Project carried out in ISRO Satellite Centre, Bengaluru

BATCH MEMBERS UNDER THE GUIDANCE OF

PARIKSHITH B J (1AH10ME031) SUNIL RAJ B A RAJEEV R BADAGANDI

PRASHANTH U (1AH10ME035) ASST PROFESSOR Scientist/Engineer – SG

SRI HARSHA S N (1AH10ME045) ACSCE Head, SRIS-3(SIG)

SRIKANTH T (1AH10ME046) ISRO Satellite Centre (ISAC)

WELCOME TO PROJECT SEMINAR ON

“DESIGN AND ANALYSIS OF MECHANICAL HOUSING FOR PCB’S IN SPACE APPLICATIONS”

LOCATION OF PCB

MODULEPCB

Vibrations coming onto the spacecraft, which will always be quite harmful to the

functioning of the components and the Printed Circuit Boards (PCB’s) during launch of the

spacecraft and its journey to the space.

Vibrations experienced by electronic package of a spacecraft during its launch phase can

damage its function

Precautionary measures like proper design and analysis to prevent mechanical failure of

electronic components due to vibration induced loads is carried out.

As space based applications such as communication and navigation depends on reliable

operation of electronics.

ABSTRACT

LITERATURE SURVEY Modern electronic equipment used in military applications must be able to survive

vibration environment. Therefore, scientists have been interested in developing

methods of examining the mechanical fatigue of printed circuit boards.

Thomas E. Renner outlined a procedure where a finite element model of a circuit

board was created incorporating laboratory test data. Force/deflection testing

coupled with simple finite element models and static analysis were used to obtain

the material properties and boundary conditions.

Q. Guo et.al performed a series of vibration experiments including plastic ball

grid array assembly in order to obtain a random experimental model random

vibration theory.

K.P.Subramanya, Jiwan Kumar Pandit, C.S. Prasad, M.R. Thyagaraj

These peoples provided alternate solution to optimize vibration by providing

vibration isolators.

During a spacecraft launch, very harsh and high intensity vibrations are

transmitted from the launch vehicle, which causes the failure of the electronic

package.

Proper Design and Analysis are to be carried out to avoid the vibration failures.

Theoretical calculations were done by using Steinberg empherical formulae.

Using Unigraphics NX v7.5 – modeling and analysis of the PCB card and

analysis of the assembly has been carried out.

METHODOLOGY ADOPTED

PCB TEST CARD

Formula used to calculate the frequency of the PCB card

= 152.4 mm = = 106mm = = 101.6mm = = 77mm = = 450.608Hz = ?= = = 2.54mm = = = =

= 0.12 ()= 0.18

The subscript 1 refers to the tabulated values obtained from the FEM analysis and

experiments on different PCB shapes conducted by Steinberg [ref]. The subscript

2 refers to the property of the PCB material FR-4 used in the current module.

= 450.60**

= 663.113 Hz

PCB CARD

FEA MODEL

Quad-4 element 2D mesh

MODE-1 OF PCB CARD OF MAXIMUM NODE 10387

BASE MODULE(TRAY)

COVER

ASSEMBLY OF PCB CARD AND TRAY

FEA MODEL OF ASSEMBLY

Quad-4 element 3D mesh

MODE - 1 OF ASSEMBLY

Value of Von Mises stress is found to be 29.34 Mpa

RANDOM VIBRATION ANALYSIS

Random vibration is vibration that can be described only in a statistical sense.

The instantaneous magnitude is not known at any given time rather the

magnitude is expressed in terms of its statistical properties.

The random load on spacecraft encompasses acoustic excitation due to rocket,

engine noise and acoustic noise. These random excitations are usually

described in terms of a power spectral density (PSD) function.

NX Nastran performs random response analysis as a post-processing step

after frequency response analysis. The frequency response analysis is used to

generate the transfer function, which is the ratio of the output to the input.

MOUNTING LOCATIONS CONNECTED TO A SINGLE NODE

Frequency(Hz) PSD()

20-100 +3dB/oct

100-700 0.1

700-2000 -3dB/oct

Table : Input PSD values for Parallel to mounting plane of PCB card and Housing

Input PSD curve

TRANSMISSIBILITY PLOT OF NODE NUMBER 10387

VALUE OF NODE 10387 IS 62.30

*The margin is –ve on one element of 1mm size at the edge of the mounting hole.Usually the stress in the first ring of elements from the hole edge is ignored. The second ring of elements has a stress of about 38 MPa (rms) which gives MOS= +0.0233Yield strength for Al 6061=140 MpaFlexural strength FR-4 = 385 Mpa

Factor of Safety (FS) = 1.2

SUMMARY OF RESULTS

In this project, Design and Analysis of a typical electronic module for satellite

Power system is carried out successfully using both classical and Finite element

methods.

The results are tabulated and the design is found to have adequate margins for

stress.

The failure criteria for stiffness like the first natural frequency for PCB (>125

Hz) and maximum acceleration loads on components (<80G) are also met.

There is very good un-coupling between the housing and the PCB card.

CONCLUSION

Use of electronic package in vacuum conditions, one has to rely only on

conduction and radiation modes to dissipate heat which makes the task

very challenging.

Using of PCB materials which have more thermal conductivity.

Using of shape memory alloys.

Using of vibration isolators.

Use of better materials which have better material than present material

used in the electronic packages.

SCOPE FOR FUTURE WORK

Dave S. Steinberg, Vibration Analysis for Electronic Equipment, John Wiley & Sons,

Inc., 2000

McKeown, Mechanical Analysis of Electronic Packaging Systems, Marcel Dekker,

Inc., 1999

G.S. Aglietti, and C. Schwingshackl, 2007, Analysis of Enclosures and Anti Vibration

Devices for Electronic Equipment for Space Applications , School of Engineering

Sciences, Aeronautics and Astronautics, University of Southampton, UK.

P.J. Zulueta, Electronics Packaging Considerations for Space Applications, 2001, Jet

Propulsion Laboratory, California Institute of Technology.

Suhir, Predicting Fundamental Vibration Frequency of a Heavy Electronic Component

Mounted on a Printed Circuit Board, Journal of Electronic Packaging, 2000

REFERENCES

THANK YOU