Bonding, Handling, and Mounting Procedures for

Chip Diode Devices

M/A-COM Products

Rev. V3

Application Note

M541

3

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and/or prototype measurements. Commitment to develop is not guaranteed.

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Solutions has under development. Performance is based on engineering tests. Specifications are

typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available.

Commitment to produce in volume is not guaranteed.

Chip Die Down Bonding Techniques

(Cont’d)

Ultrasonic thermal Compression bonding of Dice

In a small circuit, ultrasonic bonding gives a very reliable

and strong bond. The die should be free of oxides and

have no metallization. The bonding surface should have

~2.5 micrometers of a soft gold, preferably from a high

cyanide gold bath.

The stage of the bonder should be set at ~ 200-250ºC

and the bond pressure ~ 400 grams / mm

2

i.e.: ~ 50 grams for 0.010 X 0.010 inch die

~ 200 grams for 0.020 X 0.020 inch die

~ 300 grams for 0.030 X 0.030 inch die

These values can vary rather widely and some experi-

mentation may be necessary to find the best results.

The criteria for a good thermal compression bond should

be the same as for a soldered joint.

Die Bonding with Conductive Epoxies

Although some military and telecommunications systems

do not allow the use of conductive epoxies, satisfactory

die down bonds may be obtained using these epoxies.

The following precautions should be observed to obtain

consistently strong bonds.

Cleanliness

Everything should be clean and degreased. It is a good

idea to clean the circuit in a alkaline solution to remove

any traces of plating solutions. The circuit should then be

degreased.

Shelf Life

The conductive epoxy must be within the warranty shelf

and/or pot life. It is advisable to use one half the listed pot

life since manufactures tend to be optimistic on pot life

estimates. Thus, if the pot life is stated to be 2 days, it is

much safer to use new epoxy every day.

Curing

The epoxy must be cured in the air or in an oxidizing at-

mosphere. The reaction requires oxygen. The epoxy oven

should be clean (not used for other functions) and should

have a good air flow to carry fumes. The epoxy will not

cure well if there are other solvent fumes in the atmos-

phere.

Carrier Fluid

The carrier fluid must not be allowed to flow on the top of

the chip. Not only will it make the chip unbondable, it will

be almost virtually impossible to detect under normal

bonding procedures. If a vacuum tip is used to put the

chip in place remove the vacuum when the chip is 10 to

30 mils from the epoxy. Static charge will hold the chip to

the tip. If the vacuum tip touches the epoxy it will become

coated with epoxy carrier fluid and contaminate the next

chip with the carrier material. This same problem may

occur with the use of tweezers. The tweezers should be

cleaned before pickup another chip if they touch the ep-

oxy.

250

150

100

50

0

200

0.01

0.030

0.020

0.012

CHIP SIZE - EDGE LENGTH (INCHES)