Thermal Response Test to Assess Adhesive Bond Quality in a Microwave Circulator

Transcription

1 Thermal Response Test to Assess Adhesive Bond Quality in a Microwave Circulator E. C. Johnson and Y. M. Kim The Aerospace Corporation, Los Angeles, CA th International Symposium on Nondestructive Characterization of Materials June 22-26, 2015 Marina Del Rey Marriott, Marina Del Rey, California, USA The Aerospace Corporation 2015

2 Can IR imaging methods be used to assess the adhesive bond quality in an assembled microwave circulator? Potted Magnet Trunk Port Al Dielectric Ferrite Typical three-port microwave circulator.

3 Bondlines of Interest Bondlines 1, 2, and 4 are formed with epoxy. Bondline 3 contains no material (permits circulator disassembly). The bondline between the dielectric halves is ignored in this study. Bondlines Al Al Ferrite Dielectric Enumeration of the bondlines of interest.

4 Approach for Assessing Bond Quality The epoxy bond heat-sinks the ferrite triangles to the aluminum housing. One can take advantage of the symmetry of the circulator housing and apply heat in a controlled symmetrical fashion while, using an IR camera to monitor the temperature of the ferrite triangles. A relative quality difference between the left and right ferrite bonds should result in a thermal response variation between them. Heated Block Circulator IR Imager Insulation Board Arrangement for heating the circulator uniformly while monitoring the left and right ferrite temperatures.

5 Approach for Assessing Bond Quality (cont.) Note: opening above port Heated Block Raised Tape The intention was to heat the ferrites via conduction through the housing. Initial tests revealed that thermal radiance from the heated block though the top port competed heavily with the thermal conductive process. The heated block was therefore redesigned with an opening over the port. Raised tape was applied to the foam board so that the circulator could be removed and easily returned to the same position relative to the IR camera. Arrangement for heating the circulator uniformly with redesigned heated block

6 Thermal Response Test (procedure) The circulator is placed on a thick Al plate at room temperature and the heated block is place on a hot plate set at 130 F. Once thermal equilibrium is achieved, the circulator is moved to position on the foam board and the IR imager is keyed to start recording for 200 s. The heated block is then quickly placed on top of the circulator. Sample thermal response test recording The recording software permits one to outline Regions of Interest (ROIs) on the image. The ROIs are indicated by colored and numbered boxes. Four ROIs were positioned; on the heated block, the right and left ferrite and the bottom of the circulator housing. The average temperatures in these ROIs were then captured for each time interval in the recording.

7 Thermal Response Test (sample frames) 30 s 60 s 180 s 115 F F F

8 Thermal Response Test (ROI Temperature Plots) Epoxy-Epoxy-clean-Epoxy Epoxy-Epoxy-clean-paper Temperature)( F)) 130# 120# 110# 100# 90# 80# #ROI#1#.#le1#ferrite# #ROI#2#.#right#ferrite# #ROI#3#.#heater#block# #ROI#4#.#lower#housing# Temperature)( F)) 130# 120# 110# 100# 90# 80# #ROI#1#.#le1#ferrite# #ROI#2#.#right#ferrite# #ROI#3#.#heater#block# #ROI#4#.#lower#housing# 70# 70# 0# 20# 40# 60# 80# 100# 120# 140# 160# 180# 200# 0# 20# 40# 60# 80# 100# 120# 140# 160# 180# 200# Time)(sec)) Time)(sec)) Δ!=!!!!!!"#!!"# 100%!! Bondlines # 12.0# Ferrite!Thermal!Response!Test! Al Al T#(%)!! 10.0# 8.0# 6.0# 4.0# Bondlines ##Epoxy3Epoxy3clean3paper# ##Epoxy3Epoxy3clean3Epoxy# 2.0# 0.0# 0# 20# 40# 60# 80# 100# 120# 140# 160# 180# 200# Time!(sec)!

9 Thermal Response Test (Bond Material Variations) T#(%)!! 14.0# 12.0# 10.0# 8.0# 6.0# 4.0# 2.0# Ferrite!Thermal!Response!Test! (Thermal!Paste!Bonds)! Bondlines)))) )))1)))+)))2)))+)))3)))+)))4)))))))) #clean3epoxy3clean3clean# #clean3epoxy3tp3clean# #TP3Epoxy3TP3TP# #TP3Epoxy3TP3clean# #TP3Epoxy3TP3paper# 0.0# 0# 20# 40# 60# 80# 100# 120# 140# 160# 180# 200# Time!(sec)! T#(%)!! 14.0# 12.0# 10.0# 8.0# 6.0# 4.0# 2.0# Ferrite!Thermal!Response!Test! (Epoxy!Bonds)! Bondlines)))) )))1)))+)))2)))+)))3)))+)))4)))))))) #clean3epoxy3clean3clean# #clean3epoxy3tp3clean# ##Epoxy3Epoxy3clean3Epoxy# #Epoxy3Epoxy3TP3Epoxy# ##Epoxy3Epoxy3clean3paper# #Epoxy3Epoxy3TP3Paper# #Epoxy3Epoxy3clean3cracked#Epoxy# 0.0# 0# 20# 40# 60# 80# 100# 120# 140# 160# 180# 200# Time!(sec)!

10 Thermal Response Test (Bond Size Variations) T#(%)# 10.0% 8.0% 6.0% 4.0% 2.0% Ferrite#Thermal#Response#Test# (Bond#Size#Varia;on)# Bondlines)))) )))1))+))))2)))+))3)))+))4)))))))) # %Epoxy!Epoxy!TP!100%%foil% %Epoxy!Epoxy!TP!47%%foil% %Epoxy!Epoxy!TP!28%%foil% %Epoxy!Epoxy!TP!9.7%%foil% %Epoxy!Epoxy!TP!5.8%%foil% %Epoxy!Epoxy!TP!Paper% 0.0%!2.0%!4.0% 0% 20% 40% 60% 80% 100% 120% 140% 160% 180% 200% Time#(sec)# Mineral Oil Foil T#Max#(%)# 6# 4# 2# 0#!2# Bond#Size#vs.# T#Max#!4# 0# 20# 40# 60# 80# 100# Aluminum foil wetted with mineral oil was used to create a quantifiable partial bond Percent#Bonded#(%)#

11 Summary / Discussion A Thermal Response Test was developed to assess the relative quality of symmetrical adhesive bonds within a microwave circulator The test proved sensitive to the relative bond conditions. The response scaled monotonically with unbond percentage. An complete unbond or cracked bond was clearly indicated. The measurement is relative, which implies limitations. If both bonds being compared are cracked or unbonded, one would expect results similar to those for having both bonds intact. The Thermal Response Test may also prove useful as a means for monitoring the bond behavior of a circulator as it is subjected to various qualification environments such as thermal vacuum and burn-in. Acknowledgement Support from the Aerospace Corporation s Sustained Experimentation and Research for Program Applications program is gratefully acknowledged.