Process for manufacturing solid-solder-deposit printed circuit boards

Abstract

A novel process for manufacturing Solid-Solder-Deposit Printed Circuit Boards (SSD-PCBs) by directly melting dry solder powder over a bare-PCB 230 consequently forming relatively thick individual layers of solid solder over each soldering pad of said bare-PCB 230. Solid Solder Deposit (SSD) refers to a relatively thick layer of solid solder metallurgically bonded over the soldering pads of a bare-PCB 230 such as that said SSD-PCB by itself is the source for solder alloy during a subsequent soldering operation. The manufacture of SSD-PCBs provides the electronic assembly industry with ready-to-solder PCBs consequently eliminates the need to use solder paste at the assembly floor. This invention, unlike the prior art for producing SSD-PCBs, utilizes a dry solder powder pile 232 that is melted by localized heating. Specifically my invention reduces the manufacturing cost, shorten manufacturing time, reduce manufacturing energy consumption and improves SSD-PCBs' quality and reliability while requiring less manufacturing equipment than prior art.

I claim:  
     
         1 . A process for manufacturing SSD-PCBs by heating solder powder, comprising the steps of: 
 (a) supplying a bare-PCB comprising a plurality of soldering pads on a side facing upward, and    (b) spreading a solder powder pile over said side facing upward, and    (c) generating localized heating into said plurality of soldering pads for a predetermined time sufficient to cause localized melting of said solder powder pile consequently forming a layer of SSD controllable in thickness over each soldering pad forming part of said plurality of soldering pads, and    (d) removing all remnant loose particles from said side facing upward after step (c), and    (e) finally flattening the hump-shaped SSDs to obtain coplanarity among them    whereby a finished SSD-PCB is obtained.    
     
     
         2 . The process of  claim 1 , further comprising the steps of: 
 (f) placing said bare-PCB into an enclosure chamber after step (b) but prior to step (c), and    (g) shaking said pile of solder powder during step (c).    
     
     
         3 . The process of  claim 2 , further comprising the step of: 
 (h) supplying said enclosure chamber with a process gas during step (c).    
     
     
         4 . The process of  claim 3 , further comprising the step of: 
 (i) pre-heating said pile of solder powder prior to step (c).    
     
     
         5 . The process of  claim 4 , further comprising the step of: 
 (i) scrubbing or brushing and/or washing said bare-PCB after step (d) but prior to step (e).    
     
     
         6 . The process of  claim 5 , further comprising the step of: 
 (k) post-heating the hump-shaped SSDs to a temperature level under their melting temperature after step (j) but prior to step (e).    
     
     
         7 . The process of  claim 1 , further comprising the step of: 
 (l) scrubbing or brushing and/or washing said bare-PCB after step (d) but prior to step (e).    
     
     
         8 . The process of  claim 7 , further comprising the step of: 
 (m) post-heating the hump-shaped SSDs to a temperature level under their melting temperature after step (d′) but prior to step (e).