CN102184901A - Preparation method of porous core with gradient composite structure - Google Patents

Abstract

The invention relates to a preparation method of a porous core with a gradient composite structure. The method comprises the steps of mixing metal powder and a polyester ball to form three different kinds of blended powder; making the three different kinds of blended powder into a blank; conducting grinding to remove a metal layer at the outer layer of the blank after the blank is prepared; bonding the grinded blanks into a whole according to the aperture sequence from small to big of the polyester balls; and firing the three blanks which are bonded into a whole in a vacuum furnace, wherein the outer layer thickness of the blank removed is not smaller than the radius of the polyester ball. The porous core prepared has a gradient composite structure, the aperture and porosity of each layer are different, and the porous core is strong in radiating capability, good in permeability and high in heat conductivity, and can meet the requirements of a minitype heat pipe radiator on the porous core.

Description

A kind of preparation method of gradient composite construction porous core

Technical field

The present invention relates to a kind of manufacture method that is used for the porous core of dissipation from electronic devices, belong to the heat sink material technical field.

Background technology

Development along with digitlization and network informationization, demand to microelectronic component performance and speed is more and more higher, at present, semiconductor technology has entered nanometer scale, can on the IC chip, make more transistor, based on light and need the demand of integration function, also develop at present towards the system single chip direction.Among the IC during active device computing such as transistor, produce a large amount of heats, along with transistorized number in the chip is more and more, caloric value is also increasing, under the situation that chip area does not significantly increase thereupon, device heating density is more and more higher, problems of excessive heat has become the bottleneck of present restriction electronic device technical development, is example with CPU, and its caloric value increases gradually along with the raising of speed, reached at present more than the 115W, corresponding density of heat flow rate also increases considerably.Heat dissipation problem has become the biggest obstacle of restriction microelectronic component development, and has caused concern widely.

The microelectronic component caloric value improves constantly, and the heat dissipation technology that is complementary is not with it in time caught up with, and makes the development of CPU face great bottleneck gradually.Estimate according to ITRS, the caloric value of every DRAM in 2006 will be increased to 2W from about 1W, in order to enlarge the memory module capacity, present many companies begin to adopt 3D to pile up the encapsulation of form, though improved the application efficiency of chip, also made heat dissipation problem seem more and more important.According to statistics, account for over half that electronic device lost efficacy by the caused inefficacy of heat.Temperature is too high to cause the damage of semiconductor device except meeting, also can cause electronic reliability to reduce and decreased performance, for the solution of heat dissipation problem, must seek comprehensive technical solution scheme.In addition, heat dissipation problem also is one of key technology difficult problem that influences the LED life-span.

Common porous core heat exchanger generally comprises evaporating area, adiabatic region and condensing zone, each zone is to adopt compacted density, the aperture porous core (porous alloy heat pipe) identical with porosity, in microstructure, when working medium undergoes phase transition, its internal pressure can sharply increase, cause poor permeability, thermal conductivity reduces, and influences radiating effect.

Summary of the invention

The present invention is directed to the problem that the existing porous core heat exchanger porous core that is used for dissipation from electronic devices exists, provide that a kind of heat-sinking capability is strong, the preparation method of good penetrability, porous core that thermal conductivity is high with gradient composite construction.

Preparation method with porous core of gradient composite construction of the present invention may further comprise the steps.

(1) with metal powder and polyester pellet by volume ratio be respectively 1: 5, mixed in 1: 4 and 1: 3, form three kinds of different mixed powders, metal powder is meant iron powder, aluminium powder, the mixture of nickel powder or three kinds of metal powder arbitrary proportions, three kinds of different mixed powders are respectively applied for preparation radiator evaporating area porous core, radiator adiabatic region porous core and radiator condensing zone porous core, evaporating area porous core mixed powder, the diameter of polyester pellet increases successively in adiabatic region porous core mixed powder and the condensing zone porous core mixed powder, three kinds of mixed powders is added adhesive respectively cohere;

The diameter of polyester pellet is determined according to following formula in three kinds of mixed powders:

ln(p/p ₀)＝-(2γV _m/rRT)cosθ (1)；

In the formula, p ₀Saturated vapour pressure when being the plane for the working media liquid level, p are the saturated vapour pressure of porous in-core liquid-working-medium, V _mBe the molal volume of corresponding phase, γ is the surface tension of corresponding phase in each district, and R is a constant, and T is an absolute temperature, and θ is the contact angle of liquid-working-medium and porous core metal layer wall; When correspondence is meant real work mutually, the situation of working media in radiator evaporating area, adiabatic region and the condensing zone, the evaporating area working media is a liquid phase, and the adiabatic region working media is the vapour-liquid two-phase, and the condensing zone working media is a vapour phase;

(2) the different mixed powder of three kinds of ratios after will cohering is pressed into evaporating area porous core blank, adiabatic region porous core blank and condensing zone porous core blank by mould, and the pressed density of each blank is 0.2g/cm ³--1.3g/cm ³

The blank height of radiator evaporating area porous core, radiator adiabatic region porous core and radiator condensing zone porous core can be determined according to following formula:

With

H wherein ₁Be the height of evaporating area porous core, H ₃Be the height of condensing zone porous core, H ₂Be the height of adiabatic region porous core, H is three region height sums; V _iBe liquid phase topping up volume, φ ₁Be evaporating area porous core porosity, V _gBe vapour phase volume, φ ₃Be condensing zone porous core porosity, L is the length in arbitrary zone, and W is the width in arbitrary zone.

(3) after blank preparation is finished, grind for outer layer metal layer and the blank that polyester pellet is tangent or metal level exceeds two kinds of situations of polyester pellet, the outer field metal level of removal blank, the blank outer layer thickness of removal should be more than or equal to the radius of polyester pellet;

(4), cohere into an integral body by from small to large order of the polyester pellet aperture that the is comprised order of evaporating area porous core, adiabatic region porous core and condensing zone porous core (promptly according to) the blank after grinding;

(5) will cohere three whole blanks in vacuum furnace, to fire, when sintering temperature reaches the fusing point of the minimum metal of fusing point in the metal powder, be incubated 10-60 minute, naturally cool to room temperature then, promptly obtain having the porous core of gradient composite construction.The vacuum degree of vacuum furnace is 0.001Pa-0.1Pa.

The porous core that the present invention prepares has the gradient composite construction, and every layer aperture is different with porosity, can satisfy the demand of micro heat pipe radiator to the porous core, and heat-sinking capability is strong, good penetrability, thermal conductivity height.In preparation process, pay attention to the collocation situation of different size resin balls and metal powder, adopt the integral sintered preparation technology's sintering of layering pressed compact, avoid the appearance of blind hole, guarantee that porous in-core portion micropore is unimpeded.

Description of drawings

Fig. 1 is the area schematic of radiator.

Fig. 2 is the situation of the height of polyester pellet greater than the metal level height.

Fig. 3 is the tangent situation of polyester pellet and metal level.

Fig. 4 is the situation that the polyester pellet external diameter has with a certain distance from metal level.

Wherein: 1, evaporating area, 2, adiabatic region, 3, condensing zone, 4, metal level, 5, polyester pellet.

Embodiment

As shown in Figure 1, heat exchanger generally is divided into evaporating area 1, adiabatic region 2 and condensing zone 3, and when real work, the working media matter of evaporating area 1 mainly is liquid phase, and adiabatic region 2 working medium are vapour-liquid two-phases, and condensing zone 3 working medium mainly are gas phases.Reach best radiating effect, will make the porous core aperture minimum of evaporating area 1, the porous core aperture maximum of condensing zone 3, the porous core aperture of adiabatic region 2 fall between (the porous core in each zone adopts identical compacted density, aperture and porosity at present).Like this when the porous core in three zones of preparation (evaporating area, adiabatic region and condensing zone), will consider the preparation technology at three regional porous cores and evaporating area and adiabatic region critical surface and adiabatic region and condensing zone interface, avoid producing blind hole, keep the critical surface place unimpeded critical technical problems that becomes up and down at critical surface.

1. the design of porous core aperture and porosity

Utilize the continuity equation of saturated porous alloy, Darcy's law, the energy equation of consideration gravitational effect that trizonal working medium transport process is carried out mathematical modeling:

$\frac{\∂\left(\mathrm{\φ\ρ}\right)}{\∂\mathrm{\τ}}+\▿\·\left(\mathrm{\ρv}\right)=0---\left(2\right)$

In the formula, φ is the porosity of porous core, and ρ is the density of fluid, and v is the superficial velocity of fluid.

$q_V=-\frac{\mathrm{kA}}{\mathrm{\μL}}[(p_1-p_2)+\mathrm{\ρgL}]---\left(3\right)$

In the formula, q _VBe volume flow, k is the permeability of porous core, and μ is the dynamic viscosity of fluid; A is that cell cross-section is long-pending, and L is a cell cube length.

${\left(\mathrm{\ρc}\right)}_m\frac{\∂T}{\∂\mathrm{\τ}}+{\left({\mathrm{\ρc}}_P\right)}_{f}V\·\▿T=\▿\·({\mathrm{\λ}}_m\▿T)+{\mathrm{\φq}}_m^{\′\′\′}---\left(4\right)$

Wherein (ρ c) _m=(1-φ) (ρ c) _s+ φ (ρ c _p) _fλ _m=(1-φ) λ _s+ φ λ _fQ " ' _m=(1-φ) q " ' _s+ φ q " ' _f

In the formula, subscript s and f represent that respectively solid phase and fluid are mutually; C is the specific heat of solid; c _pSpecific heat at constant pressure for fluid; λ is a conductive coefficient; Q " ' for the heat of the unit volume that endogenous pyrogen produced.

Use fractal theory then, set up the expression formula of porous core porosity and permeability:

$\mathrm{\φ}=\frac{V_p}{V_b}=\frac{\mathrm{AD\π}}{{4A}_0(3-D-D_T)}{L}_0^{D_T-1}{\mathrm{\λ}}_{\max }^{3-D-D_T}(1-{\mathrm{\τ}}^{3-D-D_T})---\left(5\right)$

$k=\frac{\mathrm{\&mu;}{L}_{0}Q}{\mathrm{\&Delta;p}{A}_0}=\frac{\mathrm{\&pi;}}{128}\frac{A}{A_0}\frac{\mathrm{<figure-callout\; id="3"\; label="D"\; filenames="HDA0000055391340000011.png"\; state="\{\{state\}\}">D</figure-callout>}}{3+D_T-D}{L}_0^{1-D_T}{\mathrm{\&lambda;}}_{\max }^{3+D_T-D}---\left(6\right)$

In the formula, D is a porous core distribution of pores fractal dimension, and DT is the tortuous fractal dimension of porous core hole, and Q then is the total flow by the unit section A.

Parameter expression according to above acquisition obtains evaporating area 1, adiabatic region 2 and condensing zone 3 pairing mean pore size

For: ln (p/p ₀(the 2 γ V of)=- _m/ rRT) cos θ

In the formula, p ₀Saturated vapour pressure when being the plane for the working media liquid level, p are the saturated vapour pressure of porous in-core liquid-working-medium, V _mBe the molal volume of corresponding phase, γ is the surface tension of corresponding phase in each district, and R is a constant, and T is an absolute temperature, and θ is the contact angle of liquid-working-medium and porous core metal layer wall; When correspondence is meant real work mutually, the situation of working media in radiator evaporating area, adiabatic region and the condensing zone, the evaporating area working media is a liquid phase, and the adiabatic region working media is the vapour-liquid two-phase, and the condensing zone working media is a vapour phase.

Porosity according to obtaining obtains evaporating area 1, condensing zone 3 and adiabatic region 2 and highly distributes:

With

H wherein ₁Be the height of evaporating area 1, H ₃Be the height of condensing zone 3, H ₂Be the height of adiabatic region 2, H is three region height sums; V _lBe liquid phase topping up volume, φ ₁Be evaporating area porous core porosity, V _gBe gaseous phase volume, φ ₃Be condensing zone porous core porosity, L is the length in arbitrary zone, and W is the width (referring to Fig. 1) in arbitrary zone.

2. the preparation technology of gradient composite construction porous core of the present invention

The parameter (aperture, porosity, thickness) of evaporating area, condensing zone and the adiabatic region that obtains according to aforementioned calculation is mixed metal powder, polyester pellet and adhesive respectively in certain proportion, pressed compact.Be far smaller than the diameter of polyester pellet 5 because of the particle diameter of metal powder in the metal level 4, therefore, the skin of institute's roughcast is minimum less than the porosity in the scope of polyester pellet 5 radiuses, as shown in Figure 2, this is the more satisfactory state that forms after three kinds of different mixed powder of ratio are pressed into blank, can see, the height of polyester pellet 2 is greater than the height of metal level 4, like this after carrying out sintering, enter in the air because of becoming gas under polyester pellet 2 high temperature, can form on the remaining metal level 1 and allow the free-pouring hole of working medium, therefore not need in this state blank is ground.But the situation that tangent situation of polyester pellet shown in Figure 35 and metal level 4 and polyester pellet 5 external diameters shown in Figure 4 have with a certain distance from metal level 4 may appear, the both of these case metal powder covers polyester pellet 5 fully, behind sintering, metal level 4 will occur with the form of a whole layer, if no longer carry out necessary PROCESS FOR TREATMENT, just may occur aperture " obstruction " phenomenon at metal level 4 places, and can't finish flowing of working medium, cause prepared core loss of function at last.Therefore must the skin of institute's roughcast be ground, the thickness that grinding is removed should be more than or equal to the radius of polyester pellet 5, to eliminate aperture " obstructions " phenomenon that to occur, avoid taking place to finish flowing of working medium and the situation generation that causes prepared porous core loss of function.

For overcoming above-mentioned phenomenon, the preparation method of porous core of the present invention takes following steps.：

(1) with iron powder, aluminium powder, the mixture of nickel powder or three kinds of metal powder arbitrary proportions mixes with polyester pellet, form three kinds of different mixed powders, three kinds of different mixed powders are respectively applied for preparation radiator evaporating area porous core, radiator adiabatic region porous core and radiator condensing zone porous core, evaporating area porous core mixed powder, the volume ratio of metal powder and polyester pellet was respectively 1: 5 in adiabatic region porous core mixed powder and the condensing zone porous core mixed powder, 1: 4 and 1: 3, three kinds of mixed powders are added adhesive respectively to be cohered, evaporating area porous core mixed powder, the size of polyester pellet is different in adiabatic region porous core mixed powder and the condensing zone porous core mixed powder, and the polyester pellet size determines according to formula (1) in the mixed powder;

(2) three kinds of different mixed powders of ratio are put into mould respectively, be pressed into three blanks, the pressed density of blank is greater than 0.2g/cm ³, and less than 1.3g/cm ³

Can be by narrating previously

With

Determine the height of evaporating area porous core, condensing zone porous core and adiabatic region porous core.

(3) after blank preparation is finished, the blank that tangent or metal level 4 exceeds the situation of polyester pellet 5 for outer layer metal layer 4 and polyester pellet 5 grinds, and removes the outer field metal level of blank, and the blank outer layer thickness of removal should be more than or equal to the radius of polyester pellet 5;

(4), cohere by from small to large order of the polyester pellet aperture that the is comprised order of evaporating area porous core, adiabatic region porous core and condensing zone porous core (promptly according to) and to be integral ground blank;

(5) will cohere three whole blanks in vacuum furnace, to fire, when sintering temperature reaches the fusing point of the minimum metal of fusing point in the metal powder, be incubated 10-60 minute, naturally cool to room temperature then, promptly obtain having the porous core of gradient composite construction.The vacuum degree of vacuum furnace is 0.001Pa-0.1Pa.Firmly cohering all-in-one-piece evaporating area porous core, adiabatic region porous core and condensing zone porous core is exactly the gradient composite construction porous core of the present invention's preparation.

Claims (3)

1. the preparation method of a gradient composite construction porous core may further comprise the steps:

(1) with metal powder and polyester pellet by volume ratio be respectively 1: 5, mixed in 1: 4 and 1: 3, form three kinds of different mixed powders, metal powder is meant iron powder, aluminium powder, the mixture of nickel powder or three kinds of metal powder arbitrary proportions, three kinds of different mixed powders are respectively applied for preparation radiator evaporating area porous core, radiator adiabatic region porous core and radiator condensing zone porous core, evaporating area porous core mixed powder, the diameter of polyester pellet increases successively in adiabatic region porous core mixed powder and the condensing zone porous core mixed powder, three kinds of mixed powders is added adhesive respectively cohere;

(2) the different mixed powder of three kinds of ratios after will cohering is pressed into evaporating area porous core blank, adiabatic region porous core blank and condensing zone porous core blank by mould, and the pressed density of each blank is 0.2g/cm ³--1.3g/cm ³

(3) after blank preparation is finished, grind for outer layer metal layer and the blank that polyester pellet is tangent or metal level exceeds two kinds of situations of polyester pellet, the outer field metal level of removal blank, the blank outer layer thickness of removal should be more than or equal to the radius of polyester pellet;

(4) the blank after grinding, cohere into an integral body by the polyester pellet aperture order from small to large that is comprised;

(5) will cohere three whole blanks in vacuum furnace, to fire, when sintering temperature reaches the fusing point of the minimum metal of fusing point in the metal powder, be incubated 10-60 minute, naturally cool to room temperature then, promptly obtain having the porous core of gradient composite construction.

2. the preparation method of gradient composite construction porous core according to claim 1 is characterized in that, the diameter of polyester pellet is determined according to following formula in described three kinds of mixed powders:

ln(p/p ₀)＝-(2γV _m/rRT)cosθ

In the formula, p ₀Saturated vapour pressure when being the plane for the working media liquid level, p are the saturated vapour pressure of porous in-core liquid-working-medium, V _mBe the molal volume of corresponding phase, γ is the surface tension of corresponding phase in each district, and R is a constant, and T is an absolute temperature, and θ is the contact angle of liquid-working-medium and porous core metal layer wall; When correspondence is meant real work mutually, the situation of working media in radiator evaporating area, adiabatic region and the condensing zone, the evaporating area working media is a liquid phase, and the adiabatic region working media is the vapour-liquid two-phase, and the condensing zone working media is a vapour phase.

3. the preparation method of gradient composite construction porous core according to claim 1 is characterized in that, the blank height of described radiator evaporating area porous core, radiator adiabatic region porous core and radiator condensing zone porous core is determined according to following formula:

With H wherein ₁Be the height of evaporating area porous core, H ₃Be the height of condensing zone porous core, H ₂Be the height of adiabatic region porous core, H is three region height sums; V _lBe liquid phase topping up volume, φ ₁Be evaporating area porous core porosity, V _gBe vapour phase volume, φ ₃Be condensing zone porous core porosity, L is the length in arbitrary zone, and W is the width in arbitrary zone.

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