Double-sided boards

Figure 6-6 A Recommended Buck Switcher Layout on a Double-sided Board... 

Type II A double-sided board, with SMDs on both sides. The top side may have aU sizes of active and passive SMDs, as well as through-hole components, whereas the bottom side carries passive SMDs and small active components such as transistors. This type of board requires both reflow and wave soldering, and will require placement of bottom-side SMDs in adhesive. 

FOR SINGLE-SIDED BOARDS. THERE IS NO SOLDER FILL OF THE THROUGH-HOLE IN THE PCB FOR DOUBLE-SIDED BOARDS, THETOP AND BOTTOM FILLETS ARE IDENTICAL... 

FOR DOUBLE-SIDED BOARDS, THERE IS COMPLETE SOLDER FILL OFTHETHROUGH-HOLE IN THE PCB THROUGH-HOLE SOLDER FILL VOLUME IS = THE VOLUME OF THE HOLE (PI R2 T) MINUS THE VOLUME OF THE LEAD IN THE HOLE (PI R22T), WHERE HOLE LENGTH T IS = PCB THICKNESS VOLUME OF THE TRUNCATED CONE THAT DEFINES THE TOP AND BOTTOM FILLET IS ... 

By definition, double-sided boards (DBs) have circuitry on both sides of the boards.They can be classified into two categories ... 

FIGURE 5.4 Cross-section multilayer board with buried via holes. Buried vias are built into each of the double-sided boards that make up the final multilayer structure. 

The original external conductor chart was developed in 1956. It was assembled from trace heating test data taken from boards of different materials, different thicknesses, and different copper weights, as well as from boards with and without copper planes.The external charts are nonconservative for thin double-sided boards without copper (power, ground, or thermal) planes. Nonconservative in this context means that the traces are higher in temperature for a given current level than the charts suggest. The temperature differences are discussed later in the chapter. 

Circuit boards can be extremely different from one design to another. They can vary from a double-sided board the size of a postage stamp to a 40-layer board that is 2 ft. wide and 4 ft. long. The environment in which they operate is also a consideration— for example, whether they are used on earth, in space, or on some other planet. 

The industry, however, still has a need to produce simpler products, such as single-sided and double-sided boards these are still in demand. Multilayer boards with lower layer counts (four to eight) fall in this category also. 

Fig. 8.13 The steps involved in the subtractive technique for the manufacture of printed circuit boards. A very simplified schedule is shown to obtain a double-sided board, i.e. one which has copper tracks on each side interconnected by plated-through holes.

TABLE 33 A Full Factorial 3 Parameter Variation Experiment Performed with the Alloy Sn-3.8Ag-0.7Cu-0.25Sb on a Dedicated Single-Sided Test Board and on a Double-Sided Board with Plated Through Holes... 

For double-sided boards with plated holes ... 

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