How to Cost a PCBA
PCBA costing requires the following:
1 A version of aPriori that supports PCBA.
2 A version of the PCBA Assembly VPE that has been customized for your company, including a Component Library that reflects your Bills of Materials.
3 A version of the “project-management-plugin” that supports PCBA.
4 User Defined Attributes (UDAs) that support PCBA.
5 Mappings in the BOM Loader that assigns BOM column headings to fields in aPriori.
These prerequisites should have been addressed by aPriori Professional Services working in concert with your company’s aPriori administrator(s).
To import and cost a new PCBA assembly
1 In the aPriori client, click the PCBA button.
2 IF you already have a PCBA open, aPriori prompts you to specify whether you want to import a new PCBA for the first time, or modify the settings of the open PCBA. Select Import New PCBA then click OK. (If no existing PCBA is open, aPriori assumes that you are importing a new PCBA and takes you to the next step.)
3 This displays the PCBA Costing dialog, where you input important values that describe attributes of the PCBA which are not defined in the BOM. The first page of this dialog allows you to specify “Global Inputs” such as board dimensions which may be needed by several different processes.
Here is a summary of the values that you should provide in this dialog:
Scenario Information – This is where you specify the BOM to import. (It’s a good practice to incoporate the part number in the name of the file.)
BOM File –Use the navigation button to specify the full path name of the BOM .csv.
Part Number – IMPORTANT: The value you enter here MUST be exactly the same as part number as entered in Line #1 of the .csv file.
Scenario Name Suffix – Specify a string that will indicate the level, status, or some other aspect of this costing, such as “initial”, “test”, “asia”, etc. (Full scenario name is reflected in the read-only “Scenario Name” field on the next line.)
Production Settings – With the exception of the checkbox, these settings are the same settings that you find on the Cost Guide (see.”Cost Guide” section of the aPriori User Guide for details).
Modify Production Settings – This checkbox enables you to update production inputs. These inputs are pushed down to all child components. This checkbox is only available when recosting PCBAs, and when checked you can change the VPE, Annual Volume, Batch Size and Production Life settings. Note: Enabling this option will cause costing to be slower since all subcomponents will be recosted.
VPE – It is critical that you select a VPE that supports PCBA. In most cases, aPriori will not display any non-PCBA VPE. But if your system for some reason is configured to allow this, be aware that selecting a non-PCBA VPE (such as “aPriori USA”), will cause your costing attempts to fail.
Annual Volume – Number of units you expect to manufacture in one year.
Batch Size – Typically Annual Volume/12
Production Life – Number of years you expect the part to be manufactured
Board Dimensions – Physical aspects of the printed circuit board.
PCB Length (in) – Self-explanatory.
PCB Width (in) – Self-explanatory.
Surface Mount Side Count – Specify Single-Sided, Double-Sided, or None.
Plated Through Hole Side Count -- Specify Single-Sided, Double-Sided, or None.
Percent of Components on Bottomside (%) – Required if you have specified Double-Sided above.
Panelization – Use this section to specify if multiple PCBAs are built at the same tme, and then separated into individual boards.
Boards Per Panel – Lengthwise -- Self-explanatory.
Boards Per Panel – Widthwise -- Self-explanatory.
Depanelization – This checkbox enables you to force depanelization for a 1 x 1 panel. This enables you to more accurately account for the processing required to manufacture boards that come in a sheet that must be trimmed, such as circular or other non-rectangular boards. This checkbox is only available when 1 x1 panels are specified. Depanelization is assumed for any settings greater than 1 x 1.
Depanelization Method – Specify Manual or Automated. (If manual, cost calculations will take into account breaking the panels apart by hand. If Automated, use of a band saw is assumed.
When done filling in these fields, click Select Secondary Processes
4 Use the Optional Processes dialog to indicate which processes should be executed for this PCBA.
The options in this dialog box map to each of the optional assembly processes documented later in this chapter. Use the following links to navigate to descriptions of these processes and their related Process Steup Options (PSOs).
Component Prep:
Surface Mount:
• Solder Paste Inspection – Top -- Solder Paste Inspection
• Solder Paste Inspection – Bottom – Solder Paste Inspection
• Automated Optical Inspection –- Top -- Automated Optical Inspection
• Automated Optical Inspection –- Bottom -- Automated Optical Inspection
• Automated XRay Inspection –- Top -- Automated Xray Inspection
• Automated XRay Inspection –- Bottom -- Automated Xray Inspection
Testing:
• Flying Probe Validation -- Flying Probe Validation
• InCircuit Test -- InCircuit Test
• Bake In Test -- Bake In Test
Special Processes:
5 Click OK when done, then click OK on the PCBA Costing dialog box.
aPriori begins to cost the PCBA based on the inputs you have provided.
Note: When using the PCBA model for the first time, it’s not uncommon to see one or more messages similar to “Could not find a feasible routing”. This typically indicates that aPriori could not find a match between a part in the BOM and the Component Library. Read the following sections for information about how to proceed.
To validate your initial costing
aPriori recommends that you validate your results, especially when first getting started with PCBA costing. This means manually checking for feasibility or costing errors, and checking the number of components in the assembly against the number of components listed on your PCBA BOM.
1 Common errors include:
• Something is not typed correctly.
• The component is missing from the Component Library (or it exists in the library but does not have a price, or is missing a type designation).
• The inputs you provided in the PCBA Costing dialog conflict with the data extracted from the BOM and Component Library. This typically involves the settings of Surface Mount Sides and Plated Through Hole Sides. For example, if your BOM contains no surface mount components but you specify Single Sided or Double Sided rather than None. Or conversely, if you specify None, yet your BOM contains components of the specified type.
2 Another adjustment that you can make would be to add additional operations that might not be called out explicitly on the original BOM. For example, labeling operations might not be in the BOM and therefore would not automatically show up in the Assembly Details tab. To manually add such an operation, bring up the Routing Selection editor by selecting the assembly and clicking Edit > Routing Selection in the Manufacturing Process panel). Add the missing process and adjust the quantity in the Process Setting Options. (For more information, see the "Selecting a process routing" section of the aPriori User Guide.
Once you have successfully imported your PCBA, validated it, and obtained a reasonable initial costing, you can proceed to use it in aPriori in much the same way you would work with a geometry-based assembly and its component parts.
If you get a failed costing
If you get a failed costing due to a component or component cost missing from the Component Library, you can workaround this failure:
For the short term, you can open the component and change it to a manually costed part and provide a material cost (if available) that will capture most of the cost impact of the missing component.
In parallel, you should contact your VPE manageradministrator who is responsible for maintaining and updating the Component Library to implement a permanent fix..
To recost an existing PCBA
In most cases, you should use the PCBA button to recost, following the same procedure described for importing and costing a new PCBA. Just select Modify Current PCBA when prompted. aPriori displays the costing dialog boxes populated with values that you entered from the previous costing.
However, if you simply want to recost using different production settings (volume, batch size, etc.) and not vchange any other PCBA settings, it may be more efficient to use the standard Cost Guide. In this case, you would update the production settings, cost the assembly, copy the production volumes to the children, and then deep cost the assembly. See the aPriori User Guide for more information information about using the Cost Guide and assembly deep costing.