iNEMI Cleanliness PPT 9-16-19 Final

Characterize and Understand Functional Performance of Cleaning QFN Packages on PCB Assemblies

Presentation on behalf of the iNEMI working groupPresented byMike BixenmanKYZEN Corp.

Originally published in the Proceedings of SMTA International, Rosemont, IL, September 22-26, 2019.

Outline / Agendan Background / Context n Cleanliness Value n Test Methods n Experimental n Data Findingsn Statistical Methods n Test Suite and Spec for Cleanliness

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BACKGROUND / CONTEXT

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Higher Placement Densities n Shrinking form factors n Increased I/O densitiesn Problematic components

¨ Bottom terminated ¨ Low standoff ¨ Non-standard designs¨ Trap residues

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Process Residues n Contamination cannot be seen

¨ Makes it hard for assemblers to project life expectancy

¨ Can impact device performance

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TEST METHODS

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Cleanliness Test Methods n The ROSE and Ion Chromatography

¨ Bulk extraction test methods ¨ Provide information across the entire assembly ¨ Not ideal on site-specific components where localized residues are most

problematic

n SIR and C3 test methods¨ Better suited for detecting ionic contamination on leadless and bottom

terminated components

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BTC and Leadless Componentsn Custom test boards

¨ Can detect the activity of these residues under the bottom termination using the SIR and C3 test methods

¨ Sensors routed to the conductive pathways n Electrical testing under temperature, humidity, and bias conditionsn Extraction of residues on site specific components

¨ Combination of Electrical and Chemical Methodsn Printed Circuit Board Designn Materials Characterization n Validation / Verification

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EXPERIMENTAL

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DOE n The objective is to

¨ Quantify the effects that certain PCBA materials (solder flux), processes (cleaning), and designs (solder mask) have on the reliability of an end PCBA

n Cleanliness will be objectively measured by:¨ SIR performance¨ Ionic Contamination monitoring

n Ion Chromatography (IC)n Cleanliness underneath a component (C3)

¨ Visual methodsn Visible corrosionn Visible flux residuen Dendrite length

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Test Board n The levels tested are as follows:

¨ Test board held constant n FR4 Laminaten Liquid Photo-imageable solder maskn Immersion silver

¨ QFN four Quadrant SIR Test Boardn Q1: SMDn Q2: NSMDn Q3: No-SMn Q4: NSMD Solder Mask Webs with Thermal Vias

¨ Solder Paste (flux-bearing materials)n Water – Soluble (SAC305)n No-Clean (SAC305 R0L0)

¨ Cleaning Agents ¨ Engineered aqueous for No-Clean Solder Paste¨ DI water for the Water-Soluble Solder Paste

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DATA FINDINGS

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Bare Board Cleanliness

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Non-Populated / No-Clean Solder Paste / Not Cleaned

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Non-Populated / No-Clean Solder Paste / Cleaned

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Populated / No-Clean Solder Paste / Not Cleaned

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Populated / No-Clean Solder Paste / Cleaned

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Non-Populated / Water-Soluble Solder Paste / Not Cleaned

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Water Soluble / Not Cleaned

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Non-Populated / Water-Soluble Solder Paste / Cleaned

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Populated / Water-Soluble Solder Paste / Not Cleaned

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Populated / Water-Soluble Solder Paste / Cleaned

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Findings n Ionic contamination trapped under the component termination can

cause leakage currents n Highly active water soluble fluxes fail quickly if not cleanedn No-Clean flux trapped under the component termination lower SIR

values n Site specific extractions under the QFN found high levels of

activators ¨ This indicates that the low standoff height and high solder mass

compromise flux outgassing

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q What will make a “Reliable Product?” § Improved reliability can be obtained by focusing on “insulation”

properties § Cleanliness increases in importance when using components with tighter

distances between conductors § Printed circuit board designs that improve flux outgassing improve reliability§ Conformal coating that prevent moisture and other environmental

contaminants improve reliability

q Can assemblers use fine pitch components such as the QFN and still build a reliable product?• Understanding material properties is the key to achieving a reliable product

Key Principles Driving this Research

q If building to a No-Clean standard, are there specific process rules that should be followed? • Encroached vias that provide an outgassing channel is a critical factor• The newly published IPC 7093A BTC guidelines address these factors

q Can these parts be adequately cleaned?• To clean these parts, impingement energy, cleaning fluid and wash time are

important factors q When building high reliability products, should the use of these component

types be avoided?• Focus should be on the printed circuit board design • Solder materials selection is a critical factor

Key Principles Driving this Research

Key Objective n Develop an improved test methodology that will

help OEMs and CMs answer these questions1. Select a test board consistent with production hardware2. Materials and process characterization

1. SIR Testing2. Localized extraction 3. Process Control

3. Visual inspection 1. Cross-Sectioning2. Shear and image

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Follow-on Research n More work needs to be done to

¨ Prove out test methods that can be used at the point of the manufacturing process, just prior to the application of conformal coating

¨ Process control methods on challenging components

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Thank YouName Company

Mark Schaffer iNEMI Project Manager Mike Bixenman (Leader) KYZEN CorporationEric Camden ForesiteJohnny CH Chen WistronQin Chen Suzhou Eunow CompanyJanet Cross U.S. ArmyJeff Kautzer GE HealthcareJason Keeping Celestica Milos Lazic IndiumDavid Lober KYZEN CorporationJennifer Nguyen FlexRavi Parthasarathy ZestronSal Sparacino ZestronPike Sung WistronUmut Tosun Zestron

Chen Xu Nokia

iNEMI Cleanliness PPT 9-16-19 Final

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