CN1323650A

CN1323650A - Gas mixing device

Info

Publication number: CN1323650A
Application number: CN01101514A
Authority: CN
Inventors: J·P·汉利
Original assignee: Praxair Technology Inc
Current assignee: Praxair Technology Inc
Priority date: 2000-01-13
Filing date: 2001-01-12
Publication date: 2001-11-28
Also published as: MXPA01000430A; EP1116513A2; BR0100060A; KR20010077978A; CA2330813A1

Abstract

This invention is directed to a compact gas mixing apparatus for accurately mixing a plurality of gases. This apparatus comprises a gas panel, pressure control valves to regulate differential pressures, flow meters and a static mixing chamber. The plurality of gases may be a minor gas and a major gas, where, for example, the major gas is nitrogen, and the minor gas is air or oxygen. The major gas and said minor gas is preferably mixed in a proportion of from about 100ppm to about 10,000ppm minor gas in the major gas, more preferably in a proportion of from about 500ppm to about 2,000ppm minor gas in the major gas.

Description

Gas mixer

The present invention relates generally to the device of process gas mixture.More particularly, the present invention relates to produce the gas mixing control panel (gas mixing ganel) of the controlled atmosphere that is used in the performance that strengthens the electronic assemblies method in the reflow oven.

The controlled atmosphere that need have the specific gas characteristic usually is to improve the performance of the electronic assemblies method in reflow oven.People need provide economy and the easy device that can produce controlled air.

For obtain best backflow performance preferably at described airborne specific gas characteristic about 100ppm that is a small amount of gas comprises master's gas to about 10,000ppm, more preferably about 500ppm of a small amount of gas comprises master gas is to about 2,000ppm.For purposes of the invention, described a small amount of gas can be oxygen or air, and described main gas can be nitrogen.We believe that the oxygen in nitrogen or the concentration of air help to reduce as the defective of tombstoning and scolder splatter and in the electronic assemblies operation process, particularly improve solderability in the production at surface-mounted integrated circuit in this specific scope.Be lower than the oxygen of about 100ppm or air and some low oxygen defect can take place and be higher than approximately 10 in nitrogen in nitrogen, some high oxygen defect can take place in the oxygen of 000ppm or air.Realize the required oxygen in nitrogen of optimum performance of reflow oven or air concentration (generally at about 100ppm to about 10,000ppm) be called as " sweetspot ".

Therefore we are desirable to provide a kind of gas mixer, it is about 100ppm to about 10 that this device helps to provide the oxygen that has in nitrogen or air, the controlled air of the gas characteristic of 000ppm so that can implement described electronic assemblies method under the situation that still less or hardly has defective.

Traditional gas hybrid technology has generally been used expensive mass flow controller and huge surge tank.People have used the admixture of gas of these traditional blender production oxygen of 1% to 50% scope in nitrogen, but can not reach the ppm scope.The commercial much larger sized more expensive gas mixer that can get has appearred in nearest research.The gas mixer of lower price has appearred in the progress since nearer, and this blender uses fixing orifice plate with the measurement gas flow, and mixes in much smaller surge tank subsequently.In addition at accurately providing some gas composition also to develop other traditional blender.

Also exist other that gas mixing apparatus of gas mixture composition is provided equally in the art.At U.S. Patent number 6,614, the combination of test gas and zero gas is disclosed in 655.Described zero gas can be nitrogen or made oxygen; And described test gas (correcting gas) is not specified.' 655 patent disclosure reduce to produce the quantity of the necessary critical spray nozzle of feed stream in the product of variable concentrations.The mixing chamber of the gas mixing apparatus in the patent of ' 655 is connected with the outlet of described critical spray nozzle, has guaranteed that outlet pressure is higher than certain minimum pressure.Each critical spray nozzle between adjacent has increased by 1: 2 ratio.Because outlet pressure always is higher than critical pressure, only depend on that therefore the volume of gas of the cross-sectional area of described nozzle always is constant.Described critical spray nozzle has received test gas or zero gas.Valve with two inlets is installed in the upstream of described critical spray nozzle and can alternately opens this two inlets.Four nozzles have cross-sectional area when opening be 1: 2: 4: 8.The nozzle of maximum is installed in the place relative with the outlet of described blender.A microprocessor starts described valve and monitoring and adjusts gas pressure.Gas mixing apparatus in the patent of ' 655 has obtained 16 linear gradient concentration of test gas in described zero gas.

At U.S. Patent number 5,671,767 and U.S. Patent number 5,544,674 in all disclose with control ratio two kinds of gases are mixed.Because described mixing arrangement is to be used for respirator, therefore the gas in these patents only relates to oxygen and air.Described mixing arrangement reaches and the mixing of the irrelevant pin-point accuracy of flow velocity, therefore can high flow rate or low flow velocity use described device.Control first gas stream by the nozzle of variable area, this nozzle is supplied with described mixing chamber with described gas.For the operation too of second gas stream.When flow velocity reduced, piston was shifted to valve member.This will reduce the size of each nozzle and remain on identical ratio between the flow area of described nozzle.Thereby each the size of passage or the nozzle area at two kinds of gases described in each valve increases or reduces the ratio that identical quantity has kept gas.

In Japanese Patent No. 11,033, the gas mixing apparatus of a kind of miniaturization and simplification is disclosed in 382.In this patent, used a kind of pressure equalizing device with two kinds of gas regulation to identical pressure.These two kinds of gases pass through to mix with the ratio corresponding to the predetermined mix ratio in the zone at gas.Can adjust flow velocity by control valve.

Though have the device of many mists, but we believe do not have a kind ofly can propose economical and easy device mist has about 100ppm to 10 with production, the nitrogen product of the oxygen of 000ppm.Therefore need a kind of gas mixer with described feature.

One aspect of the present invention relates to the easy gas mixer that is used for accurately mixing composite gas (plurality gases).This device comprises gas control panel (gas panel), the pressure-control valve that is used to adjust pressure reduction, flowmeter and static mixing chamber.Described composite gas can be a kind of a small amount of gas and a kind of main gas, and wherein, for example described main gas is that nitrogen and described a small amount of gas are air or oxygen.Preferred described main gas and described a small amount of gas account for about 100ppm to about 10 with oxygen in nitrogen, the ratio of 000ppm, and more preferably oxygen accounts for about 500ppm to about 2 in nitrogen, and the ratio of 000ppm is mixed and is obtained admixture of gas.

Described pressure-control valve is adjusted pressure reduction to about ± 5 inchess of water(in H.This device forms an integral body with reflow oven (reflow oven).

When here using, oxygen can exchange with air sometimes.It should be noted about 20% of oxygen content duty gas.

When read in conjunction with the accompanying drawings, will become apparent by following detailed description of the present invention further advantage of the present invention, wherein Fig. 1 is the general illustration of the gas mixer of use difference gauge, flowmeter and static mixing chamber.

The invention provides easy gas mixer, this device uses the static mixing chamber can produce the mixture with a kind of a small amount of gas and a kind of main gas, preferred oxygen or air as described a small amount of gas and nitrogen as described main gas, the concentration of oxygen or air is that about 100ppm is to about 10 in nitrogen, 000ppm, more preferably the concentration of oxygen or air is about 500ppm to about 2 in nitrogen, 000ppm.This device comprises the baffle plate in the fixing pipeline, and this baffle plate causes that gas produces shear and vortex, has produced uniform product thus.

The invention provides oxygen concentration stable in admixture of gas, this is by mixing nitrogen and air or oxygen in mixing control panel, and measure there the nitrogen supplied with and supply oxygen pressure differential and be controlled to difference and be not more than about 5 inchess of water(in H and obtain.By described mixture transmission is passed through a static ribbon mixer with its homogenizing.This technology advantageous particularly part is wherein to be mixed into the amount foot of oxygen in the described nitrogen or air in obtaining preferably containing about 100ppm to about 10 in nitrogen, the oxygen of 000ppm or air, more preferably in nitrogen, contain about 500ppm, the final nitrogen gas concn of the oxygen of 000ppm or air to about 2.

The great difference of the present invention and prior art design is two kinds of gas streams are measured, and in surge tank mixed gas flow.

Small pressure oscillation between described main gas and a small amount of gas will produce adverse influence to accurate mixing.In order to save cost, in design, removed not expensive flowmeter, but introduced difference gauge to measure and to be controlled at pressure reduction between described main gas and a small amount of gas less than about 5 inchess of water(in H.

The present invention has used the static mixing chamber.A fixing interior baffle plate of pipeline is contained in this static mixing chamber, and this baffle plate causes that gas produces shear and vortex, has produced uniform product thus.Use static mixing chamber has compensated the expense of difference gauge, and the size of greatly having dwindled existing gas mixer.

Use mechanically-operated controller to control described nitrogen and Oxygen Flow here, and use pressure difference indicator to guarantee to adjust described two kinds of gas flowing pressure differences in 5 inches water column pressure.The flow of controlled gas stream as described in use traffic meter (as the spinner flowmeter) control, and regulate this flowmeter and carry required accurate admixture of gas.In the static mixing chamber, described two kinds of gases stream is mixed subsequently, then final admixture of gas is transferred in the reflow oven.

The present invention has produced the stabilizing gas mixture of extremely accurate ± 1ppm in the admixture of gas of 100ppm.Simple difference gauge is produced varied range of flow accurately and accurate admixture of gas to about ± 1ppm.Improve described accuracy by the identical discharge pressure (deviation ± 5 inchess of water(in H) of guaranteeing described two kinds of gases stream.Record discharge pressure among the present invention paramount for approximately ± 300 inchess of water(in H.

As an example of gas mixing control panel of the present invention, to have conceived " flat board " design and be beneficial to be installed on the spot in the described reflow oven, it can carry out revocable installation.The specification of gas mixing control panel of the present invention is as follows: size 24 " high * 24 " long * 12 " dark

(61cm height * 61cm length * 30.5cm is dark) weight 651bs (29.2kg) interface nitrogen inlet: 1/2 " FPT

Air intake: 1/4 " FPT

N ₂/ air mixed export: 1/2 " FPT

N ₂/ air biased sample: 1/4 " requirement of snap joint gas

Clean dry air is 50scfh (100psig) at least

Praxair (commerical grade nitrogen) is 3000scfh (100psig) at least

Fig. 1 provides the flow process of one embodiment of the invention.(280-2800scfh 5-50scfm) enters with the pressure of 75psig with air stream 14 (2-20scfh) nitrogen stream 12.The pressure reduction that difference gauge 24 is measured between the described stream.If described pressure reduction is too high, pressure controller 20 and 22 will be made adjustment until pressure reduction in about ± 5 inches of water(in H.Before passing through flowmeter 26 or 28, described stream is continuously by pressure relief valve 16 and 18 (being arranged on 100psi).Flow valve 30 and 32 is according to finally flowing the flow that selected concrete composition is monitored described stream.Entering gas mixer 34 (static mixing chamber) check valve 36 and 38 described air of adjustment and nitrogen before.Described gas is mixed, and the product stream 16 of emitting has about 10ppm to about 10 according to selected composition, the oxygen content of 000ppm.The flow direction of sample valve 40 guiding sample gases.

Each side of the present invention is removable.For example, can will have the difference gauge of guiding/subordinate adjusting device and be installed in pure nitrogen gas and air activity.In this design, described nitrogen adjuster will be controlled the nitrogen gas pressure of transmission, and provide signal to reach and the essentially identical pressure of nitrogen pressure with default air regulator.

Another variant that the present invention considered is to adopt easy surge tank to replace described static mixing chamber, and the inlet in described surge tank has diffuser nozzle.Described diffuser nozzle will provide essential shearing and vortex to flow and Oxygen Flow suitably to mix described nitrogen.

The one or more of the present invention concrete feature of Xian Shiing only is a purpose for convenience in the accompanying drawings, and each feature can be in conjunction with other feature according to the present invention.Those skilled in the art will recognize that these embodiments are included in the scope of claims as the embodiment of selecting.

Claims

1. be used for accurately mixing the easy gas mixer of composite gas (plurality gases), described device comprises:

(a) gas control panel (gas panel);

(b) be used to adjust the pressure-control valve of pressure reduction;

(c) flowmeter; With

(d) static mixing chamber.

2. the device of claim 1, wherein said device mixes a kind of a small amount of gas and a kind of main gas.

3. the device of claim 2, wherein said main gas is that nitrogen and described a small amount of gas are air.

4. the device of claim 2, wherein said main gas is that nitrogen and described a small amount of gas are oxygen.

5. the device of claim 2, wherein said device mix described main gas and described a small amount of gas to obtain in nitrogen approximately 100ppm to about 10, the admixture of gas of the oxygen of 000ppm.

6. the device of claim 2, wherein said control valve adjust described pressure reduction to approximately ± 5 inchess of water(in H.

7. the device of claim 1, wherein said device and reflow oven (reflow oven) form an integral body.

8. the device of claim 1, wherein said static mixing chamber comprises fixing pipeline Internal baffle.

9. the device of claim 1, wherein said flow is counted spinner flowmeter.

10. the device of claim 1 wherein adopts surge tank and diffuser nozzle to replace described static mixing chamber.