2007: the year of HDI? A reader survey reveals 2007 will be the year microvias and embedded passives make their mark.

What bare board technologies are expected to gain ground during the next 12-18 months? In a first-of-its-kind survey of some 5,100 designers and assemblers undertaken by UP Media Group in late October, we learned that 2007 will be the year when 0201s and embedded passives become mainstream and lead-free processing provides a major boost to high Tg laminates.

The survey was conducted from Oct. 24 to Nov. 7, 2006. In all, 5,118 North American subscribers of Printed Circuit Design & Manufacture or Circuits Assembly were surveyed, with 244 responding, a response rate of 4.8%. Respondents were provided a copy of the results, but no other incentive. The survey targeted PCB designers and manufacturing engineers. The PCB fabricators were not polled because they tend to be technology implementers and not the drivers.

The results establish certain trends in board technology, including:

* Laminates

* Final finishes

* Soldermask

* Lines and spaces

* Layer counts

* Components and packaging

* Advanced technology needs

* Fabricator yields and common defects

They also reveal procurement trends, including from whom boards are bought, and current and projected value of board buys.

Of those surveyed, 79.5% identified their company as an OEM, 8.2% as an electronics manufacturing services provider and 7.4% as a design services bureau. Most of those who specified "Other" were with R&D labs, engineering centers or consultants.

Of the respondents, 68.9% were printed circuit or systems packaging designers, 24.2% were process or manufacturing engineers and 2% were in procurement. More than 22% said the primary end-product designed at their location was instrumentation or industrial electronics, followed by defense, military or aerospace (19.3%); communications systems or equipment (17.2%); automotive (8.6%); computers, data processing equipment or computer peripherals (8.2%); consumer (5.7%); and medical (4.9%).

Laminate Trends

The majority of respondents expect to continue to use rigid materials (TABLE 1). The trend is toward higher Tg laminates (TABLE 2), probably because of increased use of lead-free solder alloys, which have higher melting points than their SnPb counterparts.

Design Trends

For the time being, lines and spaces of 0.004" to 0.006" remain predominant, while 0.003" lines and spaces inch toward mainstream (TABLE 3). No major changes in foil thickness are anticipated (TABLE 4). Layer counts are rising incrementally, but single- and especially double-sided boards are still common (TABLE 5). Perhaps the next data point explains why: More than half of those responding said they expect to use microvias in their designs within 18 months, up from 34% currently (TABLE 6). Embedded passive use will jump markedly as well.

Finish Trends

ENIG will remain the preferred final finish among North American companies, the survey found. Lead-free hot air leveling will supplant HASL during the next 18 months, again thanks to implementation of lead-free designs (TABLE 7). Liquid photoimageable will remain the dominant soldermask choice, with 81.6% of respondents indicating use in 12-18 months. Use of dry film (17.6%) and screen-defined masks (13.1%) will remain constant.

Component Trends

The minimum size of passives will shrink appreciably in the coming months. While 0201s have for years been mainstream in cell phones and other devices such as GPS systems, engineers expect their use to jump during the next year (TABLE 8). And the smallest available package style--01005--will begin to come into play. In all, nearly 31% of respondents predict they will use 0201 or smaller devices, double the current mark.

Board Quality

While most respondents indicated a greater than 95% acceptance rate for bare PCBs from their primary supplier, 13.5% pegged the rate at between 70 and 90% (TABLE 9). The most common defects reported on bare PCBs centered on the laminate, followed by solderability and plating (TABLE 10).

This may be remembered as the year HDI finally joined the ranks of conventional technology in North America. If embedded passive use rises in line with what the respondents indicated, that too will boost HDI use, as the two technologies go hand in hand. The reverberation of lead-free will continue to show up across many new product lines as well.

MIKE BUETOW is editor in chief of Circuits Assembly. He can be reached at [e-mail].

TABLE 1. Laminates typically specified.

                                               TODAY   12-18 MOS.

Rigid (FR-4)                                   87.3%      84.8%
Standard multilayer                            67.2%      65.2%
CEM                                             8.6%       9.0%
High-performance multilayer                    50.4%      58.2%
Paper                                           2.0%       1.6%
Flexible (polyimide or polyester)              28.7%      30.3%
Rigid-flex (including multilayer rigid-flex)   25.0%      27.0%
Don't know                                      0.8%       2.5%

Respondents were asked to check all that apply.

TABLE 2. Typical laminate Tg.

                                    TODAY   12-18 MOS.

Tg <150[degrees]C                   14.8%       9.0%
Tg 150[degrees]C to 170[degrees]C   33.6%      22.5%
Tg 170[degrees]C to 200[degrees]C   27.9%      40.2%
Tg >200[degrees]C                    9.0%      11.5%
Don't know                          14.8%      16.8%

Respondents were asked to check all that apply.

TABLE 3. Conductor widths and spacings.

                            TODAY   12-18 MOS.

0.001/0.001"                 2.9%       3.3%
0.002/0.002"                 4.9%       9.4%
0.003/0.003"                18.4%      29.9%
0.004/0.004"-0.006/0.006"   57.0%      60.7%
0.006/0.006"-0.008/0.008"   50.0%      46.3%
0.008"/0.008" or above      45.1%      40.6%
Don't know                   4.5%       6.6%

Respondents were asked to check all that apply.

TABLE 4. Copper foil thicknesses.

                       TODAY   12-18 MOS.

Semi-additive copper    1.2%       3.3%
1/8 oz.                 5.7%       6.1%
1/4 oz.                14.3%      18.9%
3/8 oz.                10.7%      13.1%
1/2 oz.                70.5%      70.1%
1 oz.                  69.3%      66.8%
1 to 5 oz.             43.9%      43.4%
More than 5 oz.         4.1%       6.1%
Don't know              7.4%       9.4%

Respondents were asked to check all that apply.

TABLE 5. Typical layer counts.

                      TODAY   12-18 MOS.

Single-sided          20.9%      20.1%
Double-sided          59.8%      57.4%
4 to 6 layers         75.0%      74.2%
8 to 10 layers        57.4%      61.1%
12 to 18 layers       38.5%      44.3%
18 to 24 layers       17.2%      21.3%
More than 24 layers    8.6%       9.8%
Don't know               0%       1.6%

Respondents were asked to check all that apply.

TABLE 6. Advanced fabrication techniques.

                                      TODAY   12-18 MOS.

Chip carriers (single and multiple)   21.3%      21.7%
Microvias (0.005 or less)             34.0%      52.5%
Blind vias (any type)                 47.5%      56.6%
Buried vias (filled and unfilled)     40.6%      48.4%
Impedance-controlled boards           66.8%      70.9%
Backdrilling                          13.5%      17.6%
Embedded passives                     11.1%      24.6%
None of the above                     19.3%      13.1%

Respondents were asked to check all that apply.

TABLE 7. PCB metallic finishes.

                        TODAY   12-18 MOS.

Copper only (OSP)       22.5%      23.0%
HASL                    55.3%      40.6%
Lead-free HASL          23.0%      37.3%
SnPb plate and reflow   18.9%      12.3%
Im. Sn                  18.0%      18.9%
SnNi                     7.0%       6.1%
Electroplated NiAu      29.5%      31.6%
ENIG                    59.0%      59.4%
Im. Ag                  27.5%      34.4%
Other                    0.8%       2.0%
Don't know               1.2%       4.1%

Respondents were asked to check all that apply.

TABLE 8. Minimum passive size.

             TODAY   12-18 MOS.

01005           0%       2.9%
0201         15.2%      27.9%
0402         56.1%      51.2%
0603         23.4%      10.2%
0804          1.6%       1.6%
1206          1.6%       1.6%
Don't know    2.0%       4.5%