PCB based semiconductor package with impedance matching network elements integrated therein
A Doherty amplifier includes a metal baseplate having a die attach region and a peripheral region; a main amplifier and one or more peaking amplifiers, each amplifier comprising a transistor die that includes at least one RF terminal; and a multilayer circuit board having a first side attached to the peripheral region and a second side facing away from the baseplate. The circuit board includes two embedded electrically conductive layers separated from the two sides by respective composite fiber layers, and an embedded dielectric layer disposed between the embedded electrically conductive layers and having a higher dielectric constant than either of the composite fiber layers. The Doherty amplifier also includes an RF impedance matching network that is electrically connected to an RF terminal of at least one amplifier transistor die, and that comprises one or more reactive components formed from at least one of the embedded electrically conductive layers.
1. A Doherty amplifier, comprising:
a metal baseplate having a die attach region and a peripheral region;
a main amplifier and one or more peaking amplifiers, wherein each amplifier comprises a transistor die that includes at least one RF terminal;
a multilayer circuit board comprising:
a first side attached to the peripheral region;
a second side facing away from the baseplate;
a first embedded electrically conductive layer that is separated from the first side by a first embedded composite fiber layer;
a second embedded electrically conductive layer that is separated from the second side by a second embedded composite fiber layer; and
an embedded dielectric layer that is disposed between the first and second embedded electrically conductive layers, and that has a higher dielectric constant than either of the first and second embedded composite fiber layers;
an RF impedance matching network that is electrically connected to an RF terminal of at least one of the amplifier transistor dies, and that comprises one or more reactive components formed from at least one of the embedded electrically conductive layers.
2. The Doherty amplifier of claim 1 , wherein the multilayer circuit board further comprises:
a first electrically conductive signal layer disposed at the second side;
a first electrically conductive ground layer embedded in the multilayer circuit board;
a second electrically conductive signal layer embedded in the multilayer circuit board; and
a second electrically conductive ground layer disposed at the first side.
3. The Doherty amplifier of claim 2 , wherein:
the first composite fiber layer separates the first signal layer from the first ground layer;
the second composite fiber layer separates the second signal layer from the second ground layer; and
wherein the thickness of the embedded dielectric layer is less than the thickness of the first embedded composite fiber and less than the thickness of the second embedded composite fiber layer.
4. The Doherty amplifier of claim 1 , wherein the embedded dielectric layer has a dielectric constant of between 4 and 30, and wherein each of the first and second embedded composite fiber layers has a dielectric constant of 3.7 or less.
5. The Doherty amplifier of claim 1 , wherein the embedded dielectric layer is formed from a polymer laminate material, and wherein the first and second embedded composite fiber layers are formed from at least one of: FR-1, FR-2, FR-3, FR-4, FR-5, FR-6, G-10, CEM-1, CEM-2, CEM-3, CEM-4, CEM-5.
6. The Doherty amplifier of claim 1 , wherein the embedded dielectric layer has a thickness of between 4 λm and 50 μm, and wherein each of the first and second embedded composite fiber layers has a thickness of at least 75 μm.
7. The Doherty amplifier of claim 2 , wherein:
the multilayer circuit board further comprises a first electrically conductive via extending through the first embedded composite fiber layer and connected to a first bonding pad;
the first bonding pad is formed by an isolated section of the first signal layer and; and
each of the one or more reactive components is electrically connected to the first via and comprises an isolated section of the second signal layer.
8. The Doherty amplifier of claim 7 , wherein:
the one or more reactive components comprise a first capacitor having a positive electrode and a ground electrode;
the positive electrode is formed by a first isolated section of the second signal layer; and
the ground electrode is formed by a first isolated section of the first ground layer.
9. The Doherty amplifier of claim 7 , wherein the one or more reactive components comprise:
a shunt inductance comprising a linear strip of the second signal layer; and
an open-circuit radial stub connected to the shunt inductance and comprising a radially-shaped portion of the second signal layer.
10. The Doherty amplifier of claim 9 , further comprising a first set of bond wires directly connected between the RF terminal and the first bonding pad.
11. The Doherty amplifier of claim 10 , further comprising:
a second bonding pad formed by an isolated portion of the first signal layer; and
a second set of bond wires directly connected between the RF terminal and the second bonding pad, wherein:
the first set of bond wires extends in a first direction between the RF terminal and the first bonding pad,
the second set of bond wires extends in a second direction between the RF terminal and the second bonding pad, and
the second direction is non-parallel to the first direction.
12. The Doherty amplifier of claim 1 , further comprising a discrete capacitor formed on or in the baseplate and connected to the one or more reactive components.
13. The Doherty amplifier of claim 12 , wherein:
the multilayer circuit board comprises a third bonding pad formed by an isolated portion of the first signal layer;
the discrete capacitor is a surface-mount capacitor that is directly mounted on the third bonding pad; and
the third bonding pad is electrically connected to the one or more reactive components by a second electrically conductive via extending through the first embedded composite fiber layer.
14. The Doherty amplifier of claim 1 , wherein the RF impedance matching network is an output power combiner network that is electrically connected to an RF output terminal of the main amplifier transistor die and to RF output terminals of each of the peaking amplifier transistor dies.
15. The Doherty amplifier of claim 14 , further comprising a further RF impedance matching network that is electrically connected to an RF input terminal of the main amplifier transistor and to RF input terminals of each of the peaking amplifier transistor dies, wherein the further RF impedance matching network comprises one or more further reactive components formed from at least one of the embedded electrically conductive layers.
16. The Doherty amplifier of claim 1 , wherein the RF impedance matching network is electrically connected to an RF input terminal of the main amplifier transistor die and to RF input terminals of each of the peaking amplifier transistor dies.
17. A Doherty amplifier assembly, comprising:
the Doherty amplifier of claim 1 ; and
a global printed circuit board, wherein the multilayer circuit board connects the RF terminals of the respective amplifier transistor dies to the global printed circuit board.
18. The Doherty amplifier assembly of claim 17 , wherein the RF impedance matching network is an output power combiner network that is electrically connected to an RF output terminal of the main amplifier transistor die and to RF output terminals of each of the peaking amplifier transistor dies.
19. The Doherty amplifier assembly of claim 18 , further comprising a further RF impedance matching network that is electrically connected to an RF input terminal of the main amplifier transistor and to RF input terminals of each of the peaking amplifier transistor dies, wherein the further RF impedance matching network comprises one or more further reactive components formed from at least one of the embedded electrically conductive layers.
20. The Doherty amplifier assembly of claim 17 , wherein the RF impedance matching network is electrically connected to an RF input terminal of the main amplifier transistor die and to RF input terminals of each of the peaking amplifier transistor dies.