Page 40
www.us-
tech.com
December, 2016 Production PCB Prototypes & Medium Volume
Get the best Price & Service for special technology Proto‘s & volume PCB quantities
Flex PCB Prototypes Favourable pricing
FREE Stencil with every PCB-POOL® prototype order
For information, please call at
916 241 9062
www.pcb-pool.com
Convolution of the BOM: How Much Could a Resistor Cost?
By Stanley L. Bentley, P.E., Senior Technical Advisor, DIVSYS International
L
et’s evaluate the convolution of the bill of materials (BOM) with all of today’s fragmented processes, each with its own jealously protected soft- ware. A design engineer (DE) receives a project request to design a cir-
cuit. DE opens the schematic capture program and designs the circuit. As part of the design process, the BOM is started. In this BOM is entered a 1k, 1/2W resistor, designated R1, with a tolerance of 0.5 percent and 25 PPM TC. The circuit is run through a simulator and found to deliver the desired perform- ance. The package is then passed to the mechanical designer. Initial BOM columns include quantity, description, value, tolerance, temperature coeffi- cient, and reference designator. The mechanical designer produces a 3D model of the PCB with dimensions
in Solidworks that shows a location for a component with dimensions of 120 x 60 mils (3.0 x 1.5 mm). The package is then passed to the CAD designer. The CAD designer imports the schematic and the model into his program
and then chooses a 1206 package for the resistor to match the size provided in the model. The designer goes to the web and downloads a .stp file for this package. The designer then creates a PCB layout by merging the physical lo- cation with the logical part in accordance with the net list. The package is then passed to the component engineer. Additional data columns not in the BOM: package, x/y location, and rotation. The component engineer (CE) takes the BOM and goes to the standard
parts list to assign a physical part to the logical part, R1. The CE discovers they do not have a standard part with these characteristics, so a new part must be created in the part master of the manufacturing system software. The BOM is then sent to the PCB engineer. Additional BOM columns: manufac- turer, manufacturer’s part number, and approved alternates. The PCB engineer is not familiar with this particular application, and
must hold a meeting to determine which standards are required. There is no precedent, so the PCB engineer copies and pastes PCB notes for a “wellhead” application. The engi- neer then amends the BOM with the description of the PCB and passes the package to document control. No additional columns are required. Document control requests
Convolution of the BOM is created by the use of specific software systems within each operating
department and exacerbated by the absence of a high level integration
ISO 9001: 2008 Certified
Gerber files from the CAD design- er and then assigns part numbers to the reference designators in the BOM. The solid model, the Gerber file and the BOM are now “controlled” in the manufacturing software. The BOM is sent to the strategic ops manager to determine which of the
system that can deal with disparate software systems and their unique extracts.
global sourcing directors are needed to negotiate the pricing for the PCB and the resistor. Two are needed because PCBs usually have a unique commodity code. The BOM is imported into the ERP software which only accepts the at- tributes of quantity, price, description, manufacturer, manufacturer’s part number, and alternates, with the rest of the engineering data often omitted. Once the price negotiations are complete, orders are placed, and document control is instructed to provide the PCB specifications to the winning fabrica- tor. Following the resolution of all EQs, the single resistor and the PCB are received, inspected, and inventoried. The strategic ops manager now directs global sourcing to select a con-
tract manufacturer with the right technical capabilities. The parts kit is pulled from inventory and shipped to the supplier. The CM receives a copy of the BOM from the ERP system, but (since the kit was provided) much of the purchasing data is not relevant. The data columns needed by the CM are in the original CAD design package, which is stored in the customer’s manufac- turing system. The CM’s CAM engineer is put in contact with the customer’s document control. It is determined that document control has a BOM with ref- erence designator, value and tolerance, but does not have the CAD file con- taining the package, x/y location, and rotation that are needed for program- ming an SMT machine. These must be procured from design engineering. It is also determined that document control does not have the stencil file
STATIC DISSIPATIVE POLISH COVERING ALL FLOORING TYPES
WWW.ACLSTATICIDE.COM INFO@ACLSTATICIDE.COM (800) 782-8420
from the PCB vendor as it was not requested by global sourcing. The CM now becomes the “integrator” requesting the data they need from each of the groups within the OEM and dealing with the various software packages used by each department. To be successful, the CM must assemble a BOM that has all the columns required to build the product by merging the design and CAD BOMs with the manufacturing and ERP BOMs. This satiric convolution of the BOM is created by the use of specific soft-
ware systems within each operating department and exacerbated by the ab- sence of a high level integration system that can deal with disparate software systems and their unique extracts. The simplicity of a single engineer manag- ing an entire project is lost in this compartmentalization of product data. The irony is that an outside resource, the CM, now emulates that simplicity by act-
ing as the “de facto” single engineer. Contact: DIVSYS International, LLC, 8110 Zionsville Road,
Indianapolis, IN 46268 % 317-405-9427 E-mail:
sales@divsys.com Web:
www.divsys.com r
PCB-POOL® is a registered trademark of Beta LAYOUT GmbH
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84
