Thou Shalt Document!

Estimated reading time: 19 minutes

Have you ever wondered how to get involved in IPC standards development? If so, I'm going to give you an opportunity to participate right here, right now! The IPC is currently in the process of updating IPC-D-325 Documentation Requirements into the new IPC-2610 series:

IPC-2611 Generic Requirements for Electronic Product Documentation
IPC-2612 Sectional Requirements for Electronic Diagramming Documentation
IPC-2613 Sectional Requirements for Assembly Documentation
IPC-2614 Sectional Requirements for Board Fabrication Documentation
IPC-2615 Printed Board Dimensions and Tolerances
IPC-2616 Sectional Requirements for Electrical and Mechanical Part Descriptions
IPC-2617 Sectional Requirements for Discrete Wiring Documentation
IPC-2618 Sectional Requirements for Bill of Material Documentation
IPC-2619 Sectional Requirements for Product Performance or Process Control

Four of these have been released into the world for comments, and we will begin this little experiment with two of them. Ready? Here we go!

The IPC wants us to pay attention to the word "shall" in all of its publications. This word is always highlighted in bold font, and each document contains a specific paragraph about how the word should be interpreted. Here it is:

1.3 Interpretation

The word "shall," the emphatic form of the verb, is used throughout this standard whenever a requirement is intended to express a provision that is mandatory. Deviation from a "shall" requirement may be considered if sufficient data is supplied to justify the exception. The words "should" and "may" are used whenever it is necessary to express non-mandatory provisions. "Will" is used to express a declaration of purpose. To assist the reader, the word "shall" is presented in bold characters.

I thought it would be interesting to scan through the new documents looking for the word "shall." I chose the generic requirement (IPC-2611 Electronic Product Documentation) and one of the sectional requirements (IPC-2614 Fabrication Documentation) just to see what I would find.

These are in final draft form now and up for ballot, so very soon these will be official requirements that you shall use if you are going to build your documentation methods on the foundation that IPC provides. Here they are:

From IPC-2611 (applies to ALL electronic documentation)

In the event of any conflict in the development of new designs, the following order of precedence shall prevail:

1. The procurement contract
2. An approved documentation package (w/deviation list, if applicable).
3. Company specific manufacturing standard
4. This standard.
5. Other applicable documents.

The grade of documentation and completeness mode shall be described in the contract.

Grades and completeness may be A1, B1, C1, A2, B2, C2, A3, B3, or C3 see 3.2.1, 3.2.2, and 3.2.3. In the event that no grade is specified grade B2 shall be considered as the default.

In addition to the documentation grade, a data completeness mode and a function characteristic shall also be defined.

Any deviation from this standard in the documentation package shall have been recorded on the appropriate document as prescribed in the IPC-2610 series or a customer-approved deviations list.

In order to be able to accept intelligent data formatting the supply chain partners shall agree to the format used to describe the details of the documentation package. All information descriptions shall be provided in computer transferrable media on what the documentation package contains and how it may be interpreted. This should include date of generation, tool used and revision level, other manufacturing or ordering details.

The drawing sizes and format used to prepare the fabrication, assembly, schematic, etc. drawings shall be in accordance with ASME-Y14.1 & ASME-Y14.1M

When ANSI-Y14.1 is required, the standard drawing sizes A, B, C or D shall be used.

When continuation sheets of the drawing are used they shall be on standard sheet sizes, with a standard continuation sheet title block located in the lower right corner of each sheet.

The projection requirements shall be 3rd angle.

When ANSI-Y14.1M is required the standard drawing sizes identified in ISO 216 shall be used.

When using the ISO 216 image formats the angle of projection shall be first angle in accordance with Figure 4-3.

The title block shall contain the appropriate title of the document, the scale, the drawing number, the cage code number of the facility preparing the master drawing, if applicable, plus the appropriate approval block.

On continuation sheets without revision blocks, the title block shall contain provisions for recording the revision.

Signatures shall have a minimum of 3 signatures; who drew the document, who it was for and who checked the document.

Titles and subtitles for hard copy or electronic documentation shall always be shown in uppercase letters. The names of items used as titles for drawings shall be brief, descriptive, and of uniform definition. Titles shall consist of a basic noun or noun phrase and shall include sufficient modifiers to differentiate like items in the same major assembly.

The date format shall be the year (XXXX), month (XX) and day(XX). (i.e., 20040821, 20051122). The following characters shall not be used \ / : * ? " < > @ ~ |.

The drawing revision description block shall identify the specific changes made. It is not acceptable to just reference to the Engineering Change Proposal (ECP) or other engineering document that initiated the change.

Data file approval shall be contained within the data file.

When a drawing or electronic document is created using multiple sheets, the first sheet of the drawing shall contain the revision status block.

When multiple files are used in order to define the data used in the documentation package they shall be identified in a clear and unambiguous manner in order to facilitate data searches and configuration management.

The number assigned to a document (hard copy or electronic) or data file ID may consist of any alphanumeric including a dot, dash or underscore punctuation. Any letters that become part of the number shall be in upper case.

Every part, drawing, data file shall have a unique identifier that is part of an overall system The identifier assignment shall be managed through a consistent set of rules that can provide objective evidence that the system is robust and free of ambiguities.

The use of an alias (unique company identification or part number) representing internal IDs is a successful way of managing a variety of situations through the use of a consistent system intended to avoid confusion or to simplify information access. A method shall be established in order to validate that the alias is a legal ID assignment, and that a truth table concept is available in order to insure the cross reference to the other forms of identification can be ascertained easily.

In the event that a particular part, drawing or data file is not available that fully meets the form, fit and function requirements of the end product, a documented substitution may be authorized by the user. Since the substitute is not completely identical a new alternate shall be used in order to have the substitute be part of the system.

The first production change for any released document or data file shall be Revision ‘‘A'', with subsequent and sequential letters being used for additional revisions; i.e., Revision ‘‘B'', Revision ‘‘C'', etc.

Whenever the drawing, or computer transferrable media, requires a revision, the description shall identify whether the revision impacts form, fit, function.

The first engineering change, considered the first production change, shall be assigned the letter ‘‘A''. Subsequent changes shall follow in sequence: ‘‘B'', ‘‘C'', ‘‘D'', etc. Uppercase letters shall be used in alphabetical sequence. The letters ‘‘I'', ‘‘O'', ‘‘Q'', ‘‘S'', ‘‘X'', and ‘‘Z'' shall be omitted. When revisions are numerous enough to exhaust the alphabet, the revision following ‘‘Y'' shall be ‘‘AA'', and the next ‘‘AB'', then ‘‘AC'', etc. Should ‘‘AA'' to ‘‘AY'' be exhausted, the next sequence shall be ‘‘BA'', ‘‘BB'', etc.

The contract for the manufacturing supplier shall reference the documentation package, any applicable external standards or specifications, and the interpretation of the requirements related to the manufacturing of the end product.

The contract shall define the order of precedence when multiple date standards are referenced.

The contract shall define all deliverables from the manufacturer including requested time lines and quantity as well as any allowable yield oriented product being delivered in the set.

From IPC-2614 Board Fabrication Documentation

Classification of printed board documentation shall meet the requirements of IPC-2611, and shall be defined by Grade and completeness mode.

A specific grade shall consist of a letter to define the differences between hard copy and electronic data. In addition a second classification, consisting of a number, is required that defines the completeness mode of the documentation procurement package.

The output from the design process shall be consistent for the products being documented from the design process or the CAD system.

Conductor layer identification starting with the primary side, the next conductive layer shall be Layer 2. (For assemblies with components on both sides the most complex or densely populated side shall be Layer 1.)

Terms used on the Fabrication data set shall conform to this standard and IPC-T-50.

A Printed Board requiring a change shall be updated by raising the revisions of the following:

a) the fabrication drawing, including revisions of all cognizant pattern description;
b) the ‘‘bare board marking revision''; solder paste stencil pattern;
c) metal core pattern; laminated heatsinks, etc.
d) An update to a fabrication data set is permissible, provided the following criteria is met: the change shall not affect form(shape), fit (dimensional size) and function (electrical characteristics).
e) The assembly drawing (if the drawing duplicates information on the PWB drawing--e.g., artwork views)."

Whenever a printed board requires a change which does affect the form, fit, or function, the board shall be assigned a new part number and treated as a new design. The revision in this situation shall be treated the same as an initial release; therefore, the fabrication data set, pattern description and board revisions are assigned a dash (-) revision.

When the revisions do not affect form fit or function, the changed board shall be assigned the next revision identification, consistent with the revision system.

All CAD system output data shall meet the requirements of IPC-2580 series format and/or other industry acceptable standard formats as agreed to between trading partners. This requirement shall be part of the grade and completeness descriptions documented in the contractual agreements.

The fabrication drawing as a part of the data set shall be prepared in accordance with the requirements of this specification. Typical fabrication drawing documentation requirements are shown in Table 3-2.

The data pattern shall contain as a minimum, the following information:

A. Board part number and revision.
B. Layer number
C. For composite printed boards, a complete set of quality conformance coupons is required for the top board, the bottom board and the composite board.
D. Three fiducials (or registration targets) shall be located on grid and on each layer of data pattern. Each additional layer or data pattern shall have fiducials located at the same points which, shall register with each other, layer to layer.
E. Marking or silkscreen data patterns (when required) shall have a minimum of two alignment fiducials to coincide with the center-line of features located on the board surface to be marked.
F. Component pedestal data patterns (when required for no-lead parts) shall have a minimum of two fiducials to coincide with the center line of features located on the board surface.
G. Special tooling data patterns: During the formal design review and prior to layout, special tooling requirements which can be generated during design should be considered.

When a production master is not provided as part of the data set, the fabricator shall have responsibility for creating the production master from the data pattern master, the accuracy of which shall meet the requirements of the fabrication data set

When production masters are supplied as a supplement to the engineering fabrication data set, they shall be supplied as readily usable 1:1 precision masters including all manufacturing allowances.

When conformance test circuitry is required in order to validate the production quality the test coupon images shall be included in the single image production master.

The method of excising individual boards shall be included in the assembly pallet description.

Automated systems, such as CAD equipment, computer aided engineering (CAE) equipment, computer aided manufacturing (CAM) equipment, test equipment, photoplotters, automated assembly equipment (auto insertion and/or pick and place equipment), automated optical inspection (AOI) equipment, shall be capable of communicating with each other.

Generation of master patterns and measurement techniques shall be in accordance with the requirements of IPC-D-310. The appropriate pattern tolerances and processing allowances shall be incorporated into the production master.

Titles for printed boards shall consist of a noun phrase used to define the product type followed by an adjective that provides the specific use or function of the product type.

The noun phrases shall be followed by an approved separation character or format. The preferred separation character is a dash. Naming for files may use underscores as a name separator or have the capital letter of each word be the delimiter. e.g., PrintedBoardSynthesiser.

In the electronic format files can be intermixed in order to ease the processing capability by the manufacturer, however the first file shall identify the mixing and matching of different electronic formats.

Content formats are directly computer processable and require observance of the standard protocol and shall not be mixed with other format except to permit a reference to an external URL. In this instance the proper link shall be supplied and assurance provided that the link remains active through the life of the data file.

The number assigned to a format for an individual product shall be unique.

A contract number shall be part of the fabrication information and should be maintained in a separate location in order to avoid changing many data items when the contract changes. When a contract number appears in multiple format locations it shall be consistent without ambiguity.

A distribution list should be developed for all fabrication data set recipients. The list shall be related to the contract, mode or usage of the data set, and be updated periodically.

A revision control system shall be established for all formats that become part of the fabrication data set. The system shall include a method to define the original release of the data as well as changes made when the product is in full production.

Revision letters used to define different characteristics of the fabrication data shall be made up of single letters of the alphabet without use of the letters I, O, Q, S, X, Z as defined in IPC-2611. If revision requirements go beyond the 20 available characters a double letter shall be used starting with revision AA.

At times a temporary revision of a product is required in order to select the best possible solution to a variety of conditions either fabrication, assembly or any condition where further evaluation might be necessary. In this instance a dash shall be used behind the original revision letter followed by a unique number for any variation being explored. The first number used shall be 1 followed by sequential numbering. The affectivity (number of units to be produced) shall be identified as part of the fabrication data set.

Configuration control shall be maintained between and among all elements of the fabrication data set.

The fabrication data set shall describe the final configuration of the printed board in sufficient detail to ensure fabrication of the end product board. In addition to the configuration details, information shall also be supplied as to the performance requirements expected of the printed board throughout its life cycle.

All notes shall be numbered sequentially, starting with number 1. (1, 2, 3, 4 etc.) In order to categorize similar notes sub-letters may be added to the number such as 1A, 1B, 1C, or they A, B, and C may be indented under note 1 in an outline format. Those notes which are referenced elsewhere on the fabrication drawing shall be enclosed in a square or flag. The corresponding reference number(s) delineated elsewhere on the drawing shall also be enclosed in a square or flag. Those notes that are elsewhere in the fabrication set shall be enclosed in a diamond. The first item behind a note in a diamond shall be the note location such as a URL or document number.

The placement of notes on the fabrication data set shall be on the first file or image and located in the upper left-hand corner starting with Note 1.

In the event that no design or board performance requirements are noted, the manufacturer shall assume that Class 2 Level B is intended.

The fabrication construction shall be described using a cross sectional view, or table indicating the construction and stackup of the board.

The fabrication construction in mode 2 and mode 3 completeness formats shall include:

a) The core thicknesses and tolerances; prepreg and tolerances; constraining core and construction, (when required) including thickness and tolerance;
b) Individual layer locations; solder mask information (top and bottom, when required);
c) silk screen information (top and bottom, when required);
d) primary and secondary (top and bottom) identification plus an overall dimension including tolerance.
e) Power plane layers shall be identified by their voltage; i.e., +5V, +15V, 15V RTN, etc. Split plane layers shall be identified with the voltages separated by an underscore or slash delimiter; i.e., +12V_-5V_GND.

The layout or board design shall be viewed from the primary side of the board.

Unless otherwise specified, conductor layers shall be numbered consecutively, starting with the primary (component) side as layer 1.

The accuracy and scale of any data set, design layout or check plot shall show sufficient detail to eliminate inaccuracies in interpretation during the pattern generation process.

The location of blind and/or buried vias shall be identified for each layer pair and should be illustrated on the drawing or electronic Image. When controlled depth drilling is used to create blind vias (usually filled with conductive or non-conductive material), the drill depth from top or bottom shall be included in the separate drill list data.

When creating documentation illustrating constraining core printed boards the following parameters shall be considered:

a) Substrate drawings or data, illustrating constraining core construction, shall use the same coordinate zero feature location as the printed board(s).
b) clearance holes required for the top-to bottom plated through-hole interconnects
c) profile dimensioning
d) thickness(es)
e) materials used, processing requirements
f) coupon clearance holes.

The coupon shall be designed in accordance with IPC-2221.

The Fabrication Data Set shall have a chart titled "Hole Schedule."

Each unique hole diameter shall be assigned a separate hole schedule symbol or code letter (optional) for reference. The hole schedule shall also correspond with the plotted ‘‘Drill Pattern'' illustrating all drill locations.

Every hole shall be identified (by symbol) and shall contain the following information in the hole schedule:

a) Diameter,
b) Tolerance range,
c) Maximum hole considered when developing circumscribing land (Optional)
d) Plating requirements, (plated or nonplated).
e) Additional information used to identify tooling holes,
f) Tented holes or filled holes.

The drill pattern shall be included as part of the Fabrication Data Set for mode 2 and 3.

The drill pattern (viewed from the primary side) shall include quality conformance coupons as agreed to between user and supplier.

The methods for dimensioning the profile (board outline) shall be in accordance with IPC-2615. The methods for depicting feature size, position and location, form and associated tolerances. Tolerances shall be in accordance with IPC-2615.

The board thickness shall be dimensioned in an end view or depicted in the board construction crosssectional view.

Board thickness shall be specified on the Fabrication Data Set and, unless otherwise specified, shall include metallic deposition. In critical areas, such as connector contact areas, the thickness tolerances may be more stringent and shall be detailed with specific size conditions (MMC and LMC), and should, wherever possible, be limited only to those areas where needed.

When printed board features fall off grid, they shall be individually dimensioned and toleranced on the Fabrication Data Set.

Grid systems shall be located with respect to a minimum of two datum points.

The grid increment shall be specified on the Fabrication Data Set.

The fabrication data set shall include the relationships and acceptable tolerances between all datum features as established in accordance with IPC-2615. A minimum of two holes located on grid shall be dimensioned and toleranced with respect to a datum reference frame.

The values of printed board dimensions and tolerances shall be in accordance with IPC-2615. The dimensioning and tolerancing convention used on the fabrication data set shall be in accordance with IPC-2615.

Datum features shall be specified on the fabrication data set by means of datum symbols per IPC-2615; implied datums shall not be used. Datum features shall be functional features of the printed board, and should relate to mating parts such as mounting holes, connectors, or component leads or terminations. All datum features should be located on grid or establish the grid criterion, and they shall be located within the printed board profile.

Unplated through hole patterns, especially tooling and mounting holes (board mounting holes, interface connector mounting holes, board top plate/mounting bracket mounting holes, etc.) are generally drilled in separate drilling operations as one of the last fabrication operations. They shall be explicitly dimensioned and toleranced, even if they occur on grid.

A minimum of two holes on grid shall be dimensioned and toleranced with respect to a datum reference frame in order to locate the grid.

When specified on the fabrication data set, boards and assemblies shall be marked by appropriate inks, labels, etched characters, or other permanent methods.

If a conductive marking ink is used, it shall be permanent and appropriately isolated by spacing or coating from the balance of the circuitry.

Markings shall be of sufficient size, clarity, and location to allow legibility during processing, inspection, storage, installation, and field repair.

The fabrication drawing shall specifically indicate the location for the date code, fabricator's I.D. and UL marking, user's cage code, ESD symbol and all other required traceability markings.

ESD, military or Underwriters Laboratories requirements may include special marking considerations which shall become a part of the master drawing.

A note on the fabrication data set shall specify the acceptable bow and twist requirements.

Coupons or their technical equivalent shall be used to determine the quality of the final product; user and supplier agreement for alternate methods shall be required.

When process control coupons are used in lieu of quality conformance coupons, they shall be depicted on the Fabrication Data Set or Contract.

Target patterns (fiducial targets or marks) shall be provided on all surface mount image.

Whew! That's a lot of shalls.

The prospect of wading through an entire series of new documents is intimidating to most people, so maybe reviewing this abbreviated list is an easier approach for some of you. If you are involved in circuit board design and are familiar with fabrication drawings, you will know which of these can be implemented without too much trouble, and which of them might be difficult or unneccessary.

If you have short comments on any of these, e-mail them to me at pcbjack@gmail.com I will collect them and submit them as a group to the committee by March 25, 2009. Editorial comments are easy, but for technical comments you should know enough about the subject to suggest an alternative.

If any of these statements are worthy of open discussion, the best forum is probably the Designer's Council listserve. You can join by sending "subscribe DesignerCouncil (yourname)" in the body of an e-mail (no subject required) to listserv@ipc.org.

If you are interested in the subject of electronic documentation, please help us out! Download the entire document and official comment forms here.

Thanks for your help.

Jack Olson is a circuit board designer at Caterpillar and member of IPC's 2-40 Electronic Documentation Technology Committee. He can be reached at pcbjack@gmail.com.