One, printed circuit board analysis of temperature rise element

The immediate cause that causes printed board temperature rise is the existence as a result of parts of an apparatus of circuit power comsumption, electronic parts all differs power comsumption of level land existence, calorific intensity changes along with the size of power comsumption.

 

2 kinds of phenomena of the temperature rise in printed board:

(1) local temperature rise or bedding face accumulate temperature rise;

(The temperature rise when 2) is short or long temperature rise.

 

When analytic PCB heats up power comsumption, be analysed commonly from the following respects.

 

1.Electric power comsumption

(1) analyses the power comsumption; on unit area

(2) analyses PCB of the power comsumption on circuit board distributing.

 

The structure of 2. printed board

 

(The dimension; of 1) printed board

 

(The material of 2) printed board.

 

The installation means of 3. printed board

 

(1) installs means (like perpendicular installation, the level is installed) ;

 

(2) sealed circumstance is apart from with what leave housing.

 

4. heat radiation

 

(The radiation coefficient; of surface of 1) printed board

 

(The difference in temperature between 2) printed board and photograph adjacent surface and their absolutely temperature;

 

Heat is conducted

(1) installs radiator;

(The conduction of structural member of 2) other installation.

 

6. thermal convection current

(; of 1) natural convection

(2) forces cooling convection.

 

From PCB the efficient way that the analysis of afore-mentioned each elements is the temperature rise that solves printed board, often mix in a product these elements in the system are cross correlation is mixed depend on, most element should be analysed according to actual condition, in the light of some only ability of specific and actual condition compares correctly computation or estimation gives the parameter such as temperature rise and power comsumption.

 

2, circuit board comes loose hot means

1.Tall calorific parts of an apparatus adds radiator, heat conduction board

There should be a few parts of an apparatus in PCB when calorific amount is larger (little at 3) when, radiator or heat conduction pipe can be toted on calorific parts of an apparatus, when temperature still cannot fall, can use the radiator that brings fan, come loose in order to increase hot effect. Measure when calorific parts of an apparatus relatively a long time (3 over) , can use come loose greatly hot cover (board) , it is to press the special radiator with the custom-built with on any account position of calorific parts of an apparatus on PCB board or be on a big flat radiator dig or dig out with a finger or sth pointed gives different component discretion seat. Will come loose the whole that heat up a cover is buckled go up in component side, be contacted with every component and come loose hot. But as a result of yuan consistency of the discretion when parts of an apparatus installs solder is poor, medicinal powder hot result is bad. Be in normally yuan of hot photograph that softness adds on face of parts of an apparatus change heat conduction fills up improvement to come loose hot effect.

 

2.Pass PCB board itself to come loose hot

The PCB board that uses extensively at present is Fu copper / base material of cloth of annulus oxygen glass or base material of cloth of glass of phenolic aldehyde colophony, the paper that still has a few use base Fu copperplate material. Although these base material have good electric performance and treatment property, but medicinal powder hot sex is poor, serve as high calorific component medicinal powder hot way, barely hope conducts quantity of heat by PCB itself colophony, face from the watch of component however all round heat comes loose in air. But already entered component miniaturization, high density to send thermalization installation, high to assemble a times as electronic product, if rely on exterior accumulating only,very little component face comes loose heat is very insufficient. Install a large number of use of component as a result of the surface such as QFP, BGA at the same time, yuan the abundantly of quantity of heat that parts of an apparatus produces passes PCB board, accordingly, solve medicinal powder hot best method is the PCB oneself that raises as direct as calorific component contact medicinal powder heat energy force, pass PCB board to conduct go out or send out go out.

 

3.Use implementation of reasonable design taking a line to come loose hot

Because the colophony thermal conductivity in plank is poor, and the good conductor that Copper Foil circuitry and aperture are heat, because this raises Copper Foil the rest,be led and increasing heat conduction opening is to come loose hot main measure.

 

Evaluate PCB medicinal powder heat energy force, the composite material that makes to all sorts of material that differ by coefficient of thermal conductivity with respect to need one by one the equivalent coefficient of thermal conductivity that PCB uses insulation substrate (9 Eq) have consideration.

 

4.Sort the equipment with cool air to using freedom to be opposite, had better be integrated circuit (or other parts of an apparatus) arrange by lengthwise means, or arrange by horizontal long way.

 

5.The parts of an apparatus that goes up with a printed board should give out heat by its as far as possible quantity size and medicinal powder hot degree partition is arranged, calorific quantity the parts of an apparatus with small or poor hear resistance (like small signal transistor, miniature integrated circuit, electroanalysis capacitance) those who be put in cooling air current is the most genteel (the entrance is in) , calorific quantity the parts of an apparatus with big or good hear resistance (wait like circuit of power transistor, large scale integration) put in cooling air current the most downstream.

 

6.On horizontal way, high-power parts of an apparatus stands by printed board edge to decorate as far as possible, so that shrink,; of short pass hot method is on perpendicular direction, high-power parts of an apparatus stands by printed board upper part to decorate as far as possible, so that reduce the to temperature of other parts of an apparatus effect when jobs of these parts of an apparatus.

 

7.More sensitive to temperature parts of an apparatus had better find a place for the area in temperature lowest (the bottom) that is like equipment, must not put it in calorific parts of an apparatus upper part, many parts of an apparatus had better be complex overall arrangement is handed in in horizontal.

 

8.Of the printed board inside equipment medicinal powder air of hot main support flows, want to study air flow way when the design so, reasonable configuration parts of an apparatus or printed circuit board. Incline to always is when air flows at obstruction little place flows, be in so printed circuit board on when configuring parts of an apparatus, should avoid to stay in a certain area have bigger airspace. Overall in many printed circuit board configuration also should note same question.

 

9.Prevent the concentration of the heat on PCB, distributing power equably as far as possible it is on PCB board, those who hold property of PCB surface temperature is even and consistent. In often designing a process, should achieve strict distributinging equably is relatively difficult, but must avoid the area with power too high density, lest appear,heat spot affects the regular job of whole circuit. If conditional word, the hot efficiency analysis that undertakes printed circuit is very those who be necessary, if a few professional PCB design the hot efficiency quota that increases in software to analyse software module now, can help design personnel optimize circuit design.

 

10.power comsumption highest and calorific the biggest parts of an apparatus is decorated coming loose near hot optimal position. Will not give out heat taller parts of an apparatus places the corner in printed board and four periphery predestined relationship, unless have in its around arrangement,come loose shrinkage fitting buy. Choose a few bigger parts of an apparatus as far as possible when designing power resistor, and have in what when adjusting printed board position, make come loose enoughly hot space.

 

11.Parts of an apparatus of high fever dissipation should be used up when joining with substrate can reduce the thermal resistance between them. To satisfy hot characteristic requirement better, data of a few thermal conductivity can be used in chip underside (like daub) of silica gel of a heat conduction, the osculatory section that keeps certain comes loose for parts of an apparatus hot.

 

12.The join of parts of an apparatus and substrate:

(1) shortens as far as possible; of length of down-lead of parts of an apparatus

(When 2) chooses parts of an apparatus of tall power comsumption, lv of take an examination brings the thermal conductivity of line material, if possible sentence, choose down-lead horizontal stroke as far as possible paragraph the biggest;

(3) chooses pin to count more parts of an apparatus.

 

13.Of parts of an apparatus enclose choose:

(The hot conductivity; that 1) is considering to heat up what parts of an apparatus should notice when the design to enclose specification and it

(Lv of 2) take an examination is enclosed in substrate and parts of an apparatus between offer a good heat to conduct method;

(3) is conducted in heat available gas partition should avoid on method, if have,this kind of circumstance can use heat conduction material to have stuff.