6. Pcb assembly Views

The PCB assembly views should show the view of the PCB with the components placed on the board. Dimensioning is not necessary unless to define the location of a component with respect to some PCB datum. However it should be noted that SMD component locations are determined by the pad location and pad design and the tolerances will be wide, so if special tolerances are required, they should be indicated accordingly. Other dimensions shall be shown as REF DIMS.

• The drawing shall show top and bottom view, whether or not components are assembled on both sides.

• Each component shall be shown in outline.

• Polarity or orientation indicator and component reference designator shall be shown.

• The component reference shall be traceable to the schematic view and the BOM table.

• Test points shall be identified with the same detail as components.

• A 3D view of the PCB may be shown if this will improve understanding of the assembly, but it is not strictly necessary.

• Dimensions, notes and information which are related to the bare board shall NOT be included in the PCB assembly drawing, but in the Bare Board drawing.

The PCB assembly views normally occupy the last sheet of the drawing.

7. Connector Detail View

Where applicable, views showing connector dimensions, materials, plating and coining details shall be included in the PCB assembly drawing.

2. The Bare Board Drawing - 44xxx

The PCB bare board drawing is a separate drawing from the assembly drawings. The PCB 44XXX drawing will have a full title block and revisions control as shown in Figure 2. Since the PCB assembly refer to the single board, any changes will affect both drawings.

Figure 2: The standard bare board drawing border

This drawing shall detail all the mechanical dimensions and tolerances that are important to the design. It shall also clearly identify and label the Top and Bottom layers of the PCB. When applicable, intermediate inner layers shall also be identified and labelled. These shall follow the naming convention of Inner 1, Inner 2, etc..., with the first inner layer being the one closest to the top layer. Dimensioning of the holes shall only be included if critical to the assembly. The drawing shall also detail the following as applicable: -

1. Board material.

2. Copper and all other plating thickness specification and tolerances.

3. Areas of the PCB requiring additional plating processes.

4. Solder resist finishes.

5. Silk screen and identification where applicable.

6. Reference to any manufacturing standards that must be observed.

7. Carbon finishes tolerances, potentiometer resistance and linearity.

8. Edges or edge sections which shall be routed.

9. Edges or edge sections which should be scored for snap-off.

10. Indicate if the circuit tracks should be tested for continuity.

11. Indicate conformal coating if required and coating type and locations.

12. Indicate where the supplier may place their traceability identification data.

13. Indicate an unused area for the panelisation reference co-ordinates.

14. Indicate ‘keep out’ zones

The panelisation details shall only be defined when Methode are to purchase PCBs in panelised form. Otherwise a note reading “Panelisation to be defined by PCB assembly supplier” shall be included with the general notes list.

The bare board drawing does not need to the show the artwork pattern unless it aids the understanding of the design.

Flexible PCBs shall be drawn with the same details.

Artwork data

The bare board drawing shall include a table containing the file names and description of the manufacturing data of the PCB. The table shall have the following format: -

ARTWORK DATA REFERENCE TABLE 1
FILE NAME	FILE DESCRIPTION
44999-02.AST	COMPONENT ASSEMBLY TOP
44999-02.ASB	COMPONENT ASSEMBLY BOTTOM
44999-02.ELT	ETCH LAYER TOP
44999-02.IN1	ETCH LAYER INNER 1
44999-02.IN2	ETCH LAYER INNER 2
44999-02.ELB	ETCH LAYER BOTTOM
44999-02.SMT	SOLDER MASK TOP
44999-02.SMB	SOLDER MASK BOTTOM
44999-02.SPT	SOLDER PASTE TOP
44999-02.SPB	SOLDER PASTE BOTTOM
44999-02.BDR	BOARD OUTLINE DATA
44999-02.RTG	ROUTING DATA
44999-02.DDT	DRILL DATA
44999-02.DDS	DRILL SYMBOL TABLE
44999-02-XY.TXT	COMPONENT PLACEMENT COORDINATES
44999-02-TOP.DXF	TOP VIEW
44999-02-BOT.DXF	BOTTOM VIEW
NOTE: EXCELLON DRILL DATA FILES IN NCDRILL FOLDER