IC Diamond is composed mostly of diamond powder (92%), and, as such, is quite thick. This high viscosity is by design for increased reliability and it is what makes our application procedure different.
Proper application is critical to optimum performance. Squeeze, onto the center of the CPU, an amount of IC Diamond compound about the size of a pea (5.0mm to 5.5mm or approximately .2ml on the syringe) on the center of the CPU where heat is most concentrated. Place the heat sink on the CPU and press it down to spread IC Diamond over the CPU's surface, (caution: do not remove the sink to check the spread as it will introduce air into the joint). Clamp the heat sink and power up the PC.
Note, the 5.5mm example relates to a 30mm X 30mm square size. For larger or smaller square sizes you would ratio the amount i.e. 15mm X15mm = 2.75mm 1/2 pea size
Example of Correct Application
Proper application of an approximately 5.0-5.5 mm bead on the center of the IHS; the example on left utilizes a synthetic IHS. The primary reason a compression type spreading is recommended is that the best results are attained with a compression type spreading.
Here is a simulated IHS clamped between two slides with 50 psi force applied; the 5.0mm-5.5mm bead application spread pattern created by the recommended compression technique. Note paste is smooth and even with no visible air pockets.
In addition to the 2 dimensional area coverage, the dimension of the void space between sink and HIS must be added in. Intel, for example, has a spec of Flat and parallel // to .002. - To fill that gap/volume, a .05 ml volume of compound is needed for a 30mmk X30mm area, about the size of a grain of rice.
The other side of the thermal joint equation is the heat sink base. The heat sink bases may vary as much as .010 and, to cover the contingency of irregular contour on both sink & HIS, .1 ml should additionally be added for a total of 0.15ml.
Another issue is Laplacian Growth which occurs when inadequate amounts of paste form viscous, finger-like extentions and reform to encapsulate air into the joint. These air bubbles, with heat and pressure, expand and create voids which degrade thermal performance and reliability.
To counter this process, the addition of another .05ml to the application amount is recommended making for a total of .2ml of IC Diamond.
Note on Application amount
Inncorrect Line Application with Lapacian Growth
Acceptable Line Application
A 3/4 compound line is acceptable on a rectangular piece as long as width of the die does not exceed 1.5cm.
More than that will likely initiate Lapalcian Growth and entrain air into the thermal joint.
Incorrect Manual Spread Application
This assembly shows bubbles of air that, under thermal load, will expand and migrate together creating voids that affect thermal performance and reliability
The manual Spreading of a compound is highly discouraged; the manipulation, folding of the compound, as well as surface iregularities will add air into the final assembly.
Final Reminder -Use the Correct Amount
Resulting assembly is an example of Laplacian Growth; note the entrained air in the radial halo
Laplacian Growth shown on the left with a low viscosity competition compound and applied with a compression spread with a glass slide. This demontrates that while visually the area seems to be covered the entrainment of air is obvious and certainly inadequate to fill any void space.
Always use enough+ thermal compound, excess is squeezed out till the paste reaches it's average particle size or BLT or aka "curing".
Moderate overkill on this point will save time, money and aggravation by avoiding forced reapplications.
Laplacian Growth - with rice sized application amount shown above
Under Application with a 3mm Bead on a 30mmX30mm Die is not enough.