TABLE OF CONTENTS Although many substrate technologies exist, the main substrates utilized in the low-cost wireless module industry are LTCC and laminate. The laminate substrates are typically Bismaleimide-Triazine (BT) or GTEK. Although LTCC is more expensive in bulk than laminate, it can embed more capacitors and RF functionality. Typically, a laminate module is lower cost than an LTCC module. To be cost effective, the ceramic module must yield a size reduction, which is achieved through embedding more circuitry into the many layers of LTCC. This shrinks the overall module size, using less LTCC material than laminate. LTCC can be cost competitive with laminate under these conditions, but the same-size module will almost always cost less in laminate. However, laminate can be made costly when fine pitch-flip chip die are attached. Fine-pitch flip chip devices require higher-cost high density interconnect (HDI) technology. HDI can be cheaper or more expensive than LTCC, depending on the construction. The number-one construction factor determining the cost is the micro-via structure. A lower-cost HDI design offsets the microvias from the mechanical core vias whereas a smaller module size, higher-cost design does not offset these vias [1] (see Figure 2.1). In some designs, the passives and die determine the module size. The module shown in Figure 2.2 contains two die and large-value passives that can not be embedded in LTCC. This laminate was used to embed a BALUN and a filter with a 40-dB rejection to DCS and PCS frequencies.
