LED异常8D报告

Section 1: Corrective Action Request

STATUS:

CLOSED

Failure Analysis Report # FA12P051 Customer Name Buckingham Bridgelux Sales

Contact Albert Ai

Customer Contact Name

Frank Yang

Date Initiated July 23, 2012 Customer Address No.89, Feng Shou East Road, Qian Deng Town, Kun Shan City, Jiang Su, China

Date Samples Received July 30, 2012 Customer Contact Phone #

0512-********

Bridgelux Part Number BXRB-30E0360-A Customer Contact Email Address frank@https://www.wendangku.net/doc/333090185.html, Part Description LS 1x4 WW Bridgelux Quality Contact Oscar Soriano Billy Florentino Lot Code/Date Code

Multiple – See list below Defect Array not lit Bridgelux Customer Impacted

Buckingham Quantity

47 units

Number Returns

1

Section 2: Bridgelux Response

D1: ESTABLISH TEAMS

Champion

Team Leader

Jackie McNab Oscar Soriano

Members

Billy Florentino, Phil Elizondo

D2: PROBLEM DESCRIPTION

Failure Sample

Occurred: IQC

Process

Test

End User

Description:

Buckingham has informed Bridgelux of a problem that they have found on their IQC line and product testing that the LED array unit is not lighting up.

Additional Information from Customer:

Information gathered from FA Return Checklist:

- Failed array product reported as BXRA-30E0360-A

- 4 units reported as not lit from IQC inspection using a DC source

- 43 units reported as not lit from 24 hour life test using a custom made driver

? I DRIVE = 365mA ? Vf = 11 – 13V

- Soldering iron temperature @360 with no hotplates used

Information gathered from Buckingham “HD LED异常” file:

- 24 hour test driver specifications

- IQC light up test verification test set-up

- Soldering station set-up

Information gathered from e-mail communications:

- 4 units reported as not lit from IQC inspection changed to 6 units

- 43 units reported as not lit from 24 hour life test changed to 41 units

Materials sent to Bridgelux for Analysis:

- Failed array product received by Bridgelux FA is a BXRB-30E0360-A and not the initially reported BXRA-30E0360-A.

- 6 units from IQC failures and 41 units from 24 hour test failures were received.

D3: CONTAINMENT ACTIONS

No Bridgelux array level Containment Action items needed for this analysis request.

D4: ROOT CAUSE FAILURE ANALYSIS

Summary of the Analysis:

Bridgelux examined the LED array units that were sent for analysis. There were 6 units that failed during their IQC light-up verification test process and 41 units that failed during their 24 hour life test process.

The 6 units that failed during the IQC light-up verification test were found to have slight contusions on the side of the substrate and light debris contamination on the silicone lens area. Some moderate to heavy dark line smudge marks on the backside of the arrays were observed. To cause the dark line smudge marks such as these on the array, pressure must have been applied to the array. There are approximately 4 lines that are at about the same position across all 6 unit samples. X-ray imaging has shown damage to the wire bond for the 6 unit IQC samples such as a break on the stem near the neck of bond to substrate, mid-span wire breaks and wavy disturbed wires. Buckingham IQC process set-up image shows that the array units are positioned on a rail / holder prior to being probed with test leads for light-up testing. The rail / holder set-up is suspected to be the source of dark line smudge marks on the backside of the array units.

The 41 units that were found to have no light-up during the 24 hour life test process showed solder flux residues, thermal interface material and some scratches on the solder mask areas. There were also signs of overheating on the solder pads, burn marks on the outer edge of the silicone lens area, debris contamination, solder interface material and some contamination marks on the silicone dome surface.

The backside of the 41 array units from the 24 hour life test set-up were covered with a light amount of thermal interface material with the same dark line smudges as observed on the backside of the failed IQC samples. X-ray imaging for failed arrays with scratches, contaminations and residues showed damage to the wire bond such as a break on the stem near the neck of bond to substrate/die, breaks on the neck of the bond to die and wavy / disturbed wires.

8 out of 41 units that failed from the 24 hour test set-up had severely ruptured wire damages. Severe

mechanical damage to the solder mask around the lens area that caused some lifting of the silicone dome as well as cracking and missing portions of the silicone dome were observed. Buckingham

soldering process set-up image shows that the array units are positioned on a clamping holder for soldering wire leads. The holder set-up is in close proximity to the silicone dome and is suspected to be the cause of damage to the solder mask and silicone dome of the array units. Based on the

observations in the course of this analysis, other factors that may have contributed to the damage/s on the solder mask surface and silicone dome lens have come from the luminaire assembly process. Burn marks on the sides silicone dome and edges of the solder pads should have come from the soldering process. Mechanical damage on the solder mask area, lifting and cracking of the silicone dome lens should have come from the mechanical assembly process or the preparation for soldering wire leads.

Experiments performed by Bridgelux are shown to simulate how improper handling and/or mechanical damage can cause damage the wire bonds on a Bridgelux LED array unit.

Details of the Analysis :

Buckingham sent a total of 47 array units of BXRB-30E0360-A to Bridgelux for failure analysis. There were 6 units that failed during their IQC light-up verification test process and 41 units that failed during their 24 hour life test process.

Sample Matrix of a BXRB-30E0360-A Array Unit :

6 units failed to light-up on IQC Testing process .

The 6 units that were found to have no light-up during the IQC process were verified to be non-functional. Table below details the summary of the Light-up testing, Visual Inspection and X-Ray imaging for the returned array units. X-Ray Image

Column 1

Column 2

IQC Failed Samples 24 Hour Life Test Failed Samples

Visual inspection revealed some contamination marks on the solder mask surface and some light

debris contamination on the silicone lens area. One array unit also showed a slight contusion on the left edge of the array substrate.

The backside of the array units were found to have some moderate to heavy dark line smudge marks that appears to have come from some sort of rail holder which has transferred possible contaminants, such as light oil or grease, on the back of the array units. To cause dark line smudge marks such as these on the array, pressure must have been applied to the array. There are approximately 4 lines that are at about the same position across all 6 unit samples. Applying pressure on the front side of the array may cause damage to the wire bonds of the LED device.

Unit B Unit A Unit C

Unit E Unit F

X-ray imaging has shown damage to the wire bond for the 6 unit IQC samples such as a break on the stem near the neck of bond to substrate, mid-span wire breaks and wavy disturbed wires.

Images are representative of damages to the wire bonds for the failed units from the IQC test set-up .

Wavy and/or disturbed wires are signs of improper handling which may cause broken wires. Broken wires cause breaks in the series circuit which causes an array or a series string to not light up.

Buckingham IQC process set-up image shows that the array units are positioned on a rail / holder prior to being probed with test leads for light-up testing. The rail / holder set-up is suspected to be the source of the dark line smudge marks on the backside of the array units.

Unit A

Broken wires at mid-span found on Units C and F

41 units from the 24 hour life test set-up:

The 41 units that were found to have no light-up during the 24 hour life test process were verified to be non-functional. Table below details the summary of the Light-up testing, Visual Inspection and X-Ray

Visual inspection for some of the failed arrays showed solder flux residues, thermal interface material and some scratches on the solder mask areas. There were also signs of overheating on the solder pads, burn marks on the outer edge of the silicone lens area, debris contamination, solder interface

.

The backside of the 41 array units from the 24 hour life test set-up were covered with a light amount of

thermal interface material with the same dark line smudges observed on the back side of the failed IQC samples.

Dark line smudge marks on the backside of the substrate

X-ray imaging for failed arrays with scratches, contaminations and residues showed damage to the wire bond such as a break on the stem near the neck of bond to substrate/die, breaks on the neck of the bond to die and wavy / disturbed wires.

Images are representative of damages to the wire bonds for the failed units from the 24 hour test set-up .

8 out of 41 units that failed from the 24 hour test set-up had severely ruptured wire damages. The following images show some severe mechanical damage to the solder mask around the lens area which caused some lifting of the silicone dome as well as some cracking and missing portions of the

Lifted Silicone

Dome

Missing portion of the dome lens

Unit 23 Unit 24

Lifted Silicone

Dome

Unit 36

Cracked portion of the dome lens

Lifted Silicone

Dome

Unit 38

Buckingham soldering process set-up image shows that the array units are positioned on a clamping holder for soldering wire leads. The holder set-up is in close proximity to the silicone dome and is suspected to be the cause of damage to the solder mask and silicone dome of the array units.

Based on the observations in the course of this analysis, other factors that may have contributed to the damage/s on the solder mask surface and silicone dome lens have come from the luminaire assembly process. Burn marks on the sides silicone dome and edges of the solder pads should have come from the soldering process. Mechanical damage on the solder mask area, lifting and cracking of the silicone dome lens should have come from the mechanical assembly process or the preparation for soldering wire leads.

Simulation Experiments:

Bridgelux performed some experiments to simulate how improper handling and/or mechanical damage can cause damage the wire bonds on Bridgelux LED arrays. Experiments simulate typical steps in an assembly or disassembly process. Minimal pressure was applied to the array units in the scope of the experiments performed. Excessive force and additional motion during the assembly or disassembly process (twisting, sliding, etc.) can adversely affect the degree of damage to the wire bonds.

Picking-up an LED array unit (Simulation Experiments 1, 2 and 4)

Mounting to a fixture or luminaire assembly (Simulation Experiments 1, 2, 3 and 4)

Removal from fixture or luminaire assembly (Simulation Experiments 1, 2 and 4)

Mounting to a holder (Simulation of Buckingham soldering station mounting)

Conclusion of the Experiments performed:

Contact with the Silicone Encapsulant Dome should be avoided. Applying stress to the silicone encapsulant dome area can cause damage to the product.

LED array units may also be handled with tweezers. If handling the LED array units with tweezers, select tweezers with rounded tips and always secure the LED units on the substrate

only, not using the lens. Assemblers should not touch the lens with fingers and should not apply

pressure to the lens.

D5: CORRECTIVE ACTIONS

1. No Bridgelux Corrective Actions planned for this failure.

2. Buckingham is advised to review possible issues of damaging the wire bonds of the LED array units

during the IQC and the assembly line process.

D6: IMPLEMENT CORRECTIVE ACTIONS

No Bridgelux corrective actions to implement

D7: PREVENT RECURRENCE

1. Bridgelux Field Sales to discuss with the customer Bridgelux Application Note AN11 – “Handling

and Assembly of Bridgelux LED Arrays”.

D8: CONGRATULATE THE TEAM