TW201414555A - Cooling of drills for printed circuit boards - Google Patents

Abstract

An apparatus for cooling a drill bit includes a housing having an open ended chamber therein which extends through the housing for receiving the drill bit, a first passage for providing a cooling substance to the chamber to cool the drill bit, and an outlet in communication with the chamber and through which the drill bit can extend for drilling. A method of cooling a drill bit is also provided.

Description

Cooling of drill bits for printed circuit boards

Embodiments of the invention relate to apparatus for drilling a hole in a printed circuit board.

Most types of printed circuit boards (PCBs) used in the electronics industry consist of a plurality of layers (both resin layers and metal layers). PCB manufacturers need to drill a large number of holes in each board. The holes are then plated with copper inside and copper is used as a connector between the layers of the board. During the drilling process, the resin layer of the PCB is heated and "smeared" onto the copper layer in the hole to prevent electrical contact between the layers after copper plating. Therefore, the resulting "smear" in the holes must be removed prior to the electroplating process. This results in additional undesirable PCB processing time.

Heat is generated during the cutting and grinding processes that occur during PCB drilling. The temperature can be drilled up to 300 °C. The glue produced by self-drilling on all sides of the hole is caused by the epoxy bit of the resin layer in the drill bit of the hot drill drill. In addition, the drill bit begins to wear due to repeated use and the wear tap has a tendency to exacerbate the application. One way to reduce smear is to reduce the bit speed accordingly, but this reduces the efficiency and effectiveness of the PCB drilling and assembly line process. Economies of scale determine the faster and more economical the drilling, even if it is necessary to remove the glue later.

It is therefore desirable to have a device that can be used with a drill bit to avoid smearing without sacrificing the speed of the drilling process.

10‧‧‧ device

12‧‧‧ mandrel

14‧‧‧Drill drill cone

16‧‧‧Printed circuit board

18‧‧‧ Pressure cover

20‧‧‧ side wall

22‧‧‧Open end room

23‧‧‧Ladder

24‧‧‧Under the cover

25‧‧‧ below the room

26‧‧‧ Spacer/spacer

28‧‧‧Bottom surface of the side wall

30‧‧‧Top surface of PCB

32‧‧‧ first

34‧‧‧Second

36‧‧‧Exhaust hose

38‧‧‧ gas pipeline

40‧‧‧ end part

42‧‧‧ Carbon dioxide

43‧‧‧

44‧‧‧ Pipes

45‧‧‧ spray

46‧‧‧Valves

48‧‧‧ Flowmeter

50‧‧‧ pressure gauge

52‧‧‧Nozzles

54‧‧‧ gas or liquid CO ₂

56‧‧‧Inside

58‧‧‧Nitrogen

60‧‧‧ Pipeline branch

62‧‧‧External management

For a more complete understanding of the embodiments of the present invention, reference should be made to the following description in conjunction with the drawings in which: FIG. 1 shows an apparatus embodiment of the present invention for cooling a drill bit; and Figure 2 shows a nozzle for the embodiment of the apparatus of Figure 1.

The device embodiment shown in Figure 1 is shown generally at 10 and used in conjunction with a drill bit for the illustrated mandrel 12.

A drill collar 14 is attached to a mandrel 12 of a drill bit for drilling a hole in, for example, a printed circuit board (PCB) 16. It should be understood that the drill collar 14 can be used to drill holes in other objects and articles.

The device 10 includes a pressure cap 18 or outer casing having a side wall 20 that defines an open end chamber 22 or space. The mandrel 12 can be coupled to the pressure cap 18 by mechanical fasteners such as screws. The pressure cap 18 can be fabricated from metal or plastic. As shown in Figure 1, the chamber 22 is open at both ends and is sized and shaped to receive the mandrel 12 and the drill collar 14. As shown in FIG. 1, chamber 22 is configured to have a step 23 having a diameter smaller than the chamber diameter to receive a certain depth of the mandrel 12 to the interior, the depth being drilled with a drill bit that will be drilled through and penetrated the PCB 16. The portion of the cone 14 is commensurate. In effect, chamber 22 and lower portion 24 of cover 18 cooperate to limit the downward movement of mandrel 12 in open end chamber 22. The lower portion 25 of the chamber 22 is sized and shaped to receive the drill collar 14 and is positioned to align with the area of the PCB 16 to be drilled.

The spacer member 26 or insert is disposed adjacent the outer casing and is positioned between the bottom surface 28 of the side wall 20 and the upper surface 30 of the PCB 16 as shown. The spacer 26 can be formed as part of the pressure cap 18. During drilling, the spacer 26 supports the head of the drill bit as the drill cone 14 is drilled through the PCB 16. During certain applications, when the pressure cap 18 and the spacer 26 are positioned for drilling, the spacer may form a hermetic seal to seal the chamber 22 from the atmosphere of the pressure cap and the exterior of the PCB. The spacer 26 can be fabricated from metal or plastic, but is typically fabricated from a material that is harder than the material from which the cover 18 is made.

The pressure cap 18 includes a weir or passageway in the side wall 20. The first weir 32 or passageway in the side wall 20 is for introducing a cooling substance into the open end chamber 22. The second weir 34 or passageway is used to vent or vent the atmosphere and any particulate matter from the chamber 22 by, for example, the exhaust hose 36. quality.

Referring to the first weir 32, the gas conduit 38 can extend through the first weir and is included in the chamber 22 to terminate and approximate the end portion 40 of the drill collar 14. Carbon dioxide (CO ₂ ) 42 can be introduced from a remote source (not shown) by means of a conduit 44 connected to a gas conduit 38. Valve 46 for gas, flow meter 48, and pressure gauge 50 are in fluid communication with conduit 44. The valve 46 is disposed upstream of the flow meter 48 and the flow meter is disposed upstream of the pressure gauge 50, all of which are disposed upstream of the conduit 38.

The CO ₂ 42 system is provided as liquid CO ₂ so that its phase changes to gas and solids (dry ice) as it passes through the gas conduit 38 to be injected from the end portion 40 of the conduit. The CO ₂ can be sprayed as a spray 45 or pulsed into the chamber 22. The end portion can include a nozzle. As the pressure drop along the duct 38, the liquid CO ₂ will vary as a mixture of gas and solids, and finally the solid gas will also change. The CO ₂ gas cools the drill cone 14 . The mandrel 12 rotates at a very high speed to propel the bit drill cone 14 through the PCB 16. The cooling system occurs during the time when the drill collar 14 is withdrawn or retracted from the hole it just drilled in the PCB 16. This is because the drill collar 14 is exposed to the cooling gas in the chamber 22. The holes in the PCB are small and are drilled in fractions of a second. That is, when the drill bit 14 is retracted or removed from the hole it has just drilled in the PCB 16, the drill cone is immediately exposed to gaseous carbon dioxide to cool the drill cone so that it is used for the next desire at reduced temperatures. Drill holes to reduce the chances of epoxy melting and smearing in the resin layer. By way of example only, the temperature in chamber 22 is from -10 ° C to 5 ° C due to the use of CO ₂ .

If desired, the liquid carbon dioxide can be pulsed conveyance and the coolant of CO ₂ aimed directly at the injection cone drill bit. In fact, the drill bit is cooled when it is withdrawn so that it is used at the lower temperature for the next drilling operation, thereby preventing the frictional heat from accumulating and melting the epoxy resin of the resin sheet. Alternatively, pulsed CO ₂ in contact with the cone drill bit 14 may occur in the drill bit from the tapered bore until withdrawn and a drill bit about to start of the next cone of the hole drilled in the PCB 16. To provide a pulsed CO _2, the CO ₂ used for the liquid pump 43. The pump 43 is in fluid communication with the conduit 44 and may be located upstream of the valve 46. Pump 43 may be timed to provide a CO ₂ to pulse cluster housing 22, or the pump control signal may be transmitted by the drill bit 12 from. That is, when drilling the cone 14 when the PCB 16 is retracted from the timing, or the drill bit may transmit a trigger signal to the pump 43 CO ₂ is supplied to the chamber 22. CO ₂ injection loop also begins with start and stop pulse the liquid CO ₂ when the cone drill bit withdrawn from the PCB when the contact cone drill bit 14 PCB 16.

Alternatively, the spray 45 can be continuously supplied to the chamber 22 as a spray, pulse stream or jet. However, PCB's drill 16 is generally interfere with CO ₂ has been drilled into the drill hole to cool the cone 14, when the hole until the cone drawn from the drilling. Thus, to save CO _2, only when the drill 14 may not actually drilled PCB 16 when CO is supplied to the chamber embodiment ₂₂₂ cone. That is, during drilling to provide a chamber 22 CO ₂ produced on well drilling program or sound-based PCB 16; but it will result in the use of more CO _2.

Referring to Figure 2, another type of nozzle 52 mounted to the end portion 40 of the conduit 38 is shown. The nozzle 52 (also referred to as a coaxial tube nozzle), the gas or liquid CO ₂ 54 introduced into the inner tube 56, while nitrogen gas 58 (e.g. 3 bar) is introduced into the outer tube 62 for nitrogen gas or The pipe is connected to the pipe branch 60. The inner tube 56 is disposed within the outer tube 62. CO ₂ 54 and nitrogen 58 flow along nozzle 52 such that nitrogen is external to carbon dioxide 54 and, in some applications, nitrogen blankets carbon dioxide 54 as it exits the nozzle to provide to drill bit 14 . Nitrogen will be reduced at the drill cone 14 and the moisture on the PCB 16 will condense. The inner tube 56 and the outer tube can be coaxial. The conduit 38, the nozzle 40 and the coaxial nozzle 52 can be fabricated from stainless steel.

Embodiments of the present invention reduce the amount of slag that occurs with known drilling equipment and eliminate the subsequent desmear process required for the same apparatus. Embodiments of the present invention also reduce wear on the drill bit 14 and extend its operational life. The drilled hole surface in the PCB 16 is smoother and the drilling speed is increased by substantially reducing the overheating and smearing of the drill cone.

It is understood that the embodiments described herein are illustrative only and that various changes and modifications may be made without departing from the spirit and scope of the invention. All such changes and modifications are intended to be included within the scope of the invention described and claimed herein. In addition, all of the disclosed embodiments are not required to be substituted, as the various embodiments of the present invention may be combined. Provide the desired results.

10‧‧‧ device

12‧‧‧ mandrel

14‧‧‧Drill drill cone

16‧‧‧Printed circuit board

18‧‧‧ Pressure cover

20‧‧‧ side wall

22‧‧‧Open end room

23‧‧‧Ladder

24‧‧‧Under the cover

25‧‧‧ below the room

26‧‧‧ Spacer/spacer

28‧‧‧Bottom surface of the side wall

30‧‧‧Top surface of PCB

32‧‧‧ first

34‧‧‧Second

36‧‧‧Exhaust hose

38‧‧‧ gas pipeline

40‧‧‧ end part

42‧‧‧ Carbon dioxide

43‧‧‧

44‧‧‧ Pipes

45‧‧‧ spray

46‧‧‧Valves

48‧‧‧ Flowmeter

50‧‧‧ pressure gauge

Claims (20)

An apparatus for cooling a drill cone, comprising: an outer casing having an open end chamber extending therethrough for receiving the drill tap; a first passage for providing cooling material to the chamber for cooling The drill bit is drilled; and an outlet is in communication with the chamber and the drill cone extends through it for drilling. The device of claim 1 further comprising a conduit extending through the first passage for providing the cooling material to the chamber. The device of claim 1, further comprising a second passage in communication with the chamber for discharging atmospheric and particulate matter from the chamber. The device of claim 3, further comprising a discharge conduit in communication with the second passage. The device of claim 1, further comprising a spacing member having a through hole, the spacing member being sized and shaped for positioning adjacent the housing to align the aperture with the outlet. The device of claim 5, wherein the spacer member is made of a material selected from the group consisting of metal, plastic, and a composition having a hardness greater than the hardness of the outer shell. The device of claim 1, wherein the cooling material is selected from the group consisting of carbon dioxide (CO ₂ ), nitrogen (N ₂ ), and a combination of CO ₂ and N ₂ . The device of claim 2, further comprising a nozzle coupled to the end of the conduit and positioned in the chamber for spraying the cooling material to contact the drill collar. A device according to claim 8, wherein the nozzle comprises an inner tube through which the CO ₂ is supplied and a tube surrounding the inner tube and providing N ₂ therewith. The device of claim 9, wherein the inner and outer tubes are coaxial. The device of claim 1, further comprising a pump in fluid communication with the cooling substance For conveying the cooling substance to the chamber in a pulsed manner. The device of claim 1, wherein the outer casing is formed from a material selected from the group consisting of metal and plastic. A method of cooling a drill bit of a drill bit, comprising: receiving the drill bit in a chamber of a casing; providing a cooling substance to the chamber for cooling the drill bit; and including the cooling material in the chamber. The method of claim 13, wherein the providing the cooling material occurs after drilling with the drill bit. The method of claim 13, further comprising discharging the cooled material from the chamber. The method of claim 13, wherein the providing the cooling material comprises pulsing the cooling material to the chamber at selected intervals. The method of claim 13, wherein the cooling material is selected from the group consisting of CO ₂ , N _{2 ,} and a combination of CO ₂ and N ₂ . The method of the requested item 17, wherein providing the composition CO.'S ₂ and N ₂ of the first flow comprises ℃ O ₂ of the first stream and the adjacent second stream of N ₂ is supplied to the chamber of. The method of claim 18, wherein the first and second streams are coaxial. The method of claim 13 wherein the containing the cooling material comprises sealing the chamber of the outer casing from the atmosphere outside the outer casing.