0. BB Electronics
How DfM, Virtual Prototype – General approach
V. 2.3
Claus E. Nielsen – PE/DL

1. How DfM – Virtual Prototype, General approach.
Abstract:
Due to the immense variety of possible analyses and reporting it is important to standardize the DfM approach.
How does BB Electronics manage the challenge and what tools, standards and reports are used to finalize our DfM reports.
Benefits of a supplemental BOM analysis, emphasizing the importance of compatibility of the critical process parameters of the various components in the BOM.

2. How DfM – Virtual Prototype, General approach.
Template
Standards
BOM Analysis
Tools
Design Constraints

3. How DfM – Virtual Prototype, General approach.
Template
Definitions and Categories
Proposed Manufacturing Process
Reflow Soldering
PCB Layout
Reflow / Adhesive
SMT Process
Wave Soldering
Through hole components
Selective Soldering
Summary

4. How DfM – Virtual Prototype, General approach.
26 Standards – IPC & J-STD
Acceptance:
IPC-A-610
Advanced:
J-STD-013
IPC-SM-784
Assembly:
J-STD-001
IPC-HDB-001
IPC-D-279
IPC-7351
Assembly Support:
IPC-CM-770
IPC-SM-780
IPC-7095
IPC-7525
IPC-7530
Components:
J-STD-020
J-STD-033
J-STD-075
Laminate:
IPC-4101
Printed Board:
IPC-2221
IPC-2222
IPC-4761
Printed Board Acceptance:
IPC-A-600
IPC-6012
IPC-6013
IPC-6015
IPC-6016
IPC-6018
Acceptance
IPC-A-610, Acceptability for Electronic Assemblies
Advanced
J-STD 013, Implementation of Ball Grid Array and Other High Density Technology
IPC-SM-784, Guidelines for Chip-on-Board Technology Implementation
Assembly
J-STD 001, Requirements for Soldered Electrical and Electronic Assemblies
IPC-HBD-001, Handbook and Guide to Supplement J-STD-001
IPC-D-279, Design Guidelines for Reliable Surface Mount Technology Printed Board Assemblies
IPC-7351, Surface Mount Design and Land Pattern Standard
Assembly Support
IPC-CM-770, Guidelines for Printed Board Component Mounting
IPC-SM-780, Component Packaging With Emphasis on Surface Mounting
IPC-7095, Design and Assembly Process Implementation for BGA’s
IPC-7525, Stencil Design Guidelines
IPC-7530, Guidelines for Temperature Profiling for Mass Soldering Processes (Reflow & Wave)
Components
J-STD-020, Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices
J-STD-033, Handling, Packing, Shipping and Use of Moisture/Reflow Sensitive Surface Mount Devices
J-STD-075, Classification of Non-IC Electronic Components for Assembly Processes
Laminate
Rigid
IPC-4101, Specification for Base Materials for Rigid and Multilayer Printed Boards
Printed Board
IPC-2221, Generic Standard for Printed Board Design
IPC-2222, Sectional Design Standard for Rigid Organic Printed Boards
IPC-4761, Design Guide for Protection of Printed Board Via Structures
Printed Board Acceptance
IPC-A-600, Acceptability of Printed Boards
IPC-6011, Generic Performance Specification for Printed Boards
IPC-6012, Qualification and Performance Specification for Rigid Printed Boards
IPC-6013, Qualification and Performance Specification for Flexible Printed Boards
IPC-6015, Qualification and Performance Specification for Organic Multichip Module (MCM-L) Mounting and Interconnecting Structures
IPC-6016, Qualification and Performance Specification for High Density Interconnect (HDI) Layers or Boards
IPC-6018, Microwave End Product Board Inspection and Test

5. How DfM – Virtual Prototype, General approach.
Definitions and Categories
A Major error/problem which must be altered before next revision.
B Process improvement / cost saving suggestion.
C Minor issue.
X BB Electronics internal issue.
OK Issue checked and found okay.
N/A Not Applicable: Issue is not possible / relevant to check.
Design improvements and suggestions are categorized in the following manner:
Used to classify identified issues in each sub section and eventually used for the creation of the final summary.

6. How DfM – Virtual Prototype, General approach.
Proposed Manufacturing Process
Single sided PCB
Double sided PCB
SMT
Process
Suggested
Reflow
Reflow/Reflow
Pin in paste
Reflow/Adhesive
THT
Wave soldering
Selective soldering
Hand soldering
The following processes are recommended in connection with production of the PCB.
Current example:
Instead of lead free hand soldering of lead free wave pallet soldering of the components JTP1, JTP2, J3 (center ground pins) and J4, it is recommended to use lead free selective soldering.
The main argument being that you ensure a consistent high level of quality and repeatability.
Further you avoid the costs of design and fabrication of expensive special solder pallets for wave soldering.

7. How DfM – Virtual Prototype, General approach.
PCB Layout
No.
Issue
Result
[Position:] Comments
5.09
Via hole: 0.25mm min diameter.
Min location from pads 0.254mm incl. trace.
Min edge-to-edge 0.381mm if not masked. No underneath part (wave or adhesive). No mask if used for test. Tented/Capped when wave-soldered. A
Numerous occasions, where vias are placed in pad. See comments below.

8. How DfM – Virtual Prototype, General approach.
PCB Layout
No.
Issue
Result
[Position:] Comments
5.13
No solder mask between 0402 or 0201 solder pads. A
Numerous occasions of solder mask present between pads for 0402 components. See comment below.

9. How DfM – Virtual Prototype, General approach.
PCB Layout
No.
Issue
Result
[Position:] Comments
5.15
IPC-7351 land patterns used for general SMT design. A
Numerous occasions where the recommendations listed in IPC-7351 has not been adhered to. See comments below.

10. How DfM – Virtual Prototype, General approach.
PCB Layout
No.
Issue
Result
[Position:] Comments
5.17
No natural bridges on fine pitch, networks or other areas. A
See comments below.

11. How DfM – Virtual Prototype, General approach.
PCB Layout
No.
Issue
Result
[Position:] Comments
5.24
Rework process feasible with regards to space and thermal load. C
JTP1; see comment below.

12. How DfM – Virtual Prototype, General approach.
SMT Process
No.
Issue
Result
[Position:] Comments
6.02
Min of 3-5mm free space around BGA type to allow for microscope inspection, rework possibility and mechanical fixtures for heatsinks. A
IC202, see comment below.
6.03
Component to component body spacing. Min 0.3mm
C680, C684, C686, C689, C732 & IC219. See comment below.

13. How DfM – Virtual Prototype, General approach.
SMT Process
No.
Issue
Result
[Position:] Comments
6.04
Component board edge clearance. Top side min 3mm, Bottom side min 5mm. If panelized >= 0.5mm from edge. Special considerations for ceramics. A
R301; see comment below.

14. How DfM – Virtual Prototype, General approach.
SMT Process
No.
Issue
Result
[Position:] Comments
6.09
Component has right size for layout. A
IC206, IC209, IC224, D6, F1, F2; see comment below.
6.10
Any other component issue.
C730, C989, C991; see comment below.

15. How DfM – Virtual Prototype, General approach.
Reflow Soldering
No.
Issue
Result
[Position:] Comments
8.02
Thermal distribution for individual part, total. Thermal relief for through hole/SMD with ground connection. A
C192; see comment below.

16. How DfM – Virtual Prototype, General approach.
Selective Soldering
No.
Issue
Result
[Position:] Comments
11.01
Dedicated selective soldering machine. B
JTP1, JTP2, J3, J4; see comment below.
Instead of lead free hand soldering or lead free wave pallet soldering of the components JTP1, JTP2, J3 (center ground pins) and J4, it is recommended to use lead free selective soldering.
The main argument being that you insure a consistent high level of quality and repeatability.
Further you avoid the costs of design and fabrication of expensive special solder pallets for wave soldering.

17. How DfM – Virtual Prototype, General approach.
Summary
Example:
General:
It is recommended to do a re-layout of the board due to numerous occasions of critical design issues on both sides of the board. The conclusion is especially based on deviations in the paragraphs listed below.

18. How DfM – Virtual Prototype, General approach.
5.09:
Numerous occasions of via in pad.
IC223:
Vias in ground pad.
5.09:
Numerous occasions with via in pad;
IC206, IC221, IC222, IC223 & IC802 all have vias in ground pad. Where this is considered necessary due to thermal relief, we recommend, that the vias should be plugged according to IPC-4761.

19. How DfM – Virtual Prototype, General approach.
5.13:
Soldermask between pads
Black area: Soldermask
Blue area: Pad
Specifying solder mask between pads for such small components can lead to the components "riding" on top of the solder mask webbing. We recommend that the solder mask is removed between the pads for the 0402-components. Please bear in mind also to remove any ghost traces (i.e. traces between 0402-pads), that otherwise will be exposed, when the solder mask is removed.
Green area: Soldermask opening

20. How DfM – Virtual Prototype, General approach.
5.15:
The IPC-7351 suggests the following nominal pad layout
Current PCB layout
The current 0402 chip resistor layout does not comply with the IPC-7351 recommended pad layout for this component type regarding the pad to pad distance.
The current PCB layout for the 0402 chip resistor has been measured to the following dimensions:
Outline pad to pad distance is measured to 2.12mm where IPC-7351 LP Calculator denotes an optimal distance of 1.32 to 1.72mm. (Least to most value).
Pad width is measured to 0.67mm where IPC-7351 LP Calculator denotes an optimal distance of 0.52 to 0.72mm. (Least to most value).

21. How DfM – Virtual Prototype, General approach.
5.17:
No natural bridges
Distance from protruding pin on the non mounted side for the component, JTP1 to R654 is insufficient (less than 2mm), if JTP1 should be reworked.

22. How DfM – Virtual Prototype, General approach.
5.24:
Distance too small between JTP1 and R654.
Distance from protruding pin on the non mounted side for the component, JTP1 to R654 is insufficient (less than 2mm), if JTP1 should be reworked.

23. How DfM – Virtual Prototype, General approach.
6.02:
IC202:
Several components obstruct inspection and rework possibilities for this BGA-component.

24. How DfM – Virtual Prototype, General approach.
6.03:
C680, C684, C686, C689, C706, C707:
Insufficient distance between 4 of the 6 components
6.03:
C732, IC219:
Insufficient distance between the components
6.03:
C680, C684, C686, C689, C706, C707:
Insufficient distance between 4 of the 6 components has been detected. In case of the usage of a tantalum B-size component batch with maximum physical outline ( =3.00mm), the individual distances between C680, C684, C686 and C689 are too small and there is a great risk of the components touching each other during SMT placement causing both misplacement and misalignment and missing solder joints.
The individual distance between C706 and C707 is adequate and it is therefore recommended to increase the individual distances between C680, C684, C686 and C689 to the same distance as in between C706 and C707.
C732 & IC219:
Insufficient distance between C732 and IC219 has been detected. The distance is measured to 0.115mm and is therefore below the recommended distance of 0.3mm. There is a potentional risk of the components touching each other during SMT placement causing both misplacement and misalignment and missing solder joints.

25. How DfM – Virtual Prototype, General approach.
6.04:
R301: Distance from component to board edge.
0.3mm
R301:
The distance from component to board edge is measured to 0.3mm which is below the recommended distance of 0.5mm for panelized boards. (Break-off frame for transportation).
Due to the current oversized pad layout for R301, there is a risk of the component “floating” even further towards the board edge and hereby reducing the distance to less than 0.3mm.

26. How DfM – Virtual Prototype, General approach.
6.09:
IC209: Wrong component definition.
IC209: This component is defined as SSOP20 in the BOM file but the CAD layout seems to be TSSOP20.

27. How DfM – Virtual Prototype, General approach.
WRONG
8.02:
C192: Missing thermal relief.
Could also introduce rework issues.
RIGHT

28. How DfM – Virtual Prototype, General approach.
11.01: Selective soldering
JTP1, JTP2,
J3, J4;
Instead of lead free hand soldering or lead free wave pallet soldering of the components JTP1, JTP2, J3 (center ground pins) and J4, it is recommended to use lead free selective soldering.
The main argument being that you insure a consistent high level of quality and repeatability.
Further you avoid the costs of design and fabrication of expensive special solder pallets for wave soldering.

29. How DfM – Virtual Prototype, General approach.
6.10:
C730, C989, C991:
The BOM file denotes the use of SANYO CV-AX CAN capacitors for all three components.
It seems that this particular type is obsolete or at least going to be in the nearby future and it is therefore recommended to use another type.
The SANYO OS-CON SVP series could be a recommendation assuming the right value and size can be found within this series.
The BOM file denotes the use of SANYO CV-AX CAN capacitors for all three components. It seems that this particular type is obsolete or at least going to be in the nearby future and it is therefore recommended to use another type.
The SANYO OS-CON SVP series could be a recommendation assuming the right value and size can be found within this series.

30. How DfM – Virtual Prototype, General approach.
BOM Analysis
RoHS compliance
Lead free process compliance
MSL = Moisture Sensitivity Level
PSL = Process Sensitivity Level
Process type restrictions
Peak temperature sensitivity
Limited number of process cycles
List of typical sensitive
component types
Benefits of BBE Preferred Part List
Main mission is detection of process sensitive component types / materials.
Secondary mission is finding possible cost savings

31. How DfM – Virtual Prototype, General approach.
BOM Analysis
Aluminum Capacitors
Plastic Molded Polymer Aluminum Capacitors
Film Capacitors: Non-PPS Type
Plastic Molded Polymer Tantalum Capacitors
Can/coin Type Electric Double Layer Carbon – Special Capacitors
Certain SMT Connectors
Certain Non-Solid state Relays
Certain fuses
Poly-pheny-lene Sulfide (PPS)
Can be sensitive in the following areas:
Preheat temperature (Maximum time)
TAL (Time above Liquidus Temperature).
Classification temperature
Peak temperature time
Ramp down rate / cooling rate
Number of reflows

32. How DfM – Virtual Prototype, General approach.
BOM Analysis
Benefits of BBE Preferred Part List
Components are always in stock.
BBE guaranties component value and tolerance but chooses an approved supplier.
No liability, customer only pays for used quantity – not MOQ.
Reduced NRE costs:
Time and money saved if BBE part numbers are present in the original customer BOM prior to BOM import at BBE.
NRE: Non-Recurring Engineering costs.

33. How DfM – Virtual Prototype, General approach.
Tools
Mentor Graphics VALOR MSS Process Preparation CAD software
ERF, External Rule File: Scripts
VPL, Valor Parts Library: Virtual component CAD layer.
Mentor Graphics CAMCAD Professional – CAD software
DRC: eSight Runner Scripts
RealParts: Virtual component CAD layer.
GraphiCode GC Prevue
Gerber Viewer.
PCB Matrix LP Calculator
IPC-7351B, Surface Mount Design and Land Pattern Standard.

34. How DfM – Virtual Prototype, General approach.
Tools
DRC: eSight Runner Scripts

35. How DfM – Virtual Prototype, General approach.
Tools
Virtual Component
CAD layer / Virtual Prototype
RealParts /
Wiki Components
Virtual component shapes are build based on the maximum mechanical measures of the shapes in the IPC libraries.
This is done in a separate program such as RealParts or Wiki Components.
The virtual component layer can then be placed on top of the original customer CAD data in our CAMCAD software.

36. How DfM – Virtual Prototype, General approach.
Virtual Component CAD layer / Virtual Prototype
Virtual component shapes are build from the measures of the IPC libraries.
This is done in a separate program such as RealParts or Wiki Components.
The virtual component layer can then be placed on top of the original customer CAD data in our CAMCAD software.

37. How DfM – Virtual Prototype, General approach.
Virtual Component CAD layer / Virtual Prototype
Virtual component shapes are build from the measures of the IPC libraries.
This is done in a separate program such as RealParts or Wiki Components.
The virtual component layer can then be placed on top of the original customer CAD data in our CAMCAD software.

38. How DfM – Virtual Prototype, General approach.
Tools
PCB Matrix LP Calculator

39. How DfM – Virtual Prototype, General approach.
Design Constraints:
PCB Manufacturers
IPC Standards
BBE Process capabilities

40. Thanks for your attention.
How DfM – Virtual Prototype, General approach.
Thanks for your attention.
Author: Claus E. Nielsen