Reflow method and reflow device

Abstract

For reflow soldering, radiant heating is applied to one surface of a printed circuit board on which electronic components are placed and onto which cream solder is supplied and at the same time hot air is blown locally and roughly perpendicular to to-be-connected points on said one surface of the printed circuit board. This reflow method permits secure soldering even if the hot air is set at a temperature not exceeding the heat resistance of the electronic components, which is possilbe because of its combination with the radiant heat. Moreover, this reflow method can permit soldering in such a manner that only the to-be-connected points are heated selectively, because the hot air is blown locally and roughly perpendicular to the points to be connected. Thus, this reflow method prevents heat damage to other sections than the to-be-connected points and ensures that the solder at the to-be-connected points is melted.

What is claimed is:  
     
         1 . A reflow method for reflow soldering of electronic components onto a printed circuit board comprising: 
 radiant heating one surface of a printed circuit board on which electronic components are placed and onto which cream solder is applied at to-be-connected points; and    concurrently, blowing hot air locally and roughly perpendicular to to-be-connected points on said one surface of the printed circuit board.    
     
     
         2 . A reflow method for reflow soldering of electronic components onto a printed circuit board on which cream solder is supplied comprising: 
 heating a to-be-soldered surface of a printed circuit while cooling electronic components having low heat resistance among the electronic components in the printed circuit board.    
     
     
         3 . The reflow method according to  claim 2 , wherein the electronic components placed on the printed circuit board include surface mount components and insert mount components, and these surface mount components and insert mount components undergo batch reflow soldering.  
     
     
         4 . The reflow method according to  claim 2 , wherein one surface of the printed circuit board is heated while the other surface of the printed circuit board is cooled.  
     
     
         5 . A reflow device for reflow soldering of electronic components onto a printed circuit board, comprising: 
 radiant heating means for radiant heating one surface of a printed circuit board on which electronic components are placed and onto which solder cream is applied at to-be-connected points; and    hot air heating means for blowing hot air locally and roughly perpendicular to the to-be-connected points on said one surface of the printed circuit board;    said radiant heating means and hot air heating means being juxaposed in a heating section of the reflow device.    
     
     
         6 . The reflow device according to  claim 5 , wherein said hot air heating means comprises: a hot air header forming a flat space contacting a surface of a panel heater on the printed circuit board side, and including a mask plate having blow holes formed on the surface opposed to the printed circuit board in correspondence to the to-be-connected points; and hot air supplying means for supplying hot air into the hot air header from the sides thereof.  
     
     
         7 . The reflow device according to  claim 6 , wherein the hot air header includes therein a dispersion plate which has a number of dispersedly formed through holes and is spaced apart from the mask plate, whereby hot air is supplied from the hot air supplying means into the space between the radiant heating means and said dispersion plate.  
     
     
         8 . The reflow device according to  claim 6 , wherein the mask plate is coated with a black body paint.  
     
     
         9 . The reflow device according to  claim 5 , further comprising cooling means adapted for blowing cool air to prescribed locations on the other surface of a printed circuit board than said surface which is heated by the radiant heating means and the hot air heating means.  
     
     
         10 . The reflow device according to  claim 5 , further comprising transport means for transporting a printed circuit board to the heating section, and lifting means for lifting the printed circuit board to a prescribed heating position in the heating section.  
     
     
         11 . The reflow device according to  claim 10 , wherein the lifting means is provided with a cooling device.  
     
     
         12 . The reflow device according to  claim 10 , further comprising an isolation plate for isolating cooling atmosphere and heating atmosphere by surrounding the periphery of a printed circuit board when the printed circuit board is lifted up to a prescribed heating position by the lifting means.  
     
     
         13 . A reflow device comprising: 
 a heating section for heating a printed circuit board with electronic components placed thereon by heating means; and    a cooling section for cooling components having low heat resistance among the electronic components placed on the printed circuit board heated by said heating section.    
     
     
         14 . The reflow device according to  claim 13 , further comprising conveyor means for transporting a printed circuit board to the heating section, and a cooling device arranged to be freely movable to and away from the printed circuit board transported to the heating section.  
     
     
         15 . The reflow device according to  claim 13 , further comprising a radiant heating element for radiant heating a printed circuit board as heating means of the heating section, and a mask for partially isolating radiant energy of said radiant heating element provided between the printed circuit board and said radiant heating element.  
     
     
         16 . The reflow device according to  claim 13 , wherein one surface of a printed circuit board is heated by the heating means of the heating section and the other surface of the printed circuit board is cooled by the cooling means of the cooling section, and wherein a plate for preventing intermixture of the heated atmosphere of the heating section and the cooled atmosphere of the cooling section, by surrounding the printed circuit board, is arranged roughly parallel to the transport surface of the board.  
     
     
         17 . The reflow device according to  claim 16 , further comprising, above the transport surface of the printed board: a plate for preventing intermixture of the heating and cooling temperatures which has a punched hole of a size equal to or greater than that of the exterior dimensions of the board; a board stopping mechanism for stopping a printed circuit board at a prescribed position relative to said punched hole; and a lifting means for lifting and lowering the board to such a height as to be in contact with or in close proximity with said plate, thereby to prevent intermixture of the heating and cooling temperatures.  
     
     
         18 . The reflow device according to  claim 17 , further comprising, at a location for lifting and lowering boards, a cool air blowing structure for locally cooling components having low heat resistance placed on a printed circuit.  
     
     
         19 . The reflow device according to  claim 18 , wherein, as the cool air blowing structure, the plate has holes formed in correspondence to the positions of the components having low heat resistance placed on the printed circuit board.  
     
     
         20 . The reflow device according to  claim 19 , further comprising a nozzle for adjusting the distance from the to-be-cooled portions of the printed circuit board.  
     
     
         21 . The reflow device according to  claim 18 , further comprising, as the cool air blowing structure, blow holes formed in a block of metal or resin, whereby the cool air blowing distance corresponding to the height of insert mount components is adjustable by the depth of carving of the blok.  
     
     
         22 . The reflow device according to  claim 13 , further comprising a heating section consisting of a preheating section and a main heating section both for heating a printed circuit board on which electronic components are placed, and a transport section for transporting the printed circuit board, wherein said prheating section comprisise: a heat source for preheating one surface of the printed circuit board subjected to a reflow soldering; an exhaust duct for exhausting the atmosphere on the other surface of the printed circuit board which is not especially forced to undergo heating in a direction roughly parallel to the printed circuit board and roughly at right angles to the direction of transport; and an external air intake disposed at the other surface side of said printed circuit board so as to maintain said other surface at a low temperature.