are recommended. This information should be included in the notes, though this list is not exhaustive:

* Placement guidelines.

* Routing guidelines.

* Power/current requirements.

* Signal integrity issues.

* Impedance requirements.

* Silkscreen requirements (i.e., part numbers, copyright, logo, etc.).

* Output requirements (Gerbers, DXF, database).

Avoid making changes during the design cycle. Design changes cost time and money, and can sometimes cause a lot of unneeded frustration. Plan ahead to avoid making component or circuit changes during the design phase. Make sure the components you choose for the circuitry are readily available. Almost 50% of all design changes are due to component obsolescence issues. The last thing a service provider wants to hear from you is "Oh, I forgot to mention" or "We have to make a design change." What this means to the customer is schedule delays and increased costs associated with their project. What this means to a service provider is an interruption in the normal design flow and the need to reorganize other project schedules to accommodate the newly mentioned design or manufacturing criteria.

Put it in writing PCB designers are multitaskers by nature, but giving verbal instructions to a designer could be dangerous. It's always best to follow up conversations in writing via e-mail, fax or some other type of written document. Having all of this information readily available for the designer will help streamline the layout process and may be reflected in a reduced design cost or the actual number of hours required to complete the project.

PCB Fabrication

Now that the smoke has cleared, it's time to fabricate some boards. A good fabrication package is essential to getting exactly what you want in the time frame you request. Some fabricators work on hundreds of different jobs each day, so it's very important to supply them with all of the information needed to complete each job. I personally don't like receiving calls during dinner or late into the night from the CAM engineer asking for answers that should have been defined in the lab package. A good fab package should include the following:

Gerber civets. Gerber data can come in a variety of different formats. RS274X is by far the preferred Gerber format for most fabricators. Each artwork file contains embedded aperture information, the XY data, as well as a number of other plotter control parameters. Pick a level of output precision (resolution) that matches the type of features you are trying to plot.

Fabrication drawing. The fabrication drawing is the map that puts all of the data together for the PCB manufacturer. Sending board data to a manufacturer without a drawing is like having a street map without street names. The drawing is where you specify what you expect to receive from the board vendor. There are no guarantees without one. A typical fab drawing should include the following:

* Notes, such as materials, copper thickness, surface finish, soldermask type, silkscreen color, etc.

* Dimensioned board outline.

* Layer stackup.

* Drill legend.

* Detail drawings.

Readme file. A readme file is basically an ASCII text file that should contain:

* Designer contact information, including an after-hours phone number.

* Artwork file names with descriptions.

* Gerber file format (i.e., RS274X, 2.4, ASCII).

IPC-D-356 netlist. Most of today's CAD systems are capable of directly producing this type of netlist output. This netlist is used by the fabricator to ensure that the artwork output matches the original database in terms of netlist connectivity, feature locations, etc. The IPC netlist is one of the most comprehensive means to verify the intentional artwork output from the CAD system. A Gerber netlist check simply compares the finished board with the original Gerber data for opens and shorts but fails to compare to the original CAD database.

Drill data. This is simply the NC drill output from the CAD system. The Excellon format is always a safe bet and most manufacturers can convert if needed. Drill data should include:

* XY locations for plated and non-plated drill holes.

* Tool numbers/locations.

* Drill speed/feed.

* Output precision that matches the gerber data precision.

Remember, a complete and well-organized lab package will help ensure that you receive the finished bare boards exactly as you specified.

PCB Assembly

Assembly can be pretty simple in most cases, but there are a few areas that can get you into trouble. Once again, an accurate input package is vital to the success of the finished product. Below are just a few of the items that will help your project glide right through the assembly process.

Assembly drawings. They should clearly show part outlines and reference designators (a hard copy is preferred).

Gerber data. At a minimum, always include Gerber files for the top and bottom pastemask layers. If boards have been panelized during fabrication, be sure to include the panelized artwork for the pastemask layers. A complete set of Gerber artwork is always preferred.

An accurate BOM. Unfortunately, 75% of the time, the BOM used to assemble the board does not match the BOM used to design the board. Make sure the assembly BOM matches the actual board. Content should include all items previously discussed in the design section.

Component XY data listing. This is usually in the form of an ASCII text file and should include X and Y coordinates for each component, component rotation and whether it is located on the top or bottom of the board.

Part kits. If you choose to provide a parts kit to your assembly vendor, make sure you include at least a 5-10% overage for all components. Tape and reel (T&R) components should be a minimum of 12-18" in length. All parts should be placed in individually labeled bags or reels. Clearly mark the parts with the item number from the BOM, part number, quantity and reference designators.

A spare board. If you can afford to, include a spare board that can be used for reflow profiling, programming, etc. A scrap or solder sample board is perfect for this. Chances are you will not get it back.

Readme file. This readme file should contain the designer's contact information, including an after-hours phone number, as well as contact info for the person responsible for the parts kit.

From PCB design to fabrication to assembly, an organized input package can save time, effort and money while avoiding rework and omissions at every interval of the product development cycle. The only way to avoid unwanted obstacles along the way is to organize input packages in a way that will facilitate accurate results every time.

Vendors will appreciate the extra time you spend providing a perfect package, and they should adjust your pricing to reflect that extra effort. PCD&M

CHARLES CAPERS is president and owner of Trilogy Circuits Inc., a full turnkey service organization. He is a senior-level PCB designer with 20 years of experience in design, fabrication and assembly. Capers can be reached at [e-mail].