News Column

Patent Issued for Reflow Soldering System

September 3, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventors Sukekawa, Takuji (Obu, JP); Yamada, Hiroyuki (Obu, JP); Inomata, Noriyasu (Toyota, JP), filed on November 5, 2012, was published online on August 19, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8807416 is assigned to Denso Corporation (Kariya, JP).

The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention relates to a reflow soldering system which solders a printed circuit board (PCB) wherein the system features both the high heat transfer rate of heating by contact heat transfer and the uniform heating of heating by blowing hot gas.

"In the conventional reflow soldering method of printed circuit boards, as shown in Japanese Unexamined Patent Publication No. 2004-304098, in particular FIG. 5, the practice has been to hold a printed circuit board for heating in a preheating zone of a reflow oven at a 100 to 200.degree. C. preheating temperature, then rapidly raise the temperature to the peak temperature. If soldering a printed circuit board by the conventional reflow soldering method, there were the problems that microballs were formed around the soldered part or the electronic devices deviated in position from the soldered parts.

"In particular, to handle large numbers of types of products, it is necessary to increase the oven length for thermal soaking. The heating time was forced to become longer and the facilities to become larger in size."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "The present invention, in view of the above problem, provides a reflowing soldering system which solders a printed circuit board and has both the high heat transfer rate of heating by contact heat transfer and the uniform heating of heating by blowing hot gas.

"To solve the above problem, the aspect of the invention of claim 1 provides a reflow soldering system which transports a printed circuit board on which a solder paste has been printed or coated to a sealable heating oven for reflow soldering, wherein the heating oven is provided with a contact heating unit which has a transport rail which supports an outer edge part of the printed circuit board from the bottom and a top heat transfer heater which supports an outer edge part of the printed circuit board from above, and with a hot gas blowing heating unit, the transport rail and top heat transfer heater are respectively provided with heaters which heat the outer edge part of the printed circuit board, and the transport rail or top heat transfer heater moves in an up-down direction after loading of the printed circuit board so that the transport rail and top heat transfer heater clamp and heat the outer edge part of the printed circuit board.

"The inventors took note of the high heat transfer rate by heating by contact heat transfer and the uniform heating and fast speed of heating by blowing hot gas and made joint use of heating by contact heat transfer and heating by blowing hot gas to thereby enable realization of small sized, high speed uniform heating. The outer edge part of the printed circuit board P is clamped from the top and bottom directions (i.e., the warping direction of the board) and heated by contact heat transfer, so warping of the board can be suppressed. For this reason, soldering is never performed in a state with the board warped due to the difference in heat expansion of the resin and the copper interconnects which form the board.

"The aspect of the invention of claim 2 comprises the aspect of the invention of claim 1 wherein the inside of the printed circuit board surrounded by the outer edge part is heated by the hot gas blowing heating unit while controlling the air flow and hot air temperature. Due to this, while heat is transferred from the outer edge sides, at the center part of the printed circuit board, the printed circuit board is supplied with hot air by the hot gas blowing heating unit, so the printed circuit board is uniformly heated.

"The aspect of the invention of claim 3 comprises the aspect of the invention of claim 1 wherein the transport rail is made to be able to handle different sizes of the outer edge part of the printed circuit board by being comprised of vertical and horizontal fixed outer frames and vertical and horizontal moving frames, where the transport direction of the printed circuit board is defined as the horizontal direction, and a heater is embedded inside. Due to this, different sizes of the outer edge part of the printed circuit board can be handled.

"The aspect of the invention of claim 4 comprises the aspect of the invention of claim 3 wherein the vertical and horizontal fixed frames are comprised of a horizontal direction fixed horizontal external frame rail and a vertical direction fixed vertical outer frame, and the vertical and horizontal moving frames are comprised of a first moving horizontal rail, second moving horizontal rail, intermediate vertical frames, and a positioning stopper and are designed to be able to move matching with the size of the outer edge part and number of obtained boards of the printed circuit board. Here, the 'number of obtained boards' mean the later explained two boards, four boards, or other numbers of obtained boards of a predetermined area into which the printed circuit board is divided.

"The aspect of the invention of claim 5 comprises the aspect of the invention of claim 4 wherein the intermediate vertical frames and the positioning stopper are comprised to be able to move up and down independently of each other.

"The aspect of the invention of claim 6 comprises the aspect of the invention of claim 1 wherein the reflow soldering system is provided with a preheating chamber and a cooling chamber.

"The aspect of the invention of claim 7 comprises the aspect of the invention of claim 1 which has a hot air circulation system which makes hot air which is supplied from the hot gas blowing heating unit circulate to a preheating chamber, then has a fume recovery box cool flux fumes which are produced at the heating oven to condense for recovery, then furthermore makes the hot air circulate to the cooling chamber and merge with hot air which is supplied from the hot gas blowing heating unit. Due to this, at the fume recovery box, the flux fumes which were produced at the heating oven are cooled and made to condense for recovery, so an improvement in fume recovery efficiency can be obtained by flow path circulation control.

"Note that, the above reference notations are illustrations which show the correspondence with specific examples described in the embodiments explained next."

URL and more information on this patent, see: Sukekawa, Takuji; Yamada, Hiroyuki; Inomata, Noriyasu. Reflow Soldering System. U.S. Patent Number 8807416, filed November 5, 2012, and published online on August 19, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8807416.PN.&OS=PN/8807416RS=PN/8807416

Keywords for this news article include: Electronics, Circuit Board, Denso Corporation.

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Source: Electronics Newsweekly


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