Protecting a thermal sensitive component in a thermal process

Provided is a method for protecting a thermal sensitive component mounted on a board during a thermal process. The method includes: providing the board, providing a protection apparatus which is removable and made of a thermoelectric material to protect the thermal sensitive component during the thermal process, wherein the protection apparatus cools the thermal sensitive component during the thermal process in response to applying a voltage to the protection apparatus. Further provided is the protection apparatus for the thermal sensitive component mounted on the board during the thermal process.

FIELD OF THE INVENTION

The present invention relates to a protection apparatus and method, and more particularly, to a protection apparatus and method for protecting a thermal sensitive component and preventing the thermal sensitive component from being overheated and thereby damaged during a process.

BACKGROUND

With green awareness on the rise, there is an increasing demand for a lead-free process applicable to printed circuit board assembly (PCBA) technology. For example, nowadays, printed circuit board assembly no longer employs a tin-lead solder but employs a widely-used tin-silver-copper (SAC) alloy solder or tin-copper alloy solder. Normally, the melting point of lead-free solders, tin soldering temperature, and wave soldering temperature are 20° C. to 30° C. higher than that of tin-lead solders, not to mention that lead-free solders adhere to tin less readily; as a result, assembly process providers usually raise the temperature of tin in operation with a view to enhancing the processability thereof.

During a typical printed circuit board assembly process, some thermal sensitive components can only withstand the thermal stress of a eutectic solder at low temperature, but the thermal sensitive components do not meet the high temperature requirements of a lead-free process. For example, constituent components of a liquid crystal display (LCD) include a printed circuit board, and the liquid crystal display cannot withstand the thermal stress of a lead-free wave soldering process.

To overcome the aforesaid limitation of thermal sensitive components, it is often feasible to assemble a liquid crystal display by means of hand soldering. However, the aforesaid conventional process is unreliable, cost-ineffective, and inefficient, when compared with an automated process.

BRIEF SUMMARY

In an aspect of the present invention, the present invention provides a protection apparatus and method for protecting a thermal sensitive component by preventing the thermal sensitive component from being overheated and thereby damaged during a printed circuit board assembly process.

In an aspect of the present invention, the present invention provides a reliable assembly process to be performed on a thermal sensitive component during a lead-free process to thereby meet environmental protection requirements, enhance performance, and achieve high cost-effectiveness.

According to an embodiment of the present invention, a method for protecting a thermal sensitive component during a thermal process comprises: providing a board such that the thermal sensitive component is disposed on the board; providing a protection apparatus made of a thermoelectric material and removable; and protecting the thermal sensitive component with the protection apparatus during the thermal process, wherein the protection apparatus cools the thermal sensitive component during the thermal process in response to applying a voltage to the protection apparatus.

According to another embodiment of the present invention, the protection apparatus comprises a cap body and a battery. The cap body caps the thermal sensitive component and is in thermal communication with the thermal sensitive component during the thermal process. The battery causes the thermoelectric material to produce a thermoelectric effect and thereby cools the thermal sensitive component.

In yet another embodiment of the present invention, the cap body comprises a second body portion and a first body portion disposed on the second body portion. One of the first body portion and the second body portion is made of an P-type thermoelectric material. The other one of the first body portion and the second body portion is made of an N-type thermoelectric material.

In a further embodiment of the present invention, the cap body comprises a first substrate body, a second substrate body, an P-type thermoelectric material chip and an N-type thermoelectric material chip which are disposed between the first substrate body and the second substrate body, and an electrode of an PN junction. The first substrate body and the second substrate body are hermetically sealed to define a hermetically sealed space. Before the step of protecting the thermal sensitive component with the protection apparatus, the method of the present invention further comprises the step of performing a vacuum pumping process on the hermetically sealed space of the protection apparatus.

The present invention provides, in a further embodiment thereof, a protection apparatus for use with a thermal sensitive component disposed on a board during a thermal process. The protection apparatus comprises: a removable device body having a void for containing at least a portion of the thermal sensitive component, being made of a thermoelectric material, and protecting the thermal sensitive component during the thermal process; and a battery for supplying a voltage to the removable device body to thereby enable the protection apparatus to cool the thermal sensitive component.

In a further embodiment of the present invention, the removable device body comprises a second body portion and a first body portion disposed on the second body portion. One of the first body portion and the second body portion is made of an P-type thermoelectric material. The other one of the first body portion and the second body portion is made of an N-type thermoelectric material.

In a further embodiment of the present invention, the removable device body comprises a first substrate body, a second substrate body, an P-type thermoelectric material chip and an N-type thermoelectric material chip which are disposed between the first substrate body and the second substrate body, and an electrode of an PN junction. The first substrate body and the second substrate body are hermetically sealed to define a hermetically sealed space. Before the step of protecting the thermal sensitive component with the protection apparatus, the step of performing a vacuum pumping process on the hermetically sealed space of the protection apparatus.

DETAILED DESCRIPTION

The following description begins withFIG. 1that illustrates an embodiment of the present invention with a view to describing in detail a protection apparatus and a method for use with a thermal sensitive component mounted on a board during a thermal process. Referring toFIG. 1, a panel100comprises a board104(including but not limited to, for example, a printed circuit board), wherein disposed on the board104is a thermal sensitive component108(including but not limited to, for example, a display module), and various components which surround the display module108, including, but not limited to, a man/machine interface112, a capacitor116, a switch124, a transducer128, a memory132, a micro controller136, a pressure sensor140, a light-emitting diode (LED)144, and other components (such as an inductor, a resistor, and a connector). The aforesaid components can be conventional components, such as those components for use in conventional data processing systems. The conventional components of this kind can be configured to operate in a way described below.

The printed circuit board104is a substrate on which various components are mounted and connected, such that the combination of the components achieves specific functions and advantages. The printed circuit board104typically comprises a motherboard, a display card, a panel card, and a wireless network card. The display module108is a liquid crystal display module or a plasma display module. The components are mounted on a circuit board by surface mount technology (SMT) when they are SMT components, fixed to the circuit board by wave soldering when they are pinned components, or coupled to the circuit board by any appropriate connection technique, and the present invention is not limited thereto.

In general, a wave soldering process entails turning liquid tin inside a tin furnace into a slender tin wave by means of a pump, and moving a circuit board obliquely upward to pass through the tin wave by means of a conveyor belt to enable the liquid tin to “enter holes” and “perform tin filling” at pin-connecting points of the pinned component, thereby forming solder joints. The aforesaid process is part of a conventional wave soldering process and thus is not described in detail herein for the sake of brevity.

The purpose of the surface mount technology is to mount a component on a substrate of a printed circuit board. The conventional surface mount technology entails positioning components on a circuit board by means of a surface mounter machine and then performing a subsequent process. The surface mounting technique for mounting components on a circuit board is regarded as part of the prior art and thus is not described in detail herein for the sake of brevity. Furthermore, it is also feasible that connection of a component and a circuit board is effectuated in another manner according to the prior art, and thus the present invention is not limited thereto.

Referring toFIG. 2, there is shown a schematic view of the board104(such as a printed circuit board, but the board104is not limited thereto), the thermal sensitive component108(including but not limited to a display module, an electrolytic capacitor, or a solid-state capacitor, but the thermal sensitive component108is not limited thereto), a protection apparatus200, and a related process thereof according to an embodiment of the present invention. The printed circuit board104has a front side202, a rear side204, a through hole208, and a printed circuit212. In order to be connected to the printed circuit board104, the display module108has a solder connection216; hence, the solder connection216penetrates the through hole208, and thus the solder connection216can be soldered to the printed circuit212on the rear side204. Hence, the solder connection216, the printed circuit212, and the display module108are present on different sides of the printed circuit board104, respectively. In addition to the thermal sensitive component108, electronic components288are disposed on the printed circuit board104. The electronic components288are disposed on and attached to the printed circuit board104by a soldering process, a wave soldering process, or a hand soldering process.

Thermal sensitive component108, as the name implies, is a thermal sensitive component, and is likely to be damaged in an overheated environment. Components connected to the circuit board are generally of two types, namely pin-through-hole (PTH) components and surface-mount components. The PTH components are different from the surface-mount components in terms of the degree of their tolerance to heat. The PTH components usually tolerate a temperature of less than 110° C., whereas the surface-mount components usually tolerate a temperature of less than 230° C. At temperature above 100° C., the PTH components, such as display modules, are likely to be permanently damaged because of thermal shock or thermal fatigue. Take an electrolytic capacitor or a solid-state capacitor as an example, it is likely to be permanently damaged because of capacitance splitting at a temperature above 105° C. or 110° C. approximately.

On the other hand, to achieve satisfactory soldering, a soldering process usually requires the display module108to stay in a high-temperature environment for a while. In an embodiment of the present invention, a wave soldering process involves positioning the display module108on the printed circuit board104and then increasing the temperature gradually to 70˜95° C. Afterward, a soldering process proper begins and takes place at 90˜95° C. typically for at least 30˜45 seconds before the temperature drops gradually to prepare for a condensation phase. A high-temperature process which takes place at 95° C. approximately for more than 30 seconds is especially the indication for an environmentally friendly lead-free solder with a view to manufacturing a reliable satisfactory solder joint.

Referring toFIG. 2, in an embodiment of the present invention, the protection apparatus200comprises a protection apparatus body260having a void258. The void258contains at least a portion of the thermal sensitive component108. The protection apparatus body260is made of a thermoelectric material. The protection apparatus200further comprises a battery264for applying (supplying) a voltage292to the protection apparatus body260to thereby allow the protection apparatus200to produce a thermoelectric effect whereby the thermal sensitive component108is cooled down.

In an embodiment of the present invention, the protection apparatus200comprises a cap body260and the battery264. The cap body260encloses at least a portion of the thermal sensitive component108and is made of a thermoelectric material so as to protect the thermal sensitive component108during the thermal process. The battery264applies the voltage292to the cap body260and thereby causes the protection apparatus200to produce a thermoelectric effect whereby the thermal sensitive component108is cooled down. The cap body260comprises a first body portion268and a second body portion272. The first body portion268and the second body portion272are connected. The first body portion268is electrically coupled to an anode276of the battery264, whereas the second body portion272is electrically coupled to a cathode280of the battery264. The first body portion268is made of an P-type thermoelectric material, whereas the second body portion272is made of an N-type thermoelectric material. The P-type thermoelectric material and the N-type thermoelectric material are semiconductors, semimetals, or compounds, which have high thermoelectric figure of merit, including but not limited to antimony (Sb) doped and selenium (Se) doped bismuth telluride (BiSb)2(TeSe)3series, lead telluride (PbTe) and lead-tin-telluride (PbSnTe) series, Half-Heusler intermetallic alloy series, silicon (Si) and silicon-germanium (SiGe) series, metal silicides series, or tungsten diselenide (WSe2) series. The first body portion268and the second body portion272are flat panel-shaped or are of any appropriate shape. The protection apparatus200further comprises an engaging element284, a non-engaging element, and the like which are conducive to capping, for example, a sidewall, or any element of any other appropriate shape, and the present invention is not limited thereto.

In an embodiment, the engaging element284is a pair of resilient plates connected to the removable cap body260and thereby engaged with the thermal sensitive component108. The engaging element284operates in conjunction with the removable cap body260to cap the thermal sensitive component108during a thermal process and thereby be in thermal communication with the thermal sensitive component108, thus cooling the thermal sensitive component108by the thermoelectric effect of the thermoelectric material. The engaging element284is made of aluminum or any other appropriate materials, and the present invention is not limited thereto. Details of the thermoelectric effect and a protection apparatus/method for use with the cap body260and/or the engaging element284are described below.

Referring toFIG. 3, in an embodiment of the present invention, to cater for various high-temperature environments and efficiently protect the thermal sensitive component108(such as a display module, but the thermal sensitive component108is not limited thereto) disposed on the board104(such as a printed circuit board, but the board104is not limited thereto), the present invention provides a method300of protecting the thermal sensitive component108during a thermal process. Referring toFIG. 1throughFIG. 3, the method300comprises the steps of: providing a board104(step304); providing the protection apparatus200which is made of a thermoelectric material and removable (seeFIG. 2) (step308); protecting the thermal sensitive component108with the protection apparatus200during a thermal process, wherein, in response to applying the voltage292to the protection apparatus200, the protection apparatus200cools the thermal sensitive component108during the thermal process (step312); and removing the protection apparatus from the thermal sensitive component after the thermal process (step316).

The thermoelectric effect amounts to direct conversion of temperature difference generated from a voltage and vice versa. A thermoelectric device brings about a temperature difference in response to a voltage applied thereto. In another aspect, given a temperature difference between its two ends, the thermoelectric device generates a voltage. In general, the thermoelectric effect applies to cooling an object, heating an object, generating electric power, or measuring temperature.

In general, the thermoelectric effect comprises three defined effects, namely the Seebeck effect, the Peltier effect, and the Thomson effect. Persons skilled in the art are familiar with the thermoelectric effect.

FIG. 4is a circuit diagram that illustrates the Seebeck effect. As shown inFIG. 4, the voltage generated by the Seebeck effect is expressed below, wherein SAand SBdenote the Seebeck coefficients of metal A and metal B, respectively, wherein T1and T2denote the temperatures of the two metals at the junction thereof, respectively. On the other hand, the Peltier effect is the opposite of the Seebeck effect, that is to say, if power is introduced to the loop of two different metals to generate electric potential, there will be a temperature difference at the contact point between the two metals.
V=∫T1T2(SB(T)−SA(T))dT

In an embodiment of the present invention, the thermal process is a wave soldering process, an SMT reflow process, a hand soldering process, or a rework process. Broadly speaking, the thermal process is a sub-process of a printed circuit board process, including but not limited to a repairing process, a manufacturing process, or a rework process.

Referring toFIG. 5, in an embodiment of the present invention, there is shown a schematic view of the board104(including but not limited to a printed circuit board), the thermal sensitive component108(including but not limited to a display module, an electrolytic capacitor, or a solid-state capacitor), a protection apparatus550, and a related process thereof. In addition to the thermal sensitive component108, other electronic components288are disposed on the board104. The electronic components288are disposed on and attached to the printed circuit board104by a soldering process, a wave soldering process, or a hand soldering process.

Likewise, to achieve satisfactory soldering, the thermal sensitive component108usually has to stay in a high-temperature environment for a while during a soldering process. Referring toFIG. 5, the protection apparatus550has a first substrate body554, a second substrate body558, an P-type thermoelectric material chip562and an N-type thermoelectric material chip566which are disposed between the first substrate body554and the second substrate body558, and an electrode (not shown) of an PN junction. The P-type thermoelectric material chip562and the N-type thermoelectric material chip566alternate or are arranged in a similar or equivalent manner in order to be disposed between the first substrate body554and the second substrate body558. The first substrate body554is an outer casing, whereas the second substrate body558is an inner casing. A welding portion590is formed by welding technology, such that the first substrate body (outer casing)554and the second substrate body (inner casing)558are hermetically sealed by the welding portion590to form a hermetically sealed space560for facilitating a subsequent vacuum pumping process. Likewise, the first substrate body (outer casing)554and the second substrate body (inner casing)558define a void578so as for the second substrate body (inner casing)558to contain at least a portion of the thermal sensitive component108. The protection apparatus550has the battery264for applying the voltage292to the first substrate body (outer casing)554and the second substrate body (inner casing)558in a similar manner, such that the protection apparatus550produces the thermoelectric effect for cooling the thermal sensitive component108.

The first substrate body (outer casing)554and the second substrate body (inner casing)558are made of aluminum or any other appropriate materials. The P-type thermoelectric material chip562is made of the P-type thermoelectric material. The N-type thermoelectric material chip566is made of the N-type thermoelectric material. The first substrate body (outer casing)554and the second substrate body (inner casing)558are cap-shaped or of any other appropriate shape. The first substrate body (outer casing)554and the second substrate body (inner casing)558are integrally formed as a unitary structure or are formed from flat panels welded and jointed together in a hermetically sealed manner by a welding portion594. The present invention is not limited thereto.

In an embodiment of the present invention, to cater for various high-temperature environments and efficiently protect the thermal sensitive component108(including but not limited to a display module, an electrolytic capacitor, or a solid-state capacitor) disposed on the board104(including but not limited to a printed circuit board) in various high-temperature environments, the present invention provides a method660of protecting the thermal sensitive component108during a thermal process, as shown inFIG. 6. Referring toFIG. 1throughFIG. 5, the method660comprises the steps of: providing a board104(step664); providing a protection apparatus550made of a thermoelectric material and removable (seeFIG. 5) (step668); performing a vacuum pumping process on the protection apparatus550(to decrease the pressure therein to 1 atmospheric pressure approximately) (step672), wherein the purpose of the vacuum pumping step is to prevent heat transfer and enhance cooling; protecting a thermal sensitive component108with the protection apparatus550during a thermal process, wherein the protection apparatus550cools the thermal sensitive component108during the thermal process in response to applying the voltage292to the protection apparatus550(step676); and removing the protection apparatus from thermal sensitive component after the thermal process (step680).

Referring toFIG. 7, there is shown a schematic view of protecting a thermal sensitive component108during a wave soldering process according to an embodiment of the present invention. In addition to the thermal sensitive component108, other electronic components508are disposed on the printed circuit board104. Referring toFIG. 1throughFIG. 6, the printed circuit board104has the through hole208adapted to be penetrated by the solder connection216on the thermal sensitive component108. As shown inFIG. 7, the solder connection216is connected to the printed circuit212of the printed circuit board104(wherein the printed circuit212and the thermal sensitive component108are disposed on different sides of the board104, respectively) by a wave soldering process. Referring toFIG. 7, the wave soldering process employs a conventional wave soldering device500that comprises a tunnel504, a wave soldering tank512, and other constituent components not shown. The conventional wave soldering device500further comprises an outer casing, a conveying device (for conveying a workpiece to be soldered along the tunnel504), and a pre-heating region. The aforesaid components are regarded as part of the conventional wave soldering device500and thus are not described in detail herein for the sake of brevity. A wave soldering process is performed at a typical temperature of 90° C. to 260° C. During the wave soldering process, the protection apparatus200(or the protection apparatus550inFIG. 5) is thermally coupled to the thermal sensitive component108, such that the protection apparatus200not only provides thermal insulation to the thermal sensitive component108but also provides a cold source whereby the temperature of the thermal sensitive component108is prevented from rising because of the wave soldering process. Afterward, upon termination of the wave soldering process, the protection apparatus200is removed.

Referring toFIG. 8, there is shown a schematic view of protecting a thermal sensitive component808during an SMT reflow process. In an embodiment of the present invention, during a reflow process of the SMT thermal sensitive component808, the SMT thermal sensitive component808features a heat tolerance temperature of 230° C. approximately for 20 to 40 seconds. When protected by the protection apparatus200ofFIG. 2(or the protection apparatus550ofFIG. 5), the SMT thermal sensitive component808features a heat tolerance temperature (for example, 230° C.) for an extended period of time (for example, 30 to 80 seconds.) Referring toFIG. 8, where details of an embodiment are depicted, in addition to the thermal sensitive component108, other electronic components604are disposed on the printed circuit board104. The electronic components604are mounted on the printed circuit board104by an SMT process.FIG. 8also illustrates an SMT reflow process and a device related thereto. As shown inFIG. 8, the SMT reflow process employs a conventional SMT reflow oven600that comprises a reflow oven body608and constituent components not shown. The conventional SMT reflow oven600further comprises a conveying device for conveying a workpiece through the reflow oven body608for undergoing a reflow process. The aforesaid components are regarded as part of the conventional SMT reflow oven600and thus are not described in detail herein for the sake of brevity. The SMT reflow process is performed at a typical temperature of 183° C. to 260° C. During the SMT reflow process, the protection apparatus200(or the protection apparatus550ofFIG. 5) is thermally coupled to the thermal sensitive component108, such that the protection apparatus200not only provides thermal insulation to the thermal sensitive component108but also provides a cold source whereby the temperature of the thermal sensitive component108is prevented from rising because of the SMT reflow process, thereby keeping the thermal sensitive component108below 230° C. approximately. Upon termination of the SMT reflow process, the protection apparatus200is removed.

The cooling effect produced by the wave soldering process as depicted inFIG. 7is described below. Assuming a maximum target temperature of 100° C., an expected temperature of 95° C., a current temperature of 125° C., and a process duration of 28 seconds approximately, the rate at which heat energy is removed from or introduced into a workpiece (i.e., the thermal sensitive component108), that is, Q (in watts), is calculated with the following equation:
Q=mCp(Ts−Tf)/t, wherein

m denotes mass (weight) (Kg) of a workpiece,

Hence, in an embodiment, given a workpiece with a weight of 10.6 g and Cpof 0.6 J/Kg° C., the heat to be removed is calculated as follows:
Q=10.6/1000*1000*0.6*(125−95)/28=6.8

According to a typical exemplary embodiment of the present invention, various thermal processes are advantageously characterized in that, not only is the thermal sensitive component efficiently protected and assured efficient heat dissipation and cooling, but the process/assembly efficiency is greatly enhanced, and thus the thermal processes are applicable to any workpieces which have temperature limitations. For example, the present invention improves on the prior art by improving the process/assembly efficiency which is otherwise deteriorated as a result of performing hand soldering or mini wave soldering on a thermal sensitive component; hence, the present invention is applicable to various processes and saves costs, not to mention that the high temperature-tolerant process further enhances product conforming rate efficiently.

Although a typical embodiment is exemplified by a display module and a protection apparatus having a cap body, protection apparatuses of different forms and shapes include but are not limited to a ring-shaped body and a sleeve-shaped body. In addition to a display module, the protection apparatus of the present invention is applicable to other thermal sensitive components, including but not limited to an electrolytic capacitor, or a solid-state capacitor, as the above-mentioned is not restrictive of the present invention.