CN101711095A - Copper-plating hole-filling process of HDI flexible printed circuit - Google Patents

Abstract

The invention relates to a copper-plating hole-filling process of an HDI flexible printed circuit, which aims at solving the problem of electroplating copper in a blind hole. The process adopts a pulse plating mode, i.e. based on time, the current is sometimes used for forward-direction plating and sometimes reverse-direction plating in different power supply modes, which alternate on the basis of the time scale, high-speed periodic reverse pulse current reacts with electroplate liquid and addition agents to polarize a high current density area and redistribute the electroplating current to a low current density area, and the effect is that the copper coating is reduced at the high current density area and can not be reduced at the low current density area under the same condition. Therefore, the thickness of the electroplating copper coating in a blind hole is thicker than the copper coating on the surface, thereby ensuring that the thickness of the copper coating in the blind hole tends to be the same as that of the surface copper.

Description

HDI flexible electric circuit board copper facing process for filling hole

Technical field

The present invention relates to the manufacture craft of flexible electric circuit board.

Background technology

Flexible electric circuit board has just risen HDI (high density interconnect) technology now, in order to pursue more function, need be at the littler more line of zone energy cloth, to reach better design effect, a large amount of blind holes that adopt in the HDI flexible electric circuit board, the about 50um of these blind hole diameter is to 125um, and the about 25um of the degree of depth is to 50um, and radius-thickness ratio is about 2: 1 to 5: 1, in the blind hole electroplating process, the little current DC of general employing is electroplated, because the blind hole port area of printing board surface is an areas of high current density, and is low current density areas in the blind hole, during electro-coppering in high current densities zone, it is just thick that copper deposits, and in low current density areas, it is just thin that copper deposits, copper can not well be filled out the plating blind hole, when utilizing pressing again after the direct current electrode position blind hole is electroplated glue flow and fill up blind hole, reaching the smooth purpose of plate face, but because the blind hole aperture is less, during pressing glue hole, be difficult to guarantee that glue can fill up blind hole, occur plate bursting when causing reliability testing, leave very big hidden danger.

Summary of the invention

The present invention adopts a kind of new electroplating technology, has well solved above problem, can fill up blind hole substantially, and the situation of plate bursting can not appear in reliability testing.For solving blind hole electro-coppering problem, this process using pulse plating mode, promptly according to the time chien shih electric current on supply power mode, sometimes just plating sometimes anti-plating, hocket according to time scale, the high speed cycle turns to pulse current and electroplate liquid and additive generation effect, areas of high current density is polarized, again electroplating current is redistributed to low current density areas, its effect is that the copper coating in the zone of high current density reduces, but this kind situation can not occur in low current density areas, so the copper electroplating layer specific surface copper bed thickness in the blind hole, thereby make the thickness of interior copper layer thickness of blind hole and plate face copper trend towards equalization gradually.

Description of drawings

Below by accompanying drawing the present invention is made and to further describe

Because electroplating, tradition adopt DC low current to electroplate (is traditional direct current schematic diagram as Fig. 1), the printed board particularly current density of blind hole mouth is higher, resulting copper coating is thicker, and low owing to current density in the blind hole, so the copper coating in the blind hole approaches (is direct current electrode position blind hole effect schematic diagram as Fig. 2).And when adopting pulse current to electroplate (is the pulse current schematic diagram as Fig. 3), the sense of current is according to time-interleaved, the forward electroplating time is 20 times of reverse electroplating time approximately, and reverse current is 2.5 times of forward current approximately, when the printed board on the negative electrode is in forward current, metal ion is consumed at a terrific speed near the high current density of printed board cathodic region, when being consumed to cathode interface concentration is zero or when very low, electro-deposition almost stops, and low current density areas is because the metal ion depletion rate is slow, its electro-deposition can also continue, when electric current is in when reverse, electric current and electroplate liquid and additive generation effect with the areas of high current density polarization, are redistributed to low current density areas with electroplating current again, so the areas of high current density copper plate is less, and the low current density areas copper plate is thicker, through the checker sense of current that continues, makes the thickness of interior copper layer thickness of blind hole and plate face copper trend towards equalization (is pulse plating blind hole effect schematic diagram as Fig. 4) gradually.

Claims (1)

1. be applied to flexible electric circuit board, and adopt pulse current to electroplate the copper facing process for filling hole of blind hole.

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